高分辨率单脉冲测量雷达接收机的设计

根据某些测量雷达提出的较高分辨率的要求，详细介绍高分辨率单脉冲测量雷达接收系统的理论分析和方案论证，并给出具体的实施方案。     

Spectrum estimation of interleaved pulse trains

We consider signals consisting of a finite though unknown number of periodic time-interleaved pulse trains. For such signals, we present a novel approach for determining both the number of pulse trains present and the frequency of each pulse train. Our approach requires only the time of arrival data of each pulse. It is robust to noisy time of arrival data and missing pulses and, above all, is very computationally efficient. If N is the number of pulses being processed, the computation required is of the order of N log N     

锁模脉冲列的耦合效应

本文报道了在被动锁模激光振荡器中各脉冲列的耦合效应.给出了多种实验结果.分析了产生这种效应的机制,给出了改善锁模激光振荡器性能的方法.     

Electrostrictive self-focusing of picosecond laser pulse trains

A nanosecond-long train of picosecond laser pulses theoretically can produce self-focusing by electrostriction, even though the trapping threshold for a single picosecond pulse is very high. The relative roles of electrostriction and various types of Kerr effect in picosecond pulse train self-focusing should be assessed.     

A probability inequality for band-limited pulse trains

Band-limited pulse trains derived from a discrete stochastic process are considered. An upper bound is obtained for the average probability that the magnitude of the departure of the instantaneous signal value from the mean signal value exceedslambdatimes the standard deviation, as a function oflambda. This upper bound is useful in the analysis and prediction of intersymbol interference, quantizing errors, and digit errors in digital data communication systems.     

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     

Propagation of pulse trains through a random medium

Applying the parabolic approximation, the equations for two-frequency symmetric and antisymmetric mutual intensity functions for waves propagating through a random medium are derived, including the multiple scattering effects. These functions are applied to derive the general formulas for the covariance functions of narrowband pulses. They are used to compute the signal intensities for pulse trains passing through an ionospheric irregularity slab.     

Generation of high-repetition-rate WDM pulse trains from anarrayed-waveguide grating

We present what we believe to be the first demonstration of femtosecond pulse train generation from an arrayed-waveguide grating. Terahertz-rate bursts of femtosecond pulses are produced with the rate determined by the arrayed-waveguide delay spacing     

Radar resolution of moving targets

Conventional resolution theory is based on the assumption of constant range rate, and it neglects distortions of the modulation function as well as effects of the antenna pattern. Among the generalizations of the theory reported in the literature, some include the antenna pattern and others retain higher-order range derivatives in both carrier term and modulation function. The first part of this paper is tutorial and discusses the significance of the various generalizations of the ambiguity function. It is shown that an important class of problems can be accommodated when the conventional theory is extended by permitting higher-order range derivatives in the carrier term. Target resolvability on the basis of motion then depends only on the relative phase shifts introduced over the signal duration. In the second part, the ambiguity function is formally extended to arbitrary target motion. The modified theory retains the simplicity of the conventional approach and allows utilization of well-known results.     

用腔内剪切脉冲的方法获得毫微秒脉冲系列

一、实验装置和原理 腔内剪切脉冲获得毫微秒脉冲系列的实验装置示于图1。M_1是全反射镜,M_2是部分反射(R=70％)镜。G是工作物质,工作物质为钕玻璃棒φ12×240毫米,两端磨斜2°。D是偏振元件,采用格兰棱镜,它只能透射偏振为P_1态的光。PC_1和PC_2是普克尔盒,PG_1采用KDP晶体,退压工作;PC_2采用KDP晶体,加压工作,加电压的时间7P由PC_2终端短路电缆严格确定。本实验To约6毫微秒。两块晶体都是圆柱形,环状电极。PC_1和PC_2退压和加压的开关都用光触发球隙。光触发球隙光源是通常的调Q激光器,球隙的上升时间大约为0.5毫微秒。两     

Notes on impulse equivalent pulse trains (Corresp.)

A subclass of Huffman sequences is examined and evaluated in terms of an analytically defined figure of merit which would be optimal for sequences of pulses of equal amplitude.     

Radar and DC pulse signatures

Radar and dc pulses of Gaussian shape are reflected from dry, damp, and wet earth for both vertical and horizontal polarization. The envelope of the radar pulse is retrieved following reflection and examined for distortion. The shape of the reflected dc pulse is also determined. Pulse distortion resulting from multiple reflections is easily formulated by constructing a composite transfer function consisting of the product of reflection coefficients and retardation factors.     

Periodic restoration of pulse trains in a linear dispersive medium

It is shown that a periodic pulse train is completely restored after propagating a distance in a dispersive medium that depends on the period and the dispersion. This is a fundamental property of the parabolic differential equation that governs pulse propagation in dispersive media. This phenomenon could be applicable in photonic systems.<>     

电子侦察脉冲列中重频信息提取与应用综述

脉冲重复间隔（PRI）或脉冲重复频率（PRF）是雷达辐射源最稳健的特征参数之一,体现了雷达辐射脉冲的时序规律。在功能上,重频既决定了雷达单值测距范围,又影响不模糊测速区域大小。现代雷达常采用多个重频值和多种调制类型以满足不同功能的需求。在非合作机制的电子侦察领域,PRI指2个连续脉冲上升沿的间隔,是重要的脉冲描述字（PDWs）之一。由PRI衍生的雷达重频信息包括典型重频值集、重频调制类型、重频参数时序模式,均需要从复杂的电子侦察脉冲列中提取之后才能应用至分选、识别等数据处理任务。从电子侦察系统中重频信息提取与应用的体制与技术难点出发,综述了3种重频信息提取与应用的研究现状,并对重频信息提取与应用的进一步发展做出了展望。     

Characterisation of telecommunications pulse trains by Fourier-transform and dual-quadrature spectral interferometry

The first use of two sensitive spectral interferometric techniques for the complete intensity and phase characterisation of high-data rate optical pulse trains with low average power is demonstrated. The pulses are reconstructed either by Fourier-transform or dual-quadrature spectral interferometry after characterisation of an amplified reference pulse by frequency-resolved optical gating.     

Multigigabit/s demultiplexing in optical domain using coherence properties of pulse trains from multiple, asynchronous mode-locked lasers

It is shown that the unique coherence properties of mode-locked lasers can be exploited to provide new opportunities for high-speed data transmission. Using passive Mach-Zehnder optical delay stages, very high bit rate optical data streams constructed from asynchronously combined transmitters can be demultiplexed directly in the optical domain, without imposing restrictions on the source wavelength. Potential implementation and performance of the technique are discussed.<>     

Radar signal design for target resolution

Target resolution involves the recognition of a particular target in an arbitrary target environment. While pulse compression methods have solved the problem of separating two closely spaced targets of about the same cross section, this separation is usually accomplished at the expense of introducing "sidelobes" in the matched filter response, which may mask weak targets and prevent their detection altogether. The paper investigates the nature of the constraints on combined range and range rate resolution in a matched filter radar and establishes a clear tie between the uncertainty relation and the practical limitations on the resolution performance of radar. It is found that, in general, an optimum radar waveform for target resolution cannot exist. Radar signal design for target resolution consists of matching the waveform to the characteristics of the target environment, and a signal can be optimum only in that it achieves the best match. These findings are illustrated by examples of matching the radar waveform to a given target environment.     

Reducing muscle fatigue in FES applications by stimulating withN-let pulse trains

Applications of electrical stimulation for restoration of functional movements such as standing, gait, and grasp have always been hindered by the rapid fatigue of stimulated muscle. This paper describes an experimental investigation of stimulation with N-lets (a set of N closely spaced stimulation pulses) as a means of producing contractions with improved fatigue characteristics. Experiments were conducted on 27 able-bodied and four SCI human subjects using surface stimulation of the quadriceps muscle to produce isometric knee joint torque. Based upon evidence from the literature on muscle fatigue, parameters of the N-let trains for N=1-6 were optimized to produce the most force per pulse. The results demonstrated that: 1) nonlinear summation of the twitch response occurs in human subjects with N-let surface stimulation; 2) for most subjects, doublet stimulation (N=2) with a pulse interval of about 5 ms produced the maximum torque-time integral per pulse of the resulting twitch; and 3) on average, optimal N-let stimulation resulted in a 36% increase in isometric torque tracking when compared to traditional singlet stimulation. The results have immediate implications for alleviating the problem of premature fatigue during functional electrical stimulation