Some observations on phase noise from local oscillator
毕业设计 英文资料
Compensation of Control System1．Multiple Constrains in DesignThe performance of a feedback control system is of primary importance.We have found that a suitable control system should have some of the following properties.1)It should be stable and present acceptable response to inputcommand,i.e,the controlled variable should follow the changes in the input at a suitable speed without unduly large oscillations or overshoots.2)It should operate with as little error as possible.3)It should be able to mitigate the effect of undesirabledisturbances.A feedback control system that provided an optimum perfprmance without any necessary adjustments is rare ually it is necessary to compromise among the many conflicting and demanding specifications and to adjust the system parameters to provide a suitable and acceptable performance when it is not possible to obtain all the desired optimum specifications.The preceding chapters have showen that it is often possible to adjust the system parameters in order to provide the desired system response.When the achievement of a simple performance requirement may be met by selecting a particular value of K, the process is called gain compensation.However,we often find that it is not sufficient to adjust a system parameter and thus obtain the desired performance.Rather we are required to reconsider the structure of the system and redesign the system in order to obtain a suitable one.That is ,we must examine scheme of the system and obtain a new design that results in a suitable system.Thus the design of a control system is concerned with the arrangement of the systemstructure and the selection of suitable components and parameters.When we are not able to relax several perfprmance requirements,we must alter the system in some way.The alteration or adjustment of a control system in oreder to provider a suitable performance is called compensation.In redesigning a control system to alter the system response,an additional component or device is inserted within the structure of the feedback system to compensate for the performance deficiency.The compensating device may be electric,mechanical,hydraulic,pneumatic,or some other type of devices or networks and is often called a monly an electric network serves as a compensator in many control systems.Quite often,in practice,the best and simplest way to improve the performance of a control system is to alter,if possible,the plant itself.That is,if the system designer is able to specify and alter the design of the plant,then the performance of the system may be readily improved.For example,to improve the transient behavior of a servomechanism position controller,we often can choose a better motor for the system.Thus a control system designer should recognize that an alteration of the plant maybe result in an improved system.However,often the plant is unalterable or has been altered as much as possible and still result in unsatisfactory performance.Then the addition of compensator becomes useful for improving the performance of the system.2．Types of CompensationThe compensator is placed in a suitable location within the system,and can be done in several ways .An additional component may be interested in the forward path.This is called the cascade or serial compensation.The transfer function of the compensator is designated as Gc(s),whereas that of the original plant(or process)is denoted by Gp(s).Alternatively,the compensator may be placed in the feedbackpath .This is called the feedback compensation. A combination of these two schemes.The selection of the compensation scheme depends upon a consideration of the specifications, the power levels at various signal nodes in the system,and the compensators available for us.3.Cascade CompensationAlthough many different types of compensators can be used,the simplest among them are cascade phase-lead,phase-lag,and phase-lag-lead networks.Each of these can be realized by using an operational amplifier network.The Bode diagram is used to determine a suitable cascade compensator in preference to other frequence plots.The frequence response of the cascade compensator is added to the frequency response of the uncompensated system.It is assumed, in below discussion, that the compensator Gc(s),is used with an uncompensated system so that the overall open-loop gain can be set to satisfy the steady-state error requirement,then Gc(s) is used to adjust the system dynamics favorably without affecting the steady-stste error.For convenience,the open-loop transfer function of the uncompensated system,Gp(s)H(s),is denoted by Go(s).At first,consider a system described by the open-loop transfer functionGo(s)=k/s(0.2s+1)Suppose we wish the closed-loop system to meet the following performance requirements:a)The steady-state error for a unit ramp is to be no more than 0.00316.b)The phase margin is to be no less than 45.For the first requirement,the static velocity error constant can be cocalculated from equationεss=1/Kv=1/K≦0.00316and thus the required open-loop gain is K=Kv=3.16It may also be seen that the phase margin will be about 45.at w=5 rad/s;therefore,to meet the second requirement,the magnitude must be zero at this frequency.Obviously,it is not possible to satisfy both system performance requirements with a singular value of gain.The system needs to be modified in some way,i.e,the shape of the Bode diagram has to be altered in some way to allow it to achieve both perfprmance requirements. The system perfprmance requirements stated in the example are typical of those found in many design cases;a steady-state error determines one value of gain while a desired transient response determines anthor.Note how each requirement relates to a different region of frequency acxis in the Bode diagram.(1)The steady-state error relates to the slope and magnitude at lowfrequency.(2)The phase margin relates to the gain crossover frequency,which usuallyoccurs at higher frequency.4．Approaches to System DesignThe performance of a control system can be specified by requirement of certain maximum overshoot and setting time for a step input. Furthermore it is usually necessary to specify the maximum allowable steady-state error for several test signal inputs and disturbances .These performance specifications are related to the location of the poles and zeros of the closed-loop transfer function.Thus the location of the closed-loop poles and zeros can be specified.As we found in chapter4,the locus of the roots of the closed-loop system can be readily obtained for the variation of one system parameter.However,when the locus of roots does not result in a suitable root configuration,we must add a compensator to alter the locus of the roots as parameter is varied.Therefore we can use the root locus method and determine a suitsble compensator transfer function so that the resultant root ;ocus yields the desired closed-looproot configuration.Alternatively,the performance of a control system can be specified in terms of the relative resonant peak,resonant frequency,and bandwidth of the closed-loop frequency response,or in terms of the phase margin, gain margin and gain crossover frequency of the open-loop frequency response.We can add a suitable compensator,if necessary,in order to satisfy the system perfprmancr.The design of the compensator is developed in terms of the frequency response as portrayed on the polar plot,the Bode diagram,or the Nichols chart.Because a cascade transfer function is readily accounted for on a Bode diagram by adding the frequency response of the compensator,we usually prefer to approach the frequency response method by utilizing the Bode diagram.5．Phase-Lead Compensation1. Phase-Lead CompensationThe phase-lead compensator is a form of high-pass filter,through which the signals at high frequencies are amplified relatively than that at low frequencies.It introduces a gain at high frequencies,which in general is destabilizing.However,its positive phase angle is stablilzing .Hence,we must carefully choose two break frequencies so that the stabilizing effect of the positive phase angle is dominant.ments on the Applicability and ResultsPhase-lead compensation has some distinct advantages over other forms of compensation,wherease it may also be difficult to use .Some observations from the example just analyzed allow a few generalizations to be made regarding phase lead compensation.1)The phase-lead compensation method provides an additional phaselead to limit the system’s overshoot to a required value.2)The open-loop(and usually the closed-loop)bandwidths isincreased.This is usually beneficial since the inclusion ofhigher frequencies in the response results in a faster response.Itmay cause problem,however,if noise exists at the higherfrequencies.3)Problem may occur when the uncompensated phase plot has a steeoslope in the vicinity of φm.This occurs because,as the new gaincrossover point moves to the right ,larger and larger phase leadis required from the compensator,demanding very large value ofα.This is difficult to achieve when the compensator is realizedwith physical components.For this reason ,value of α>15 shouldbe avoided,and methods to compensate the system using othertechniques,such as phaselag,should be investigated.6．Phase-Lag Compensation1.Phase-Lag Compensation ProcessIn phase-lag compensation,the magnitude part of the uncompensated Bode diagram is attenuated in order to reduce the gain crossover frequency,thereby allowing the uncompensated phase plot to produce the necessary phase margin.The phase-lag compensator is used to provide an attenuation and therefore to lower the crossover frequency of the system.Furthermore,at lower crossover frequency,we usually find that the phase margin of the system is increased,and the specifications can be satisfied.Of cause,the influence of the phase lag caused by the compensator should be taken into ually,the lag phase is about 5~12 if the break frequency corresponding to the zero of the compensator is wz=(0.1~0.2)wc.ments on the Applicability and Results1)The phase-lag method provides the necessary damping ratio in orderto limit the overshoot to the required value.2)The compensation process is somewhat simpler than the phase-leadcompensation in that the selection of the break frequencies is not too critical.3)As can be seen from the compensated system,the phase-lag techniquereduces the open and hence the closed-loop bandwith,which results ina slower response.4)Unlike phase-lead compensation,theoretically,phase lag compensationmay change the phase margin by more than 90.7．Phase Lag-Lead CompensationIn the compensator design it is usual to assume that the two break frequencies of the lag portion are lower than the two break frequencies of the lead portion.Further features of the Bode diagram include the following.1)The magnitude at lower frequencies is 0 db while the magnitude athigher frequencies is 20lg(αβ)ually,the compensator provides attenuation only and no gain.2)The phase angle first lags and then leads ,but the high-andlow-frequency phases are both zeros.3)The maximum phase-lag and the maximum phase-lead occur between theirrespective break frequencies.The phase lag-lead compensator utilizes the best feature of the individual lag and lead portions,usually without their disadvantages.For example,the lag-lead compensation allows the introduction of phase lead to stabilize a system,while providing attenuation at higher frequencies to filter out noise.8．Feedback CompensationIn order to improve the system performances,besides the cascade compensation,the feedback compensation is often used as another scheme.By using local feedback compensation,almost same effect,as that of cascade compensation,can be obtained.Morever ,additional specific functions forimproving system perfprmance are obtained.。
需求分析英文报告
需求分析英文报告Title: Requirements Analysis ReportAbstract:This report aims to provide an in-depth analysis of the requirements for a specific project. It will outline the process of gathering requirements, analyzing their feasibility, and translating them into functional specifications. The report will also highlight the importance of requirements analysis as a crucial step in the project development cycle.1. Introduction:The introduction will provide an overview of the project, highlighting its objectives and scope. It will also explain the significance of requirements analysis in ensuring the success of the project.2. Gathering Requirements:This section will discuss the methods and techniques used to gather requirements from various stakeholders. It will include interviews, surveys, observations, and document analysis. The report will emphasize the importance of involving all relevantstakeholders to ensure a comprehensive understanding of their needs.3. Analyzing Feasibility:After gathering the requirements, the next step is to determine their feasibility. This section will discuss the criteria for evaluating the feasibility of requirements, such as technical, economic, and operational feasibility. It will also address potential challenges that may arise during this phase and propose strategies to overcome them.4. Translating Requirements into Specifications:Once the feasibility analysis is complete, the gathered requirements need to be translated into functional specifications. This section will outline the process of converting user requirements into technical specifications that can be implemented by the development team. It will emphasize the importance of clear communication and collaboration between users and developers.5. Importance of Requirements Analysis:In this section, the report will highlight the significance of requirements analysis in the project development cycle. It will discuss the risks associated with neglecting the requirements analysis phase andthe benefits of properly conducting this critical process. It will stress that requirements analysis lays the foundation for successful project delivery.6. Conclusion:The conclusion will summarize the main findings of the report and reiterate the importance of requirements analysis in project development. It will also emphasize the need for continuous refinement and updates to the requirements throughout the project lifecycle.7. Recommendations:Lastly, the report will provide some recommendations for future projects, based on the lessons learned from this requirements analysis process. These recommendations will focus on improving the efficiency and effectiveness of gathering and analyzing requirements.Overall, this report will serve as a comprehensive guide for understanding and executing requirements analysis for any project. It provides a systematic approach for gathering, analyzing, and translating requirements into functional specifications. By following the recommendations outlined in this report, project teams can ensure a successfuloutcome by meeting the needs and expectations of all stakeholders.。
数学专业英语 第六讲 论文写作 常见错误分析
不要过于烦琐.
• 不要用On the Study of ... 或On the Existence of... 之类作为 标题.
• 标题通常是一个名词性短语, 不是一个完整的句子,
• 无需主、谓、宾齐全, 其中的动词一般以分词或动名词的 形式出现, 有时冠词可以省略. • 偶尔有以疑问句为标题的论文, 但不应以陈述句为标题. • 为方便二次检索, 标题尽量避免使用复杂的数学式子.
• [2] name(s) of author(s), title of the book (in italics),
publishinghouse, city of publication, year of publication.
16
Mathematical English
• [3] name(s) of author(s), title of the paper, in: title of the book (in italics), publishing house, city of publication, year of publication, numbers of the first and last pages of the paper.
improvements for you.
9
Mathematical English
数学论文对英语的要求其实并不高. 而且我们有功能强大的 LATEX(WinEdt) 编辑软件, 可以轻而易举地编排出有复
杂公式、美观漂亮的版面.
但是, 有些作者在论文写作中存在不少问题.
下面从论文的各个组成部分对一些常见的错误进行分析并举
发表论文的目的, 一是公开自己的成果并得到学术界的承认, 二是为了同行之间的交流.
燃气专业外语翻译
1.1工程热力学基础Thermodynamics is a science in which the storage, transformation, and transfer of energy are studied. Energy is stored as internal energy (associated with temperature), kinetic energy (due to motion), potential energy (due to elevation) and chemical energy (due to chemical composition); it is transformed from one of these forms to another; and it is transferred across a boundary as either heat or work.热力学是一门研究能量储存、转换及传递的科学。
能量以内能（与温度有关）、动能（由物体运动引起）、势能（由高度引起）和化学能（与化学组成相关）的形式储存。
不同形式的能量可以相互转化，而且能量在边界上可以以热和功的形式进行传递。
In thermodynamics, we will derive equations that relate the transformations and transfers of energy to properties such as temperature, pressure, and density. Substances and their properties, thus, become very important in thermodynamics. Many of our equations will be based on experimental observations that have been organized into mathematical statements or laws; the first and second laws of thermodynamics are the most widely used.在热力学中，我们将推导有关能量转化和传递与物性参数，如温度、压强及密度等关系间的方程。
完整的设计流程
完整的设计流程Design process is a critical part of creating a successful product. 设计流程是创建成功产品的重要组成部分。
It involves a series of steps and considerations, from understanding user needs to finalizing the details of the product. 这涉及一系列步骤和考虑，从理解用户需求到最终确定产品的细节。
The process is not only about creating something that looks good, but also about ensuring that it meets the needs of the users and can be produced efficiently. 这个过程不仅仅是关于创造出好看的东西，而且也关于确保它满足用户的需求，并且可以高效生产。
Different designers may have different approaches and methods to the design process, but there are some common stages that are generally followed. 不同的设计师可能有不同的设计流程方法，但通常会遵循一些共同的阶段。
Let's take a closer look at the complete design process and the various stages involved. 让我们更仔细地看看完整的设计流程以及涉及的各个阶段。
The first stage in the design process is usually the research and analysis phase. 设计流程中的第一个阶段通常是研究和分析阶段。
测试报告英文
测试报告英文(Test Report English)IntroductionTesting is an essential part of the software development process. It helps ensure that the software meets the required quality standards and performs as expected. In this test report, I will present the findings, observations, and recommendations from the testing phase of a software application.1. ObjectiveThe objective of the testing phase was to evaluate the functionality, performance, and usability of the software application. The testing was conducted to identify any defects or issues that may have been overlooked during the development process.2. Test EnvironmentThe testing was performed on a variety of platforms and environments to ensure compatibility and assess the software's performance under different conditions. The test environment included Windows 10, macOS Mojave, and Android 9.0. Various browsers,including Chrome, Firefox, and Safari, were used for compatibility testing.3. Testing MethodologyThe testing followed a structured approach, including both functional and non-functional testing. The functional testing focused on verifying whether the software application meets the specified requirements. It involved test scenarios, test cases, and test data designed to cover different aspects of the software's functionality.Non-functional testing included performance testing, which assessed the software's response time under varying loads, and usability testing, which evaluated the user-friendliness of the application.4. Test ResultsDuring the testing phase, several defects and issues were identified. These are categorized as follows:4.1 Functional Issues- The login page displayed an error when incorrect credentials were entered.- The search functionality did not return accurate results in certain cases.- The file upload feature failed to handle large-sized files.4.2 Performance Issues- The software application experienced significant delays when processing a large number of data entries.- The website response time was longer when accessed from Internet Explorer compared to other browsers.4.3 Usability Issues- The navigation menu was not intuitive, making it difficult for users to find desired features.- The font size and color combinations used in the UI impacted readability, especially for visually impaired users.5. RecommendationsBased on the test results, the following recommendations are made to improve the software application:5.1 Functional Recommendations- The login page should display clear error messages when incorrect credentials are entered.- The search functionality needs to be refined to ensure accurate and relevant results.- The file upload feature should be optimized to handle large files more efficiently.5.2 Performance Recommendations- The software should be optimized to handle a larger volume of data entries without experiencing significant delays.- Enhancements should be made to improve the website's performance on Internet Explorer.5.3 Usability Recommendations- The navigation menu should be redesigned to improve user-friendliness and ease of use.- The UI should be enhanced to ensure better readability for visually impaired users by adjusting font sizes and color combinations.ConclusionThe testing phase of the software application identified several functional, performance, and usability issues. The recommendations provided aim to address these issues and improve the overall quality of the software application. Implementing these recommendations will enhance the user experience, ensure better performance, and minimize the occurrence of defects. It is crucial for the development team to review and address the issues highlighted in this test report promptly. By doing so, the software application can be refined and meet the desired quality standards.。
Modern Application of mooc课后章节答案期末考试题库2023年
Modern Application of Optoelectronic Technology_南京邮电大学中国大学mooc课后章节答案期末考试题库2023年1.Reconstructive spectrometer is based on compressive sensing theory.参考答案:正确2.Photoconductive detector gain depends on the difference of electron andhole drift speed参考答案:正确3.As tandem structure can increase solar cell efficiency, so we can add as manycells as possible to increase the overall absorption and energy conversionefficiency.参考答案:错误4.The solar cell performance can be degraded by参考答案:Series resistance_Defects in semiconductors_Shunt resistance5.The optical transition in silicon devices is usually indirect参考答案:正确6.Write the bandgap (300k) of silicon _______ eV.参考答案:1.117.The commercial solar cell panels are still dominated by silicon photovoltaics.参考答案:正确D means __________________________参考答案:charge coupled device9._____________________are the study and application of _________________ devices andsystems that source, detect and control ______________.参考答案:Optoelectronics, electronic, photon##%_YZPRLFH_%##Optoelectronics, electronic, light10.Which of the following factors affect the LED output spectrum？参考答案:Operation temperature_Semiconductor bandgap_Dopingconcentration_Applied voltage/current11.Conventional spectrometers used in laboratories are参考答案:Based on dispersive optics_High resolution12.Some typical research results show that graphene hybrid photodetectors can参考答案:Cover a wide detection bandwidth from UV to MIR._Have highresponsivity_Use both planar and vertical heterostructures._Have high detectivity13.The equation to express photoelastic effect is【图片】, which means therefractive index changes with strain参考答案:正确14.What are the four typical layers of optical fibers?____________,___________,____________,_____________.参考答案:core, cladding, protective polymeric coating, buffer tube15.Second harmonic generation happens when an intense light beam offrequency ω passing through an appropriate crystal (e.g., quartz) generates a light beam of half the frequency, 1/2ω参考答案:错误16.The two regimes in acousto-optic modulators are Raman-Nath regimeand___________参考答案:Bragg regime17.Optically anisotropic crystals are called __________ because an incident lightbeam may be doubly refracted. There is also a special direction in abirefringent crystal, called the optic axis.参考答案:birefringent18._____________ is the rotation of the plane of polarization by a substance参考答案:optical activity19.What efficiency is typical of a commercial PERC solar panel?参考答案:20%20.The advantages of perovskite materials include参考答案:High quantum yields_Low-cost_High quantum yields21.Typical optoelectronic process includes参考答案:Light transmission_Light modulation_Light detection_Light generation22.The two operation principles of photonic crystal fibers are ___________________and _____________________.参考答案:total internal reflection, photonic bandgap23.The propagation modes in waveguide can be classified in terms of____________________(TE) mode and ____________________(TM) mode?参考答案:transverse electric field, transverse magnetic field24.Kerr effect can be used to induce birefringence参考答案:正确25.The lattice constant of AlGaAs alloy follows nonlinear mixing rule参考答案:错误26.Which of the following is not a challenge for 2D semiconductor technology?参考答案:Materials choice27.In the space charge region, a high doping concentration results a shortdepletion width参考答案:正确28.CMOS means __________________________参考答案:complementary metal oxide semiconductor29.Photodetectors convert ___________________ to an electrical signal such asa____________________.参考答案:light, voltage or current##%_YZPRLFH_%##photon, voltage or current。
Effect of Alkali-NaOH Solution on the Nature of Sy
J. Chem. Chem. Eng. 5 (2011) 246-249Effect of Alkali-NaOH Solution on the Nature of Synthesized Zeolite from 2:1 Tunisian Clays: XRD and MAS-NMR InvestigationMahdi Meftah1, Walid Oueslati1, 2 and Abdesslem Ben Haj Amara11. Laboratoire de Physique des Matériaux Lamellaires et Nanomatériaux Hybrides, UR05/13-01 (PMLNMH) Faculté des Sciences de Bizerte, 7021 Zarzouna, Tunisia2. Faculté des Sciences de Gafsa, Département de Physique, Campus Universiatire Sidi Ahmed Zarrouk, 2112 Gafsa, Tunisia Received: October 12, 2010 / Accepted: November 17, 2010 / Published: March 30, 2011.Abstract: This work focuses the effect of alkali-NaOH solution on the nature of synthesized zeolite from 2:1 Tunisian clays. This study was achieved using correlation between results obtained from X-ray diffraction (XRD) and MAS-NMR analysis. Preliminary treatment was adopted to prepare the starting sample that is placed in contact with NaOH solution at variable concentration. A specific hydrothermal reactor, allowing the control of pH > 9, temperature and a continuous stirring of the sample in the NaOH solution, was used to achieve these syntheses. The obtained results showed that, for concentration value ≈1N, the final complex presented characteristic XRD and MAS-NMR line of zeolite P. For 3N solution concentration we obtained zeolite HS. All synthesize process are controlled by XRD and MAS-NMR investigation.Key words: Alkali-NaOH solution, hydrothermal reactor, zeolite P, HS.1. IntroductionZeolites are crystalline aluminosilicates with a 3-dimensional and open anion framework consisting of oxygen-sharing TO4 tetrahedral, where T is Si or Al. Their framework contains interconnected voids which can be occupied with adsorbed molecules or cations. The general empirical formula is M x/n Al x Si(2-x)O4·mH2O where n is the valence of the exchangeable cation M, m water content and 0 ≤ x ≤ 1. The flexibility of the zeolite Si-O-Si bond explains the fact that more than 200 structures have been determined. The synthesized process of zeolite from natural clay minerals (i.e. 1:1 and 2:1 clay) was studied by several authors [1, 2]. In 1948, the first confirmation of zeolite synthesis had been traced by Barrer who reported the synthesis of the modernite [3].Corresponding author:Mahdi Meftah, Ph.D., research fields: materiel sciences, zeolite synthesize, spectroscopic methods, condensed matter. E-mail:********************.At the same time Milton and Back succeeded in synthesizing other zeolite, using lower temperature (≈100 ℃) and higher alkalinity [4]. Later, great successful progress is recorded by discovering one of the most commercially zeolite type Linde A (LTA) [5]. After that, the applied zeolite field was integrated in all industry aspect with the use of zeolite A: (1) to substitute the phosphate in detergent. Later zeolite P and X, AX (80% A, 20% X) were also introduced into the marked for detergent [6, 7], (2) in catalysis, ion exchange, molecular sieves, photochemistry and solar energy conversion [8]. In other way, zeolite type HS was synthesized using well and poorly ordered kaolinites and metakaolinites [9]. Indeed, the experimental protocol adopted on zeolite synthesis process does not be considered like novelty but some experimental parameters as the starting material, the particle size and the preparation mode influence the resulting material andcrystallisation rate. The main objective of this workAll Rights Reserved.Effect of Alkali-NaOH Solution on the Nature of Synthesized Zeolite from 2:1 Tunisian Clays: XRD andMAS-NMR Investigation247consists of characterizing zeolite synthesis process from 2:1 Tunisian clay and demonstrating the effect of alkali-NaOH concentration on the final obtained product.2. Materials and Methods2.1 Starting MaterialsThe starting materials are originated from the region Bir El Hfay (southern Tunisia). It is an irregular interstratified illite-smectite. The < 2 µm fraction was prepared according to the classic protocol of extraction which was developed by Tessier et al. [10]. The obtained structural formula per half unit cell is: (Si 4.00)(Al 1.10, Fe 0.50, Mg 0.40)O10(OH)2(M+ 0.4) with M+ is a monovalent cation. Preliminary treatment consisted of preparing an amorphous phase by heating the host mineral. This process is assured by heating ~50 g of solid at T > 800 ℃ [11].2.2 Experimental ProtocolA total of 100 mL of a given NaOH solution was heated to 100 ℃ in 250 mL reactor provided with a refrigerant system. A total of 10 g of clay was introduced. Reaction was maintained with magnetic stirring for periods of time ranging from 2 to 24 h. The final mixture was centrifuged to 10,000 rpm. The solid phase was washed several times with distilled water until pH 9.5-10, dialyzed with distilled water and dried at 80 ℃.2.3 Characterizing Method2.3.1 XRD AnalysisPowder X-ray diffraction patterns were obtained by a BRUKER D8 Advance diffractometer using Cu-Kαradiation and the 2θ range between 5-50° and operating at 40 KV and 30 mA. The determination of the lattice parameters from the XRD patterns requires identification of the peak positions, which can normally be achieved using a peak-search process, provided that all systematic errors have been eliminated by careful measurements of the zero-point detector position. The pattern indexing was performed using the indexing software TOPAS.2.3.2 MAS-NMR AnalysisThe Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectra were recorded on a BRUKER-300 MHz Ulrashield spectrometer. Experiments were performed using a 7.1 T magnetic field intensity corresponding to resonance frequencies 78.22 MHz and 59.62 MHz respectively for the core 27Al and 29Si. Impulse period has been optimized for each signal and does not exceed some μs. The numberof accumulation is higher than 500 in the case of the core 29Si (4.6% of abundance) and about 200 for the core 27Al (100% of abundance) for the two cores (27Al and 29Si).3. Results and Discussion3.1 XRD InvestigationWe reported in Fig. 1 that the XRD spectra of the solids obtained after reaction of clay with 1N NaOH solutions during different periods of time (i.e. 2 h, 4 h and 24 h). We noted that little change is observed for reaction times (Fig. 1) of 2 and 4 h. After 24 h, new peaks appeared, the most intense ones were situated at 12.44, 17.67, 21.62, 27.97 and 33.30° 2θ (Cu-Kα). They correspond to the P-zeolite as it was described by Ref. [2]. After a reaction time of 24 h the diffraction peaks of clay became very weak.Fig. 1 Experimental XRD patterns of heated illite-smectite and 1N NaOH treated at T = 100 ℃ during (a) 2 h; (b) 4 h; (c) 24 h, phases of zeolite P.All Rights Reserved.Effect of Alkali-NaOH Solution on the Nature of Synthesized Zeolite from 2:1 Tunisian Clays: XRD andMAS-NMR Investigation248When 3N NaOH solutions were used, changesappeared after a reaction time of 4 hours (Fig. 2). A newphase appeared having the following XRD peaks, 14,24.3, 27.99, 33.28 and 34.65° 2θ (Cu-Kα), according toRefs. [12, 13], this corresponds to the HS zeolite. Fromthe comparison of the patterns reported in Fig. 2, wenoted that after 24 h of reaction, it is clear that the peaksintensity related to the HS phase increase. This is in linewith the increasing amount of the zeolite phase.3.2 MAS-NMR AnalysisAccording to the NMR study of zeolite [14], the 29Sisignal of the sample obtained from treated startingmateriel with 1N NaOH solution. Fig. 3a presents achemical shifts observed at 79.82, 86.52, 91.36, and102.97 ppm with a low intensity corresponding tozeolite P. After 24 h of alkaline treatment, the 27AlMAS-RMN spectrum in Fig. 3b shows a line ofresonance at 58.21 ppm which can be attributed totetrahedral aluminium.The 29Si MAS-NMR and 27Al MAS-NMR spectra ofHS zeolite obtained by 3N NaOH solution treatmentare reported respectively in Figs. 4a and 4b. After 24 htreatment, we obtained five lines of chemical shiftlocated at -107.35, -106.92, -97.28, -91.87, -87.25 ppmfor 29Si and -58.32 ppm for 27Al. These shifts arerelated to zeolite HS [14, 15].Fig. 2 Experimental XRD patterns of heated illite-smectite and 1.5N NaOH treated at T = 100 ℃ during (a) 2 h; (b) 4 h;(c) 24 h, phases of zeolite HS. Fig. 3 (a) 29Si MAS-NMR spectrum of zeolite P obtained from heated illite-smectites. (b) 27Al MAS-NMR spectrum of zeolite P obtained from heated illite-smectites.These results demonstrate that the concentration of alkaline NaOH solution affect the final product nature (i.e synthesized zeolite). Indeed, zeolite can be synthesized using respectively low and high concentration value of NaOH solution.The characteristics and structural parameters for all synthesized phases are summarised in Table 1.4. ConclusionsIn this work we demonstrate that zeolite P is the main crystalline products obtained when heated interstratified illite-smectite is used as a starting materials with a low value of NaOH concentration.(a)(b)All Rights Reserved.Effect of Alkali-NaOH Solution on the Nature of Synthesized Zeolite from 2:1 Tunisian Clays: XRD andMAS-NMR Investigation249Fig. 4 (a) 29Si MAS-NMR spectrum of zeolite HS obtainedfrom heated illite-smectites. (b) 27Al MAS-NMR spectrumof zeolite HS obtained from heated illite-smectites.Table 1 Characteristics and structural parameters for allsynthesized phases.Sample heated illite-smectite T > 800 ℃NaOH solution 1.5N 3NTemp (℃) 100 100Time reaction (h) 24 24XRD analysis zeolite P zeolite HSComposition of material Na6(H2O)12[Si10Al6O32]Na6(H2O)8|[Si6Al6O24]Cell parameters a = b = c = 10.043 Åα = β = γ = 90°a =b =c = 8.848 Åα = β = γ = 90°NMR spectroscopy Si/Al ratio ≈1= 1Whereas zeolite HS is obtained by increasing the amount of NaOH solution.AcknowledgmentsThe manuscript was much improved by the constructive reviews of two anonymous reviewers. The editorial assistance of the editorial staff of the Journal of Chemistry and Chemical Engineering is acknowledged.References[1]M. Murat, A. Amokrane, J.P. Bastide, L. Montanaro,Synthesis of zeolites from thermally activated kaolinite,Some observations on nucleation and growth, Clay Miner.27 (1992) 119-130.[2] D.W. Breck, Zeolite Molecular Sieves: Structure,Chemistry and Uses, Wiley, New York, 1974.[3]R.M. Barrer, Syntheses and reactions of mordenite, J.Chem. Soc. 23(1948) 2158- 2163.[4]R.M. Milton, U.S. Patent 2 882 244, 1959.[5] A. Carlos, R. Ríos, D.W. Craig, M.C. Oscar, Synthesis ofzeolite LTA from thermally treated kaolinite, Rev. Fac. Ing.Univ. Antioquia 53 (2010) 30-41.[6]R.C. Adams, L. Xu, K. Moller, T. Bein, W.N. Delgass,Zeolite encapsulated vanadium oxo species for the catalyticreduction of NO by NH3, Catalysis and Photocatalysis onMetal Oxides 33 (1-3) (1997) 263-278.[7]H.G. Hautal, Laundry, Detergent Zeolites in anEcobalance Spotligt-Sepawa, Tagung Bad Diirkheim, 1996.[8] A. Corma, C. Corell, J. Perez-Pariente, Synthesis andcharacterization of the MCM-22 zeolite, Zeolites 15 (1995)2-8.[9] D.S. Coombs, T. Whetten, Geological society of americacomposition of 4-analcime from sedimentary and burialmetamorphic rocks, GSA Bulletin 78 (2) (1967) 269-282.[10]H.B. Rhaim, D. Tessier, A.B.H. Amara, Mineralogy of the< 2 µm fraction of three mixed-layer clays from southernand central Tunisia, Clay Mineral 35 (2) (2000) 375-381.[11]M. Meftah, W. Oueslati, A.B.H. Amara, Synthesis processof zeolite P using a poorly crystallized kaolinite, PhysicsProcedia (2009) 1081-1086.[12]R.M. Barrer, E.A.D. White, The hydrothermal chemistryof silicates, part I: Synthesis lithium aluminosilicates, J.Chem. Soc. (1951) 1267.[13]I. Hassan, H.D. Grundy, The crystal structures ofsodalite-group minerals, Acta Cryst. B 40 (1984) 6-13. [14] A. Madani, A. Aznar, J. Sanz, J.M. Serratosa, 29Si and27Al NMR study of zeolite formation from alkali-leachedkaolinites: Influence of thermal preactivation, J. Phys.Chem. 94 (1990) 760-765.[15]N. Benharrats, M. Belbachir, A.P. Legrand, J.B.D’Espinose de la Caillerie, 29Si and 27Al MAS NMR studyof the zeolitization of kaolin by alkali leaching, ClayMiner. 38 (2003) 49-61.(a)(b) All Rights Reserved.。
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What are the effects?
The main effect in the real world comes from reciprocal mixing where that LO phase noise mixes with RF signals outside the IF passband to make noise at the signal frequency. The stronger the phase noise, the more numerous the unwanted signals, and the stronger the unwanted signals, the stronger this effect.
PLL
HP8640B Sirenza VCO 11901198 Zcom VCO 1360-1380 N5AC IC-211 -150 -130 -110 -90 -80 -70 -60 -50 -40
Crystal Free running
Noise dBc/Hz for 10 KHz offset at 1 to 1.2 GHz
Crystal Free running
Noise dBc/Hz for 10 KHz offset at 47 GHz
What are the effects?
LO phase noise can increase the receiver noise floor by mixing in RF noise using the entire LO noise spectrum and RF spectrum. Consider that for each if bandwidth of LO noise at some offset, there is RF noise to be mixed to the IF frequency. While many talk about this, none show numbers and the rough numbers I calculate show its not a problem unless the phase noise is obnoxiously strong and the system noise temperature is extremely low.
1 dB NF
-80
-70
-60
-50
-40
-30
Phase Noise - dBc/Hz
Questபைடு நூலகம்ons?
What to do?
What to do?
1. Consider not using the N5AC synthesizer as a LO, its noisy for signal populated environments. It makes receivers more sensitive to reciprocal mixing and it makes transmitters broad. Use crystals instead.
Some observations on phase noise from local oscillator strings.
By KØCQ Dr. Gerald N. Johnson, retired P.E.
Some oscillator phase noise levels
KD6OZH crystal Herley synthesizer RFMD RF2051 Modco VCO 1125-1275
What to do?
4. Consider a different PLL package. RFMD claims -140 dBc/Hz phase noise from their free running VCO at 500 MHz at 1 MHz offset. Its a lot worse at 10 Khz, even with a wide control loop its only 100 dBc/Hz at 500 MHz.
What to do?
3. Use a better VCO. On-chip VCOs historically have been poor, often cross coupled RC free running flipflops accompanied by much digital noise and with a wide tuning range making the tuning sensitivity a MHz per 10 millivolts. That sensitivity demands the tuning line noise be nanovolts and that level of quiet is not possible in a chip. Thermal noise is more than that.
Reciprocal Mixing
Signal strength to raise the receiver noise floor 3 dB in 2 KHz IF bandwidth..
Phase noise Dynamic Range
140 120
Signal strengh
100
- dB
80 60 40 20 0 -150 -140 -130 -120 -110 -100 -90
Say what?
What was the real offset for that RFMD chip? -140 dBc/Hz is good for a crystal oscillator. Really superb for a free running oscillator!
From the RFMD 2501 data sheet.
At 10 to 12 GHz
KD6OZH crystal Herley synthesizer RFMD RF2051 Modco VCO 1125-1275
PLL
HP8640B Sirenza VCO 11901198 Zcom VCO 1360-1380 N5AC IC-211 -150 -130 -110 -90 -80 -70 -60 -50 -40
What to Do?
7. Be certain that the noise from the oscillator voltage regulator isn't modulating the oscillator at any frequency. The common 78L family isn't perfectly quiet. F9HX uses one as a noise source to modulate clean oscillators to demonstrate the effects of phase noise. Lots of wide band filter capacitors seem most appropriate. A BIG tantalum and some monolithic types should do. But watch out for piezoelectric dielectrics.
That's not so great. And it took a wide control loop bandwidth to achieve -90 dBc/Hz at 1 GHz.
Revised oscillator phase noise levels
KD6OZH crystal Herley synthesizer RFMD RF2051 Modco VCO 1125-1275
What to do?
5. Use a much wider control loop bandwidth. This does limit the step size because in traditional PLL the phase detector reference frequency needs to be significantly higher than the loop bandwidth.
What to do?
3. (cont) Consider VCOs by Modco or Serenza, with narrow band tuning they claim phase noise levels 25 dB better than the N5AC result. These choices do have very narrow tuning ranges so different transverters may need different VCOs, which shifts concerns back to the custom crystal problem and that custom crystal may be cheaper than the custom low noise VCO.
And at MUD 2004, KK7B reminded us that our transverters may supply all the spurs we need to have such reciprocal mixing, especially in the IF radio.
16
15
What are the effects?
You say your rover hill top is quiet? Are you sure? What about all those part 15 noises on 902, 2.4 and 5.6 Ghz? What about those WiFi servers using those bands partly for users and partly for point to point links?