Surge and Noise Generation in a Forward DC-to-DC Converter

Switching surge and noise voltages are analyzed under the common-mode condition in a forward dc-to-dc converter. The analysis is performed by partitioning the switching time into several states and introducing the high-frequency equivalent circuits. The equivalent circuits include not only inductive and capacitive parameters, but also the parameters related to the switching speed of the transistor and the recovery characteristics of the diode. As a result, the effects of these various parameters on the surge and noise generation are made clear quantitatively.     

基于电流驱动模式的PCB共模干扰预测分析

共模辐射干扰普遍存在于电子产品中，是造成电子产品工作失灵和辐射发射测试超标的主要原因。通过高斯定理和安培环路定理求解麦克斯韦方程组，得到PCB地平面电感的数学表达式。通过对共模辐射的模式化分析，得到电流驱动模式共模辐射的数学表达式。用近似计算简化数学推导过程得到的表达式相对简单。本结果适用于小型EMC仿真软件，也可用于计算PCB地平面电感和共模辐射的电磁兼容专家系统。     

Carrier-Tracking Loop Performance for Quaternary and Binary PSK Signals

By expressing the open-loop response voltage as a Fourier series in terms of the phase-tracking error and then utilizing a very useful mean-value expression, we assess the performance of loops suited to recovering the carrier of four-phase (quaternary) and two-phase (binary) phase-shift-keyed (QPSK and BPSK) signals. At high signal to noise ratios (SNRs) they perform comparably, but at low SNRs the former's performance deteriorates much more rapidly. The loop's ability to maintain the carrier frequency despite the noise accompanying the PSK signal is measured by the mean and the variance of the oscillator's control voltage. In particular, Spilker's loop for QPSK and the Costas loop for BPSK signals are discussed.     

基于混合控制集预测控制的永磁同步电机电流脉动抑制方法

模型预测控制(MPC)技术近年来在高动态性能电机驱动系统中应用广泛。为了克服传统MPC技术中有限控制集(FCS)造成的稳态电流脉动问题,提出了一种基于混合控制集(MCS)预测控制的永磁同步电机(PMSM)电流脉动抑制方法。分析建立PMSM预测控制系统离散数学模型,并分析电压矢量精度与电流脉动之间的关联性；在此基础上,MCSMPC将电压源型逆变器有限的有效电压矢量数,扩展为多个以占空比形式存在的虚拟电压矢量,并基于上述虚拟电压矢量完成MPC优化问题在线求解；此外,考虑到MCSMPC系统的参数敏感性问题,对MCSMPC系统反馈噪声问题进行分析讨论。最后,搭建双15 kW PMSM对拖样机测试平台进行试验分析,分析内容包括MCS方法动态跟踪特性、电流脉动稳态效果。试验结果表明所提出的MCSMPC方法在保留了传统预测控制技术高动态响应的基础上,可有效降低PMSM稳态电流脉动幅度和运行噪声。     

供电系统的干扰模式及抑制措施

供电系统的电磁干扰主要由发电机噪声、整流谐波、开关频率和它的谐波,以及在开关转换中高速电流和电压的瞬变所引起,这些干扰可通过传导和辐射的方式直接影响交流电网和用电设备。所以,本文所要讨论的主要问题就是电磁干扰的解决方法。     

Implementation of nondeterministic pulsewidth modulation forinverter drives

A single-phase power factor preregulator to improve the power quality in the input side of an ac/dc/ac converter and a random pulsewidth modulation (PWM) to reduce the emitted noise energy and the mechanical vibration for an induction motor drive is proposed. The hysteresis current control (HCC) technique for a voltage source switching mode rectifier (SMR) is adopted. A control scheme is presented such that the line current is driven to follow the reference current which is derived from the dc bus voltage regulator and the output power estimator. A random pulse position technique for a three-phase voltage source inverter system to reduce the noise energy and resonant vibration from ac machine drive is described. By randomly varying the instantaneous pulse position in each switching frequency, the frequency distribution of harmonics is spread in a wide frequency range which results in reduction of torque pulsations in the ac motor drive systems. To investigate the proposed control scheme, experimental tests based on a laboratory prototype were implemented to show the nearly unity power factor at the SMR and reduce the noise energy concentrated at the specific tones     

Noise factor of receiving system with arbitrary antenna impedancemismatch

The system operating noise factor of a receiving system is modeled for arbitrary impedance mismatch of the antenna to the transmission line feeding the receiver. The effect of this mismatch on the noise factors of the transmission line and the receiver is considered. The stochastic nature of the external noise factor is considered. The amount of mismatch that can be tolerated before the internal system noise factor exceeds the external noise factor is determined. Numerical results are presented for a VHF-FM radio receiving system with an electrically short monopole antenna. It is noted that a large impedance mismatch at the antenna-transmission-line interface of a radio receiving system can cause a significant increase in the system internal noise factor (more than a 50-dB increase for a voltage reflection coefficient of 0.999)     

一种基于电力线载波通信远程数据采集系统的设计

电力线网络覆盖范围广,用来传输数据可以节省投资。电力线上的噪声干扰和电力负载的动态变化影响了信号的可靠传输。KQ-100E采用数字信号处理技术,可以降低噪声干扰和信号衰减带来的不利影响。介绍了一种利用KQ-100E实现电力线载波通信的应用实例。实验证明,该模块在低压电力线上的通信是可靠的。     

Analysis of a PWM-resonant converter

When a parallel resonant tank is excited by a bipolar current pulse train a sinusoidal voltage develops across the tank whose amplitude depends on the duty cycle of the pulse train. An isolated secondary can be derived by applying the tank voltage to an isolation transformer whose magnetizing inductance acts as the resonant inductor of the tank circuit. A dc output voltage is obtained after rectification and filtering of the sinusoidal secondary voltage and regulation is achieved by controlling the duty cycle of the pulse train. The sinusoidal nature of the voltage across the isolation transformer alleviates some of the noise problem associated with parasitic capacitances of an isolation transformer when operated with square voltage waveform. In this work the dc and small-signal analysis of the converter is given and an equivalent small-signal circuit model is derived. Experimental results which confirm the validity of the model are presented.     

A Technique for Improving the Clutter Performance of Coherent Pulse Train Signals

The clutter performance of a radar using coherent pulse train signls depends upon the phase and amplitude weighting used on transmit and receive. This paper describes an iterative technique to determine better weightings. Each iteration improves the signal-to-interference ratio, where the interference is the sum of the mean square noise voltage and the mean square clutter voltage at the time of peak signal. Two examples are presented to illustrate the method and to demonstrate that in many cases the procedure will yield weightings that may be used in a system where the transmitter permits no amplitude weighting.     

High power factor AC/DC/AC converter with random PWM

A three-phase AC/DC/AC converter is presented with a power factor preregulator to improve the power quality in the input side and a pseudorandom noise generator to reduce the emitted acoustic noise and the mechanical vibration for an induction motor drive. The space vector modulation with hysteresis current control for a voltage source rectifier is adopted to simplify the hardware circuit. A control scheme is presented to drive the supply current following the reference current. The amplitude of reference current for the pulsewidth modulation (PWM) rectifier is derived from the DC bus voltage regulator and the estimated output power. Random switching frequency technique for a three-phase PWM inverter system to reduce the annoying tonal noise and resonant vibration from an induction motor is described. By randomly varying the instantaneous PWM switching frequency from one cycle to the next, the frequency distribution of harmonics is spread in a wide frequency range. The major advantage for using such a strategy is the nonrepetitive output spectral characteristic that results in reduction of torque pulsations in motor drive systems. The nearly unity power factor at the three-phase rectifier and the absence of acoustic noise concentrated at the specific tones which is usually present with conventional sinusoidal modulation are verified by the experimental tests     

Some Matched Filter Configurations for Infrared Systems

An analysis of the output of three alternative matched filter configurations in an infrared scanning system model is presented. The sensor is corrupted by thermal noise, generation-recombination noise, photon noise, and modulation noise, the latter providing an extreme discoloration in the signal passband. Expressions for the signal voltage density spectrum, signal pulse shape, noise power spectrum, and average noise power at the matched filter output are derived where the integral evaluations attendant to these derivations do not appear elsewhere in the literature. The paper also provides graphical displays of the signal-to-noise power ratio at the filter output versus various system parameters, noise power spectrum out of the matched filter versus ?, and the signal pulse shape out of the filter versus time. Also included are discussions of practically realizable approximations to the matched filters and curve fitting techniques for the signal pulse shape function.     

高超声速电离绕流中电子密度的静电探针测量方法研究

高焓激波风洞是开展高超声速电离绕流研究的重要地面模拟设备。在中科院力学所JF-10高焓风洞上通过新的破膜技术获得了稳定运行的试验状态,利用施加高频扫描电压的静电探针来探索模型边界层内的电子密度测量方法研究。为解决高频扫描时线路由于RC特性所带来的噪音干扰问题,针对测试环境发展了新的探针电路。结果表明：新型探针电路大大降低了线路干扰噪音,能够有效测量模型边界层内的电子密度分布规律。     

Planck-LFI 44 GHz back end module

This work describes the principle of operation, assembly and performance of one branch of the 44 GHz back end module (BEM) for the Planck low frequency instrument (LFI). This subsystem constitutes a fully representative branch of the qualification-model version (QM). It includes waveguide to microstrip transition, GaAs pseudomorphic high electron mobility transistor (PHEMT) low noise amplifiers (LNA), bandpass filter, square-law detector and dc amplifier. The fundamentals of the design of the RF part are described and all of the components have been tested individually before integration. Using single tone and wideband noise stimuli, the output voltage has been measured for several input powers, in order to obtain the sensitivity factor of the complete BEM. The effective bandwidth and the equivalent noise temperature have been calculated from the measurements, taking into account the frequency dependence on the noise source and the BEM. Finally, the low frequency output power spectrum has been obtained and a maximum 1/f knee frequency around 200 Hz has been measured with a 3 dB output signal video bandwidth above 50 KHz.     

基于算法级联的飞机座舱语音增强系统

通过对飞机座舱环境下语音信号特征的分析,提出了一种根据噪声分类逐类进行语音增强,然后依一定次序级联各类算法的语音增强方法,并讨论了级联次序对增强效果的影响。在分别实现脉冲噪声、周期噪声和宽带噪声消除算法的基础上,依据此方法开发了基于MATLAB计算环境的交互式语音增强系统,并利用该平台进行多种算法的级联实验,取得了良好的语音增强效果。     

Low-voltage CMOS Folded-cascode Mixer

The folded-cascode structure is used to realize the low-voltage low-power consumption mixer, whose performance parameters have big influence on the navigation radio receiver's performance. Adopting the folded-cascode structure, the folded-cascode mixer (FCM) has a lower power supply voltage of 1.2 V and realizes the design trade-offs among the high transconductance, high linearity and low noise. The difficulties of realizing the trade-offs between the linearity and noise performance, the linearity and conversion gain, the conversion gain and noise performance are reduced. Fabricated in an radio frequency (RF) 0.18 μm CMOS process, the FCM has an active area of about 200 μm ×150 μm and consumes approximate 3.9 mW. The test results show that the FCM features a conversion gain (Gc) of some 14.5 dB, an input 1 dB compression point (Pin-1dB) of almost -13 dBm and a dual sideband (DSB) noise figure of around 12 dB. The FCM can be applied to the navigation radio receivers and electronic systems for aviation and aerospace or other related fields.     

主要参数对面齿轮传动噪声辐射的影响分析

为研究面齿轮传动力学特性及噪声辐射,通过建立面齿轮传动的弯扭耦合动力学模型,在分析轴承支承处动载荷的基础上,结合有限元法和边界元法,形成了面齿轮传动的噪声辐射计算流程.此外,利用该计算流程,开展了算例分析,讨论了单一几何参数和工况对面齿轮传动噪声辐射的影响规律.仿真结果表明:模数和传动比对改善面齿轮传动噪声辐射有益,压力角对其噪声辐射影响不明显.研究结果为低噪声面齿轮传动的设计奠定了必要的理论基础.      

Variance Analysis of the Angle Output Voltage for an Amplitude Monopulse Receiver

The amplitude-comparison monopulse receiver utilizes two overlapping antenna patterns to determine the angle of arrival of an incoming RF signal for use in a direction-finding application. The thermal noise introduced by the receiver distorts the signal, causing an error in determining the exact angle of arrival of the signal. The analysis derives an expression for the deviation of the angle output voltage, or the angular error, due to receiver noise as a function of 1) the angle of arrival and 2) the signal-to-noise ratios of the two channels of the receiver. A receiver using a square-law detector and one using a linear detector are analyzed.     

Absolute Radiometer for the Flow Field of a Hypervelocity Projectile

As part of a hypervelocity instrumentation development program, it was desirable to include a radiometer system for measuring absolute radiation from projectile flow fields. A system employing a photomultiplier tube was designed, and laboratory and range experiments were conducted to investigate its performance characteristics. The laboratory experiments show that the linearity, saturation, and noise characteristics are suitable for this measurement; the system bandwidth is adequate to allow low frequency calibrations to be applied to high frequency measurements; and a derived expression for radiometer sensitivity variation as a function of photomultiplier supply voltage is reasonably correct. The results of the range experiments imply that the system response is sufficient to reproduce accurately input pulses as narrow as one microsecond and that a particular analytical technique for calculating the form of the radiative input to the radiometer from the projectile stagnation region is valid. Principles involved in the design of photomultiplier radiometer circuits of this type are discussed in detail.     

Effect of Electrical Generator Parameters on Transient Suppressors

In vehicular and aircraft generating systems, the voltage transient suppressor requirements for protection of utilization loads are generally based on measured values of valtage transients and the generating system impedance. This paper presents an approximate method for determining the suppressor requirements that disregards the generating system impedance. When a voltage surge due to removal of load is suppressed, the greater portion of the removed load current is transferred to the shunt-type suppressor. The influence of generating system voltage regulator design on severity of voltage transients is discussed.