川大《移动通信系统》18春在线作业2
《大学英语(四)0004》18秋在线作业2
川大《大学英语(四)0004》18春在线作业21、D2、C3、C4、A5、D一、单选题共40题，80分1、Regardless of how hard she tried, Jennie couldn’t figure out what her boyfriend thought. A珍妮努力的想都想不出她的男朋友在想什么。
B珍妮想的多么努力啊，但是还是揣摩不透她的男朋友是如何想的。
C尽管珍妮很努力，但是还是不明白她的男朋友在想什么。
D不管珍妮如何努力，都揣摩不透她的男朋友是如何想的。
正确答案是：D2、— Do you prefer tea or coffee? — _______AMilk.BYes, I like tea.CCoffee, please.DNone.正确答案是：C3、When Susan and I _______ on an article for the school newspaper, we found it difficult to work together.AcompiledBgatheredCcollaboratedDjoined正确答案是：C4、There ________ a book and some magazines on the desk. AisBareChaveDhas正确答案是：A5、— Do you think I could borrow these magazines? — _______ ANo, you can’t.BYou could borrow other magazines.CThe magazines aren’t here now.DI’m sorry, but the magazines you want are out.正确答案是：D6、— Have you got a table for four, waiter? — _______ AWelcome to our restaurant.BYes, sure. This way, please.CWe have looked the seats.DHere are the menus.正确答案是：B7、It was on the beach ____Miss White found the kid lying dead. AthatBthisCitDwhich正确答案是：A8、The publisher and the author _______ made an agreement. AisBhasCareDhave正确答案是：D9、Physics _______ always my strong point.AisBareCbeingDto be10、Peter will _______ as managing director when Bill retires.Atake offBtake overCtake onDtake in正确答案是：B11、He put forward a theory, _______ of great importance to the progress of science of technology.AI think which isBwhich I think isCwhich is I thinkDI think it is正确答案是：B12、— Hi, I'm glad to see you. — _______AThank youBMe, tooCMy name is MaryDI'm glad to hear that13、—I didn't know my identity card（身份证）was needed, sir.—______AThat's sorry.BI don't believe you.CSorry, but that's no excuse.DYou can't say that.正确答案是：C14、His answer is not correct, and _______.Aneither am IBeither is mineCneither is mineDmine is neither正确答案是：C15、We consider _______ the instrument be adjusted each time it is used. Athat it necessaryBit necessary thatCnecessary thatDnecessary of it that正确答案是：B16、The shops offer almost everything _______ ranges from cheap to expensive.AthatBwhichCwhatDIt正确答案是：A17、We moved to the front row ______ we could hear and see better.Aso asBso thatCbecauseDsuch that正确答案是：B18、The young lady coming over to us _______ our English teacher; the way she walks tells us that!Amust beBcan beCwould beDcould be正确答案是：A19、Only after I had reached the supermarket _______ that I had forgotten to take my purse with me.AI had realizedBI realizedCI have realizedDdid I realize正确答案是：D20、— I think he is a good lecturer. — _______ASorry, it doesn't matter.BSo do I.CYes. It's a good idea.DI don't mind.正确答案是：B21、—Hello! Can I get a seat on the 8 pm flight to Detroit?—_______.AHello! International AirlineBYou'd better look up the schedule firstCI'm sorry, but it's completely bookedDI'm afraid you have to change正确答案是：C22、Down the entrance hall of the school walk four eighth-grade students. Each one is carrying a small basket with a single egg inside. Soon more students join them-each one of them is also carrying a basket with an egg. The eggs in a basket are part of a new school program that helps young people understand that having a baby is a great duty.At the beginning of the program, the teacher puts the students in pairs-one girl and one boy. Each pair gets an egg, which they must take care of for two weeks. For those fourteen days, the students have to take care of the eggs as though they were real babies. Students whose eggs get broken have to start the two weeks all over again with a new egg.One person in each pair must have the egg with him or her at all times-twenty-four hours a day. At no time can they let the egg be out of sight. "If a teacher catches you without your egg," said one student, "she makes you go get it. They are really strict." The teachers also make the students spend half an hour each day sitting with the egg and just watching it. That can get pretty boring. But it's also something that parents spend a lot of time doing.Children say that the program has helped them understand the duties involved inhaving a child. "It was really hard," said one student, "You had to think all the time about the egg."(5)、From the last paragraph, we can infer that ______.Aa program is the only way to educate childrenBone has to think about a program all the timeConly one child grasps the purpose of the programDthe program is of help to children's understanding of parents正确答案是：D23、Mr. Liu, _______ at university in Changchun, works at Changhou Company now. Awhose wife I metBI met whose wifeCI met his wifeDhis wife I met正确答案是：A24、— How much is this necklace? — _______AIt's very nice.BIt's a birthday present from my parents.CIt costs fifty pounds.DIt's a bargain.正确答案是：C25、— Let's go to the library this afternoon. — _______AYes, that's right.BNo. I can't.CWhat about you?DThat's a good idea.正确答案是：D26、—Didn’t they come to the party last week? —Yes. They didn’t want to come with us at first, but then we _______ persuade them.AwouldBcouldCwere able toDhad to正确答案是：C27、Peter, whom everyone suspected, _______ to be innocent.Aturned outBturned offCturned upDturned over正确答案是：A28、—Oh dear! I've just broken a window.—_______! It can't be helped.AGreatBNever mindCThat's fineDNot at all正确答案是：B29、_______ they met each other and became good friends. AIt was in the countryside whereBBeing in the countrysideCIt was in the countrysidewhenDIt was in the countryside that正确答案是：D30、—I'd like to book a room, please.—_______ASingle or double?BGood or bad?CWhich room?DWe don't have books here.正确答案是：A31、It’s already 5 o’clock. Don’t you think it’s about time _______?Awe are going homeBwe go homeCwe went homeDwe can go home正确答案是：C32、— Hello, I would like to open an account. — _______AWhich account do you want to see?BHave you make up your mind?CWhat kind of account do you have in mind?DYou’re welcome.正确答案是：C33、She knew that society would _______ her for abandoning her children. AdiscussBblameCsayDcondemn正确答案是：D34、I won’t make the _______ mistake next time.AlikeBsameCnearDsimilar正确答案是：B35、Our child's behavior is greatly influenced by the way we react to what he has done. Our reactions help to determine whether our child will repeat his behavior or whether he will do something different. This statement is a very important part of a principle of behavioral psychology.The principle states that a behavior is influenced or affected by how the environment ---- people, places and things ---- immediately responds to the behavior. Perhaps without realizing it, you have used this principle many times.On the occasion when you told your child what a good boy he was after he cleaned up his room, you used the principle. When you sent your child to his room for fighting with his brother, you used the principle. When I gave Kim a cookie after she started to cry, I used the principle. In each of these examples, a particular behavior occurred first ----cleaning up a room, fighting, and crying.In addition, there was a reaction to each behavior ---- the child was praised, sent to his room, or given a cookie. By these actions, we have influenced the previous behaviors and have helped to determine whether those behaviors will occur again in the future.(2) On what kind of principle is the lecture based?AA principle in chemistry.BA principle in behavioral psychology.CA principle in physics.DA principle in geology.正确答案是：B36、— _______ —Yes, I’ll be happy to cash it for you.ADo you need any cash?BAre you happy with the cash?CAre you happy to cash it for me?DMay I cash a traveler’s check here?正确答案是：D37、—Bring me the bill, please.— _______AYou are welcome.BPlease wait for a moment, sir.CI'll hurry up.DBe quick正确答案是：B38、We go to the cinema ______ a week.AoftenBonceCseldomDusually正确答案是：B39、If you _______ me, I shall be very grateful to you.Amust helpBwill helpCmay helpDneed help正确答案是：B40、Unemployment is not the _______— the real problem is the decline in public morality. AtroubleBmatterCissueDthing正确答案是：C二、判断题共5题，20分1、All over the world people enjoy sports. Sports help to keep people healthy, happy and help them to live longer.Sports change with the season. People play different games in winter and summer.Games and sports often grow out of people's work and everyday activities. The Arabs use horses or camels in much of their everyday life; they use them in their sports, too.Some sports are so interesting that people everywhere go in for them. Football, for example, has spread around the world. Swimming is popular in all countries near the sea or in those with many rivers.Some sports or games go back to thousands of years ago, like running or jumping. Chinese boxing, for example, has a very long history. But basketball and volleyball are rather new. Neither one is a hundred years old yet. People are inventing new sports or games all the time.People from different countries may not be able to understand each other, but aftera game they often become good friends. Sports help to train a person's character. One learns to fight hard but fight fair, to win without pride and to lose with grace.(4)、From this passage we can see that according to the author sports and games are significant to our life in many respects.A错误B正确正确答案是：B2、Albert Einstein had a great effect on science and history, greater than what only a few other men have achieved. An American university president once commented that Einstein had created a new outlook, a new view of the universe. It may be some time before the average mind understands fully the identity of time and space and so on-but even ordinary men understand now that the universe is something larger than ever thought before.By 1914 the young Einstein had gained world fame. He accepted the offer to become a professor at the Prussian Academy of Science in Berlin. He had few duties, little teaching and unlimited opportunities for study, but soon his peace and quiet were broken by the First World War.Einstein hated violence. The misery of war affected him deeply, and he sat unhappily in his office doing little. He lost interest in his research. Only when peace came in 1918 was he able to get back to work.In the years following World War I honors were increasingly heaped on him. He became the head of the Kaiser Whihem Institute of Theoretical Physics. In 1921 he won the Noble Prize, and he was honored in Germany until the rise of Nazism when he was driven from Germany because he was a Jew.(1)、The main idea of Paragraph 1 is the change in human thought produced by Einstein. A错误B正确正确答案是：B3、In 1920, barely out of his teens, Alfred Hitchcock went to work for an American film company which had opened a studio in Islington, London. His first job at the studio was writing captions （脚本）for silent movies. Within two years, he was writing scripts（剧本）and working as an assistant director.For the rest of the 1920s, Hitchcock worked on one film after another in Britain and Germany. Filming was often a rough-and-ready（匆忙做成的）affair and the assistant director was required to step in and plug gaps. A cameraman went missing, Hitchcock became a cameraman. A scene needed rewriting, Hitchcock rewrote it. Someone needed to be in charge of money when the film crew was on location, Hitchcock looked after the money.At the same time, this being the era of silent movies, Hitchcock was learning the language of cinema: telling a story－not through dialogue, but through visual images（视觉影象）. This led to his success later.When he began to direct his own films, first in Britain and later in Hollywood, he was determined to make films that held the audience's attention and kept tension（紧张感）. He succeeded. Hitchcock's ability to put you on the edge of your seat makes him one of the greatest makers of suspense（悬念）movies.(5)、He had taken up different jobs before he succeeded.A错误B正确正确答案是：B4、In 1920, barely out of his teens, Alfred Hitchcock went to work for an American film company which had opened a studio in Islington, London. His first job at the studio was writing captions （脚本）for silent movies. Within two years, he was writing scripts （剧本）and working as an assistant director.For the rest of the 1920s, Hitchcock worked on one film after another in Britain and Germany. Filming was often a rough-and-ready（匆忙做成的）affair and the assistant director was required to step in and plug gaps. A cameraman went missing, Hitchcock became a cameraman. A scene needed rewriting, Hitchcock rewrote it. Someone needed to be in charge of money when the film crew was on location, Hitchcock looked after the money.At the same time, this being the era of silent movies, Hitchcock was learning thelanguage of cinema: telling a story－not through dialogue, but through visual images（视觉影象）. This led to his success later.When he began to direct his own films, first in Britain and later in Hollywood, he was determined to make films that held the audience's attention and kept tension（紧张感）. He succeeded. Hitchcock's ability to put you on the edge of your seat makes him one of the greatest makers of suspense（悬念）movies.(3)、Telling a story through dialogue prepared Hitchcock for his success later.A错误B正确正确答案是：A5、Until 1983, Tillson Lake had been a lovely weekend and vacation place for many families. Then everything changed. During the Fourth of July weekend, residents woke up one morning to find that the lake had disappeared.Some people didn't believe what they were seeing. They looked again, but to their amazement they found they had been right the first time. The lake was simply no longer there. In its place was a big muddy hole, 30 feet deep. It was as if the lake had been a giant bathtub and someone had pulled the plug.The lake's owner, Joseph Unanue, did indeed pull the plug. That's exactly what happened. The dam that held back the water to form the lake was falling apart, sogovernment officials ordered him to repair it. They issued him a permit to lower the dam level "five feet or more."He did much more. Mr. Unanue found repairs to the dam would cost $100,000. He didn't want to spend that much, so he opened the dam and lowered the water level until the lake was completely emptied. People living above the dam ended up with no lake. People living below the dam ended up with tons of mud and lots of dead fish. Everyone involved was angry with Mr. Unanue.Area residents believed Mr. Unanue acted out of spite（恶意）. They said he wanted to get back at them because the town wouldn't let him develop an amusement park on the lakeshore. When he couldn't build his park, he just went away and took his lake with him.(2)、The lake was compared to a bathtub because it could be emptied out.A错误B正确正确答案是：B。
四川大学《移动通信系统》21秋在线作业2-00001
《移动通信系统》21秋在线作业2-00001随机多址技术包括（）。
A:ALOHA协议和时隙ALOHAB:载波侦听多址(CSMA)C:预约随机多址D:全部答案：D以下数字调制中，不能采用包络检波进行解调的是（）。
A:ASKB:OOKC:FSKD:PSK答案：D下列哪个模型不属于多径信道的冲激响应模型（）。
A:GSM标准中的多径信道模型B:COST-207模型C:IMT-2000模型D:Hata模型答案：D以下不属于移动通信的特点的是（）。
A:必须利用无线电波进行信息传输B:在复杂的干扰环境中运行的C:利用的频谱资源非常有限,移动通信业务量需求基本稳定D:网络结构多种多样，网络管理和控制必须有效答案：C移动台和基站收发信机（BTS）之间的接口是（）。
A:Abis接口B:空中接口C:A接口D:U接口答案：B下列关于7号信令说法错误的是（）。
A:7号信令主要用于交换机之间、交换机与数据库(如HLR、VLR、AUC)之间交换信息；B:7号信令系统的协议，它包括MTP、SCCP、TCAP、MAP、OMAP和ISDN-UP等部分；C:消息传递部分(MTP)提供一个面向连接的消息传输系统；D:7号信令网络是与现在PSTN平行的一个独立网络。
它由三个部分组成：信令点(SP)、信令链路和信令转移点(STP)。
答案：C下列关于调制的说法有误的是（）。
A:高的频谱利用率要求已调信号所占的带宽窄；B:高的抗干扰和抗多径性能要求在恶劣的信道环境下，经过调制解调后的输出信噪比较小或误码率较低；C:调制可分为模拟调制和数字调制；D:对数字调制而言，频谱利用率常用单位频带内能传输的比特率来表征。
答案：B基站和移动台支持的切换方式（）。
A:软切换B:CDMA到CDMA的硬切换C:CDMA到模拟系统的切换D:ABC答案：D比较GSM、D-AMPS和PDC三种蜂窝系统特征，下列错误的是（）。
A:都采用TDMA/FDMA的多址方式；B:话音编码速率GSM最高；C:GSM系统的容量最高；D:GSM的载频间隔最大。
四川大学《通信系统原理》20春在线作业1.doc
1.分组码110110与100011的码距为：A.2B.3C.4D.5【参考答案】: B2.在八进制中(M=8)，已知码元速率为1200B，则信息速率为：A.3600b/sB..400b/sC.1200b/sD.2400b/s【参考答案】: A3.量化是把时间离散、幅度连续的信号变换为：A.时间连续、幅度连续的信号B.时间离散、幅度离散的信号C.时间连续、幅度离散的信号D.时间离散、幅度连续的信号【参考答案】: B4.用同一个调制信号分别对载波进行以下四种调制，已调信号中占用频带宽度最窄的是：A.AMB.SSBC.VSBD.DSB【参考答案】: B5.数字基带信号不能通过以下哪种信道进行传输：A.卫星B.同轴电缆C.双绞线D.对称电缆【参考答案】: A6.最小码距为3的纠错码，以下描述有误的是：A.检错2位B.纠错1位C.不能同时完成检错和纠错D.检错1位同时纠错1位【参考答案】: C7.在抗加性高斯白噪声性能方面，2ASK、2FSK、2PSK从优到差的次序为：A.2FSK\2ASK\2PSKB.2ASK\2PSK\2FSKC.2ASK\2FSK\2PSKD.2PSK\2F SK\2ASK【参考答案】: D8.数字通信系统中，压缩信息数据频带的措施不包括：A.信源编码B.信道编码C.多进制调制D.码型变换【参考答案】: B9.一分组码110110，其码长和码重分别为：A.6、2B.6、3C.6、4D.4、2【参考答案】: C10.以下不属于通信系统工作方式的是：A.全双工B.移动通信C.单工D.半双工【参考答案】: B11.数字基带信号不能通过（）信道进行传输：A.对称电缆B.双绞线C.卫星D.同轴电缆【参考答案】: C12.二进制数字调制系统，当码元速率相同时，占用带宽最宽的是：A.2ASKB.2FSKC.2PSKD.2DPSK【参考答案】: B13.下列哪一项不是调制的目的：A.将基带信号变为适合于在信道中传输的信号B.提供载波分量C.便于实现频分复用D.改善系统的抗噪性能【参考答案】: B14.以下不可用于描述数字信号的是：A.便于用统一编码格式对信息进行处理与存储B.可以在编码序列中加入附加信息代码，实现控制、管理和纠错等功能C.不适用于保密通信D.可以设计不同的编码格式，表示码字的码型、波形，以提高抗干扰、抗噪声的能力【参考答案】: C15.一个简单的数字通信系统至少需要哪两种同步技术：A.载波同步、帧同步B.位同步、帧同步C.帧同步、网同步D.位同步、网同步【参考答案】: B16.以下码型中不能提取定时分量的是：A.双极性归零码B.单极性归零码C.双极性不归零码D.曼切斯特码【参考答案】: C17.某2FSK系统的码元传输速率为2MB，数字信息为”1”时的频率f1为2.048MHz，数字信息为“0”时频率f2为1.024MHz，其已调信号的第一零点带宽为：A.4.096MHzB.5.024MHzC.3.072MHzD.6.144MHz【参考答案】: B18.对于偶校验码，以下码元发生误码的是：A.110111B.100100C.111111D.101010【参考答案】: A19.当DPCM系统中量化器电平数为2时，DPCM系统变为：A.ADPCM系统B.PM系统C..NBFM系统D.DM系统【参考答案】: D20.采用相干解调方式时，相同误码率条件下，所需信噪比从高都低排列是：A.2ASK2PSK2FSKB.2ASK2FSK2PSKC.2FSK2ASK2PSKD.2PSK2FSK2ASK 【参考答案】: B21.数字通信系统常用的最佳接收准则包括A.最大输出信噪比准则B..最小均方误差准则C.最大似然接收准则 D.以上都是【参考答案】: ABCD22.下列关于白噪声的说法正确的是：A.白噪声的功率谱在全频域均匀分布B.白噪声的自相关函数是阶跃函数 C.理想白噪声并不存在 D.白噪声的时域波形是大量相互统计独立且随机发生的及窄脉冲的集合【参考答案】: ACD23.下列属于幅度调制的是：A.ASKB.AMC.PAMD.PCM【参考答案】: ABC24.常用的最佳接收机包括：A.相关接收机B.匹配滤波器C.包络检波器D.相干解调器【参考答案】: AB25.对于SSB调制技术而言，下述正确的是：A.传输带宽比AM和DSB少一半B.同等条件下比AM和DSB节省功率C.信道利用率降低一半D.在军用短波通信中应用广泛【参考答案】: ABD26.差错控制方式主要包括：A.检错重发B.前向纠错C.反馈校验D.以上都是【参考答案】: ABCD27.数字通信中，同步方式包括：A.载波同步B.位同步C.群同步D.网同步【参考答案】: ABCD28.脉冲编码调制的主要过程包括：A.采样B.量化C.去噪D.编码【参考答案】: ABD29.可以采用包络检波进行解调的是：A.ASKB.FSKC.PSKD.DPSK【参考答案】: AB30.下列属于无线信道的是：A.微波中继B.对称电缆C.卫星中继D.光纤【参考答案】: AC31.对于受到高斯白噪声干扰的连续信道，若信源的信息速率R小于或等于信道容量C，则理论上可以实现无误差传输。
川大《通信系统原理》18春在线作业2
(单选题) 1: 最小码距为3的纠错码，以下描述有误的是：A: 检错2位B: 纠错1位C: 不能同时完成检错和纠错D: 检错1位同时纠错1位正确答案:(单选题) 2: 有关奇偶监督码检错能力的描述正确的是：A: 能检测任意个误码B: .不能检测误码C: 能检测偶数个误码D: 能检测奇数个误码正确答案:(单选题) 3: 下列哪一项不是调制的目的：A: 将基带信号变为适合于在信道中传输的信号B: 提供载波分量C: 便于实现频分复用D: 改善系统的抗噪性能正确答案:(单选题) 4: 某线性分组码的许用码组的最小码距是4，若用于检错，可检出误码位数为：A: 1B: 2C: 3D: 4正确答案:(单选题) 5: 采用相干解调方式时，相同误码率条件下，所需信噪比从高都低排列是：A: 2ASK>2PSK>2FSKB: 2ASK>2FSK>2PSKC: 2FSK>2ASK>2PSKD: 2PSK>2FSK>2ASK正确答案:(单选题) 6: 下列关于HDB3码的描述不正确的是：A: 无直流分量B: 频带窄C: 方便提取同步信息D: 仅用于短距离传输正确答案:(单选题) 7: 下列哪种信号的传输带宽与AM信号传输带宽相同：A: 基带信号B: 双边带信号C: .单边带信号D: 残留边带信号正确答案:(单选题) 8: 二进制数字调制系统，当码元速率相同时，占用带宽最宽的是：A: 2ASKB: 2FSKC: 2PSKD: 2DPSK正确答案:(单选题) 9: 以下不属于调制目的的是：A: 提高信噪比B: 使信号适合信道传输特性C: 提高频带利用率正确答案:(单选题) 10: 数字基带信号不能通过（）信道进行传输：A: 对称电缆B: 双绞线C: 卫星D: 同轴电缆正确答案:(单选题) 11: 以下关于香农公式的描述，错误的是：A: 给定的信道容量C，带宽和信噪比可以相互换算B: 任何一个信道，信源信息速率R不大于信道容量C，则理论上可以进行无差错传输C: .信道容量描述了信道的最大传输能力D: 增大信道带宽可以使信道容量无限增大正确答案:(单选题) 12: 用同一个调制信号分别对载波进行以下四种调制，已调信号中占用频带宽度最窄的是：A: AMB: SSBC: VSBD: DSB正确答案:(单选题) 13: 在四进制中(M=4)，已知信息速率为2400b/s，则码元速率为：A: 2400BB: 1200BC: 4800BD: 600B正确答案:(单选题) 14: 一个简单的数字通信系统至少需要哪两种同步技术：A: 载波同步、帧同步B: 位同步、帧同步C: 帧同步、网同步D: 位同步、网同步正确答案:(单选题) 15: 对于偶校验码，以下码元发生误码的是：A: 110111B: 100100C: 111111D: 101010正确答案:(单选题) 16: 同等条件、正常工作时，模拟调制系统中抗噪声性能最好的是：A: AMB: VSBC: FMD: DSB正确答案:(单选题) 17: 下列关于卷积码与分组码的描述，不正确的是：A: 都是差错控制编码B: 都是信道编码C: 监督位与信息位之间是线性运算关系D: 监督位都只与本组信息位有关正确答案:(单选题) 18: 数字基带信号不能通过以下哪种信道进行传输：A: 卫星B: 同轴电缆D: 对称电缆正确答案:(单选题) 19: 在(7,4)线性分组码中，生成矩阵的行数为：A: 3B: 4C: 5D: .6正确答案:(单选题) 20: 以下码型中不能提取定时分量的是：A: 双极性归零码B: 单极性归零码C: 双极性不归零码D: 曼切斯特码正确答案:(多选题) 1: 关于信号接收机的门限效应，下列说法正确的是：A: 所有相干解调器都存在门限效应B: 使用包络检波器存在门限效应C: 使用包络检波器不存在门限效应D: 所有非相干解调器都有门限效应正确答案:(多选题) 2: 下列属于幅度调制的是：A: ASKB: AMC: PAMD: PCM正确答案:(多选题) 3: 数字通信系统常用的最佳接收准则包括A: 最大输出信噪比准则B: .最小均方误差准则C: 最大似然接收准则D: 以上都是正确答案:(多选题) 4: 二进制数字调制系统的三种基本方式为：A: MSKB: ASKC: FSKD: PSK正确答案:(多选题) 5: 常用的最佳接收机包括：A: 相关接收机B: 匹配滤波器C: 包络检波器D: 相干解调器正确答案:(多选题) 6: (4，1)重复码的许用码字包括：A: 1011B: 1111C: 0111D: 0000正确答案:(多选题) 7: 某纠错码的最小码距为5，则它可以：A: 检错4位C: 纠错2位同时检错1位D: 纠错1位同时检错2位正确答案:(多选题) 8: 下列属于无线信道的是：A: 微波中继B: 对称电缆C: 卫星中继D: 光纤正确答案:(多选题) 9: 通信系统的主要性能指标包括：A: 有效性B: 稳定性C: 可靠性D: 抗噪性正确答案:(多选题) 10: 数字通信中，同步方式包括：A: 载波同步B: 位同步C: 群同步D: 网同步正确答案:(判断题) 1: 双极性不归零码不包含直流分量。
川大《劳动经济学1164》18春在线作业2
------------------------------------------------------------------------------------------------------------------------------ (单选题) 1: 实际工资与物价指数（）A: 正相关B: 负相关C: 不相关D: 不确定正确答案:(单选题) 2: 引起劳动力需求量变动的根本原因是（）A: 工资率B: 生产技术C: 货币资本规模D: 企业的性质正确答案:(单选题) 3: 个人劳动力供给曲线是（）的。
A: 向前弯曲B: 向后弯曲C: 从左下向右上倾斜D: 从左上向右下倾斜正确答案:(单选题) 4: 下列选项中，属于延期支付方式的是（）A: 带薪休假B: 免费工作午餐C: 折价优惠商品D: 失业保险正确答案:(单选题) 5: 劳动力需求曲线不变，劳动力供给曲线左移，对均衡工资率和均衡就业量的影响为（）A: 减少，减少B: 减少，增加C: 增加，减少D: 增加，增加正确答案:(单选题) 6: 技术进步对（）的就业影响较大。
A: 熟练工B: 非熟练工C: 技工D: 女工正确答案:(单选题) 7: 如果两类劳动力是总替代关系，则一类劳动力的工资率上升会引起另一类劳动力（）A: 供给的增加B: 供给的下降C: 需求的增加D: 需求的下降------------------------------------------------------------------------------------------------------------------------------ 正确答案:(单选题) 8: 劳动力流动成为人力资本投资方式之一的原因在于（）A: 劳动力流动费用直接形成人力资本存量B: 劳动力流动费用直接增加人力资本存量C: 劳动力流动费用直接抵消人力资本存量D: 劳动力流动是实现人力资本价值和增值的必要条件正确答案:(单选题) 9: 在动态均衡模型中，“收敛型蛛网”形成的前提条件是（）A: 劳动力供给弹性小于劳动力需求弹性B: 劳动力供给弹性等于劳动力需求弹性C: 劳动力供给弹性大于劳动力需求弹性D: 劳动力供给弹性大于工资弹性正确答案:(单选题) 10: 一般培训的成本通常由（）来支付。
川大《通信电子技术》17春在线作业2
2017秋春川大《通信电子技术》17春在线作业2一、单选题（共16 道试题，共64 分。
）1. 题目：A. 62B. 72C. 67.7D. 77.7正确答案：2. 有一调频广播发射机的频偏△f = 75kHz ，调制信号的最高频率Fmax = 15kHz，当忽略载频幅度10% 以下的边频分量时，此调频信号的频带宽度是（）kHz。
A. 180B. 380C. 30D. 110正确答案：3. 在相同条件下，双调谐回路放大器和单调谐回路放大器相比，下列表达正确的是：A. 双调谐回路放大器的选择性比单调谐回路放大器好，通频带也较窄B. 双调谐回路放大器的选择性比单调谐回路放大器好，通频带也较宽C. 双调谐回路放大器的选择性比单调谐回路放大器差，通频带也较窄D. 双调谐回路放大器的选择性比单调谐回路放大器差，通频带也较宽正确答案：4. 题目：A. 2.5B. 4.59C. 8.59D. 1.59正确答案：5. 在变容二极管电路中，中心频率fC为5 MHz，调制信号频率为5 kHz，最大频偏为2 kHz。
通过三倍频后，调制信号频率为（）kHz。
A. 4B. 5C. 6D. 7正确答案：6. 题目：A.B.C.D.正确答案：7. 题目：A. 62B. 72C. 67D. 77正确答案：8. 某信号的中心频率为10.7MHz，信号带宽为6 MHz。
输入信号为1 mV。
若采用多级单调谐放大器放大该信号，在保证放大器的输出信号不小于0.7V 的情况下，所构成的放大器增益为（）dB。
A. 50B. 60C. 70D. 65正确答案：9. 题目：A. 0.5B. 1.5C. 2.5D. 3.5正确答案：10. 某信号的中心频率为10.7MHz，信号带宽为6 MHz。
输入信号为1 mV。
若采用多级单调谐放大器放大该信号，在保证放大器的输出信号不小于0.7V 的情况下，需要采用（）级增益为10 的单调谐放大器A. 5B. 6C. 3D. 4正确答案：11. 某接收机工作频段fS = 2 ～30 MHz，中频fI = 1.3MHz，本振fL＞fS 。
川大《计算机网络与通信》18春在线作业1
(单选题) 1: 190.233.27.13是( )IP地址。
A: A类B: B类C: C类D: D类正确答案:(单选题) 2: 使用距离矢量路由选择协议的路由器通过以下哪种方式获得最佳路径A: 通过向相邻路由器发送一次广播以询问最佳路径B: 运行最短路径优先（SPF）算法C: 将接收到的路径的度量增加1D: 测试每条路径正确答案:(单选题) 3: 下列功能中，属于表示层提供的功能是( )。
A: 拥塞控制B: 透明传输C: 死锁处理D: 文本压缩正确答案:(单选题) 4: Web上每一个页都有一个独立的地址，这些地址称作统一资源定位器，即( )。
A: URLB: WWWC: HTTPD: USL正确答案:(单选题) 5: 下面四种答案中，哪一种属于网络操作系统( )。
A: DOS操作系统B: Windows98操作系统C: WindowsNT操作系统D: 数据库操作系统正确答案:(单选题) 6: 一条线路每1/16秒采样一次，传输信号共有16种状态，则其传输速率为( )。
A: 16bpsB: 48bpsC: 64bpsD: 256bps正确答案:(单选题) 7: 接收端不但能发现差错，而且能确定差错发生的位置从而加以纠正的差错控制方法为( )。
A: 反馈重发ARQB: 前向纠错FECC: 停止等待方法D: 选择重发方法正确答案:(单选题) 8: DNS的中文含义是( )。
A: 邮件系统B: 地名系统C: 服务器系统D: 域名服务系统正确答案:(单选题) 9: 下面对计算机网络体系结构中协议所做的描述，错误的是( )。
A: 网络协议的三要素是语法、语义和同步B: 协议是控制两个对等层实体之间通信的规则的集合C: 在OSI参考模型中，要实现第N层的协议，需要使用N+1层提供的服务D: 协议规定了对等层实体之间所交换的信息的格式和含义正确答案:(单选题) 10: OSI（开放系统互联）参考模型的最低层是( )。
四川大学《通信系统原理》20春在线作业2.doc
1.最小码距为3的纠错码，以下描述有误的是：A.检错2位B.纠错1位C.不能同时完成检错和纠错D.检错1位同时纠错1位【参考答案】: C2.有关奇偶监督码检错能力的描述正确的是：A.能检测任意个误码B..不能检测误码C.能检测偶数个误码D.能检测奇数个误码【参考答案】: D3.下列哪一项不是调制的目的：A.将基带信号变为适合于在信道中传输的信号B.提供载波分量C.便于实现频分复用D.改善系统的抗噪性能【参考答案】: B4.某线性分组码的许用码组的最小码距是4，若用于检错，可检出误码位数为：A.1B.2C.3D.4【参考答案】: C5.采用相干解调方式时，相同误码率条件下，所需信噪比从高都低排列是：A.2ASK2PSK2FSKB.2ASK2FSK2PSKC.2FSK2ASK2PSKD.2PSK2FSK2ASK 【参考答案】: B6.下列关于HDB3码的描述不正确的是：A.无直流分量B.频带窄C.方便提取同步信息D.仅用于短距离传输【参考答案】: D7.下列哪种信号的传输带宽与AM信号传输带宽相同：A.基带信号B.双边带信号C..单边带信号D.残留边带信号【参考答案】: B8.二进制数字调制系统，当码元速率相同时，占用带宽最宽的是：A.2ASKB.2FSKC.2PSKD.2DPSK【参考答案】: B9.以下不属于调制目的的是：A.提高信噪比B.使信号适合信道传输特性C.提高频带利用率D.远距离传输【参考答案】: A10.数字基带信号不能通过（）信道进行传输：A.对称电缆B.双绞线C.卫星D.同轴电缆【参考答案】: C11.以下关于香农公式的描述，错误的是：A.给定的信道容量C，带宽和信噪比可以相互换算B.任何一个信道，信源信息速率R不大于信道容量C，则理论上可以进行无差错传输C..信道容量描述了信道的最大传输能力D.增大信道带宽可以使信道容量无限增大【参考答案】: D12.用同一个调制信号分别对载波进行以下四种调制，已调信号中占用频带宽度最窄的是：A.AMB.SSBC.VSBD.DSB【参考答案】: B13.在四进制中(M=4)，已知信息速率为2400b/s，则码元速率为：A.2400BB.1200BC.4800BD.600B【参考答案】: B14.一个简单的数字通信系统至少需要哪两种同步技术：A.载波同步、帧同步B.位同步、帧同步C.帧同步、网同步D.位同步、网同步【参考答案】: B15.对于偶校验码，以下码元发生误码的是：A.110111B.100100C.111111D.101010【参考答案】: A16.同等条件、正常工作时，模拟调制系统中抗噪声性能最好的是：A.AMB.VSBC.FMD.DSB【参考答案】: C17.下列关于卷积码与分组码的描述，不正确的是：A.都是差错控制编码B.都是信道编码C.监督位与信息位之间是线性运算关系D.监督位都只与本组信息位有关【参考答案】: D18.数字基带信号不能通过以下哪种信道进行传输：A.卫星B.同轴电缆C.双绞线D.对称电缆【参考答案】: A19.在(7,4)线性分组码中，生成矩阵的行数为：A.3B.4C.5D..6【参考答案】: A20.以下码型中不能提取定时分量的是：A.双极性归零码B.单极性归零码C.双极性不归零码D.曼切斯特码【参考答案】: C21.关于信号接收机的门限效应，下列说法正确的是：A.所有相干解调器都存在门限效应B.使用包络检波器存在门限效应C.使用包络检波器不存在门限效应D.所有非相干解调器都有门限效应【参考答案】: BD22.下列属于幅度调制的是：A.ASKB.AMC.PAMD.PCM【参考答案】: ABC23.数字通信系统常用的最佳接收准则包括A.最大输出信噪比准则B..最小均方误差准则C.最大似然接收准则 D.以上都是【参考答案】: ABCD24.二进制数字调制系统的三种基本方式为：A.MSKB.ASKC.FSKD.PSK【参考答案】: BCD25.常用的最佳接收机包括：A.相关接收机B.匹配滤波器C.包络检波器D.相干解调器【参考答案】: AB26.(4，1)重复码的许用码字包括：A.1011B.1111C.0111D.0000【参考答案】: BD27.某纠错码的最小码距为5，则它可以：A.检错4位B.纠错2位C.纠错2位同时检错1位D.纠错1位同时检错2位【参考答案】: ABD28.下列属于无线信道的是：A.微波中继B.对称电缆C.卫星中继D.光纤【参考答案】: AC29.通信系统的主要性能指标包括：A.有效性B.稳定性C.可靠性D.抗噪性【参考答案】: AC30.数字通信中，同步方式包括：A.载波同步B.位同步C.群同步D.网同步【参考答案】: ABCD31.双极性不归零码不包含直流分量。
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(单选题) 1: 下列关于接收信号功率中值的说法错误的是（）。
A: AB: BC: CD: D正确答案:(单选题) 2: 如图，电波传播方式沿路径①从发射天线直接到达接收天线的电波称为（），它是VHF和UHF频段的主要传播方式；沿路径②的电波经过地面反射到达接收机，称为（）；路径③的电波沿地球表面传播，称为（）。
A: 地表面波地面反射波直射波B: 直射波地面反射波地表面波C: 直射波地表面波地面反射波D: 地面反射波直射波地表面波正确答案:(单选题) 3: n=15的m序列发生器码序列周期是（）。
A: AB: BC: CD: D正确答案:(单选题) 4: 在用户的忙时话务量a确定之后，每个信道所能容纳的用户数m为（）。
A: AB: BC: CD: D正确答案:(单选题) 5: 在GSM系统中，采用（）抵抗多径效应造成的时散现象，采用（）纠随机干扰，采用（）抗突发干扰，此外，还可采用（）进一步提高系统的抗干扰性能。
A: 卷积编码、自适应均衡、交织编码、跳频技术B: 卷积编码、交织编码、跳频技术自适应均衡C: 自适应均衡、交织编码、卷积编码、跳频技术D: 自适应均衡、卷积编码、交织编码、跳频技术正确答案:(单选题) 6: 下列关于越区切换说法错误的是（）。
A: 越区(过区)切换(Handover或Handoff)是指将当前正在进行的移动台与基站之间的通信链路从当前基站转移到另一个基站的过程；B: 越区切换分为两大类：一类是硬切换，另一类是软切换。
硬切换是指在新的连接建立以前，先中断旧的连接。
而软切换是指既维持旧的连接，又同时建立新的连接，并利用新旧链路的分集合并来改善通信质量，当与新基站建立可靠连接之后再中断旧链路；C: 在移动台辅助的越区切换中，网络要求移动台测量其周围基站的信号质量并把结果报告给旧基站，网络根据测试结果决定何时进行越区切换以及切换到哪一个基站；D: PACS、IS-95和GSM系统采用了移动台辅助的越区切换。
正确答案:(单选题) 7: 以下不属于移动通信的特点的是（）。
A: 必须利用无线电波进行信息传输B: 在复杂的干扰环境中运行的C: 利用的频谱资源非常有限,移动通信业务量需求基本稳定D: 网络结构多种多样，网络管理和控制必须有效正确答案:(单选题) 8: 假定输入的信息序列为01101（0为先输入），经过（2，1）卷积编码器后的输出信息序列应为（）。
A: 001110011B: 0110101101C: 1100011100D: 0011100111正确答案:(单选题) 9: 16QAM属于的调制方式是（）。
A: 混合调制B: 幅度调制C: 频率调制D: 相位调制正确答案:(单选题) 10: 下列关于MSK和GMSK的说法错误的是（）。
A: GMSK通过引入可控的码间干扰（即部分响应波形）来达到平滑相位路径的目的，它消除了MSK相位路径在码元转换时刻的相位转折点；B: GMSK信号在码元转换时刻其信号和相位不仅是连续的而且是平滑的；C: GMSK信号在一个码元周期内的相位增量，不像MSK那样固定为+-π/2，而是随输入序列的不同而不同；D: 二比特延迟差分检测的误码性能优于二比特延迟差分检测，但比相干检测的误码性能差。
正确答案:(单选题) 11: CDMA系统中的无线信道包括（）。
①导频信道②同步信道③寻呼信道④正向业务信道⑤接入信道⑥反向业务信道A: ①②③④⑤B: ②③④⑤⑥C: ①②④⑤⑥D: ①②③④⑤⑥正确答案:(单选题) 12: 设发送数字信息为110010101100，下列波形示意图分别是（）信号。
A: 2FSK、2DPSK、2PSKB: 2PSK、2FSK、2DPSKC: 2FSK、2PSK、2DPSKD: 2 DPSK、2PSK、2 FSK正确答案:(单选题) 13: 移频键控调制(FSK)信号的带宽（）。
A: AB: BC: CD: D正确答案:(单选题) 14: 下列关于扩频通信系统说法错误的是（）。
A: 目前扩频通信系统可分为：直接序列扩频（DS）、跳频（FH）、跳时（TH）、线性调频（Chirp）以及上述几种方式组合；B: 直接序列(DS)扩频，就是直接用具有高码率的扩频码（PN）序列在发端去扩展信号的频谱。
而在接收端，用相同的扩频码序列去进行解扩，把展宽的扩频信号还原成原始的信息。
C: 直接序列扩频通信的优点：抗干扰、抗噪音、抗多径衰落、具有保密性、可多址复用和任意选址、功率谱密度低，具有隐蔽性和低的截获概率；D: 跳频不能有效地改善多径衰落和瑞利衰落。
正确答案:(单选题) 15: 对数字通信系统的主要优点可归纳为（）。
(1)频谱利用率高，有利于提高系统容量；(2)能提供多种业务服务，提高通信系统的通用性；(3)抗噪声、抗干扰和抗多径衰落的能力强；(4)能实现更有效、灵活的网络管理和控制；(5)便于实现通信的安全保密；(6)数据传输较快，主要是话音业务；（7）可降低设备成本和减小用户手机的体积和重量。
A: （1）（2）（3）（4）（5）（6）B: （1）（3）（4）（5）（6）（7）C: （1）（2）（3）（4）（5）（7）D: （2）（3）（4）（5）（6）（7）正确答案:(单选题) 16: 如图，天线的高度分别为ht和hr，两个天线顶点的连线AB与地面相切于C点。
下列说法错误的是（）。
A: AB: BC: CD: D正确答案:(单选题) 17: 随机多址技术包括（）。
A: ALOHA协议和时隙ALOHAB: 载波侦听多址(CSMA)C: 预约随机多址D: 全部正确答案:(单选题) 18: 下列说法错误的是（）。
A: GSM系统的频段分为：上行890—915MHz和下行935—960MHz；B: 系统的收发频率间隔为960-915=45MHz；C: GSM的调制方式是高斯型最小移频键控(GMSK)方式，矩形脉冲在调制器之前先通过一个高斯滤波器；D: 小区覆盖半径最大为50km，最小为500m。
正确答案:(单选题) 19: CDMA系统的有效频带宽度1.2288MHz，语音编码速率为9.6kb/s，比特能量与噪声密度比为6dB，则系统容量为（）。
A: 30B: 22C: 33D: 40正确答案:(单选题) 20: 下列关于TDMA帧的说法错误的是（）。
A: 在GSM系统中，每帧含8个时隙，时隙的宽度为0.577ms，其中包含156.25bit；B: 由若干个TDMA帧构成复帧，其结构有两种：一种是由26帧组成的复帧，另一种是由51帧组成的复帧；C: 由51个业务复帧或26个控制复帧均可组成一个超帧，超帧的周期为1326个TDMA帧，超帧长51×26×4.615×10-3≈6.12s；D: GSM的上行帧和下行帧所用帧号相同，所以没有区别。
正确答案:(单选题) 21: 下列哪个模型不属于多径信道的冲激响应模型（）。
A: GSM标准中的多径信道模型B: COST-207模型C: IMT-2000模型D: Hata模型正确答案:(单选题) 22: 对于集群移动通信系统的说法正确的是（）：①属于调度系统的专用通信网，对网中的不同用户常常赋予不同的优先等级。
②集群通信系统根据调度业务的特征，通常具有一定的限时功能，一次通话的限定时间大约为15～60s(可根据业务情况调整)。
③集群通信系统的主要服务业务是无线用户和无线用户之间的通信,在集群通信系统中也允许有一定的无线用户与有线用户之间的通话业务，但一般只允许这种话务量占总业务量的5%～10%。
④集群通信系统一般采用半双工(现在已有全双工产品)工作方式，因而，一对移动用户之间进行通信只需占用一对频道。
⑤在蜂窝通信系统中，可以采用频道再用技术来提高系统的频率利用率；而在集群系统中，主要是以改进频道共用技术来提高系统的频率利用率的。
A: ①②③④B: ①②③④⑤C: ②③④⑤D: ①②④⑤正确答案:(单选题) 23: 蜂窝式组网将一个移动通信服务区划分成许多以（）为基本几何图形的覆盖区域，称为蜂窝小区。
A: 正六边形B: 正五边形C: 正四边形D: 正八边形正确答案:(单选题) 24: 下列关于PSK说法错误的是（）。
A: PSK可采用相干解调和差分相干解调；B: FSK的性能优于PSK；C: QPSK信号是两个PSK信号之和，因而它具有和PSK相同的频谱特征和误比特率性能；D: π/4-DQPSK是改变了DPSK的最大相位跳变，从而改善了了频谱特性。
正确答案:(单选题) 25: 关于正交幅度调制QAM的说法错误的是（）。
A: 在QAM中，数据信号由相互正交的两个载波的幅度变化表示；B: QAM调制器的原理是发送数据经过串并变化被分成两路，经过高通滤波器，然后分别与一对正交调制分量相乘，求和后输出；C: 接收端完成相反过程，正交解调出两个相反码流，均衡器补偿由信道引起的失真，判决器识别复数信号并映射回原来的二进制信号；D: 模拟信号的相位调制和数字信号的PSK（相移键控）可以被认为是幅度不变、仅有相位变化的特殊的正交幅度调制。
正确答案:(单选题) 26: 比较GSM、D-AMPS和PDC三种蜂窝系统特征，下列错误的是（）。
A: 都采用TDMA/FDMA的多址方式；B: 话音编码速率GSM最高；C: GSM系统的容量最高；D: GSM的载频间隔最大。
正确答案:(单选题) 27: 瑞利衰落是由（）引起的。
A: 多径效应B: 路径损耗C: 码间干扰D: 多址干扰正确答案:(单选题) 28: 下列关于时分多址的说法错误的是（）。
A: 时分多址是指把时间分割成周期性的帧，每一帧再分割成若干个时隙(无论帧或时隙都是互不重叠的)；B: TDMA系统既可以采用频分双工(FDD)方式，也可以采用时分双工(TDD)方式；C: TDMA时隙结构的设计要考虑信息多径的影响，但不需要考虑同步；D: 在频分双工(FDD)方式中，上行链路和下行链路的帧分别在不同的频率上；在时分双工(TDD)方式中，上下行帧都在相同的频率上。
正确答案:(单选题) 29: MSK特点不包括（）。
A: 频率调制，振幅不变；B: 两个频率相互正交；C: 在每一个码元周期内，相位线性变化π：D: 码元变化时刻，相位是连续的。
正确答案:(单选题) 30: 最简单的产生高斯最小频移键控（GMSK）信号的方法是通过在FM调制器前加入（），称为预制滤波器。
A: 高斯低通滤波器B: 高斯高通滤波器C: 高斯带通滤波器D: 高斯带阻滤波器正确答案:(单选题) 31: GSM系统在通信安全方面采取了（）措施。
A: 位置登记B: 鉴权与加密C: 呼叫接续D: 以上都有正确答案:(单选题) 32: 下列哪种调制不属于模拟调制（）。