CFAR integration processors in randomly arriving impulseinterference

Time diversity transmission is often used to circumvent the high probability of a deep fade on a single transmission which may result in loss of the signal. One way to combat deep fades is to postdetection integrate the received observations from each range resolution cell. The false alarm rate of the postdetection integrator (PI) is extremely sensitive to randomly arriving impulse interference. Such interfering pulses may be unintentionally generated by nearby radars or intentionally generated by pulse jammers seeking to destroy the visibility of the radar. The binary integrator (PI) which uses an M-out-of-L decision rule is insensitive to at most M-1 interfering pulses. We consider the adaptive implementation of the PI and BI detectors for constant false alarm rate (CFAR) operation. We show that the CFAR BI detector when the “AND” (L-out-of-L) decision rule is used exhibits more robust false alarm control properties in the presence of impulse interference at the expense of severe detection loss when no interference is present. The CFAR adaptive PI (API) detector is proposed to alleviate this problem. The CFAR API detector implements an adaptive censoring algorithm which determines and censors with high probability the interference samples thereby achieving robust false alarm control in the presence of interference and optimum detection performance in the absence of interference     

A Postdetection Method of Measuring Predetection RF Signal-to-Noise Ratio

A method of determining the predetection signal-to-noise power ratio in a radio receiving system by measurement of average postdetection signal-plus-noise and noise-only voltages (dc output of the detector) is described. The principle has actually been known for many years, but does not seem to be well known or widely used, possibly because of some associated computational difficulties. Some digital computer tabulated results are presented which remove these difficulties, and measurement techniques are discussed. The calculation of expected signal-to-noise ratio for radio and radar systems is briefly reviewed.     

Discriminator Detection of Wide-Band PCM/FM

The performance of discriminator detection of wide-band PCM/FM is investigated. Formulas are derived that allow one to predict system performance with the effects of both predetection and postdetection filtering accounted for. In particular, for a postdetection equivalent noise bandwidthbit time product b0T=2, it is shown that best results are obtained with a modulation index ?=0.6. Furthermore, it is shown that performance to within 1.5 dB of theoretical can be obtained.     

Cascaded detector for multiple high-PRF pulse Doppler radars

A postdetection design methodology for a multiple high-pulse-repetition frequency (PRF) pulse Doppler radar has been developed. The postdetection processor consists of an M out of N detector where range and target ambiguities are resolved, followed by a square-law detector which enhances the minimum signal-to-noise (S/N) power-ratio per pulse burst performance. For given probabilities of false alarm and detection, formulas are derived from which the three thresholds associated with the cascaded detector can be found. Fundamental tradeoffs between the minimum S/N required, number of ghosts, and the number of operations (NOPs) that the cascaded detector must perform are identified. It is shown that the NOPs and the number of ghosts increase and the minimum S/N required decreases as the binary M out of N detector passes more detections to the square-law detector     

Optimal and Suboptimal Perfomance of a PCM/FM Communication System

Theoretical results are presented on probability of error in the detection of binary FM signals for various frequency deviations with fixed bit rate, restricted predetection filter bandwidth, ideal limiterdiscriminator reception, and integrate-and-dump postdetection filter decision. The results show that suboptimal system performance can be achieved by choosing the largest possible value of deviation index which lies approximately at 0.7 + 2n, where n = 0, 1,...,k. k is determined by the reconstructability of signal after the bandpass filter.     

Convergence properties of Gram-Schmidt and SMI adaptive algorithms.II

For pt.I see ibid., vol.26, no.1, p.44-56, Jan. 1990. Theorems and relationships associated with the convergence rate of the Gram-Schmidt (GS) and sampled matrix inversion (SMI) algorithms are presented. Two forms of the GS canceler are discussed: concurrent block processing and sliding window processing. It is shown (as has been stated by other researchers) that the concurrent block processed GS canceler converges rapidly to its optimal signal-to-noise ratio. However, it is also shown that the result is deceptive in that the output residue samples may be highly correlated, which would significantly degrade postdetection processing. It is demonstrated that a specific form of a sliding window GS canceler has the same convergence properties as the concurrent block processed GS canceler     

Simple Expressions for Determining Radar Detection Thresholds

The threshold value required to obtain a specified false-alarm probability, when postdetection integration follows a square-law or an envelope detector, is frequently needed in theoretical and practical studies of radar signal processor performance. The determination of such threshold values requires a substantial numerical computational effort. In this correspondence, simple expressions are presented with which these thresholds can be determined with excellent accuracy using only a scientific calculator.     

Performance Evaluation of Postdetection Integrators with Partially Correlated Noise

A simple procedure for calculating receiver operating characteristics (ROC) for postdetection integration of arbitrary partially correlated noise samples is presented. The approach is based on the application of the ?effective number of independent integrated noise samples? to the classical theory of Marcum and Swerling and has been justified by Monte-Carlo simulation.     

Logarithmic Detection with Postdetection Filtering

An analysis is presented of the performance of a logarithmic detector or followed by a low-pass filter, under the assumption of a large ratio of IF bandwidth to postdetection bandwidth. This allows for the probability of detection and similar quantities to be computed in a straightforward manner. The mean and variance of the filter output are found by first deriving the autocorrelation function of the logarithmic detector output and then obtaining the power spectral ral density. A useful engineering approximation is made for the variance which is valid for all signal-to-noise ratios.     

基于LMI的涡扇发动机抗积分饱和PI控制

针对航空发动机控制计划中加减速供油线对主燃油限制的控制计划,基于状态空间理论和线性矩阵不等式LMI(Linear Matrix Inequality)的方法,提出了用于解决航空发动机控制中由于主燃油供油量超加减速供油线后导致控制效果明显变差甚至出现震荡问题的抗积分饱和IWP(Integral Wind-up Protection)算法,给出了同时保证闭环稳定性和饱和抑制性的LMI解。以某涡扇发动机为被控对象,基于LMI方法在已有的控制器上进行了IWP的设计,并进行了发动机非线性动态系统性能仿真验证。结果表明,在已设计的PI控制器结构中嵌入IWP补偿器构成具有抗积分饱和作用的PI控制器,能提高控制系统的动静态性能。     

Adaptive Radar Detection with Asymptotically Regulated False-Alarm Rate

An adaptive detection procedure is described by which the detection threshold is so adjusted as to provide an asymptotic false-alarm probability PFA that is approximately invariant with changes in radar clutter return amplitude probability density functions (pdf's) in a broad class. The class includes Rayleigh, chi, Weibull, and lognormal pdf's. The receiver noise is also taken into account. The clutter-plus-noise pdf is approximated by a truncated generalized Laguerre series, the coefficients of which are estimated from the radar returns using "cell averaging" techniques. This estimation is assumed to be perfect. The results obtained indicate that the "bias" error, defined as the normalized difference between the design PFA and the asymptotic PFA corresponding to the computed threshold, lies within a fraction of an order of magnitude for 10-3?PFA ? 10-6. For PFA ?10-6 the bias error is more than an order of magnitude. These results are for the case when a single independent radar return is processed at a time. The bias error decreases as the number of postdetection integrations of independent returns increases.     

转子时间常数在线校正的感应电机转速观测

基于磁链的模型参考自适应算法中,转子时间常数失准会影响电流模型精度。建立了消除耦合关系的可同时辨识转速和转子时间常数的模型。针对纯积分环节造成的电压模型磁链失准问题,采用了包含两个神经元自适应滤波器的积分器代替传统积分器,消除了直流漂移和积分初始条件的影响。仿真结果表明:设计的模型参考自适应转速观测系统不受转子时间常数变化和直流漂移的影响,系统动态性能良好。最后在DSP电机控制试验平台上进行试验,验证了该方法的有效性和高性能。     

Second time around radar return suppression using PRI modulation

A technique for suppressing second-time-around radar returns using pulse-repetition interval (PRI) modulation is presented and analyzed. It is shown that a staggered PRI radar system can offer considerable improvement over a nonstaggered radar system in rejecting second-time-around returns which cause false alarms. This improvement is a function of detector implementation (noncoherent integrator or binary integrator), the number of staggered PRIs, the quiescent false alarm number, the Swerling number of the false return, the transmitted signal power, the second-time-around noise power, and the quiescent noise power of the radar. Small changes in transmitted signal power can be traded off with the quiescent false alarm number to suppress the bogus return significantly. In addition, for a noncoherent integrator, all other parameters being equal, if the second-time-around return is a Swerling case II or IV target, then there is an optimum number of staggered PRIs that can be chosen to minimize the likelihood of its detection. It is also shown that the binary integrator significantly reduces the number of second-time-around return detections when compared with the noncoherent integrator. However, there is an accompanying loss of detection     

发动机稳态与过渡态控制集成设计仿真验证

研究了某型涡扇发动机全飞行包线稳态与过渡态控制集成设计问题.首先利用根轨迹分析法和时域分析法设计了从慢车状态到最大状态的多个比例积分(PI)设定点控制器,并利用增益调参和换算参数得到了全飞行包线的稳态控制器参数.然后将加减速控制计划与稳态控制通过max/min逻辑进行集成,考虑了抗积分饱和功能及设计了相应的抗积分饱和模块,最后得到的集成控制系统在软件MATLAB/Simulink下进行了仿真验证.仿真结果表明集成控制系统稳态时抗扰动性能良好,过渡过程中曲线平滑,有效利用了各种限制条件还兼有抗积分饱和功能并且能进行平滑切换.      

切换拓扑下无人机集群系统时变编队控制

针对多无人机(UAV)间通信拓扑可能发生变化的情况,研究了具有二阶积分特性的无人机集群系统的轨迹跟踪与时变编队控制问题。基于一致性方法设计了编队控制器,将编队控制问题转换成闭环系统的稳定性问题,引入了切换拓扑平均驻留时间的概念,并在此基础上利用线性矩阵不等式(LMI)方法,给出了控制器设计步骤。通过构造分段连续Lyapunov函数,证明了切换拓扑下无人机集群系统能够实现对指定轨迹的跟踪并且实现时变编队飞行。以三维空间运动的无人机集群系统为例进行了仿真验证,结果表明本文所提方法能够解决切换拓扑下无人机集群系统的轨迹跟踪与时变编队问题。     

基于级联型SOGI的永磁同步电机谐波电流抑制方法研究

伺服驱动器由于具有很强的非线性,导致永磁同步电机(PMSM)的定子电流中含有大量的高次谐波并且引发较大的转矩脉动。针对这一问题,提出基于级联型二阶广义积分器(SOGI)的谐波抑制方法,将级联型SOGI与电流环d、q轴的PI控制器并联,利用级联型SOGI提取d、q轴电流中的6次谐波分量,并将其注入到PI控制器的输出电压中,从而抵消参考电压中的谐波。仿真结果表明:采用基于级联型SOGI的电压补偿法进行谐波抑制,电流波形的畸变得到了明显改善,证明了所提算法的有效性。     

Comparison of Two Scanning Radar Detectors: The Moving Window and the Feedback Integrator

A comparison is made between the moving window and feedback integrator detectors for a scanning radar. Detection probabilities and position estimates are calculated by using a Monte Carlo simulation. The moving window is a slightly better detector than the feedback integrator: it provides 0.5-dB better detection capability and 8 percent more accurate estimate of position. However, the feedback integrator can be implemented more easily.     

光纤陀螺探测器微弱信号I/V转换电路设计和实现

本文针对光纤陀螺光电信号检测,输出电流信号微弱、噪声大的特点,研究并设计了采用高精度开关积分器的模拟选通积分I/V转换电路.试验结果表明,在同等条件下与光电探测器组件相比,该方法有效降低了随机游走系数.     

Simple Radar Detection Calculation

Barton's [1] procedure is further simplified to require only the use of a single-valued detector loss curve plus ideal detector curves to calculate the performance of envelope detectors with postdetection integration.     

一种大椭圆轨道卫星星历预报方法

针对大偏心率轨道长时间星历预报,稠密输出星历的低效率问题,提出了一种新的星历预报方法。该方法通过建立卫星摄动力模型,对卫星运动方程进行数值积分来获取卫星星历。该方法的轨道积分器以标准的8阶Adams-Cowell多步法为基础,针对大偏心率轨道的特性,在一个轨道周期的不同时段内采用不同的积分步长,同时引入了用于生成小间隔等间距卫星星历的插值公式。该方法降低了卫星运动方程右函数的计算次数,尤其适用于需要稠密输出卫星星历的情况。以STK(Satellite Tool Kit,卫星工具包)的HPOP(High Precision Orbit Propagator,高精度轨道预报)模型为验证基准,通过数学仿真校验了该方法的有效性和精度。算例表明,该方法在预报精度损失很小的情况下,计算时间远小于标准的多步法和HPOP模型。