集中式MIMO雷达多模式一体化波形设计

集中式多输入多输出（multiple input multiple output, MIMO）雷达系统基于波形分集优势，可灵活改变发射方向图形状和指向方向空间合成信号的特性，从而实现多种雷达工作模式。提出了一种集中式MIMO雷达多模式一体化波形设计方法，采用方向图模板拟合、模糊函数模板拟合以及通信波形拟合的方式优化不同方向上的合成信号，使其具有不同特性，从而在单脉冲时间内实现搜索、跟踪和通信功能。采用最大块增量优化算法对构造的恒模四次多项式优化模型求解。实验结果表明，该方法可以得到具有低旁瓣模糊函数的搜索与跟踪波形，并且满足通信需求。     

编码跳频信号的低截获性能分析

结合截获接收技术的发展,在低截获概率的基础上阐述了低利用概率的新概念,并定义了雷达信号截获利用因子.分析了目前截获接收机最为常用的解线性调频和循环谱分析2种截获处理方法,在此基础上,通过仿真对比了编码跳频信号以及其他4种低截获雷达信号的截获处理增益和截获利用因子.仿真结果表明,编码跳频信号由于其大的时带积和波形的随机性,对于解线调与循环谱两种截获处理方法,都具有良好的抗截获性能.     

中功率二极管激光器脉冲驱动源研制

介绍了激光二极管脉冲驱动源的控制技术。采用单片机与可编程逻辑器件实现电流脉冲宽度脉冲频率的调节;通过误差反馈和驱动电压叠加实现脉冲恒流控制。运用两点校正法分段拟合MOSFET门极驱动电压与LD电流对应关系曲线,单片机依据曲线修正驱动电压值,对温度引起的LD电流变化进行补偿。实验结果表明采用此方式获得的电流脉冲波形优于采用PID控制方法的实验波形。该方法具有温度补偿功能,在温度变化时输出电流稳定。     

超混沌调相信号抗干扰技术研究

该文根据超混沌映射初值敏感性、内随机性和高维超混沌等特点,提出了一种新的脉内混沌调相-脉间随机编码的SAR信号。文中详细比较了4种超混沌映射调相信号的特点,并在此基础上选择了超混沌Logistic映射调相信号作为SAR发射信号,仿真实验表明,这种信号的确具有高保密性和较强的抗干扰性能。     

基于状态方程法的不同ESD电路对比分析

针对IEC 61000-4-2中规定的典型静电放电(electrostatic discharge, ESD)电流波形存在拟合多样性且不易通过具体电路实现这一问题, 采用求解电路状态方程组的方法对四种ESD模拟器电路进行了计算.得到了四种指数形式的ESD电流解析表达式, 绘制了相应的电流曲线, 分别讨论了四种ESD模拟器电路产生的ESD电流波形解析式的连续性和可导性, 并对不同电路产生的ESD电流波形与IEC 61000-4-2标准规定电流波形之间的差异进行了对比分析.结果表明不同ESD电路产生的电流波形的四个主要指标符合IEC 61000-4-2标准规定, 但由于电路的拓扑结构和元件参数不同, 求得的电流波形解析式的连续性和可导性存在差异, 因此在选择ESD模型时, 应根据实际的人体参数和放电枪参数确定合适的电路结构.该计算方法适用于求解集总参数电路, 为ESD电磁脉冲辐射场仿真计算提供了新的电流解析式.     

采用真有效值测量方式的AC／DC钳形表

AC／DC钳形表3288-20采用真有效值测量方式（TrueRMS）来对应测量失真波形，就算在电源环境恶劣的情况下电气信号产生畸变也能正确测量电流，可以用于变频器的点检、维护等。3288-20还具有最大能测到1000A大电流（AC／DC）的特点，适用于无停电电源装置（UPS）备用的电池组和电动车用电机的点检与维护。     

数字瞬时测频——波形拟合法测频

在本节中,我们将给出一种叫做波形拟合法的测频算法。所谓波形拟合法就是用一个理想的正余弦函数去近似给定的信号波形,我们努力的方向是使拟合尽可能地逼近信号,这时理想函数的频率将可以最接近地表示信号的频率。我们很清楚,一个单频信号具有三个参数,那就是它的频率、初始相     

一种基于中频采样的多模雷达波形产生器的设计

提出了一种基于中频采样的数字化波形产生方法及其硬件实现方案，对其中的一些关键问题进行了定量分析。在此基础上完成了一套数字波形产生器，可产生30余种带宽为3MHz或10MHz的多种工作模式的线性调频、非线性调频信号。测试结果表明，其谐波与杂散均优于-60dB，完全达到工程应用的要求。     

载波编码多载波相位编码雷达信号 抗间歇采样干扰研究

根据间歇采样转发干扰时域不连续采样特点,本文创造性地提出了一种具有抗间歇采样转发干扰特性的基于载波编码（CC）和多载波相位编码（MCPC）雷达信号,即CC-MCPC信号。与目前常用的滤波器设计抗干扰方法不同,CC-MCPC信号是从波形设计的角度出发,采用具有良好伪随机性的混沌序列对时域中的每个符号进行编码,频域中采用巴克码对每个子载波进行编码。载波编码增加了雷达波形脉冲的伪随机性,降低了雷达回波与间歇采样干扰的相关性,从而有效地抑制了假目标的干扰。CC-MCPC与常用滤波器设计方法互不冲突,可叠加使用。本文设计了两个仿真实验,验证了CC-MCPC的有效性和可行性。实验结果表明,在文中所述的典型参数下,CC-MCPC信号与传统的MCPC信号和LFM信号相比,CC-MCPC信号经脉冲压缩后的SJR改善因子优化了1-1.5dB。      

一种高精度的电流采样跟踪电路的设计

本文设计了一种用于DC/DC开关电源转换器的新型电流采样电路,提出了一种利用采样电阻实现跟踪采样信号的新型电流采样电路,并给出了详细的计算公式和仿真波形,通过实践证明此电路采样电流精度更高,跟踪电路滞后更小。     

A method for spark rejection in ultraviolet flame detectors

A novel method is presented to render ultraviolet (UV) flame detectors insensitive to ignition spark radiation. The method involves isolating the signal due to the sparks from the UV sensor output and subtracting a DC signal proportional to it from the output of the flame detector sensor system. A practical demonstration of the method is given using a commercially available UV flame detector with the addition of an analog circuit to perform the necessary signal processing. A selectivity improvement to spark radiation of greater than 130 has been obtained. The method is robust in that it is independent of the distance between the light source and the flame detector and has been designed to work with different spark generators found on the market. The analog circuit is simple, requiring few components, thus ensuring rugged, fail-safe operation and low cost     

Engine performance evaluation using a combustion probe signal analyzer

A two-channel combustion probe signal analyzer to detect variations in the combustion quality in spark ignition engines was built and its performance investigated. The combustion probe signal was obtained by applying a small positive bias to the center electrode of the spark plug of interest. This was accomplished by the insertion of an adaptor between the distributor cap and the spark plug wire. Use of the adapter showed no apparent effect on engine operating characteristics. Experiments investigating the correlation between several engine operating parameters and the combustion quality parameters "impaired combustion" and "slow combustion" were carried out. The parameters varied were A/F (air to fuel ratio), spark advance, engine speed, nonenriched cold start, and NOxand hydrocarbon concentrations in the exhaust. Dynamometer mounted 400 CID production engine was used. Good agreement was found to exist between the variation in the combustion probe signal analyzer's counts and progressively induced impairments of the combustion process.     

Time-resolved resistance during spark gap breakdown

The breakdown voltage and the time derivative of the current through a spark gap terminating a transmission line were measured as a function of 4 gas species, 3 gap pressures, and 2 gap spacings. From these measurements, the time-varying channel resistance, the power, and the energy dissipated in the discharge can be determined for the first 1500 ps of breakdown. Data were obtained with a 74-cm-long transmission line, open at the charging end, and terminated by a spark gap at the other end. The line was pulse charged with a 2-µs rise time pulse having a maximum voltage of 3 kV. The breakdown voltage was determined by monitoring the charge voltage waveform while adi/dtprobe close to the spark gap provided a sampling oscilloscope with the other desired signal. The latter waveform was then digitized and the data were reconstructed using Fourier techniques on a computer to account for the frequency response of the required signal delay line.     

Monitoring the combustion quality in internal combustion engines using the spark plug as a plasma probe

A method of monitoring the quality of combustion in spark ignition gasoline engines using the spark plug's center electrode as a plasma probe is presented. Due to the ionized species remaining in the burned gases after combustion, a current is induced in a network attached to the spark plug's center electrode. The time dependence of this induced current is shown to correlate with the presence or absence and the time of occurance of the pressure component due to combustion in pressure transducer signals recorded simultaneously. Based on these correlations, three types of burns could be recognized from plasma probe signals: good burns, slow burns, and misfires. The specific correlation between the absence of a pressure component due to combustion and a corresponding absence of a plasma probe signal was used to form the basis for the operation of a one-channel engine misfire monitoring circuit.     

Position determination of an acoustic burst along a Sagnac interferometer

We report on a method to measure the longitudinal position of an acoustic burst, or spark, using an all-fiber Sagnac interferometer (SI). A focused pulsed /spl sim/10 ns laser is used to ionize air creating the spark. This ionization point is situated near a coil of test fiber connected to the SI but acoustically separated from the bulk of the SI. A fast Fourier transform (FFT) performed on the temporal signal of the SI shows a series of s from which the position of the acoustic signal is determined. Over an SI length of /spl sim/35 km, longitudinal positions are determined to within tens of meters, corresponding to a best run percent uncertainty of 0.07%.     

Transmission properties of spark preionization radiation inrare-gas halide laser gas mixes

A charge collection apparatus was used to measure photocharge yields and transmission properties of light emitted from a spark preionizer discharge through various rare-gas halide laser gas mixes as well as through their component gas mixes. The data indicates that for HCl partial pressure (p) and photon path length (d) pd products ⩾100 Torr-cm, a narrow transmission window (114-124 nm) for preionization of XeCl and KrCl lasers occurs. In contrast, fluorine based rare-gas halide laser gas mixes were largely transparent over a critical 100-150 nm spectral window responsible for preionization. The role of gaseous impurities, two photon ionization processes, the photoelectric effect, passivation and air contamination on the photocharge signal and light transmission are described     

Methods for engine supervision and control based on cylinderpressure information

The increasing demands for low emissions and low fuel consumption in modern combustion engines require improved methods for online diagnosis and best possible control of the combustion process. It is demonstrated that the cylinder pressure signal can successfully be used for this task. After introduction of some theoretical background, several application examples are presented: an online supervision of fuel injection, some results on feedforward emission control, and a concept for feedback control of spark timing. Experimental results obtained from stock car diesel and spark ignition engines are included to support the automation concepts     

Relationship Between Spark Plugs and Engine-Radiated Electromagnetic Interference

The ignition system of any spark-ignited internal combustion engine-powered device is well recognized as a major source of radiated electromagnetic interference (EMI). Spark plus designs can be selected to aid in reducing ignition-related EMI. The effects of various spark plug designs such as resistor spark plugs, inductor spark plugs, and shielded spark plugs upon both EMI and ignition system performance are presented. In addition to studying the effect of spark plug design, the use of the SAE standard (J551b) and other EMI measurement techniques to determine effect of spark plug suppression designs are discussed. Generally, the addition of a resistor to the spark plug provides the most effective spark plug suppression. However, other designs may be effective as an addition to the resistor or as a substitute where resistors cannot be practically used.     

A direction-finding technique for wide-band impulsive noise source

A direction-finding technique for wide-band impulsive electromagnetic interference is presented. An experimental investigation was performed using a spark generator as the impulsive noise source. The signals were captured using a two-antenna array directly sampled at 1 Gs/s. A digital signal processing based correlation technique allowed assessment of the time delay between the antennas. The results in a nonideal radio propagation environment show the bearing can be estimated to an accuracy of 20     

Laser radiation scattering by the optical breakdown plasma

The spatial distribution measurements of laser radiation, scattered in the laser spark, were accomplished for various laser radiation wavelengths (1060, 530, 353, and 265 nm) and various pressures of the gas (air at 10-760 mm Hg). The interference structure of the laser light scattering cone behind the laser spark was observed for the first time. It is proposed to consider the observed structure as a result of interference of the laser radiation, scattered by two or more self-focusing centers in laser spark air plasma. The experimental dependence of the maximal angle of the light scattering on the gas pressure and on the laser radiation wavelength was obtained