On the estimation of interleaved pulse train phases

Some signals are transmitted as periodic pulse trains where information is in the timing of the arrival of the pulses. A number of pulse trains arriving over the same time interval are said to be interleaved. We propose an on-line method for estimating pulse train phases and fine-tuning pulse repetition frequency (PRF) estimates of a known number of interleaved pulse trains. The computational effort is of order N, where N is the number of pulses received. In particular, we employ an extended Kalman filter, where discontinuities in the signal model are appropriately smoothed.     

The limits of extended Kalman filtering for pulse traindeinterleaving

Some signals are transmitted as periodic pulse trains. If more than one pulse train is transmitted over the same communication channel, a challenge is to separate them for source identification at the receiver. This is known as pulse train deinterleaving and is clearly a fundamental problem in the study of discrete-event systems. Frequently, the only relevant information at the receiver is the time of arrival (TOA) data, which is usually contaminated by jitter noise. Perhaps there are also missing or overlapping pulses. In this paper, we present an approach for deinterleaving pulse trains and estimating their periods using an extended Kalman filter (EKF). A naive application of EKF theory is not attractive because of discontinuities in the signal model. Here, a form of smoothing of the discontinuities is proposed so that the EKF approach becomes attractive. The advantage of this EKF approach is that it is less computationally expensive than most previously proposed methods, which are of order N², where N is the number of pulses being processed. The computation required here is of order N. The method proposed appears to give useful results for up to seven or so pulse trains, particularly when there is some a priori information on the pulse frequencies, which can be obtained using computations of order N log N     

Multipath time delay estimation using regression stepwise procedure

Consider a multipath signal whose individual signals are deterministic known pulses. Our problem is to estimate the amplitudes and delay times of individual signals. Our main idea is to consider the multipath signal as a multiple regression model where each time sample is considered to be a possible arrival time of a pulse that may not be real. We use the regression stepwise procedure to select true pulses and eliminate the false pulses. By using this procedure, the number of pulses in a multipath signal does not need to be known. The results of a Monte Carlo simulation study with sinusoidal and trapezoidal pulses are presented to demonstrate the accurate estimation of arrival times and amplitudes by the regression stepwise procedure     

基于滑动时间窗的雷达脉冲列分选方法

电磁空间中大量存在着相互交错的固定重频雷达脉冲列,例如海面大量舰船发射的导航雷达信号、机载脉冲多普勒雷达在不同时段发射的相干脉冲列等。这些脉冲列以时间片段的形式存在,电子侦察分析系统无法事先确定其起止时刻,给这类雷达的重频参数估计和脉冲分选造成了较大困难。该文首先分析脉冲列的短持续时间特性给传统脉冲分选方法性能造成的负面影响,然后引入滑动时间窗思想来削弱这一影响,并据此提出脉冲重频间隔(PRI)高精度估计和脉冲分选方法。仿真结果验证了新方法的重频参数估计和脉冲分选性能。     

Deinterleaving pulse trains using discrete-time stochasticdynamic-linear models

Pulse trains from a number of different sources are often received on the one communication channel. It is then of interest to identify which pulses are from which source, based on different source characteristics. This sorting task is termed deinterleaving. the authors propose time-domain techniques for deinterleaving pulse trains from a finite number of periodic sources based on the time of arrival (TOA) and pulse energy, if available, of the pulses received on the one communication channel. They formulate the pulse train deinterleaving problem as a stochastic discrete-time dynamic linear model (DLM), the “discrete-time” variable k being associated with the kth received pulse. The time-varying parameters of the DLM depend on the sequence of active sources. The deinterleaving detection/estimation task can then be done optimally via linear signal processing using the Kalman filter (or recursive least squares when the source periods are constant) and tree searching. The optimal solution, however, is computationally infeasible for other than small data lengths since the number of possible sequences grow exponentially with data length. The authors propose and study two of a number of possible suboptimal solutions: 1) forward dynamic programming with fixed look-ahead rather than total look-ahead as required for the optimal scheme; 2) a probabilistic teacher Kalman filtering for the detection/estimation task     

Radar resolution properties of pulse trains

The concept of pulse compression has stimulated interest in the range and Doppler resolution properties of radar signals, but most of the theoretical investigations to date have been concerned with single pulse signals. The properties of coherent pulse trains, a practically important class of radar signals, have not received adequate treatment in the literature. Little information appears to be available on pulse trains using pulse-to-pulse waveform coding, frequency shifting, or repetition period staggering. The present paper attempts to fill a gap in the radar literature by analyzing the resolution potential of pulse trains. The treatment is limited to the practical class of pulse trains where all component pulses have identical envelopes and bandwidths, but the waveforms under these envelopes, frequency bands and repetition interval are left arbitrary. The results of the study convey an understanding of the effects of pulse train coding and thus give a clear indication of both the potential and the limitations of pulse trains in radar applications.     

An interval-amplitude algorithm for deinterleaving stochastic pulsetrain sources

We consider the deinterleaving of pulse trains transmitted by N independent sources. The deinterleaving problem considered has applications in spectral estimation, where N (known number) stochastic parameterized sources are sampled using a fast sensor recording the sign of the signal from each source. Due to communication constraints, the recorded signals-pulse trains or sequences of zeros and ones-are superimposed and transmitted through a single Gaussian communication channel. The aim of this paper is to estimate the parameters that characterize the sources and identify those sources that are responsible for the observed noisy pulses. Our proposed algorithm, subject to modeling assumptions, optimally combines hidden Markov model and binary time series estimation techniques and yields maximum likelihood parameter estimates of the sources     

一种脉组间步进频雷达速度估计误差的改进方法

在脉组间步进频信号的脉组内利用傅里叶变换测速时,针对测速误差对合成距离像的影响,提出了二分迭代法。该方法通过log2N次迭代操作便可使测速精度提高N倍(N为脉组个数),通过相关补偿后的合成距离像的走动不超过半个距离分辨单元。此外,由于测速精度提高速率是以2为底的指数增长,且每次迭代为脉组内FFT操作,因此该方法具有较少的运算量。仿真实验验证了该方法的有效性。     

制导激光编码信息识别技术研究

激光脉冲编码是半主动激光制导武器采用的一种抗干扰措施,为满足对抗半主动激光制导武器的需要,以激光信号的脉冲到达时间为参数,在分析现有各种码型及其识别方式的基础上,对激光脉冲编码信息逐次逼近,即在得到极少量的激光脉冲样本后,同步拟合解算不同码型参数,并结合模糊决策思想,预测下一脉冲的到达时刻,下达发射干扰脉冲的指令,同时侦测敌方目标指示器的后续脉冲到达时刻,在样本不断增长的过程中,对预测码型不断调整,逐步达到精确复制敌方编码信号的目的。试验结果表明,对常见的编码模式,该技术能通过较少的脉冲信息有效的识别脉冲编码规律。     

Malfunctioning of Microcontroller Irradiated with Ultrashort Ultrabroadband Pulse Trains

Effect of the number of ultrashort ultrabroadband pulses with a repetition rate of 1 kHz on malfunctioning of microcontroller in radio transparent housing is studied when the device is irradiated using pulse trains at a pulse duration of about 10^–10 s and radiation frequencies ranging from 1 to 30 GHz. The radiation is received by internal conducting stripes that connect the electronic circuit and external outputs. The malfunction probability is determined by the number of pulses in the pulse train, pulse number, and electric field strength. It is shown that malfunctioning is predominantly caused by the leading pulses in the pulse train.     

基于Pearson相关性的雷达交叠信号识别

针对复杂电磁环境下多部雷达同时到达信号频域交叠时难以分选识别的问题,分析了信号交叠对于雷达信号识别模块性能的影响;在此基础上面向识别需求,基于Pearson算法研究了交叠信号分选的处理方法。从信息论视角来说,两个信号脉冲波形相关性越弱,则其所表达的信息量越大,特征相关度越低。在信号脉冲数一定时,基于Pearson算法可以选择相关性较弱的信号脉冲载波,以削弱同时信号交叠的影响。通过实验,发现利用选择后的弱相关信号脉冲载波特征来表达信号特性,能有效降低数据维度,尽可能减少信息丢失,有利于达到鲁棒的识别效果,因此该方法可为同时到达信号交叠下的信号识别提供有效途径参考。     

Spectra of PSK Signals with Overlapping Baseband Pulses

This paper derives a new power spectrum formula for constant-envelope PSK signals. The only signal constraints are that the baseband pulses be of finite duration and the pulse amplitudes be mutually independent. The computer program used to implement the formula is made highly efficient by the use of fast Fourier transform (FFT) algorithms. The key contribution of the new result is the high degree of baseband pulse overlap permitted before the computation cost becomes excessive. In some computation approaches, this cost grows as L^N, whereLis the number of modulation levels andNis the number of data periods spanned by the pulse. In the approach developed here, the cost is independent ofLand grows roughly linearly withN. The cost improvement, which is substantial for largeLandN, is exploited here by using the new approach for a wide variety of baseband pulses. Results are given which demonstrate the potential value, in terms of narrower spectra and lower sidelobes, of using overlapping pulses.     

多输入多输出信道空域相关性评估简化模型

针对任意散射环境的多输入多输出(MIMO)信道,提出一种基于角度域脉冲采样的空域相关性评估简化模型,推导常见采样脉冲空域相关系数的近似简化解析式,并详细分析简化模型中采样脉冲数目和加权系数的选取依据,大大降低MIMO衰落信号空域相关性分析的复杂度.仿真结果表明:当到达波角度扩展为5到20度且采样脉冲数目大于36时,本文...     

A sequentially self-seeded Fabry-Perot laser for two-dimensional encoding/decoding of optical pulses

Multiwavelength optical pulse trains with variable two-dimensional (2-D) code patterns formed by a single encoder have been generated from a self-seeded gain-switched Fabry-Perot (F-P) laser for the first time. Mechanically tunable cascaded fiber Bragg gratings (FBG) are used to construct the reconfigurable encoder, which acts as a discrete nonlinear dispersive component in the subharmonically pulse-gated external cavity of the laser to generate multiwavelength pulse trains with a variable 2-D code pattern defined by the settings of the FBG string. Four distinct repetitive patterns (corresponding to four different 2-D codes) of optical pulse trains, each made up of up to four pulses generated sequentially with different wavelengths, have been produced at a repetition rate of 250 MHz. The output pulses obtained by this method are much more intense and stable than those obtained from a free-running F-P laser. Furthermore, the different pulse patterns obtained show that the scheme can allow easy switching among different 2-D codes by simply reconfiguring the FBG string. Hence this laser with the embedded reconfigurable encoder should be a viable optical source for incoherent 2-D fiber-optic code-division multiple access (FO-CDMA) applications. Near-error-free transmission of data at 250 Mbit/s employing this laser/encoder over 9.5 km standard single mode fiber has been successfully demonstrated, thus confirming its performance and viability for FO-CDMA.     

On periodic pulse interval analysis with outliers and missingobservations

Analysis of periodic pulse trains based on time of arrival is considered, with perhaps very many missing observations and contaminated data. A period estimator is developed based on a modified Euclidean algorithm. This algorithm is a computationally simple, robust method for estimating the greatest common divisor of a noisy contaminated data set. The resulting estimate, although it is not maximum likelihood, is used as initialization in a three-step algorithm that achieves the Cramer-Rao bound (CRB) for moderate noise levels, as shown by comparing Monte Carlo results with the CRBs. This approach solves linear regression problems with missing observations and outliers. Comparisons with a periodogram approach based on a point process model are shown. An extension using multiple independent data records is also developed that overcomes high levels of contamination     

Electric Field Pulse Trains Occurring Prior to the First Stroke in Negative Cloud-to-Ground Lightning

In this study, we examine the characteristics of electric field pulse trains that are attributed to preliminary breakdown in negative cloud-to-ground lightning discharges and compare them to those of similar pulse trains associated with attempted cloud-to-ground leaders. The data were acquired in 2006 in Gainesville, Florida. The largest pulses in the train can exceed in magnitude the following first return-stroke pulse. The arithmetic mean pulse duration and interpulse interval for pulse trains in negative cloud-to-ground discharges are 4.8 and ${65};mu$s, respectively. The arithmetic mean pulse duration and interpulse interval for pulse trains in attempted cloud-to-ground leaders are 17 and ${73};mu$s, respectively. This implies that pulse trains in ground discharges contain a larger fraction of “narrow” pulses (apparently disregarded in previous studies), defined here as those with durations equal to or less than ${4};mu$s, than the pulse trains in attempted cloud-to-ground leaders. Submicrosecond-scale pulses are observed as part of pulse trains associated with cloud-to-ground discharges, but not with attempted leaders. We also examine the occurrence of pulses of different duration and amplitude in different parts of the preliminary breakdown pulse train of ground discharges. Pulses with larger durations (${≪}hbox{4}$ $mu$s) tend to occur in the initial part of pulse train.      

Application of Nonuniform Transmission Lines to Ultra Wideband Pulse Shaping

The work presented in this letter demonstrates that nonuniform transmission lines (NUTLs) can be used for pulse shaping applications in ultra wideband pulsed systems and presents an approach to their design for this application. The pulsed waveforms generated are modified Hermite polynomials and encoded pulse trains thereof and are characterised by a broad bandwidth ranging from near DC to over 10 GHz and relatively long temporal duration in the region of nanoseconds. These pulses are more mathematically complex and at least three times higher bandwidth than previously has been reported in the literature. It is also believed to be the first time that modified Hermite polynomial pulses have been generated in practice. The NUTL design approach is verified by test structures fabricated on FR4 circuit board. The results demonstrate that NUTLs, which are completely passive structures, allow generation of complex pulse shapes in applications requiring fast, transient waveforms.      

多路光脉冲信号数据采集技术的设计

介绍了一种同时监控多路光脉冲信号的方法，它是将多路光脉冲信号合成为脉冲序列，并通过相应的软件设计，实现每路光脉冲信号的数据采集。     

用GaAs负反馈器改善被动锁模Nd∶YAG激光器的输出特性

本文报导了用高纯半导体材料GaAS片作为负反馈元件，以改善被动叙模Nd：YAG激光器的输出特住．理论分析了GaAs负反馈作用的原理，实验研究了胜的几何参数对激光输出特性的影响，获得了稳定的长序列初模脉冲激光输出，序列脉冲数达65个，单脉冲能量～10J，脉冲宽度＜20ps，脉冲-脉冲能量抖动＜2％．     

Principles of high-resolution radar based on nonsinusoidal waves.III. Radar-target reflectivity model

For pt.II see ibid., vol.31, no.4, p.369-75 (1989). A target-reflectivity model is developed for carrier-free nonsinusoidal waves with the time variation of a Gaussian pulse or a sequence of positive and negative Gaussian pulses representing a binary code, as was introduced in pt.I (see ibid., vol.31, no.4, p.359-68 (1989)). It is shown that the impulse response of a complex target that is composed of a finite number of scattering centers can be expressed as a sequence of Gaussian pulses. The characteristics of the Gaussian pulses, e.g. peak amplitude and nominal duration, are functions of the physical properties of the scattering centers, which are unique for each target. Hence, the impulse response waveform of a target can be regarded as a one-dimensional image in time (or range), which is valuable information for target classification and recognition. A signal processing technique is developed for obtaining an approximation of a target impulse response waveform from the backscattered and received signals. The signal processor is specifically developed for radar signals with the structure of complementary code pairs whose autocorrelation function is a single narrow pulse with no time sidelobes