微波功率测量中的小信号检测

现代微波功率测量仪器大多采用基于微波二极管检波方式的微波功率传感器进行功率测量。二极管功率传感器具有功率测量动态范围大、灵敏度高的优点,但在进行微波小信号检测时输出电压非常小,受噪声影响大,非常难以检测。分析了微波功率传感器中影响小信号检测的噪声来源,针对这些影响小信号功率测量的噪声,从检波电路、斩波电路以及数据采集电路等方面综合进行设计,有效地提高了微波小信号的功率测量灵敏度和准确度。应用于新型微波功率测量仪器中,取得了很好的效果。     

GaAs FETs [microwave devices]

The field effect transistor (FET) at microwave frequencies using GaAs has been a cornerstone of research in solid state microwave devices for the past 30 years. It is an established item in the microwave systems of today in such applications as low noise amplifiers, mixers, oscillators, power amplifiers, switches and multipliers. Indeed, many microwave systems would not be possible at their present day performance levels if it were not for the GaAs FET     

ADF4350低相噪频率合成器在射频无线通信设备中的应用

现代射频和微波电子系统中要求频率源具有高频低相噪,且具有可靠性好、体积小、功耗低的特点。ADF4350频率合成器具有全集成、低相位噪声的优点,内置片上VCO（压控振荡器）与PLL（锁相环）,可以工作在极宽的连续频率范围内,广泛用于无线基础设备及测试设备,无线LAN,CATV和时钟发生器中。本文简要介绍了ADF4350的主要功能,详细给出了基于ADF4350用作直接变换调制器以及和ADuC812,ADSP-21xx的接口连接的设计方案。     

考虑寿命和畸变率的极低频功率放大器开关频率优化控制策略

开关功率放大器在民用和军事中都有着广泛的应用,如电动振动试验台、通信系统和声纳探测等重要领域。文中针对应用于极低频电磁波通信的开关功率放大器,提出基于改进粒子群算法的最优开关频率控制策略,通过该方法可以在满足一定输出电压畸变率的同时,降低极低频工况的功率器件热摆幅,延长开关功率放大器的寿命。首先分析开关功率放大器的热应力控制自由度。然后对影响设备寿命长短的重要因素——热摆幅和表征输出效果的指标——谐波畸变率(total harmonic distortion,THD),这2个变量的影响因素进行研究。在此基础上,综合考虑热摆幅和THD,提出基于改进型粒子群优化算法的最优开关频率控制策略。最后,通过仿真和实验对所提控制方法进行验证。     

Active integrated antennas

Even with microwave techniques, however, signal losses in materials and decreased gain and power from solid-state devices become significant obstacles to creating low-cost, high-frequency wireless systems. Perhaps the most dramatic effect occurs when a circuit component becomes a significant fraction of a wavelength. At this point it may begin to function well as an antenna. For microwave and mm-wave signals, this can occur with circuits that are only centimetres in size. With conventional circuit techniques, this radiation may cause drastic signal losses, spurious coupling between circuit elements, and radio interference with other. However, with new techniques, it is possible to create circuits that use these effects to advantage. Known as active integrated antennas, these circuits have sparked interest as possible solutions to problems in designing the next-generation wireless systems. Active integrated antennas are a combination of solid-state devices and circuits with printed antenna structures. They comprise integrated radio-system elements that are fabricated using inexpensive printed-circuit techniques     

On the responses of strip-line interconnects with discontinuities excited by external fields

An algorithm is developed to evaluate the responses of discontinuous coplanar strip-lines excited by external electromagnetic fields. The algorithm uses the cascade chain matrix method which employs the distributed circuit parameters to model the external field coupling to the line and it is applicable to most commonly encountered discontinuities in microwave integrated circuit interconnects on lossy substrates. A general CAD program is developed based on this model and it is applied to realistic coplanar strip-line interconnections with geometric and resistive discontinuities to illustrate the capabilities of the algorithm. These interconnect models are selected from a practical microwave integrated circuit design. Simplicity and fast speed of the algorithm enable computer-aided analysis of externally induced electromagnetic noise in integrated circuits to be carried out. The effects of dielectric losses in the integrated circuit substrates and the discontinuities in the conducting tracks on the wave coupling are investigated in isolation.     

Feedback Made Easy for the Undergraduate

The increased use of linear integrated circuit amplifiers, which require feedback stabilization, has resulted in increased emphasis on teaching feedback techniques to undergraduates. This paper describes the method used at the Polytechnic Institute of Brooklyn to teach juniors how to analyze and design feedback circuits. We have found that these students can, after taking the course, analyze and design complicated feedback circuits, and test feedback amplifiers to determine (and adjust) the feedback present in an amplifier. The procedure presented in this paper is different from that used by other instructors in that we teach by example. Therefore, we do not use a block diagram approach which students have difficulty in relating to real amplifiers, but instead analyze and design actual circuits. Generality is sacrificed for clarity.     

高压直流换流站中换流阀传导骚扰时域仿真分析

换流站中换流阀的周期性导通和关断过程会产生宽频量等二次系统产生传导电磁骚扰。采用基于时域宽频等值电路的仿真计算方法,对换流站稳态运行过程、传导骚扰产生和传播过程统一进行仿真分析,充分考虑工作状态、器件特性对传导骚扰特性的影响。提出了关键设备的宽频等值电路模型,用宏模型模拟骚扰源特性,所有模型均同时考虑了设备的工频和高频特性,采用与设备规范和标准试验相配合的参数提取方法,适用于系统级全波电磁分析。通过现场试验验证了该方法的正确性,并定量评估了贵广II回±500kV换流站换流回路的电磁骚扰水平。     

微小型UUV无刷直流电机驱动控制系统

无刷直流电机(BLDCM)具有高功率密度、高效节能、高可控性、低噪声等优点,尤其适用于对占用空间有着严格限制的应用场合。针对微小型无人潜航器(UUV)内部空间狭小问题,对其电力驱动系统硬件方面进行小型化设计,在满足功率要求的前提下合理运用集成功能芯片对电路功能模块所占用空间的压缩,实现系统中控制电路、驱动电路的小型化设计。经功率试验验证,在微小型UUV内部空间限制条件下,所设计的电机驱动控制系统在速度控制精度、带载驱动性能方面均满足了微小型UUV对电动力的性能需求。     

Low‐Noise Fully Differential Amplifiers Using JFET‐CMOS Integration Technology for Smart Sensors

In this paper, CMOS‐based low‐noise amplifiers with JFET‐CMOS technology for high‐resolution sensor interface circuits are presented. A differential difference amplifier (DDA) configuration is employed to realize differential signal amplification with very high input impedance, which is required for the front‐end circuit in many sensor applications. Low‐noise JFET devices are used as input pair of the input differential stages or source‐grounded output load devices, which are dominant in the total noise floor of DDA circuits. A fully differential amplifier circuit with pure CMOS DDA and three types of JFET‐CMOS DDAs were fabricated and their noise performances were compared. The results show that the total noise floor of the JFET‐CMOS amplifier was much lower compared to that of the pure CMOS configuration. The noise‐reduction effect of JFET replacement depends on the circuit configuration. The noise reduction effect by JFET device was maximum of about − 18 dB at 2.5 Hz. JFET‐CMOS technology is very effective in improving the signal‐to‐noise ratio (SNR) of a sensor interface circuit with CMOS‐based sensing systems. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Integrated MOSFET Inverter Module for Low-Power Drive System

This paper introduces a new MOSFET inverter module for driving small brushless dc motors used in fans and water-pump applications. The proposed power module integrates six MOSFETs and three dedicated gate-driving high-voltage integrated circuits (HVICs) in a transfer-molded full-pack package. It provides optimized loss and epoxy molding compound characteristics by using particularly designed MOSFET and dedicated HVIC. This paper describes the package design, the MOSFET, and the HVIC of the proposed module used in motor-drive applications, where power dissipation, electromagnetic interference, and noise immunity are primary concerns.     

Wide bandgap semiconductor transistors for microwave poweramplifiers

Explores the RF power performance of microwave amplifiers fabricated from wide bandgap semiconductor transistors and demonstrates that microwave power amplifiers fabricated from 4H-SiC and AlGaN/GaN transistors offer superior RF power performance, particularly at elevated temperatures. Theoretical models predict room temperature RF output power on the order of 4-6 W/mm and 10-12 W/mm, with power-added efficiency (PAE) approaching the ideal values for class A and B operation, available from 4H-SiC MESFETs and AlGaN/GaN HFETs, respectively. All calculations were thoroughly calibrated against dc and RF experimental data. The simulations indicate operation at elevated temperature at least up to 5000°C is possible. The RF output power capability of these devices compares very favorably with the 1 W/mm available from GaAs MESFETs. The wide bandgap semiconductor devices will find application in power amplifiers for base station transmitters for wireless telephone systems, HDTV transmitters, power modules for phased-array radars, and other applications. The devices are particularly attractive for applications that require operation at elevated temperature     

500/220 kV电磁环网开环运行分析

在电力系统中,高低压电磁环网运行的弊端很大,各电力系统已经陆续解开了220/110kV电磁环网;但近年来新的500/220kV电磁环网又在不断形成;根据影响线路传输能力的3个因素（线路导线的热稳定电流、稳定传输的有功功率、自然功率）的理论研究,以及实例分析,可得出从安全和经济两方面来看,解开500/220kV电磁环网运行将更好.     

Simulation of Single-Stage Tunable Amplifier Using Ferroelectric Materials

The non-linear electric field dependence of ferroelectric thin films can be used to design frequency and phase agile components. Tunable components have traditionally been developed using mechanically tuned resonant structures, ferrite components, or semiconductor-based voltage controlled electronics, but they are limited by their frequency performance, high cost, high losses, and integration into larger systems. In contrast, the ferroelectric-based tunable microwave component can easily be integrated into conventional microstrip circuits and attributes such as small size, light weight, and low-loss make these components attractive for broadband and multi-frequency applications, many of these components are essential elements in the design of a microwave sensor and/or circuit. It has been reported that with a thin ferroelectric film placed between the top conductor layer and the dielectric material of a microstrip structure, and the proper DC bias scheme, tunable components above the Ku band can be fabricated. Components such as phase shifters, coupled line filters, and Lange couplers have been reported in the literature using this technique. In this work, simulated results from a full wave electromagnetic simulator are obtained to show the tunability of a single stage amplifier. Input and output matching networks are simulated on a ferroelectric thin film to control the frequency response of the amplifier.     

三相不接地系统短路故障限流器的研究

介绍了一种适用于三相不接地系统的短路故障限流器。给出了其主电路拓扑结构 ,针对不接地系统可能出现的两相短路和三相短路故障 ,分析了限流电路的工作机理和控制策略 ,并用电力电子专用仿真软件 PSIM对其进行了仿真验证。理论分析和仿真结果证明 ,这种限流器具有对电力系统的正常运行无明显影响 ,在短路故障发生时无延时自动插入限流 ,断开故障电流时不会引起附加振荡和过电压 ,控制方法灵活 ,可实现无电流冲击的软自动重合闸等显著优点。     

电动汽车用驱动电机电磁噪声仿真方法研究

电动汽车的噪声、振动和声振粗糙度(NVH)与燃油车有较大的不同,尤其是电机的高频电磁噪声,很容易引起消费者的投诉。文章对电磁激励、结构的仿真及试验模态等进行了分析和研究,并在此基础上,计算了电机系统阶次的等效声功率,为纯电驱动电机的噪声分析及解决提供了指导。     

强激光脉冲电源远控装置的电磁兼容设计

为保证强电磁干扰环境下微机控制系统的正常工作,对强激光脉冲电源远方控制装置进行了电磁兼容性设计。基于PSPICE软件建立了仿真模型,从电源供电回路、控制信号输出通道、通讯网络、接地及屏蔽等方面研究了有关的电磁兼容性问题,并针对调试中的问题改进了设计。仿真和现场试验表明,该设计可以有效减少经由共阻抗耦合、供电电源耦合以及空间电磁辐射耦合途径传输的电磁干扰,远方微机控制装置工作正常。     

三类宽带高增益超声检测调理电路设计与比较

针对医用宽带超声小信号检测的不同效益需求,以分立元件、分立元件与集成运放结合、专用集成芯片3类可变增益放大电路为核心,分别给出不同类型的超声检测调理电路设计方案,并对其优缺点和适用范围进行了讨论。最后以PR5800超声收发器作为标准源,测试了基于放大器AD8334的实验电路,对脉冲超声信号进行放大和滤波,获得稳定的80 dB放大波形,并通过计算其信噪比换算了电路的输入噪声密度为0．7 nV／ Hz。所述电路能很好地达到80 dB最大增益、30 M Hz带宽＠80dB、输入噪声密度＜5 nV／ Hz的设计要求,为超声前端设计的成本、灵活度、方便性等问题提供了很好的参考。     

A High-Efficiency Audio Power Amplifier Using a Self-Oscillating Switching Regulator

A new high-efficiency audio power amplifier has been developed. This amplifier consists of a conventional power amplifier and a self-oscillating switching power supply which is arranged to vary the power supply output voltage according to the input signal voltage. The new amplifier achieves a higher efficiency than the conventional amplifier, by making the collector voltage of the emitter-follower-transistor follow the waveform of the output signal. Applying this idea to class A amplifiers, a one-third power dissipation can be achieved compared with the conventional class A amplifier. A power MOSFET is used as a switcher. The switching frequency is from 150 kHz to 300 kHz. The new amplifier shows sufficient favorable characteristics. Switching noise is suppressed to a low noise level, which has no influence on the AM tuner or other audio equipment. By stabilizing the single-ended push-pull (SEPP) output transistors, the amplifier can reproduce high quality tone. The present idea is also applicable to dass B power amplifiers and may be suitable for PA or car audio power amplifiers.     

单片机控制的SPWM三相Scott逆变器研制

由单片机产生两路固定开关角正弦调制波SPWM和余弦调制波CPWM，经各自的驱动电路和功放电路放在，然后用Scott方式连接的两个变压器转换成三相对称交流电，并在直流端实现调压，该逆变器具有结构简单，工作可靠，波形失真小的特点。