Generation of radio frequency OAM radiation modes using circular time-switched

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2020年上海杨浦教师进修学院附属中学高三英语下学期期末考试试题及参考答案

2020年上海杨浦教师进修学院附属中学高三英语下学期期末考试试题及参考答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项ACome and enjoy Vivaldi's TheFour Seasonsperformed by live musicians!Tickets△Zone A Sating (Excellent Visibility, $75)△Zone B Seating (Great Visibility, $60)△Zone C Seating (Good Visibility, $45)△Zone D Seating (Restricted Visibility, 30)Zone A and Zone B audiences will get the chance to take pictures with the performers on the stage after the show.Highlights* A beautiful venue bathed in candlelight.*Classical music performance by the Angel Strings quartet*A safe and socially-distanced event, ensuring you are comfortable and at ease.General Info*Dates and times: Various dates, at 6:30 pm and 8:30 pm (select during purchase).*How long: 65 minutes. Doors open 45 minutes before the start time. We recommend you arrive at least 30 minutes before the start of the event, as late entry is not permitted.*Where: Events on Oxlade*Age requirement: Must be 8 years old or older to attend. Anyone under the age of 16 must be accompanied by an adult.*Please note: The 6:30 pm seating will take place during daylight hours outdoors, and the space will not be that dark. In the case of rain, the event will be moved to the indoor area of the venue.DescriptionWhether you're looking for a beautifully unique classical music performance or a romantic candlelit experience, this performance is for you. You don't need to know all things about Vivaldi to enjoy the evening;simply sit back and admire the wonderful atmosphere and the pieces you'll hear.Join our musicians for an evening under the stars, and prepare to be taken into the clouds with Vivaldi' s most treasured masterpieces!1.What can someone with a $45 ticket do?A.Perform on the stage.B.Enjoy good visibility.C.Select a seat in Zone B.D.Take photos with the musicians.2.What should potential audiences keep in mind?A.Arrive at the venue on time.B.Learn about Vivaldi in advance.C.The performance lasts 45 minutes.D.The event will be canceled if it rains.3.What do we know about the 8:30 p.m. performance?A.It welcomes children under the age of 8.B.Its performers differ on different dates.C.Its stage will be decorated with candles.D.It will be shown in the indoor area of the venue.BAs is commonly known,Antarcticais an icy continent with extreme environment. However, a new study provides evidence that the area had a rainforest in the past.The researchers collected a piece of Earth sediment from under the seafloor off the coast ofAntarctica. In the sediment, they discovered forest material that was estimated to be about 90 million years old. At that period, dinosaurs were the ruler animals of the land.Johann Klages, a German geologist, was the lead writer of a study on the findings, published in the journalNature. He said the sediment was collected from a depth of about 30 meters below the ocean floor. Klages said an examination showed that the material didn’t form in the ocean.The researchers estimate that the area — about 900 kilometers from the South Pole — had average yearly temperatures of about12°Cto13°C. The soil included fine dirt particles and hard clay, as well as substances linked to at least 65 different kinds of plants, the study found. Although no animal remains were found, Klages said there were likely dinosaurs, flying reptiles and many insects in the environment.The research represents new evidence of the major climate changes Earth experienced in the past — and is currently undergoing today. The soil in the sediment dates back to the planet’s warmest period of the past 140 million years, with sea level about 170 meters higher than today. The researchers said that the rainforestenvironment inAntarcticawas especially surprising because each year, the area experiences a four-month polar night when there is no sunlight to fuel plant life. Klages said no ice sheets were present during the time, but seasonal snowfall was likely.4. What can we learn about the sediment collected?A. It formed in the age of dinosaurs.B. It was found on theAntarcticaland.C. Ancient forest material was found in it.D. Some dinosaur remains were found in it.5. How did the researchers reach their findings?A. By analyzing the Earth sediment.B. By exploring ice inAntarctica.C. By collecting data on climate.D. By researching special plants.6. What can be indicated in the last paragraph?A. Seasonal snowfall made the forest disappear.B. Antarctica was much colder 140 million years ago.C. Antarctica’s natural environment has changed greatly.D. Polar nights inAntarcticaare getting shorter than before.7. What is the main idea of the text?A. Rainforest disappeared fromAntarctica.B. Antarctica had a different history of climate.C. Researchers studied a piece of Earth sediment ofAntarctica.D.Antarcticahad an extreme environment containing ice and snow.CThe far side of the moonis a strange and wild region, quite different from the familiar and mostly smooth face we see nightly from our planet. Soon this rough space will have even stranger features: it will be crowded with radio telescopes.Astronomers are planning to make the moon's distant side our newest and best window on the cosmic(宇宙的) dark ages, a mysterious era hiding early marks of stars and galaxies. Our universe was not always filled with stars. About 380,000 years after the big bang, the universe cooled, and the first atoms of hydrogen formed. Gigantic hydrogen clouds soon filled the universe. But for a few hundred million years, everything remained dark, without stars. Then came the cosmic dawn: the first stars flickered, galaxies came into existence and slowly the universe's largescale structure took shape.The seeds of this structure must have been present in the darkage hydrogen clouds, but the era has beenimpossible toprobeusing optical(光学的) telescopes—there was no light. And although this hydrogen produced longwavelength(or lowfrequency) radio emissions,radio telescopes on Earth have found it nearly impossible to detect them. Our atmosphere either blocks or disturbs these faint signals; those that get through are drowned out by humanity's radio noise.Scientists have dreamed for decades of studying the cosmic dark ages from the moon's far side. Now multiple space agencies plan lunar missions carrying radiowavedetecting instruments—some within the next three years—and astronomers' dreams are set to become reality.“If I were to design an ideal place to do lowfrequency radio astronomy, I would have to build the moon,”says astrophysicist Jack Burns of the University of Colorado Boulder. “We are just now finally getting to the place where we're actually going to be putting these telescopes down on the moon in the next few years.”8. What's the purpose of building radio telescopes on the moon?A To research the big bang. B. To discover unknown stars.C. To study the cosmic dark ages.D. To observe the far side of the moon.9. What does the underlined word “probe” in Paragraph 3 possibly mean?A. Explore.B. Evaluate.C. Produce.D. Predict.10. Hydrogen radio emissions can't be detected on Earth because ________．A. there was no light in the dark agesB. they cannot possibly get through our atmosphereC. gigantic hydrogen clouds no longer fill the universeD. radio signals on Earth cause too much interference11. What can we infer from theunderlined sentence in the last paragraph?A. Scientists have to rebuild the moon.B. We will finally get to the moon's distant side.C. The moon is a perfect place to set up radio telescopes.D. A favorable research environment will be found on the moon.DThe British poet Matthew Byrne moved to Beijing in 2013 and felt that the capital city's poetry scene was lacking．His obsession（痴迷）for starting poetryevents led to the foundation of the Spittoon Collective in May 2015．“At that time，the literary activity in Beijing was The Bookworm based in Sanlitun，”Byrne says．While some of Beijing's literary institutions would go on to close in the fall of 2019，Spittoon would continue to grow as a community for poets and writers，as well as musicians and others in the creative scene．Byrne describes the Spittoon Collective as a platform for people to share ideas，from literary works to different forms of art，with projects developing from the creative energy within the community．Spittoon originally started as a poetry night at the Mado Bar in Dongcheng District 's Baochao Hutong．Byrne says，“In Beijing，you have these wonderful hutongs，ancient structures where you can walk down and visit cool bars，so I thought it would be good to have a poetry event as it seemed like poetry belonged naturally to this area．”He adds，“The objective now is to discover Chinese voices and broadcast them to the rest of the world．We create a kindof theme park-like atmosphere where every Thursday is occupied by a different literary style or art form．”The readings would mainly be in English，but with an international community，a new section called“Poetry-in-Translation”was started，which featured works in Chinese，French，Arabic，Russian，Spanish and other languages．Joining organized activities like Spittoon can be a major help for those caught up in a boring life．And it's especially important for the people who have moved to China as they need to buildnew relationships while living in a different country．12. What can we know about the Spittoon Collective?A. It was closed in 2019．B. It was set up in 2013 in Beijing．C. It's popular with literature lovers．D. It's a community just for foreigners．13. Why did Byrne start the Spittoon Collective in Baochao Hutong?A. To attract students' love of poetry．B. To expandChina's literature globally．C. To makeBeijing's hutongs famous．D. To combine poetry with the hutong．14. What effect would the Spittoon Collective have on Chinese culture?A. Beneficial．B. Negative．C. Challenging．D. Controversial．15. What is the author's attitude to the Spittoon Collective?A. Unclear．B. Intolerant．C. Doubtful．D. Favorable．第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。

2019-2020学年浙江省慈溪中学高三英语上学期期中考试试卷及参考答案

2019-2020学年浙江省慈溪中学高三英语上学期期中考试试卷及参考答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项AYou have to praise the smoothness（顺畅）of ants on the move. No matter how many of them are going toward a place, there's never a hold-up. A new research paper shows how ants keep traffic flowing by changing their behavior to meet changing conditions.For their experiments, researchers from the University of Toulouse focused on Argentine ants, animals that often move from colony（群落）to colony depending on where the food is. Making use of Argentine ants' talent for fast travel, the researchers built bridges connecting their colonies. The bridges were different in width from a fifth to three-quarters of an inch. The colonies, too, were of different sizes, ranging from 400 to more than 25,000 ants.Then the researchers sat back andmonitoredthe traffic. To their surprise, even when those narrower bridges were full of ants, there were no "traffic accidents". "When the number of ants on the bridge increased, ants seemed to be able to understand the situation and adjusted（调整）their speed accordingly to avoid making the traffic flow stop. "the authors note. "Moreover, ants avoided entering a busy road and made sure that the bridge was never too packed to cross.”The lesson for humans? The traffic problem may lie in our inability to adjust our driving habits for the good of the whole. Driving is fun when there are few cars on the road. Then the traffic moves very slowly. And yet, some impatient driver still acts like he's alone on the road.The research suggests that projects, like the ever-widening of highways, may never free us from traffic jams. As long as we drive along with our own habits, no matter how many other people are on the road, we'll always end up in a traffic jam. Indeed, less space may actually be a good thing. It leaves less room for individual choice and forces us to take a page from the driving book of ants.1. What is Paragraph 2 mainly about?A. The results of the experiments.B. The purpose of the experimentsC. The preparation of the experiments.D. The requirements of the experiments2. What does the underlined word "monitor" in paragraph 3 probably mean?A. watch and check.B. seek and improveC. design and planD. discuss and practise3. What is the best title for the text?A. Is widening highways a solution?B. Why don't ants need traffic lights?C. Can we learn safe driving from ants?D. What can ants teach us about traffic jams?BAmerican football was the fastest-growing sport for US young players last year, according to a survey sponsored by the sport's governing body.But it was the game's no tackle variety that showed the biggest increase－a finding that may reflect concerns about injury. In American football, a tackle (抢断球) refers to an attempt to stop an opponent by forcing them to the ground.The number of participants in football grew in 2015 while most other sport, except baseball, posted a decline, USA Football said on Monday, citing(引用) the findings of a survey of 30,000 children and teenagers.Participation in flag football (a no-tackle type of football) increased by 8.7 percent among children aged 6 to 14, while tackle football rose by 1.9 percent. For that age group, the only other sport that grew was baseball, with a 3. 3 percent increase.In the 15-to-18 age group, flag football rose by 10. 5 percent, while tackle grew by 2.5 percent.Basketball was the third, with a 1. 1 percent increase. Participation in all other sports declined.Tom Farrey, executive director of the Aspen Institute's Sports & Society Program, said he was surprised that flag football participation rose so much.“The trend suggests that parents aremarching to the beat of a different drummer, in pursuing flagas an alternative for their kids," he said.The findings come at a time of increasing concern about the risk associated with youth sports, particularly hockey (曲棍球) and football, where medical researchers have warned about the risk of concussions (damagesto the brain caused by violent blows to the head) and death linked to brain injury.USA Football, anIndianapolis,Indianabased nonprofit funded in part by the National Football League, believed that the increases resulted from better safety and health education."Football participation increases, even modest increases, may signal that programs such as our Heads Up Football program and practice guidelines are making a positive difference," said Scot Hallenbeck, USA Footballchief executive, in a statement.Robert Cantu, aBostonUniversityneurosurgery professor and investigator at the school's chronic Traumatic Encephalopathy (CTE) Center said the increase in fag football participation signaled that more parents were directing children to a safe alternative4. What can we learn about the two age groups?A. Flag football grew the fastest in the 6-to-18 group.B. Tackle football grew he fastest in the 6-to-14 group.C. Participation in baseball declined the most in both groupsD. Participation in tackle football increased the most in both groups.5. The underlined part probably means ________.A working at a different paceB. behaving in a different wayC. ignoring the major differencesD. trying to accept different opinions6. The popularity of flag football is inked with the fact thatA. its rules have been adapted for young playersB. it receives more funds than other varietiesC. tackle football is an old-fashioned gameD. experts worry about children's safety7. What is the cause of football growth according to USA Football?A. Their safety programs are successful.B. More children show interest in the game.C. Football is less likely to cause concussions.D. There are different types of football to choose from.CThe far side of the moonis a strange and wild region, quite different from the familiar and mostly smooth face we see nightly from our planet. Soon this rough space will have even stranger features: it will be crowded with radio telescopes.Astronomers are planning to make the moon's distant side our newest and best window on the cosmic(宇宙的) dark ages, a mysterious era hiding early marks of stars and galaxies. Our universe was not always filled withstars. About 380,000 years after the big bang, the universe cooled, and the first atoms of hydrogen formed. Gigantic hydrogen clouds soon filled the universe. But for a few hundred million years, everything remained dark, without stars. Then came the cosmic dawn: the first stars flickered, galaxies came into existence and slowly the universe's largescale structure took shape.The seeds of this structure must have been present in the darkage hydrogen clouds, but the era has been impossible toprobeusing optical(光学的) telescopes—there was no light. And although this hydrogen produced longwavelength(or lowfrequency) radio emissions,radio telescopes on Earth have found it nearly impossible to detect them. Our atmosphere either blocks or disturbs these faint signals; those that get through are drowned out by humanity's radio noise.Scientists have dreamed for decades of studying the cosmic dark ages from the moon's far side. Now multiple space agencies plan lunar missions carrying radiowavedetecting instruments—some within the next three years—and astronomers' dreams are set to become reality.“If I were to design an ideal place to do lowfrequency radio astronomy, I would have to build the moon,”says astrophysicist Jack Burns of the University of Colorado Boulder. “We are just now finally getting to the place where we're actually going to be putting these telescopes down on the moon in the next few years.”8. What's the purpose of building radio telescopes on the moon?A To research the big bang. B. To discover unknown stars.C. To study the cosmic dark ages.D. To observe the far side of the moon.9. What does the underlined word “probe” in Paragraph 3 possibly mean?A. Explore.B. Evaluate.C. Produce.D. Predict.10. Hydrogen radio emissions can't be detected on Earth because ________．A. there was no light in the dark agesB. they cannot possibly get through our atmosphereC. gigantic hydrogen clouds no longer fill the universeD. radio signals on Earth cause too much interference11. What can we infer from theunderlined sentence in the last paragraph?A. Scientists have to rebuild the moon.B. We will finally get to the moon's distant side.C. The moon is a perfect place to set up radio telescopes.D. A favorable research environment will be found on the moon.DYour best friend that follows you around when the sun comes out - your shadow - doesn’t serve an important function like your heart or brain, but what if you could use shadows to create electricity? When using solar panels (电池板) that are powered by light, shadows can be boring because it means electricity can’t be created. However, researchers from the National University of Singapore have engineered a way to create power from the shadows present everywhere.A team of the university created a machine that can collect energy from shadows. It is created by placing a thin coating of gold onto silicon (硅). Like in a normal solar panel, when put in light, the silicon electrons (电子) become energized and the energized electrons then jump from the silicon to the gold. The voltage (电压) of the part of the machine that is placed in the light increases to the dark part and the electrons in the machine flow from high to low voltage. They are sent through an external circuit (外电路) creating a current that can be used to power another machine. The greater the contrast between light and dark, more energy is provided by the machine.The team isworking on improving the performance of the machine, borrowing approaches from solar panels to gather light. Increasing the amount of light the machines can receive allows them to better make use of shadows, as well as developing shadow energy collecting panels that can successfully gather from indoor lighting. The team is also researching the use of other materials other than gold to drop the price of the machine, meaning they would be more cost effective and easier to apply in society.Shadows are present everywhere and perhaps one day in the future we will be able to collect energy from them by placing the shadow-effect energy machine around the world in places that have been considered unfit for solar panels to work, or indoors. “A lot of people think that shadows are useless,” Tan says, but “anything can be useful, even shadows.”12. What is Paragraph 1 mainly about?A. Your best friend always stays with you after the sunrise.B. The shadow has the same function as the heart and brain.C. Shadows can stop solar panels from creating electricity.D. Researchers have found a way to create power from shadows.13. What is the key working principle of the machine mentioned in the text?A. The silicon produces electricity when it is in the light.B. The gold produces power with the help of the silicon.C. The energized electrons flow from high to low voltage.D. An external circuit creates current using another machine.14. How does the team improve the performance of the machine?A. Using solar panels in the machine.B. Increasing the amount of light received.C. Developing light energy collecting panels.D. Bringing down the price of gold.15. Which of the following is the best place to apply the machine?A. A gym.B. A park.C. A farm.D. A playground.第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。

2020-2021学年北京青年政治学院附属中学高三英语下学期期末考试试题及参考答案

2020-2021学年北京青年政治学院附属中学高三英语下学期期末考试试题及参考答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项AWashingtonD.C.SightseeingWith the information below, you’re not missing anything in D.C.! Click Here to find the perfect hotel for your stay as well.TheOldTownTrolley TourIt offers something for the whole family. Not only will it give them something fun to do, but it will give them a history lesson. This tour will last about three hours and it’s proper for people of all ages.African American History TourBe sure to take this tour because African Americans have had an important role in the making of our country. Take this historical four-hour tour, where you will visit some important sites includingMuseumofAfrican American Historyand Culture.Comedy WalksWashingtonD.C.This is a great experience allowing you to enjoy the capital in a new way. The walking tour lasts for about one hour and thirty minutes, which takes place in less than a mile journey from the starting place.D.C. Twilight TourCheck out the D.C. Twilight Tour for a unique view of some of the most famous sites! What makes this two-hour guided tour truly unique is that you can view many wonderful sites at night time!1. Which tour is recommended to a tourist who is fond of hiking?A. TheOldTownTrolley TourB. African American History TourC. Comedy WalksWashingtonD.C. D. D.C. Twilight Tour2. Which tour lasts longest?A. TheOldTownTrolley TourB. African American History TourC. Comedy WalksWashingtonD.C. D. D.C. Twilight Tour3. Where will you read this text most likely?A. In a guidebook.B. In a magazine.C. In a newspaper.D. On the Internet.BLight pollution is a significant but overlooked driver of the rapid decline of insect populations, according to the most comprehensive review of the scientific evidence to date.Artificial light at night can affect every aspect of insects' lives, the researchers said. "We strongly believe artificial light at night — in combination with habitat loss, chemical pollution.invasive (入侵的) species, and climate change — is driving insect declines, " the scientists concluded after assessing more than 150 studies.Insect population collapses have been reported around the world, and the first global scientific review published in February,said widespread declines threatened to cause a "catastrophic collapse of nature's ecosystems".There are thought to be millions of insect species, most still unknown to science, and about half are active at night. Those active in the day may also be disturbed by light at night when they are at rest.The most familiar impact of light pollution is moths (飞蛾) flapping around a bulb, mistaking it for the moon. Some insects use the polarisation of light to find the water they need to breed, as light waves line up after reflecting from a smooth surface. But artificial light can scupper (使泡汤) this. Insects areimportant prey (猎物) for many species, but light pollution can tip the balance in favour of the predator if it traps insects around lights. Such increases in predation risk were likely to cause the rapid extinction of affected species, the researchers said.The researchers said most human-caused threats to insects have analogues in nature, such as climate change and invasive species. But light pollution is particularly hard for insects to deal with.However, unlike other drivers of decline, light pollution is ly easy to prevent. Simply turning off lights that are not needed is the most obvious action, he said, while making lights motion-activated also cuts light pollution. Shading lights so only the area needed is lit up is important. It is the same with avoiding blue-white lights, which interfere with daily rhythms. LED lights also offer hope as they can be easily tuned to avoid harmful colours and flicker rates.4. What is discussed in the passage?A. Causes of declining insect populations.B. Consequences of insect population collapses.C. Light pollution: the key bringer of insect declines.D. Insect declines: the driver of the collapsed ecosystem.5. What is the 5th paragraph mainly about?A. How light travels in space.B. How light helps insects find food.C. How the food chain is interrelated.D. How light pollution affects insects.6. What does the underlined word"analogues"in Paragraph 6probably mean?A. Selective things.B. Similar things.C. Variations.D. Limitations.7. What is the purpose of the last paragraph?A. To offer solutions.B. To give examples.C. To make comparisons.D. To present arguments.CThe far side of the moonis a strange and wild region, quite different from the familiar and mostly smooth face we see nightly from our planet. Soon this rough space will have even stranger features: it will be crowded with radio telescopes.Astronomers are planning to make the moon's distant side our newest and best window on the cosmic(宇宙的) dark ages, a mysterious era hiding early marks of stars and galaxies. Our universe was not always filled with stars. About 380,000 years after the big bang, the universe cooled, and the first atoms of hydrogen formed. Gigantic hydrogen clouds soon filled the universe. But for a few hundred million years, everything remained dark, without stars. Then came the cosmic dawn: the first stars flickered, galaxies came into existence and slowly the universe's largescale structure took shape.The seeds of this structure must have been present in the darkage hydrogen clouds, but the era has been impossible toprobeusing optical(光学的) telescopes—there was no light. And although this hydrogen produced longwavelength(or lowfrequency) radio emissions,radio telescopes on Earth have found it nearly impossible to detect them. Our atmosphere either blocks or disturbs these faint signals; those that get through are drowned out by humanity's radio noise.Scientists have dreamed for decades of studying the cosmic dark ages from the moon's far side. Now multiple space agencies plan lunar missions carrying radiowavedetecting instruments—some within the next three years—and astronomers' dreams are set to become reality.“If I were to design an ideal place to do lowfrequency radio astronomy, I would have to build the moon,”saysastrophysicist Jack Burns of the University of Colorado Boulder. “We are just now finally getting to the place where we're actually going to be putting these telescopes down on the moon in the next few years.”8. What's the purpose of building radio telescopes on the moon?A To research the big bang. B. To discover unknown stars.C. To study the cosmic dark ages.D. To observe the far side of the moon.9. What does the underlined word “probe” in Paragraph 3 possibly mean?A. Explore.B. Evaluate.C. Produce.D. Predict.10. Hydrogen radio emissions can't be detected on Earth because ________．A. there was no light in the dark agesB. they cannot possibly get through our atmosphereC. gigantic hydrogen clouds no longer fill the universeD. radio signals on Earth cause too much interference11. What can we infer from theunderlined sentence in the last paragraph?A. Scientists have to rebuild the moon.B. We will finally get to the moon's distant side.C. The moon is a perfect place to set up radio telescopes.D. A favorable research environment will be found on the moon.DMark Bertram, 46, lost the tips of two fingers at work in 2018 when his hand became trapped in a fan belt. “It's life-changing but it's not life-ending,” he says. “Doing work is harder now. Everything is just a little different.”After two surgeries and occupational therapy, Bertram decided to make light of his condition by asking Eric Catalano, a tattoo (纹身) artist, to create fingernail tattoos. The idea made everyone in the studio laugh—until they saw the final result. “The mood changed,” Catalano recalls from his Eternal Ink Tattoo Studio. “Everything turned from funny to wow.”When Catalano posted a photo of the tattoos, a pair of fingernails that looked so real that no one could believe their eyes, he had no idea the image would eventually be viewed by millions of people around the world.The viral photo pushed Catalano, 40, further into the world of paramedical (辅助医疗的) tattooing. Now people with life-altering scars come from as far away as Ireland to visit his shop. They enter Eternal Ink looking for the artistic healing they saw online. Using flesh-toned (肉色的) inks and a needle, Catalano transforms his clients'view of themselves.Leslie Pollan, 32, a dog breeder in Oxford, was bitten on the face by a puppy in 2014. She underwent countless surgeries to correct a scar on her lip.“Plastic surgery gave me no hope,” she says. “So I looked for other options.” She ultimately traveled six hours to meet with Catalano. He hid Pollan's lip scar, giving her back a piece of her confidence.“ You don't understand until you've been through it,” Pollan says. “It made me have a different look on life.”Catalano performs up to eight reconstructive tattoos. While he charges $100 per regular tattoo, he doesn't charge for paramedical tattoos. “Financially, it doesn't make sense,” Catalano says. “But every time I see that emotion from my customers, I'm 100 percent sure this is something that I can't stop doing.”12. What best describes people's attitude when first hearing of fingernail tattoos?A. Indifferent.B. Ridiculous.C. Confident.D. Surprised.13. What did Catalano do to help Leslie Pollan?A. He drew an artistic puppy.B. He inked scars on her face.C. He created a lip tattoo.D. He performed plastic surgeries on her.14. What can we infer from the passage?A. Cosmetic surgery is of no use.B. Tattoos earn Mark Bertram a good fame.C. Catalano is a kind and generous person.D. Fingernail tattoos are popular around the world.15. What could be the best title for the text?A. A Life-changing EventB. Miracle TattoosC. An Amazing ArtistD. A Promising Business第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。

SignalShark实时频谱分析监测接收器RF方向找器与定位系统说明书

The new generation in signal analysisReal-Time Spectrum AnalyzerMonitoring ReceiverRF Direction Finding andLocalization SystemMore and more devices have to share the available frequency spectrum as aresult of new technologies such as the Internet of things (IoT), machine tomachine (M2M) or car to car (C2C) communications, and the rapidly growing4G/5G mobile networks.It doesn’t matter whether you are making a wideband measurement of entirefrequency ranges, or searching for hidden signals, or needing to reliablydetect very short impulses, or localizing interference signals –SignalSharkgives you all the measurement solutions you need to cope with the increasinglycomplex radio frequency spectrum. Its design and excellent performance makeit ideal for on-site measurements as well as for fully-fledged laboratory use. SignalShark. Seven senses for signalsSignalShark –there’s a reason for the name. Just like its namesake, theSignalShark is an extremely efficient hunter, perfectly designed for its task.Its prey: interference signals. Its success rate: Exceptional. The real-timeanalyzer is a successful hunter, thanks to the interplay of its highly developedseven sensory functions. Seven senses that don’t miss a thing, and that makeit easy for you to identify and track down interferers in real-time./watch?v=pSZdR27j5LQ&t=14s• Frequency range: 8 kHz to 8 GHz• Weight: Approx. 4.1 kg / 9 lbs (with one battery)• Dimensions: 230 × 335 × 85 mm (9.06ʺ× 13.19ʺ× 3.35ʺ)Make it your deviceSignalShark is ready for the future, thanks toits many expansion facilities, and it can beoptimally adapted as needed to the widestvariety of applications.SignalShark – the 40 MHz real-timespectrum analyzerWhether you are in the lab or out in thefield, you will have the right analysis toolin hand with the SignalShark. You will beconvinced by its truly outstanding RF perfor-mance, as well as by its easily understood,application-oriented operating concept.The high real-time bandwidth with very highFFT overlapping ensures that you can reliablycapture even extremely brief and infrequentevents. The unusually fast scan rate results invery short measurement times even if youneed to cover wider frequency bands thanthe real-time bandwidth. Comprehensiveevaluation tools make sure that you canperform current and future measurementand analysis tasks up to laboratory instru-ment standards reliably, simply, and faster.SignalShark – the monitoring receiverThe extremely High Dynamic Range (HDR) ofthe SignalShark ensures that you can reliablydetect even the weakest signals in the pre-sence of very strong signals, and not confusethem with the artifacts of a normal receiver.This is a basic requirement for most tasksin the field of radio monitoring. Alongsidethe real-time spectrum analyzer, there is areceiver for audio demodulation, level mea-surement, and modulation analysis, whichcan be tuned to any frequency and channelbandwidth within the 40 MHz real-timebandwidth. And, if you need even more thanthe analysis tools of the SignalShark, you canprocess the I/Q data from the receiver exter-nally as a real-time stream and store themon internal or external data storage media.SignalShark – the direction findingand localization systemIt is often necessary to locate the positionof a signal transmitter once the signals havebeen detected and analyzed. SignalSharksupports the new Automatic Direction-Finding Antennas (ADFA) from Narda,allowing you to localize the source veryquickly and reliably. In fact, localization ischild’s play, thanks to the integrated mapsand localization firmware. Conveniently,homing-in using an ADFA mounted on amoving vehicle is also supported. Powerful,state of the art algorithms minimize theeffects of false bearings caused by reflectionsoff urban surroundings in real-time. Extre-mely light weight and easy to use manualdirection finding antennas are availablefor ”last mile“ localization.V I D E OVideo display port for external monitor or projector USB 2.0 for keyboard, mouse, printer, etc.fast, convenient measurementBuilt-in loudspeaker gives clear,loud sound reproduction, even in noisy environments/watch?v=0jqrwU_jPcsV I D E OSignalShark is a handy, portable, battery powered measuring device, yet it boasts performance that is otherwise only found in large, heavy laboratory grade equipment. It can be readily used instead of such expensive equipment because of its wide range of connection facilities and measurement functions.SignalShark –the real-time spectrum analyzer• HDR: extremely low noise and distortion, simultaneously • real-time bandwidth: 40 MHz – FFT overlap: 75 % (Fspan > 20 MHz)– FFT overlap: 87.5 % (Fspan ≤20 MHz, RBW ≤400 kHz))– FFT size: up to 16,384• Minimum signal duration for 100 % POI: 3.125 µs at full amplitude accuracy • Minimum detectable signal duration: < 5 ns • Persistence: up to 1.6 million spectrums per second • Spectrogram time resolution: down to 31.25 µs • Spectrogram detectors: up to three at the same time • RBW: 1 Hz - 800 kHz in real-time spectrum mode, 1 Hz - 6.25 MHz in scan spectrum mode• Filters conforming to CISPR and MIL for EMC measurements • Scan speed: Scan rate up to 50 GHz/s • Detectors: +Pk, RMS, Avg, -Pk, Sample• Markers: 8, additional noise power density and channel power function •Peak table: shows up to 50 highest spectral peaksReliable detection of extremely short and rare events in a 40 MHz real-time bandwidthA real-time analyzer calculates the spectrum by applying the FFT on overlapping time segments of the underlying I/Q data within its real-time bandwidth. The real-time band-width is only one of the key parameters for a real-time analyzer. The probability of inter-cept, POI, is easily just as important. This parameter describes the minimum time that the signal must be present for it to be always detected without any reduction in level. This time is affected by the maximum resolution bandwidth RBW and the FFT overlap. The SignalShark is a match for established laboratory analyzers with its minimum duration of 3.125 µsec for 100 %POI and full amplitude accuracy. The mini-mum detectable signal duration is < 5 nsec.SignalShark accomplishes this by a large signal immunity in combination with a very low intrinsic noise as well as a high FFT overlap and its large resolution bandwidth.That is outstanding for a hand-held analyzer. To accomplish this, SignalShark generally operates with an 87.5 % overlap, which is again outstanding for a hand-held analyzer.This means that even the shortest impulses are detected and the full signal to noise ratio is maintained for longer signals.Spectrogram shows more details than everWith SignalShark, you can use up to three detectors at the same time for the Spectrogram view. This makes it possible for you to easily visualize impulse inter-ference on broadcast signals and get much more information from the spectrogram. The extraordinarily fine time resolution of 31.25 µs means that you can completely reveal the time signatures of many signals.With the I/Q Analyzer option, you can resolve the spectrogram even more, to less than 200 ns.Persistence ViewA color display of the spectrum shows how often the displayed levels have occurred. This enables you to detect signals that would be masked by stronger signals in a normal spectrum view.=SignalShark is not just a very powerful real-time spectrum analyzer. It is also the ideal monitoring receiver, thanks to its near ITU-ideal spectrum monitoring dynamic capabilities, second receiver path and demodulators.SignalShark –the monitoring receiver• HDR: extremely low noise and distortion, simultaneously • CBW: 25 Hz - 40 MHz (Parks-McClellan, α= 0.16)• Filters for EMC measurements: CISPR, MIL • Detectors: +Pk, RMS, Avg, -Pk, Sample• EMC detectors: CPk, CRMS, CAvg (compliant with CISPR)• Level units: dBm, dB µV, dB(µV/m) …• Level uncertainty: < ±2dB • AFC• Audio demodulators: CW, AM, Pulse, FM, PM, LSB, USB, ISB, I/Q • AGC & squelch for audio demodulators • Modulation measurements: AM, FM, PM • I/Q streaming: Vita 49 (sample rate ≤25,6 MHz)• Remote control protocol: SCPIThe benefit of HDRThe extremely high dynamic range (HDR) of the SignalShark ensures that you can reliably detect even the weakest signals in the presence of very strong signals. The SignalShark’s pre-selector allows it to suppress frequencies that would other-wise interfere with the measurement. The excellent dynamic range of the SignalShark is the result of the ideal combination of the displayed averaged noise level (DANL)with the so-called large-signal immunity parameters, i.e. the second and third order intermodulation intercept points (IP 2and IP 3).It is important that these three factors are always specified for the same device setting (e.g. no attenuation, no pre-amplifier), as they vary considerably according to the setting.DDC 2, the additional receiver pathThe tuning frequency and the channel band-width of an additional receiver path, DDC 2,can be set independently from the real-time spectrum analyzer path, DDC 1, within the real-time bandwidth of the SignalShark. The I/Q data can be streamed to external devices in real-time, or they can be processed by the SignalShark itself for level measurements,audio demodulation, and modulation measurements. The very steep cutoffchannel filters capture 100 % of the signal in the selected channel without any degra-dation while completely suppressing the adjacent channels.CISPR compliant EMC detectors now also available for on-site applications The facility for selecting all the filters and detectors necessary for CISPR or MIL com-pliant EMC measurements is also available for the receiver as well as for the spectrum. If an interferer is detected, you can now decide on the spot whether or not the device needs to be taken out of service because of violating EMC regulations.EQDDC 1Overlap BufferFFT DetectorsPersist.Persistence StreamSpectrum StreamADC DataDDC 2DetectorsDetectorsI/Q BufferTrigger UnitDemodulatorsAGCLevel StreamDem. Det.StreamDem. Audio StreamAM & FM StreamI/Q StreamI 2+Q2I 2+Q2PATH 1PATH 2The block circuit diagram shows the two, independent digital down converters (DDC). These make it possible e.g. to observe the spectrum of the signal spectrum and demodulate it at the same time independently within the real-time bandwidth.Automatic Direction Finding Antenna ADFA 1 + 2Narda offers a large number of automatic and directional antennas for the SignalShark. Their unique characteristics combined with the SignalShark makes them unbeatable.Automatic Direction Finding Antenna ADFA 1The frequency range of ADFA 1 makes it particularly suitable for localizing interferers,e.g. in mobile communications networks:Frequency range: 200 MHz - 2.7 GHz Nine dipoles arranged on a 380 mm diameter circle for DFA central monopole is used as a reference element for DF or as an omnidirectional monitoring antennaBuilt-in phase shifter and switch matrix Direction finding method: correlative interferometerBearing uncertainty: 1° RMS (typ.)Built-in electronic compassBuilt-in GNSS receiver with antenna and PPS outputDiameter: 480 mmAutomatic Direction Finding Antenna ADFA 2 (available 2019)This ADFA is suitable for a wide range of localization tasks due to its wide frequency range:Frequency range: (500 kHz) 10 MHz -8 GHz Two crossed coils for DF at low frequencies Nine dipoles arranged on a 380 mm dia-meter circle for DF at medium frequencies Nine monopoles arranged on a 125 mm diameter circle for DF at high frequencies A central monopole is used as a reference element for DF or as an omnidirectional monitoring antennaBuilt-in phase shifter and switch matrix Direction finding method: Watson-Watt or correlative interferometerBearing uncertainty (10 MHz - 200 MHz): 2° RMS (typ.)Bearing uncertainty (200 MHz - 8 GHz): 1° RMS (typ.)Built-in electronic compassBuilt-in GNSS receiver with antenna and PPS output Diameter: 480 mm Automatic Direction Finding Antenna ADFA accessoriesConnecting cable, length 5 m or 15 m,low lossTripod including mounting accessories Mounting kit for magnetic attachment to a vehicle roofMounting kit for mast attachmentAfter you have localized the signal by SignalShark and ADFA using the car, you will need for last mile or to enter a building Narda’s handy, feather-light directional antennas and active antenna handle. They are the ideal choice in this situation. The antenna handle does more than just hold the antenna. Among other features, it has a built-in operating button that allows you to perform the main steps during manual direction finding, making the combination unbeatable.and take bearings on very weak or distant signals. The preamplifier gain is taken into account automatically when you make field strength or level measurements.The integrated operating button lets you make the main steps in the manual direction finding process.The following antennas to fit the antenna handle are available:• Loop Antenna: 9 kHz - 30 MHz• Directional Antenna 1: 20 MHz - 250 MHz • Directional Antenna 2: 200 MHz - 500 MHz • Directional Antenna 3: 400 MHz - 8 GHz A plug-in adapter with male N connector allows you to take advantage of the features of the handle even when you are using third-party antennas or external filters.Directional antenna 3400 MHz - 8 GHz350 g / 0.77 lbsDirectional antenna 1 20 MHz - 250 MHz 400 g / 0.88 lbs Loop antenna 9 kHz - 30 MHz 380 g / 0.84 lbs Directional antenna 2 200 MHz - 500 MHz 300 g / 0.66 lbs Active antenna handle with integrated compass and preamplifier 9 kHz - 8 GHz 470 g / 1.04 lbsAdapter,male N connectorN Antenna Elements0°90°180°270°Element SwitchReference Elementn1Quadrature Phase Shifter(Smart Antenna)+The Narda antenna handle and directional antennas are extremely light, making for fatigue-free signal searches.The convenient plug-in system allows you to change antennas very quickly.SignalShark recognizes the antenna and applies the appropriate antenna factors for field strength measurements automatically.SignalShark receives the azimuth,elevation and polarization of the antenna from the 3D electronic compass built into the handle, so manual direction finding could hardly be simpler.The preamplifier built into the handle is activated and deactivated bySignalShark, so you can further reduce SignalShark’s low noise figure to detectYou will often need to locate the position of a signal transmitter once thesignals have been detected or analyzed. SignalShark combined with Narda’snew automatic direction finding antennas (ADFA) and the very powerfulmap and localization firmware provides reliable bearings in the twinklingof an eye. The bearing results are processed by the SignalShark withoutneeding an external PC. Reliable localization of transmitters has not beenpossible before with so few hardware components.Transmitter localizationSignalShark simplifies transmitter localizationby autonomously evaluating all the availablebearing results and plotting them on a map,using a statistical distribution of bearinglines. The result is a so-called “heat map”,on which the possible location of the trans-mitter is plotted and color-coded accordingto probability. SignalShark also draws anellipse on the map centered on the estima-ted position of the transmitter and indicatingthe area where the transmitter has a 95 %probability of being located. The algorithmused by SignalShark to calculate the positionof an emitter is extremely powerful. It candetermine the position of the emitter bycontinuous direction finding when movingaround in a vehicle, even in a complexenvironment such as an inner-city area.The calculation is continuous inreal-time, so you can viewthe changing heat mapon the screen of theSignalShark andFast automatic direction findingSignalShark supports the new automaticdirection finding antennas (ADFA) fromNarda, which let you take a completebearing cycle in as little as 1.2 ms.The omnidirectional channel power and thespectrum are also measured during a bearingcycle, so you can monitor changes in thesignal level or spectrum concurrently withthe bearings. The AFDAs use differentantenna arrays, depending on the frequencyrange. At low frequencies, a pair of crossedcoils are used for the Watson-Watt methodof direction finding. At medium and highfrequencies, a circular array of nine dipolesor monopoles is used for the correlativeinterferometer direction finding method.SignalShark –The RF direction finding and localization system• Frequency range ADFA 1: 200 MHz - 2.7 GHz• Frequency range ADFA 2: 10 MHz - 8 GHz• Azimuth and elevation bearings• DF quality index• Complete bearing cycle: down to 1.2 ms• Omnidirectional level and spectrum during DF process• Uses OpenStreetMaps, other map formats can be imported• Easy to use, powerful map and localization software• The map and localization software runs on the handheldunit itselfThe SignalShark is a very powerful platform that Narda is continuously expanding. Options that will be available for delivery in 2019 are described below. Only the firmware of the SignalShark will be used to realize these options, which will be capable of on-site activation.High time resolution spectrogram HTRSalso available in the spectrum pathIn real-time spectrum mode, the ring buffer ofthe SignalShark records the I/Q data from thereal-time spectrum path rather than from thereceiver I/Q data. If you or a trigger eventhalts the real-time analyzer, the last up to200 million I/Q samples of the monitoredfrequency range are available. This correspondsto a timespan of at least 4 s, so you can zoomin on the spectrogram with a resolution ofbetter than 200 ns when the analyzer is halted.The FFT overlap can be up to 93.75 %, and nodetectors are needed that could reduce thetime resolution. You can even subsequentlyalter the RBW. The persistence view also adjustsso that it exactly summarizes the spectrumsin the time period covered by the zoomedsegment. This ensures that all the time orspectral details in the I/Q data can be madevisible. You can of course also save the I/Qdata of the zoomed segment.DF SpectrumThe SignalShark can find the directions ofseveral transmitters simultaneously in DFspectrum evaluation mode. This mode offersa persistence spectrum and a spectrogramof the azimuth in addition to the usual levelspectrum and spectrogram view. You canalso monitor frequency ranges that arewider than the real-time bandwidth of theSignalShark. You can distinguish betweendifferent transmitters much more easilythan before by means of DF spectrum mode,because the SignalShark shows you thedirection of incidence as well as the levelof each frequency bin.SignalShark I/Q analyzerSignalShark has a ring buffer for up to 200 million I/Q samples. The receiver I/Q data are normally written continuouslyto the ring buffer. The recording can be stopped by a trigger event. The recorded I/Q data are then transferred to the CPU of the SignalShark, where they are further processed.The following trigger sources are available: Frequency mask triggerReceiver levelExternal trigger sourceTimestampUser inputFree runThe following I/Q data views are available: I and Q versus timeMagnitude versus time (Zero-span) Vector diagramHigh time resolution spectrogram Persistence You can of course also save the I/Q data as adata set, and you can even stream the datadirectly to permanent storage media in orderto make very long recordings of the I/Q data.You can then replay such long-term recor-dings using the integrated I/Q analyzer, orprocess them externally.2 x 10 MHz LTE signal recorded in a HTRS. Time resolution1 µs. The extremely high time resolution renders the signaltransparent at low traffic levels (right), so you can spotpossible interference within the frame structure.More Information about technical details andaccessories like transport case and car chargerunit can be found in the SignalShark data sheet./en/signalsharkNarda is a leading supplier …N S T S 06/18 E 0333A T e c h n i c a l a d v an c e s , e r r o r s a n d o m i s s i o n s e x c l u d e d .© N a r d a S a f e t y T e s t S o l u t i o n s 2014. ® T h e n a m e a n d l o g o a r e t h e r e g i s t e r e d t r a d e m a r k s o f N a r d a S a f e t y T e s t S o l u t i o n s G m b H a n d L 3 C o m m u n i c a t i o n s H o l d i n g s , I n c .—T r a d e n a m e s a r e t h e t r a d e m a r k s o f t h e i r o w n e r s .r o e n e r -d e s i g n .d eNarda Safety Test Solutions 435 Moreland RoadHauppauge, NY11788, USA Phone +1 631 231-1700Fax +1 631 231-1711**************************… of measuring equipment in the RF test and measurement, EMF safety and EMC sectors. The RF test and measurement sector covers analyzers and instruments for measuring andidentifying radio sources. The EMF safety product spectrum includes wideband and frequency-selective measuring devices, and monitors for wide area coverage or which can be worn on the body for personal safety. The EMC sector offers instruments for determining the electro-magnetic compatibility of devices under the PMM brand. The range of services includes servicing, calibration, accredited calibration, and continuous training programs.Narda Safety Test Solutions GmbH Sandwiesenstraße 772793 Pfullingen, Germany Tel. +49 7121 97 32 0Fax +49 7121 97 32 790********************* /en/signalshark。

5G基站建设与维护高职全套PPT完整教学课件

GSM-Global System for Mobile communications 全球移动通信系统CDMA-Code Division Multiple Access 码分多址接入DCS-Digital Cellular System 数字蜂窝系统
第二代移动通信系统（2G）
在90年代，爱立信 GH337 是第一款登陆中国的 GSM 手机，当时广东省的 GSM 网络刚刚开通，GH337 作为一款数字手机，其性能各方面都完爆其他手机，火爆程度不言而喻。开启中国手机的“老前辈”爱立信并不是我们现在熟知的索尼爱立信，而是一家来自瑞典的公司。早在80、90年代和西门子公司占领了当时的大部分的手机市场。
5G基站建设与维护
项目1 5G技术特点和网络架构认知.pptx项目2 5G NR原理认知.pptx项目3 5G基站设备安装.pptx项目4 5G基站硬件测试.pptx项目5 5G基站设备验收.pptx项目6 5G基站业务开通.pptx项目7 5G基站故障处理.pptx
全套PPT课件
项目一 5G技术特点和网络架构认知
2G
2.5G
2.75G
3G
3.5G
3.75G
3.9G
GPRS
EDGE
HSDPAR5
HSUPAR6
MBMS
4G
MBMS
CDMA 2000 1X EV-DO
802.16 e
802.16 m
HSDPA
HSPA+R7
FDD/TDD
4G
GSM
TD-SCDMA
WCDMAR99
802.16 d
CDMAIS95
CDMA2000 1x
第二代移动通信系统（2G）
3.主要技术：TDMA+数字技术

24GHz射频前端频率合成器设计

第48卷第1期（总第187期）2019年3月火控雷达技术Fire Control Ｒadar TechnologyVol.48No.1（Series 187）Mar.2019收稿日期：2018-10-24作者简介：饶睿楠（1977－），男，高级工程师。

研究方向为频率综合器及微波电路技术。

24GHz 射频前端频率合成器设计饶睿楠王栋余铁军唐尧（西安电子工程研究所西安710100）摘要：随着微波射频集成电路集成度越来越高，24GHz 频段的高集成雷达收发芯片逐渐大规模使用。

其中英飞凌科技公司的24GHz 锗硅工艺高集成单片雷达解决方案就是其中具有代表性的一种，被大量应用在液位或物料检测、照明控制、汽车防撞、安防系统。

FMCW 为此种应用最多采用的信号调制方式。

本文采用锁相环频率合成方案，产生系统所需的FMCW 调制信号。

关键词：24GHz 射频前端；FMCW ；频率综合器BGT24AT2ADF4159中图分类号：TN95文献标志码：A 文章编号：1008－8652（2019）01－066－04引用格式：饶睿楠，王栋，余铁军，唐尧．24GHz 射频前端频率合成器设计［J ］．火控雷达技术，2019，48（1）：66－69．DOI ：10．19472/j．cnki．1008－8652．2019．01．014Design of a Frequency Synthesizer for 24GHz ＲF Front EndsＲao Ｒuinan ，Wang Dong ，Yu Tiejun ，Tang Yao（Xi'an Electronic Engineering Ｒesearch Institute ，Xi'an 710100）Abstract ：With the increasing integration of microwave and radio-frequency integrated circuits ，highly integratedradar transceiver chips in 24GHz band have gradually found large-scale applications．Among those chips ，Infineon's24GHz SiGe monolithic radar solution is a typical one．It has found wide applications in liquid （or material ）detec-tion ，lighting control ，automotive collision avoidance ，and security systems．FMCW is the most widely used signal modulation method in these applications．This paper uses PLL frequency synthesis scheme to generate FMCW mod-ulation signals required by the system．Keywords ：24GHz ＲF front end ；FMCW ；frequency synthesizer ；BGT24AT2；ADF41590引言24GHz 频段雷达大量用于液位检测、照明控制、汽车防撞、安防等领域。

电器电子辞汇英语翻译

模拟数字转换器模数转换器 a d converter 缓冲存储器 abbreviated code快速呼唤 abbreviated dialing象差 aberration?异样辉光放电 abnormal glow discharge 异样反射 abnormal reflections磨耗 abrasion?磨粉 abrasive dust磨料喷射加工 abrasive jet machining? 磨料喷射蝶 abrasive jet trimming磨蚀剂 abrasive paste?研磨蝶 abrasive trimming磨料 abrasive?急剧退化 abrupt degradation突变异质结 abrupt heterojunction 突变结 abrupt junction绝对亮度阈absolute threshold of luminance吸收功率 absorbed power吸收剂 absorber?吸收能力 absorbing capacity?吸收电路 absorbing circuit吸收层 absorbing layer吸收媒质 absorbing medium?吸收跃迁 absorbing transition吸收带 absorption band吸收长度 absorption length吸收线 absorption line吸收损失 absorption loss?吸收测定 absorption measurement吸收灯 absorption modulation吸收点 absorption point吸收电阻 absorption resistance 吸收 absorption?对接 abutment joint?截割水晶片 ac cut quartz ac加速老化 accelerated aging?加速粒子 accelerated particle 加速实验 accelerated test?加速阳极 accelerating anode加速周期 accelerating cycle?加速电极 accelerating electrode 加速栅极 accelerating grid加速缝 accelerating slit加速管 accelerating tube?加速波 accelerating wave? 带电粒子加速acceleration of charged particles加速空间 acceleration space加速电压 acceleration voltage?加重 accentuation较佳对照度 acceptable contrast ratio受主 acceptor受汁子 acceptor atom受中心 acceptor center受周度 acceptor density受钟质 acceptor impurity受周级 acceptor level受滞半导体 acceptor type semiconductor存取码 access code访问方式 access method适应性第 accommodation第系数 accommodation coefficient? 积存层 accumulation layer再生精准度 accuracy in reproduction 精准定位 accurate positioning改良型专用射极耦合逻辑 ace消色差区 achromatc region消色差透镜 achromatic lens?消色差阈值 achromatic threshold针状结晶 acicular crystal酸侵蚀 acid etch橡实管 acorn tube吸声系数 acoustic absorptivity?滤声器 acoustic filter?声频 acoustic frequency? 声像 acoustic image声阻抗 acoustic impedance?声迷路 acoustic labyrinth声动录音机acoustic manipulated recorder声面波 acoustic surface waves声能转换器 acoustic transducer声学处置 acoustic treatment音波 acoustic wave表面声波振荡器 acoustic wave oscillator声延时线 acoustical delay line受钟质 acceptor impurity受周级 acceptor level受滞半导体 acceptor type semiconductor存取码 access code访问方式 access method适应性第 accommodation第系数 accommodation coefficient? 积存层 accumulation layer再生精准度 accuracy in reproduction 精准定位 accurate positioning改良型专用射极耦合逻辑 ace消色差区 achromatc region消色差透镜 achromatic lens?消色差阈值 achromatic threshold针状结晶 acicular crystal酸侵蚀 acid etch橡实管 acorn tube吸声系数 acoustic absorptivity?滤声器 acoustic filter?声频 acoustic frequency? 声像 acoustic image声阻抗 acoustic impedance?声迷路 acoustic labyrinth声动录音机acoustic manipulated recorder声面波 acoustic surface waves声能转换器 acoustic transducer声学处置 acoustic treatment音波 acoustic wave表面声波振荡器 acoustic wave oscillator声延时线 acoustical delay line酌半径 action radius?活化阴板 activated cathode活化分子 activated molecule?激活能 activation energy?激活 activation?有源区 active area有效分量 active component踊跃干扰 active counter measures 活性粉尘 active dust有源元件 active element有源元件组 active element group 活性纤维 active fiber有源滤波器 active filter织制导 active guidance织寻的制导 active homing guidance 有源激光元件 active laser element 激光皮捉质 active laser substance 活性液体 active liquid有源波模同步 active mode locking 有源寄生元件 active parasitics有源 q 开关 active q switching有源备份 active redundancy有源中继器 active repeater有源四端网络的反射损耗 active return loss有源卫星转发器active satellite repeater有源衬底 active substrate有源衬底蝶 active substrate trimming传动机构 actuator?锐度 acuity适应性均衡器 adaptability equalizer适应 adaptation?套筒式联轴器 adapter coupling转接器 adapter?自适应相关器 adaptive correlator自适应增量灯 adaptive delta modulation自适应接收机 adaptive receiver吸附原子 adatom爱德考克天线 adcock antenna爱德考克测向仪 adcock direction finder附加元件 add ons加色法混合 additive color mixture加色法合成 additive color synthesis加色法系统 additive color system基色的相加混合additive mixing of primaries加色法原色 additive primaires印刷电路的添加技术additive printed circuit technique加色法 additive process? 寻址系统 addressing system附着 adherence?粘着强度 adhesion strength?粘合剂 adhesive粘合剂涂敷 adhesive coating芯片粘附 adhesive die attachment胶粘密封 adhesive sealing粘合带 adhesive tape邻道伴音载波 adjacent audio carrier相邻信道 adjacent channel邻信道衰减 adjacent channel attenuation邻信道干扰adjacent channel interference邻频道抑制器 adjacent channel rejector相邻信道选择性adjacent channel selectivity相邻线路 adjacent lines邻信道图象载波 adjacent picture carrier相邻图象载波距离adjacent picture carrier spacing邻频道图象载波陷波器 adjacent picture carrier trap可单减器 adjustable attenuator可堤路 adjustable short可敌值金属氧化物半导体adjustable threshold mos蝶 adjustment?导纳矩阵 admittance matrix导纳 admittance?混合物 admixture?吸附质 adsorbate吸附剂 adsorbent?吸附层 adsorption layer? 吸附 adsorption?低劣半导体材料adulterated semiconductor material超前角 advance angle?改良型低功耗肖特基晶体管晶体管逻辑电路 advanced low power schottky ttl改良型自对准多晶硅栅工艺advanced polysilicon self aligned process改良型肖特基晶体管逻辑电路advanced schottky transistor logic改良型肖特基晶体管晶体管逻辑电路 advanced schottky ttl天线阵 aerial array天线衰减器 aerial attenuator天线电缆 aerial cable天线电容 aerial capacity天线扼力 aerial choke天线电路 aerial circuit天线藕合 aerial coupling天线藕合线圈 aerial coupling coil 天线电流 aerial current天线效率 aerial efficiency天线鼓励 aerial excitation天线馈电 aerial feed天线馈线 aerial feeder天线阻抗 aerial impedance天线电感 aerial inductance天线引入线 aerial lead in透镜天线 aerial lens天线损耗 aerial loss天线噪声 aerial noise天线功率 aerial power 天线辐射电阻aerial radiation resistance天线电抗 aerial reactance天线电阻 aerial resistance天线系统 aerial system天线接头 aerial terminal天线杆 aerial tower?天线党电容器 aerial tuning capacitor天线党线圈 aerial tuning coil天线 aerial?航空电子学的 aeroelectronic航空电子学 aeroelectronics?无线电报 aerogram导航电台 aeronautical station飞机天线 aeroplane antenna飞机反射的干扰信号 aeroplane flutter俄歇电子能谱学 aes音频 af?亲合力 affinity?后加速 after acceleration余晖 afterglow余像 afterimage后处置 aftertreatment?老化条件 ageing condition老化 ageing?集聚 aggregate?雪崩注入 ai雪崩注入二极管 aid半自动跟踪 aided tracking雪崩感生徙动 aim空气隔离型单片集成电路 aimic 空气轴承台 air bearing stage间隙 air clearance?空气冷却式激光器 air cooled laser空对地通信 air ground communication空气隔离 air isolation空气隔离型集成电路air isolation integrated circuit空气隔离型集成工艺air isolation process漏气 air leak?空气氧化物隔离 air oxide isolation空中位置指示器 air position indicator吹气清洗 air purge侦查海面舰艇的飞机监视雷达air to surface vessel radar风动传送设备 air track飞机无线电信标 airborne beacon空传污染 airborne contamination机载雷达 airborne radar机载电视接收机airborne television receiver拦截飞机雷达aircraft interception radar飞机电台 aircraft station机场信标 airport beacon机场危险信标 airport danger beacon机场交通操纵 airport traffic control气密接合 airtight joint报警信号 alarm signal?反射率测量 albedo measurement反照率 albedo?自动逻辑设计 ald 阿尔福德环形天线 alford loop antenna 铝栅 alg算法 algorithm?对准器 aligner对准精度 alignment accuracy对准误差 alignment error蝶用激光器 alignment laser对准标记 alignment mark定位锁 alignment pin?周密对准 alignment registration校准要求 alignment requirements定位 alignment?碱金属锑化物 alkali antimonide无碱环境 alkali free environment由碱可除光刻胶alkaline strippable resist全波段电视党器 all band tv tuner全扩散型集成电路all diffused integrated circuit交直两用接收机 all mains receiver全天候雷达 all weather radar分派器 allotter?允许能带 allowed band?允许能级 allowed level允许线 allowed line允许跃迁 allowed transition合金薄膜 alloy film合金结 alloy junction合金结晶体管 alloy junction transistor合金晶体管 alloy transistor合金 alloy? 合金接触 alloyed contact合金型二极管 alloyed diode合金区域 alloyed region接字母顺序的 alpha抗射线性 alpha immunity粒子轰击 alpha particle bombardment粒子爱惜 alpha particle protection粒子辐射灵敏度alpha radiation sensitivity粒子闪烁计数器alpha scintillation counter字符印字管 alphanumeric printing tube管 alphatron?更替路由 alternate route隔行扫描 alternate scanning交流 alternating current交菱量 alternating current measurement交羚阻 alternating current resistance超导交流 alternating supercurrent高度计 altimeter?高度指示器 altitude indicator?算术与逻辑部件 alu氧化铝陶瓷板划线alumina ceramic scribing氧化铝管壳 alumina package氧化铝 alumina?铝金属化 aluminizing铝硅酸盐玻璃 aluminosilicate glass铝线热压焊 aluminum bonding氧化铝陶瓷 aluminum oxide ceramics铝尖峰形成 aluminum spiking氧化物阶梯的铝覆盖aluminum step coverage铝线热压焊接 aluminum wire bond爹收音机 am receiver爹接收 am reception爹 am?爱好者 amateur业余波段 amateur band业余无线电台 amateur radio station 环境空气监测器 ambient air monitor 周围环境 ambient enviroment环境湿度 ambient humidity环境压力 ambient pressure?周围介质温度 ambient temperature 非单值性 ambiguity?双极性扩散 ambipolar diffusion?氨微波激射器氨脉泽 ammonia maser铵分子束频率标准ammonium molecular beam frequency standard无定形化 amorphization非晶态晶态转变amorphous crystalline transition对非晶半导体离子注入amorphous implantation非晶半导体 amorphous semiconductor非晶半导体掐amorphous semiconductor device非晶形状态 amorphous state?无定形结构 amorphous structure?信息量 amount of information?放大系数 amplification constant?放大谱线宽 amplification linewidth放大 amplification? 放大屁频带 amplifier band放大齐声 amplifier noise放大级 amplifier stage放大器 amplifier?放大速弟 amplifying klystron放大跃迁 amplifying transition放大管 amplifying tube特高频功率放大管 amplitron幅度校正 amplitude correction?鉴幅器 amplitude discriminator?振幅失真 amplitude distortion?振幅误差校正 amplitude error correction振幅偏移 amplitude excursion振幅频率失真amplitude frequency distortion振幅频率响应amplitude frequencyresponse?限幅歧路 amplitude limiter circuit限幅器 amplitude limiter?爹发射机amplitude modulated transmitter爹甚高频发射机 amplitude modulated vhf transmitter爹监视器 amplitude modulation monitor爹噪声 amplitude modulation noise爹抑制 amplitude modulation suppression爹器 amplitude modulator视频信号振幅 amplitude of videosignal视频信号振幅范围amplitude range of videosignal振幅特性曲线 amplitude response?振幅稳固激光器amplitude stabilized laser 酌距离 amplitude?模拟阵列 analog array模拟集成电路 analog chip模拟运算机 analog computer?模拟数字网络 analog digital network 模拟电子学 analog electronics模拟信息 analog information模拟微电子学 analog microelectronics 模拟灯 analog modulation模拟网络 analog network模拟移相器 analog phase shifter模拟记录 analog recording模拟信号 analog signal?模拟开关 analog switch模拟的 analogue模拟放大器 analogue amplifier模拟计算 analogue computation模拟式乘法运算器 analogue multiplier 分析器 analyzer?与电路 and circuit?与元件 and element或非门 and nor gate 与与操作 and operation与或电路 and or circuit无回声室 anechoic room磨角 angle lap角灯 angle modulation?射束偏转角 angle of beam deflection 发散角 angle of divergence仰角 angle of elevation? 槽倾斜角 angle of groove inclination入射角 angle of incidence?倾斜角 angle of inclination?光入射角 angle of light incidence辐射角 angle of radiation角度数字变换器 angle to digit converter角跟踪 angle tracking倾斜离子注入 angled ion implantation角散布 angular distribution?角分辨率 angular resolution?阴离子互换尸 anion resin阴离子 anion?蛤异性侵蚀 anisotropic etch蛤异性侵蚀断面图anisotropic etch profile蛤异性侵蚀性质anisotropic etchproperty蛤异性侵蚀剂 anisotropic etchant 蛤异性材料 anisotropic material? 蛤异性 anisotropy?退火炉 annealer?退火杂质活化 annealing activation 退火覆盖层 annealing cap热处置 annealing?广播员 announcer环形锯片 annular blade环形接触 annular contact环形锯片切割 annular cutting环状电阻器 annular resistor 环状旋转接头 annular rotary joint 环形锯 annular saw环状裂缝 annular slot阳极特性 anode characteristic阳极暗区 anode dark space阳极检波 anode detection屏极耗散 anode dissipation阳极效率 anode efficiency阳极电解侵蚀 anode etching屏极输出器 anode follower阳辉光 anode glow阳极栅极电容 anode grid capacity 屏极负载 anode load阳极中和 anode neutralization阳极氧化 anode oxidation阳极射线 anode rays屏极检波 anode rectification阳极电阻 anode resistance阳极溅射 anode sputtering?阳极寄生振荡抑制器 anode stopper 阳极电源 anode supply阳极端子 anode terminal阳极电压 anode voltage阳极 anode?阳极的 anodic阳极处置 anodization 异样晶体生长 anomalous crystal growth应答塞绳 answering cord应答装置 answering device应答塞 answering plug天线放大器 antenna amplifier天线电容器 antenna capacitor天线转换开关 antenna change over switch天线接线 antenna connection天线耦合电容器 antenna coupling condenser天线效应 antenna effect天线元件 antenna element天线电动势 antenna emf天线输入阻抗 antenna feed impedance天线场强增益 antenna field gain天线接地开关 antenna grounding switch平均地表面上天线高度 antenna height above average terrain天线引线 antenna lead天线插座 antenna socket天线仰角 antenna tilt防撞雷达 anti collision device消感网络 anti induction network抗氧化层 anti oxidation layer天线收发转换开关 anti transmit receive switch 对阴极 anticathode?预报信号 anticipating signal反符合电路 anticoincidence circuit 抗衰落犬线 antifading antenna抗衰落装置 antifading device反铁电体 antiferroelectric阻厄电路 antihunt circuit抗干扰接收机 antijam receiver抗干扰装置 antijamming unit锑 antimony?抗噪声 antinoise反雷达 antiradar反雷达导弹 antiradar missile反雷达学 antiradiolocation反卫星导弹 antisatellite missile防静电剂 antistatic agent防静电设备 antistatic aids防静电组装 antistatic assembly防静电袋 antistatic bag防静电手套 antistatic gloves防静电掩模底版 antistatic mask blank防静电台 antistatic station防静电表面处置 antistatic surface treatment防静电工具 antistatic tool反斯托克斯线 antistockes line收发开关盒 antitrans mit receive box常压化学汽相淀积 apcvd非党天线 aperiodic antenna非周期电路 aperiodic circuit 张角 aperture angle孔径失真补偿 aperture compensation 孔径耦合 aperture coupling孔径失真 aperture distortion孔径均衡 aperture equalization针孔透镜 aperture lens孔径损失 aperture loss多孔障板 aperture mask孔镜 aperture mirror孔径光阑 aperture stop口径 aperture?外观检查 appearance inspection?苹果彩色显象管 apple tube敷料器 applicator应用全息照相术 applied holography 进场信标 approach beacon进场治理 approach control进场指挥雷达 approach control radar 水清洗器 aqueous cleaner水处置 aqueous processing电弧阴极 arc cathode弧光灯鼓励 arc lamp pumping电弧等离子体 arc plasma弧 arc? 逆弧 arcback构造 architecture?电弧放电 arcing显光管 arcotron区域码 area code面积型成像机 area imager氩激光器 argon laser?氩 argon?运算装置 arithmetical unit?盗丹振荡器 armstrong oscillator 排列 arrangement?阵列 array阵列式芯片 array chip阵列集成电路 array device阵列布图 array layout阵列逻辑 array logic存贮企列 array memory阵列图象形成 array patterning阵列间距 array pitch阵列处置 array processing阵列结构 array structure输入电流 arrival current掺砷发射极 arsenic doped emitter掺砷外延层 arsenic doped epi砷搀杂 arsenic doping涂布的砷溶液 arsenic spin on solution 砷 arsenic? 砷化物 arsenide可听清楚度 articulation?假天线 artificial aerial人工老化 artificial ageing?仿真天线 artificial antenna黑电平测试信号 artificial black signal 仿真延迟线 artificial delay line假回波 artificial echo人造电子眼 artificial electronic eye 仿真全息图 artificial hologram仿置线 artificial line版图检查工具 artwork checking tool原图设计 artwork design图形发生 artwork generation 图形发生器 artwork generator 原图制备刀 artwork knife照相底图 artwork master原图 artwork?超声波水下探测器 asdic长宽比 aspect ratio?微观粗糙度 asperity汇编程序;装配器 assembler组装错误 assembly defect装配图 assembly drawing?装配设备 assembly equipment 装配夹具 assembly fixture? 装配室 assembly room 组装台 assembly station?组装成品率 assembly yield组装 assembly?分派频率 assigned frequency交莲磁 assistating current magnetic biasing相联存储器 associative memory非稳固电路 astable circuit非稳态多谐振荡器 astable multivibrator 像散现象 astigmatism天文电子学 astrionics天体电子学 astronics天体脉泽 astronomical maser天文航海 astronomical navigation非对称振幅灯 asymmetric amplitude modulation不对称边带传送 asymmetric sideband transmission不对称偏转 asymmetrical deflection异先操作 asynchronous operation异步应答方式 asynchronous response mode异步传输 asynchronous transmission切割晶体 at cut crystal at自动测试设备 ate大气模型 atmosphere model 大气 atmosphere?大气吸收带 atmospheric absorption band 大气吸收 atmospheric absorption?大气衰减 atmospheric attenuation大气波导 atmospheric duct大气电场 atmospheric electric field大气波导管 atmospheric guide大气压激光器 atmospheric pressure laser大气透射带 atmospheric transmission band大气透射系数 atmospheric transmittance 大气窗 atmospheric window?大气干扰 atmospherics原子吸收分光光度法 atomic absorption spectrophotometry原子束频率标准 atomic beam frequency standard原子束激光器 atomic beam laser原子钟 atomic clock?原子发射光谱仪 Atomic Emission Spectrometer AES原子频率标准 atomic frequency standard原子氢 atomic hydrogen原子型杂质 atomic impurity原子电离 atomic ionization原子激光器 atomic laser原子谱线宽度 atomic linewidth原子核 atomic nucleus?原子时标准 atomic time standard自动测试系统 ats可达清楚度 attainable resolution衰减常数 attenuation constant? 衰减器 attenuation pad?衰减 attenuation?听觉的 audio声频放大器 audio amplifier伴音载波 audio carrier伴音中心频率 audio center frequency伴音通道 audio channel声频放大 audio frequency amplification 音几回带 audio frequency band音频扼力 audio frequency choke音频发生器 audio frequency generator音几回率计 audio frequency meter音频峰值限幅器 audio frequency peak limiter音频变压器 audio frequency transformer音频电平指示器 audio level indicator音频混频器 audio mixer音频回音装置 audio output unit音频范围 audio range音频信号 audio signal音几回谱 audio spectrum音几回谱分析器 audio spectrum analyzer声道 audio track音频发射机 audio transmitter听力图 audiogram 听力计 audiometer测听技术 audiometry三极检波管 audion检查 audit?听能听能 audition俄歇电子发射 auger electron emission 俄歇电子 auger electron?俄歇微探针 auger microprobe俄歇复合 auger recombination俄歇能谱仪 auger spectrometer俄歇跃迁 auger transition无线电导航有声信标 aural radio range 收听 aural reception伴音发射机 aural transmitter南极光 aurora australis北极光 aurora borealis极光 aurora?故障 autage确认 authentication自动加速 autoacceleration自动补偿器 autocompensator自动操纵 autocontrol?自相关数 autocorrelation?自差接收法 autocyne reception 自搀杂 autodoping自差 autodyne 自拍接收机 autodyne receiver自动标引 autoindexing自动掩模对准器 automask aligner自动设计 automated design?自动应答装置 automatic answering device对照度与亮度自动平稳 automatic balance of contrast and brightness自动黑电平电路 automatic black level circuit自动黑电平操纵 automatic black level control自动查验 automatic check?自动色度蝶 automatic chrominancecontrol自动元件装卸装置 automatic componenthandler自动运算机 automatic computer对照度自动蝶 automatic contrast control自动操纵系统 automatic control system?自动消磁 automatic degaussing自动电话互换机 automatic exchange自动聚焦 automatic focusing自动频率操纵特性 automatic frequency control characteristic自动频率操纵 automatic frequency control?自动增益操纵 automatic gain control自偏压 automatic grid bias自动色地制 automatic hue control自动插入 automatic insertion自动布图技术 automatic layout technique 自动行同步 automatic line phasing直接远程拨号 automatic long distance service自动监视器 automatic monitor自动图象稳固操纵 automatic picture stabilization自动定线器 automatic router自动停机 automatic stop?自动副载波平稳操纵 automatic subcarrier balance control自动电报 automatic telegraphy自动电话互换局 automatic telephone exchange自动电话互换系统 automatic telephone switching system自动发射机 automatic transmitter自动党 automatic tuning自动真空淀积系统 automatic vacuum deposition system自动视频杂波限制器 automatic video noise limiter自动白电平操纵 automatic white control汽车收音机 automobile radio汽车电话 automobile telephone自对准 autoregistration辅助阳极 auxiliary anode辅助栅极 auxiliary grid辅助塞孔 auxiliary jack 辅助存储器 auxiliary memory辅助信号 auxiliary signal备份发射机 auxiliary transmitter可用功率 available power雪崩酌 avalanche action雪崩哗 avalanche breakdown雪崩哗电压 avalanche breakdown voltage雪崩二极管 avalanche diode雪崩注入多层栅金属氧化物半导体 avalanche injection stacked gate mos雪崩电离 avalanche ionization雪崩倍增 avalanche multiplication雪崩倍增系数 avalanche multiplication factor雪崩噪声 avalanche noise雪崩光电探测器 avalanche photodetector雪崩光电二极管 avalanche photodiode雪崩晶体管 avalanche transistor雪崩渡越时刻二极管 avalanche transit time diode雪崩渡越时刻二极管振荡器 avalanche transit time oscillator电子雪崩 avalanche?平均亮度 average brightness平均图象电平 average picture level求平均数 averaging?轴向电子感应加速岂荡 axial betatron oscilations轴向侵蚀不均匀性 axial etch nonuniformity轴向通量分米波超高功率四极管 axial flow resnatron轴向注入 axial injection 轴向引线成形设备 axial lead former 轴心线 axial lead?轴向稳固性 axial stability轴向鼓励激光器 axially excited laser 波导管轴 axis of a waveguide方位角精度 azimuth accuracy方位蝶 azimuth adjustment方位角驱动 azimuth drive方位角仰角指示器 azimuth elevation indicator方位角损失 azimuth loss方位角分辨率 azimuth resolution方位角;方位角 azimuth?方位角群聚 azimuthal bunchingDN A及蛋白质的测序和合成仪-- Sequencers and Synthesizers for DNA and Protein。

高考英语一轮复习 Unit 11 The Media课时练1

入舵市安恙阳光实验学校 Unit 11 The Media 课时练(一) 阅读理解提速练——练速度(限时：35分钟)Ⅰ.阅读理解A(2018·甘肃省第一次高考诊断试卷)In China, there are usually two reasons why people receive messagesfrom friends and relatives from whom they haven't heard for a while. Thefirst is about New Year greetings, which are always welcome. The secondreason is often unpleasant, however; people are increasingly contactinglonglost friends, or even casual acquaintances, and urging them to castonline votes for their children or grandchildren in competitions.The practice, which has been growing rapidly, has now reached thepoint where people are becoming tired and may even feel annoyed.The results of a recent survey conducted by the Jinhua Evening Newsin East China's Zhejiang Province show that 94 percent of 384interviewees were once asked by friends or relatives to cast votes onlinefor their children. The contests range from the “cutest baby” todancing competitions, but in many cases the people receiving the messages haven't heard from the sender for a long time and have never met the child involved.Although the competitions may appear to be harmless fun, some education professionals are concerned that they could have a negative effect on children.Tang Sulan, a member of the CPPCC's National Committee (全国政协会), proposed a ban on online competitions featuring children to prevent future psychological issues. She was also concerned that public disclosure of a child's personal information and publication of photos cause a potential risk to the child's safety.Li Hongyan, the mother of an 11yearold girl and an 18monthold boy in Beijing, said she has never urged others to vote for her children. Although on the surface the children are competing among themselves via their parents' social networks, the competitions are also about parents seeking a “sense of victory” for themselves, she said. “It feels as though parents are using their babies as tools to win glory for themselves, rather than truly respecting their kids' dignity and nature.” However, despite her dislike of the contests, she has twice voted for the babies of close friends because “it would be embarrassing to say no”．【语篇解读】本文介绍了最近社会上常见的一种现象，有些家长为了给孩子在网上拉票，可谓不择手段，甚至要求不常联系的朋友和不熟悉的朋友投票。

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2012 Loughborough Antennas & Propagation Conference 12 - 13 November 2012, Loughborough, UK Generation of radio frequency OAM radiation modes using circular time-switched and phased arrayantennasAlan Tennant Department of Electronic and Electrical Engineering University of Sheffield, Mappin Street, S1 3JDSheffield, UKa.tennant@Ben AllenCentre for Wireless Research University of Bedfordshire Park Square Luton, LU1 3JUUnited KingdomBen.Allen@Abstract— A circular array antenna is used to generate radiation modes which correspond to the modes associated with Orbital Angular Momentum (OAM) theory. Initially the circular array is used to generate OAM radiation by configuring it as a conventional phased array system with appropriate phase excitation. The array is then configured to operate as a time-switched array (TSA). The OAM modes generated by the TSA are compared to those obtained from the phased array system. Results are presented to show that the TSA radiates simultaneous multiple OAM modes at the harmonic frequencies generated by time switching the array.Keywords-Antennas; phased array; OAM; time-switched arraysI.I NTRODUCTIONIt is anticipated by leading policy makers that the world's population will reach seven billion this year and peak at nine billion by mid-century [1]. This will put pressure on communications and especially on mobile communications. We observe bandwidth demands are growing faster with the increasing popularity of multimedia services such as mobile TV and content rich internet. According to ABI research, by 2014, the global mobile data sent-and-received each month will be around 1.6EB (1.6 billion GB). The aforementioned facts will no doubt impact on the spectrum resource requirement of future wireless networks, as laid out in reference [2]. To this end a number of technologies have been developed that provide highly spectrum efficient communications, but it is inevitable that further break-through technologies are required in order to service this growing demand.Recently, Orbital Angular Momentum (OAM) has been proposed as a means of improving the spectral efficiency of radio transmissions [3]. This has been made possible by utilising properties of OAM associated with the helicoidal phase profile of an electromagnetic wave in the direction orthogonal to the propagation axis. Despite being relatively new to radio communications, OAM has its origins in optical signalling [4] and OAM behaviour has only very recently has been demonstrated by radio transmissions at much lower frequencies [3][5]. In [3] two radio signals on the same frequency are demonstrated to be separated and successfully demodulated through the use of OAM transmissions at one of the transmitters. This was achieved by synthesising a helical phase profile using a modified parabolic dish antenna, and in [5] a spiral reflector was used. Whereas in [6] and [7], a uniform circular array (UCA) with appropriate element phasing was successfully used to demonstrate properties of OAM radio transmission, where [6] demonstrates an equivalence to MIMO communications in terms of available channel capacity, and [7] demonstrates how a circular array can be configured to obtain a number of OAM modes.Phased arrays are well known to be able to electronically steer an array in a certain direction through the application of phase shifters. The phase is chosen to direct the array in a desired direction to maximise a signal or minimise interference [8]. In references [6] and [7], the antenna elements of the UCA are fed with the same input signal, but with an incremental phase delay between the elements. The delay is such that, after a full turn, the phase is changed by an integer multiple k of 2π, where k corresponds to the largest OAM number. According to [9], for an array of N antenna elements the largest OAM number, k, that can be resolved is |k|<N/2.Time Switched Arrays (TSA) provide an alternative method to achieve the functions of phased array antennas, but at much lower cost. The concept of using time as an additional parameter, or a fourth dimension, in the design and control of array antennas was first proposed in [10] and later advanced in [11]. The fundamental principle of a TSA is to periodically energize the elements of the array by switching each element on and off using high speed RF switches in such a way that the pattern radiated by the array conforms to a prescribed function. There are two basic functions that can be realized using TSA: pattern shaping and harmonic beam steering. Current work on TSA has concentrated on controlling sideband radiation [12] and on developing TSA topologies for achieving advanced signal processing functions [13]. In this contribution we return to the basic properties of TSA and show how a circular TSA can be configured to generate multiple OAM radiation modes, and compare this to a phased array similarly configured for OAM generation.II.A RRAY SYSTEMThe base of our investigations is a circular array consisting of M equally spaced, isotropic radiating elements located on a circle of radius R and centred at the origin in the x-y plane of a standard Cartesian coordinate system. The array is assumed to radiate at a fundamental sinusoidal frequency f0. The conventional way to generate OAM radiation modes from a circular array is to apply a fixed, uniform, progressive phase shift to each element of the array. So, for example, to generate the l=1 OAM mode the incremental phase shift applied to the elements is given by 2π/M, which generates a complete 2πphase change around the array. To generate higher order, integer OAM modes the incremental phase shift is given by 2πl/Μ, where l represents the order of the OAM mode. To operate the same array in time-switched mode, the topology of the array is modified so that the phase shift components in the array feed network are replaced by simple binary, SPST switches to form a TSA. The pattern radiated by the TSA is then controlled by switching, or energising the elements of the TSA for fixed periods of time according to a prescribed sequence. To configure the TSA to generate OAM modes the elements of the array are excited with unit amplitude and uniform phase at a fundamental operating frequency f0, but are energised sequentially such that each element is only switched on for a time period given by τs=T s M�, where T s is the overall sequence switching period (i.e. the time to sequentially switch all M array elements). The process of switching the array elements generates a set of radiation patterns at the fundamental frequency, f0, and at discrete sideband harmonic frequencies which are determined by the switching period Ts. Hence the array radiates at the frequencies: (f0±f s,f0±2f s, f0±3f s etc where f s=1T s�.III.NUMERICAL E XAMPLESTo illustrate and compare the OAM modes generated by conventional phase shift techniques with those produced by a TSA, we consider a specific example of a circular array which consists of 11 isotropic elements equally spaced around a circle of radius 0.95λ. The far-field radiation patterns generated by both the TSA and phased array systems are calculated and compared. All the simulated far-field patterns are presented as false-colour intensity plots representing the amplitude and phase of the radiated patterns calculated as a circular 2-D map as a function of the far-field direction cosines S x=sinθcosϕ; S y=sinθsinϕ. The plots therefore represent the far-field hemispherical radiated field distribution projected onto a 2-D surface with limits on the visible region determined by the constraint S x2+S y2≤1.Figure 1 shows the phase and amplitude patterns generated by the circular phased array and the time switched array for the l=1 OAM mode. To generate the l=1 OAM mode from the 11 element circular phased array, the elements are progressively phased with an incremental phase shift of 2pi/11. For the TSA, the l=1OAM mode is automatically generated at the first harmonic frequency (f0+f s)when the array is energised with a periodic switching sequence in which the individual element energisation time is Ts/11 – as shown in [14]. The far-field responses show that the amplitude patterns exhibit a null in the boresight direction, and that the phase pattern has an azimuthal angular variation that exhibits a with a progressive, uniform phase shift that completes 2pi radians in one geometrical rotation. The amplitude and phase responses correspond to the l=1 OAM mode and exhibit the so called twisted vortex response pattern [3].Figure 2 shows the radiation patterns generated by the two array configurations which correspond to the l=2 OAM mode. For the phased array the incremental phase shift is 4pi/11 but for the TSA, the individual element energisation time is still given by Ts/11. This is because the TSA l=2 OAM mode is automatically produced at the second harmonic frequency (f0+2f s)radiated by the array. Further analysis shows that the higher order harmonic radiation modes generated by the circular TSA directly correspond to the equivalent higher order OAM modes. The TSA also generates negative harmonic frequencies and an interesting characteristic of the negative modes is that they generate an OAM phase rotation which is in the opposite direction to those generated at the corresponding positive harmonic frequencies. As an example Figure 3 shows the radiation pattern at the fourth negative TSA harmonic frequency (f0−4f s). Here it is observed that the radiation pattern shows a three-fold or 8pi angular phase shift in one geometrical rotation which correspond to the l=-4 OAM mode.Finally, and for completeness, we consider the l=0 OAM mode. This mode is generated by the circular phased array when the incremental phase shift is zero – i.e. a uniform circular array. For the TSA, the l=0 mode is generated at the fundamental frequency (f0) of radiation and is independent of the form of the switching sequence provided that the time-averaged element amplitude weighting is uniform. Figure 4 shows the far-field amplitude and phase patterns generated by both arrays for the l=0 OAM mode.Figure 1. Far-field (Sx,Sy) amplitude (left) and phase (right) patterns generated by the circular phased array (top) and the TSA (bottom). The TSA mode is generated at the first positive harmonic frequency of radiation (f0+f s) and which correspond to the l=1 OAM mode. (Rainbow-scale patterns 0 to -40dB amplitude and 0 to 2pi phase).Figure 2. Far-field (Sx,Sy) amplitude (left) and phase (right) patterns generated by the circular phased array (top) and the TSA (bottom). The TSA mode is generated at the second positive harmonic frequency of radiation (f0+2f s) and which correspond to the l=2 OAM mode. (Rainbow-scale patterns 0 to -40dB amplitude and 0 to 2pi phase).Figure 3. Far-field (Sx,Sy) amplitude (left) and phase (right) patterns generated by the circular TSA at the fourth negative harmonic frequency of radiation (f0−4f s) and which correspond to the l=-4 OAM mode. (Rainbow-scale patterns 0 to -40dB amplitude and 0 to 2pi phase).Figure 4. Far-field (Sx,Sy) amplitude (left) and phase (right) patterns generated by the circular phased array (top) and the TSA (bottom). The TSA mode is generated at the fundamental frequency of radiation (f0) and which correspond to the l=0 OAM mode. (Rainbow-scale patterns 0 to -40dB amplitudeand 0 to 2pi phase).C ONCLUSIONSTheoretical simulations have been presented to demonstrate that a circular time-switched array can be configured to generate OAM radiation modes. The OAM modes generated by the TSA have been compared to those generated by a circular phased array of similar geometry. The phased array system must use specific, individual phase shifts to generatedifferent OAM modes. In contrast the TSA simultaneouslygenerates all OAM modes at the harmonic frequencies of the TSA switching period. The positive harmonics generated by the TSA correspond to the positive OAM modes of corresponding order and the negative harmonics of the TSA generate the corresponding negative order OAM modes.R EFERENCES[1]John Beddington, ‘Food, Energy, Water and the Climate: Aperfect Storm of Global Events?/assets/bispartners/goscience/docs/p/perfect-storm-paper.pdf[2]Ofcom, ‘Final report on Predicting Areas of SpectrumShortage’,April,2009,/binaries/research/technology-research/shortage.pdf[3]Tamburini F, Mari E, Sponselli A, Romanato F, Thidé B, Bianchini A,Romanato F, “Encoding many channels on the same frequency through radio vorticity: first experimental test”, New Journal on Physics, 14 (2012), 17pp[4]Gibson G, Courtial J, Padgett M J, Vasnetsov M, Pas’kov V, Barnett SM, Franke-Arnold S, “Free Space Information Transfer using Light Beams Carrying Orbital Momentum”, Optical Express, Vol. 12, pp5448-56, 2004[5] F Tamburini, E Mari, B Thidé, C Barbieri, F Romanato, “ExperimentalVerification of Photon Angular Momontum and Vorticity with Radio Techniques”, Applied Physics Letters, 99, 204102 (2011) [6]Edfos O, Johansson A J, “Is orbital angular momentum (OAM) basedradio communication an unexploited area?”, IEEE Trans. Antennas and Propagation, Vol. 60, No. 2, Feb 2012[7]Mohammadi S M, Daldorff L K S, Bergman E S, Karlsson R L, ThidéB, Forozesh K, Carozzi T D, Isham B, “Orbital angular momentum in radio – a system study”, IEEE Trans. Antennas and Propagation, Vol.58, No. 2, Feb 2012[8] B Allen, M Ghavami, “Adaptive Array Systems”, Wiley[9] B Thidé, H Then, J Sjőholm, K Palmer, J Bergman, T DCarozzi, Y N Istomin, N H Ibraginov, R Khamitova, “Utilisation of photon orbital angular momentum in low-frequency radio domain”, Phys. Rev. Letters, Vol. 99, No. 8, Aug 2007[10]H. E. Shanks and R. W. Bickmore, “Four-dimensional electromagneticradiators,” Canadian Journal of Physics., vol.37, pp 263-275, 1959. [11]W. H. Kummer, A. T. Villeneuve, T. S. Fong, and F. G. Terrio, “Ultra-low sidelobes from time-modulated arrays,” IEEE Transactions on Antenna and Propagation, vol. 11, pp. 633-639, Nov, 1963.[12]L. Poli, P. Rocca, L. Manica, and A. Massa, “Handling sidebandradiations in time-modulated arrays through particle swarm optimization,” IEEE Transactions on Antennas and Propagation, vol.58, no. 4, pp. 1408-1411, April 2010.[13]Y Tong and A Tennant, “A Two-Channel Time Modulated Linear ArrayWith Adaptive Beamforming”, IEEE Transactions on Antennas and Propagation, vol. 60, issue 1, pp. 141-147, Jan 2012[14]A Tennant and B Allen "Generation of multiple OAM radiation modesusing a circular time-switched array" , IETY Electronics Letters. under review, unpublished。