定时抖动对动目标显示滤波器性能的影响

本文分析了发射定时抖动和取样抖动对多脉冲杂波对消系统的影响,并求出由于定时抖动而产生的剩余杂波功率净增量的显式表示。发现均方误差的增量与抖动方差成正比,且两种抖动的作用几乎相等。所分析的系统可含有递归或非递归动目标显示器,柞为特例后者含有惯用的两脉冲和三脉冲对消器。看出由抖动引起的三脉冲对消器剩余杂波功率的增量比两脉冲对消器约高4.8dB。     

测量距离末端处的恒虚警率

恒虚警率（ＣＦＡＲ）检测方法广泛地使用在雷达信号处理系统中，连在教科书中都有描述，但是，在距离取样起端和末端存在实现方面的问题，在那里，将丢失一个平均滑窗内的数据。普通的实现方法是假定丢失滑窗内的值为零。这使距离取样两端的虚警率增高。除非在这些区域内有气象杂波，否则这个问题通常并不明显，因此，异常虚警率将作为“气象突破”出现。     

无载波脉冲探地雷达收发技术的研究

本文对无载波探地雷达的关键部件－收发技术进行了研究。首先分析了取样频率，取样门管参数对取样头性能的影响，设计了发射天线所需要的高速脉冲源和高速取样头以及收发双工开关，最后对取样过程的稳定问题进行了讨论。实验证明了我们研制有取样头性能良好，它可以用在无载波探地雷达系统中作为信号采集器。     

非均匀取样周期信号时间偏差估计算法研究

本文在非均匀取样一般理论的基础上，提出了一种估计非均匀取样时间偏差的算法，并给出一种可校正非均匀取样周期信号时间偏差的波形数字化器结构的设想，仿真结果表明，当输入测试信号为多频正弦信号时，用一个８ｂｉｔ的量化器，剩余时间偏差可减小至取样周期的０．１５％。     

频率综合器锁频环技术及应用

相参雷达需要采用频率综合器。间接式频率综合器，由于电磁兼容问题较易处理，且设备量较少，因而优先采用。在间接式频率综合器中、除锁相环外，锁频环也是不可缺少的。这里着重介绍频率综合器锁频环技术及其应用效果；提供间接式频率综合器锁频环及跳频控制系统的几种实施方案。     

基于Talbot效应的电光调制位相阵列器

利用周期极化反转的铌酸锂晶体设计与制备圆形周期单元六角结构排列的可调位相阵列器,对位相阵列器的Talbot效应光衍射成像进行理论和实验研究,得到了不同位相差和不同分数Talbot距离条件下阵列器近场衍射的理论仿真和实验观测图像,实验结果与理论研究相符.计算衍射场取样区域内平均强度,获得取样区内强度随位相差和Talbot距离变化的曲线,揭示了位相差和衍射位置对阵列器衍射强度分布的影响.     

综合孔径雷达中激光源的工作频率

本文以综合孔径雷达的线性调频信号为出发点、利用取样定理讨论了综合孔径雷达的激光源的脉冲间隔Ｔ，并估计了它的数量级。     

BOXCAR积分器

Boxcar平均器或称Boxcar积分器是一种基于信号平均技术的微弱信号检测装置,同样是利用了相关原理。它可对被测微弱信号进行取样和积分,从而再现深埋在噪声中的周期重复微弱信号的快速时间变化和测量重复脉冲     

初始相位随机变化信号的匹配滤波

本文讨论了雷达回波信号初相随机变化对最佳匹转配波器和准匹配滤波器的影响。分析表明匹配滤波器的输出信噪比相对于理论上的最佳值有3dB 的统计平均损失,并指出在雷达的工作环境中,统计平均峰值信噪比(SNR)的概念更具有实际意义。最后,简单介绍了解决问题的方法。     

列车测速仪标准装置传感器检查器

列车测速仪标准传感器检查顺是用于对列车测速仪传感器的检测。传感器是列车测速仪的取样部分，而作为取样的传感器，其误差大小直接影响到列车测速仪测速的准确程度，本文介绍了传感器检查器的设计思路及检测方法。     

Distributions of results of analysis by means of spectrum analyzer with ideal band pass filter and true integrator

The theoretical model of the probability density functions of results of Gaussian white noise spectrum analysis is constructed and experimentally verified. The analyzer of the ‘filtering-squaring-averaging’ type is assumed with true integrator as the averager and with the ideal filter with very narrow and maximum wide pass band. Simple approximative ways for probability density functions calculation are derived. It is found that these distributions do not coincide with χ²-distributions. Previously derived estimates of the spectrum analysis statistical error are also experimentally verified.     

FTIR光谱仪动镜速度和采样抖动的噪声分析

分析了傅里叶变换光谱仪由动镜速度和采样抖动的随机误差引起的光谱噪声,建立了基于噪声等效辐亮度差(NERD)和噪声等效温差(NETD)的噪声模型。分析表明,动镜速度的波动与抗混叠滤波器幅频响应、时间延迟的综合作用,以及采样触发的短时抖动,都会引起系统的噪声。通过MATLAB数值模拟,对动镜速度和采样抖动的噪声影响进行了仿真分析与模型计算,验证了理论模型,评估了实际仪器的噪声水平,为动镜控制、抗混叠滤波器的设计以及傅里叶变换光谱仪的噪声定量化计算和改善提供了依据。     

Focal-Plane Signal and Noise Model–CTIA ROIC

A method for electrooptical sensor focal plane signal-to-noise analysis is developed, which consists of coupling a reset-integrator-sampler readout model to a focal plane unit cell detector-preamp model. The combined readout integrated circuit (ROIC) model may be used to evaluate the signal and noise of visible or infrared focal plane arrays that use sample-and-hold, correlated double sampling (CDS), or other sampling schemes. The analysis developed here clears up the considerable confusion regarding CDS operation by elucidating how CDS operates on both signal and noise and explains the dependence of output 1/f noise on integration and epoch times. The reset-integrator model is then coupled to a capacitive transimpedance amplifier (CTIA) preamp model, and signal and noise formulas for imagers with CTIA-CDS ROICs are developed and used to evaluate the signal and noise of example scanning and staring focal plane arrays.     

Analyzing and modeling the performance degradation of flash A/D converters due to substrate noise coupling

This paper presents a model to evaluate the impact of substrate noise on a CMOS regenerative comparator and moreover to predict the resulting performance degradation of a flash analog-to-digital (A/D) converter. The proposed approach initially relates substrate noise to the induced timing uncertainty of the comparator by means of an analytical linear model. In particular, the analysis first focuses on analyzing and expressing the resulting non-uniform sampling distortion in regenerative comparators in the presence of a deterministic ground bounce. Two sources of distortion are identified and evaluated: the input-dependent and the substrate noise-dependent one. For each error contributor, the analysis investigates two cases of timing error, based on the frequency correlation of the interfering signal with the sampling clock. The properties (number and power of distortion tones) of the sampling error spectrum are found to be highly dependent on the spectral content of the interfering signal and the sampling clock, while the model captures accurately the induced distortion. Subsequently, the linear model is extended to estimate the degradation of flash A/D converters and is utilized to predict the performance of practical flash and time-interleaved converters in the presence of substrate noise.     

斜采样技术的混叠分析及分辨率计算

 斜采样技术通过将线阵探测器倾斜一定的角度并调节积分时间的方法,利用较低成本实现了探测器的亚像元成像.本文对单线阵斜采样及超模式斜采样方式的混叠及分辨率进行了研究.通过对采样方式在频域对偶网格的分析,建立了斜采样成像系统与混叠的关系,在有效分辨率的意义下,确定了混叠与噪声最小的最佳倒易晶胞,将错位的频谱恢复到了正确的位置,提高了分辨率.实验结果表明,通过最佳倒易晶胞去除混叠的斜采样技术有效地提高了线阵采样式光学遥感器图像分辨率.     

射频直接采样系统中等效相位噪声模型分析

为了分析射频直接采样系统中的等效相位噪声模型,文中给出了射频直接采样接收机的简化构架,然后理论推导了射频直接采样接收机采样输出信噪比与采样时钟之间的关系表达式。最后,通过建立仿真实验平台对推导结论进行了实验验证,结果表明:射频直接采样系统对采样时钟的频谱纯度要求高,采样输出的信噪比和无杂散动态范围会在时钟信号频谱的基础上恶化。射频直接采样系统可视为射频本振混频和量化采样的过程,其等效相位噪声模型与常规超外差式接收机是一致的。     

Improved Single‐Tone Frequency Estimation by Averaging and Weighted Linear Prediction

This paper addresses estimating the frequency of a cisoid in the presence of white Gaussian noise, which has numerous applications in communications, radar, sonar, and instrumentation and measurement. Due to the nonlinear nature of the frequency estimation problem, there is threshold effect, that is, large error estimates or outliers will occur at sufficiently low signal‐to‐noise ratio (SNR) conditions. Utilizing the ideas of averaging to increase SNR and weighted linear prediction, an optimal frequency estimator with smaller threshold SNR is developed. Computer simulations are included to compare its mean square error performance with that of the maximum likelihood (ML) estimator, improved weighted phase averager, generalized weighted linear predictor, and single weighted sample correlator as well as Cramér‐Rao lower bound. In particular, with smaller computational requirement, the proposed estimator can achieve the same threshold and estimation performance of the ML method.     

Multilevel nonlinear filters for edge detection and noisesuppression

Two new classes of multilevel nonlinear filters are introduced for simultaneous edge detection and noise suppression, which the authors call a nested median filter/median averaging filter (NMF/MAF) pair and a delayed decision filter/embedded median trimmed filter (DDF/EMTF) pair. Median filters and median-related filter cause an edge shift in the presence of an impulse near the edge. The proposed filters reduce such edge shifting while suppressing impulsive as well as nonimpulsive noise. It is shown that at the noisy edge point the NMF and the DDF are substantially superior both theoretically and experimentally to the median filter, the α-TM filter, and the STM filter in two respects: (1) the output bias error and (2) the output mean square error. It is also shown that in the noisy homogeneous region (nonedge point), the bias errors of the MAF are zero and the output mean square errors of the MAF are substantially close to those of the optimized single-level filters: the averager, the median filter, and the min-max filter under Gaussian, Laplacian, and uniform noise, respectively. Test results confirm that the NMF/MAF pair and the DDF/EMTF structure are each robust in preserving sharp edges, inhibiting edge shifting, and suppressing a wide variety of noise     

Tracking of changes in latency and amplitude of the evokedpotential by using adaptive LMS filters and exponential averagers

The adaptive LMS algorithm in combination with exponential averagers are compared to the use of exponential averagers only in tracking latency and amplitude changes in the evoked potential. The estimator is intended for use in applications where neurologic functions are monitored by detecting changes in the evoked potential. Two different structures of the estimator are evaluated and it is found that averaging before filtering is to be preferred. It is shown that the desired signal to the LMS-filter can have a rather low SNR with only mirror influence on the estimator performance. The estimator which combines an LMS filter and an exponential averager was shown to detect changes in latency faster than the estimator which uses a nonfiltered average. The LMS filter is shown to exhibit bias in the estimate of the evoked potential due to the fact that response and background spectra has overlapping frequency ranges. The bias seems not to affect the latency estimation while amplitude estimation was clearly affected. Simulations are performed with both white noise and EEG background     

Optical transient waveform monitoring based on cross-gain modulation in semiconductor optical amplifier

An all-optical transient waveform equivalent time sampling system based on cross-gain modulation(XGM) in semiconductor optical amplifier(SOA) is presented.A noisy SOA dynamic model and PIN equivalent circuit function are employed for system evaluating.The results show this SOA-XGM sampler with subtracting postprocessing can achieve picosecond sampling window.The shape of sampling window can be adjusted by SOA bias current and amplitude of control pulse.Compared with amplified spontaneous emission(ASE) noise of SOA and thermal noise in PIN,the jitter of sampling control pulse causes most sampling error.Simulations show that this SOA-XGM sampler can be a capable candidate for transient waveform sampling.