基于希尔波特解调的多相码调制信号的识别

首先给出了希尔波特解调过程，研究了相位编码信号的识别算法，接着对识别过程中存在的相位模糊问题提出了针对性的解决方法。基于上述算法，文中对二相编码信号、四相编码信号及多相码调制信号进行了仿真试验，得到了较好的效果，验证了文中算法的正确性和有效性，最后将算法应用于某雷达接收机的测试系统中，验证了其经济性和实用性。     

相位编码体制雷达码型选择综合分析

对相位编码体制雷达信号中常用的几种二相编码进行了简要的性能分析;从工程实现的综合性能角度出发,对其中两种比较典型的编码——L序列码和随机序列码的自相关和互相关性进行仿真、分析、比较,提出在实际工程应用中最好选用随机序列码作为相位编码体制雷达的码元。     

MIMO雷达混沌相位编码信号设计与分析

传统的优化算法需要进行组合优化过程,存在算法复杂、耗时的问题,为此,设计了能够快速获得MIMO(Multiple Input and Multiple Output)雷达正交相位编码信号的方法.基于混沌映射信号良好的相关特性和类随机特性,对Henon和Logistic混沌映射序列进行采样截取和二值量化得到二相码元,最后调制得到正交相位编码信号.仿真结果表明,利用这两种混沌映射序列可以快速获得符合条件的正交相位编码信号.     

基于MAC序列的相位编码准连续波的研究与应用

本文在讨论用二相编码信号构成的准连续波的数学模型和模糊函数的基础上,引入新的二元序列--MAC序列,并对其产生以及自相关特性进行了详细研究。通过对采用该序列编码的准连续波信号的周期单码重复时和多码重复的模糊函数进行仿真,其结果具有很好的图钉状,即有较高的距离和多普勒分辨率;并将MAC序列的相位编码准连续波应用在波形设计中,脉压仿真结果表明相比较m序列码,MAC序列更适用于目标检测。     

数域处理的二相编码信号旁瓣抑制技术研究

该文从二相编码信号的频谱结构分析入手,采用频域数字处理方法,研究了二相编码长码雷达信号距离旁瓣频域抑制加权技术,提出一种适用于各种码长不同码序列的编码信号旁瓣抑制滤波器(SSF)频域设计方法。并以127位二相编码信号为例,对SSF处理的性能进行仿真分析和实验测试。当fd=0时,仿真与实测结果的主副比分别达到50dB和43dB。这表明采用这种方法所设计的二相码信号SSF可以应用于现代雷达系统,并得到满意的性能指标。     

基于天底点的二相编码解调算法及实现

针对雷达高度表二相编码回波信号受多普勒和回波相位差双重调制问题,在深入分析雷达高度表回波信号模型及回波功率分布特征的基础上,提出了基于天底点的二相编码解调算法。该算法通过检测天底点回波中的多普勒和相位差信息,进行相应补偿从而实现码解调。仿真和实验表明:该算法多普勒频率检测误差小于20 Hz,相位检测误差小于2°,可有效实现码解调。     

硬限幅相位编码信号检测性能的改善

本文提出了一种新的恢复信号包络的算法。用这种算法能够克服通常算法所引起的硬限幅相位编码信号在某些初相时检测性能的下降。并且分析了四相连续相位编码(QCPC)信号的取样特性。证明了四相连续相位编码信号的取样损失此二相编码信号小。特别是当新算法和四相连续相位编码信号一起使用时,硬限幅相位编码信号能够取得更好的检测性能。     

基于遗传算法的多相码设计及旁瓣抑制

由于信号波形的“随机性冶易于实现“捷变冶,多相码序列在一定程度上可以提高雷达系统的抗截获能力,在雷达系统中得到广泛应用。文中采用自适应遗传算法进行全局搜索来优化多相码设计,以获得主副瓣比接近理论最优的多相编码。针对小时带宽积相位编码信号高脉压副瓣的特点,提出基于迭代加权最小二乘算法的预失配滤波器设计方法,从而降低多相码序列的脉压副瓣并扩展多普勒容限。通过仿真分析,验证了该方法的可行性及有效性。     

用Al00芯片实现四相码脉冲压缩

介绍了一种用四片Ａ１００芯片级联实现的１２８位以内四相码脉冲压缩系统。四相码信号作为一种大时宽带宽积编码信号，其频谱降落、接收滤波器失配损失、距离取样损失等性能均优于矩形相位码，正被日益广泛地应用到雷达中去。这里设计了一种四相码脉冲压缩系统，运用ＭＣＳ１９６做主控制器，ＩＭＳＡ１００芯片做处理器，具有１０ＭＨｚ的流水处理速度，且可以在１２８位码以内任意改变码元序列，在不增加硬件设备的情况下，也可完成１２８位以内二相码的压缩。     

一种新的二相码旁瓣抑制滤波器

二相编码是一种在雷达脉冲压缩中得到广泛应用的波形,但是一般的二相码波形的旁瓣抑制算法只适用于短码(如Barker码等),且设计得到的滤波器阶数比较高。本文提出了一种新的基于时域综合的二相码旁瓣抑制滤波器,能适用于各种长度的二相码,包括m序列等。文中给出了m序列和Barker码旁瓣抑制滤波器结果,并与现有的滤波器性能进行了比较。     

混沌二相编码的雷达脉冲压缩信号

二相编码信号是一种常用的雷达脉冲压缩信号,其相位编码是具有良好的自相关特性的二元伪随机序列.针对目前常用的伪随机编码的缺点,分析了混沌序列作为二相编码序列的可行性和优越性,并给出了混沌二相编码信号的生成方案.仿真实验证明,混沌二相编码信号具有良好的自相关特性和大时宽带宽积,是一种理想的雷达脉冲压缩信号.最后,提出了用Lyapunov指数作为准则优选混沌编码序列.     

Multiple symbol trellis coding of CPFSK

This paper describes a technique related to the design of a trellis encoder, combined with the full response M-ary continuous phase frequency shift keying (CPFSK) with modulation index 1/M. A new representation of CPFSK waveforms in N signaling intervals, is proposed as a function of an (N+1)-D vector. We also decompose the generation of the proposed CPFSK waveform into two stages, an N-consecutive continuous phase encoder (NCPE) and a memoryless modulator (MM). This decomposition makes it possible to design binary convolutional encoders with various code rates, cascaded to the NCPE. Specific optimal outer convolutional encoders of two and three-consecutive full response four-ary CPFSK with modulation index 1/4 are designed following Ungerboeck's (1982) set partitioning approach. These codes achieve asymptotic coding gains up to 4.77 dB for the two consecutive case with code rate 3/4, and asymptotic coding gains up to 5.45 dB for the three-consecutive case with code rate 5/6     

On the use of a compressive receiver for signal detection

The performance of a compressive receiver is compared to that of a wideband radiometer in order to determine if there is any significant loss in detection performance that accompanies the added feature of frequency estimation in the compressive receiver. The waveforms to be detected are either sine waves or phase-shift keyed signals, where the latter waveforms can represent either narrow-band binary phase-shift keyed (PSK) signals or direct sequence spread spectrum waveforms. It is shown that the compressive receiver outperforms the radiometer in detecting the presence of a sine wave. The compressive receiver is also shown to exhibit superior performance when the input contains a binary PSK signal and the system is operating under the conditions of low input signal-to-noise power ratio and low probability of false alarm     

随机多元码脉位调制和脉间二元序列相位调制的混合波形设计

本文提出了一种利用随机多元码脉位调制（ＰＰＭ）和脉间伪随机或随机二元序列相位调制（ＰＭ）相结合的混合波形设计方法．推导并分析了这种混合波形的平均模糊函数．结果表明这种混合波形不仅具有结构简单、易于处理等特点，而且具有良好的测距和测速性能，以及良好的ＥＣＣＭ性能．     

The Performance of Coded Diversity Systems on a Slowly Fading Rayleigh Channel

A new diversity technique has been developed that uses message waveforms consisting of a sequence of RF bursts at a number of different frequencies. Furthermore, the ensemble of message sequences is a code with large minimum Hamming distance. Hence, reliable communications are possible in spite of channel fading and additive noise. The new diversity technique has been integrated into a troposcatter communication system that was first tested in 1967. The new technique is illustrated and its performance predicted assuming both correlated and uncorrelated fading between the RF frequencies. A particular code is presented that achieves a 4-dB coding improvement beyond that generally obtained using binary modulation and frequency diversity techniques of the same order. Theoretical predictions of system performance and actual empirical data taken on two operational links agree very closely.     

A Bipolar Signal Waveform Generator

Bipolar signal waveforms for digital communication are normally accomplished by coding the message sequence first and then pulse shaping the bipolar signal. The coding is relatively simple to mechanize; the pulse shaping may present some difficulty and approximation techniques may have to be used. A hybrid digital-analog mechanization of a bipolar signal waveform generator in which the bipolar encoding and pulse-shaping operations are combined is described.     

Probability distributions of noiselike waveforms generated by a digital technique

This letter discusses the probability distributions of waveforms obtained by a weighted summation of digits stored in an n stage feedback shift register which is generating a binary sequence of periodic length 2n or 2n?1.     

基于协方差矩阵的MIMO雷达离散编码设计

MIMO雷达相对于传统的相控阵雷达,可以更自由地选择发射波形来匹配所需要的发射方向图。文中首先给出了一个带有限制条件的优化问题以寻找发射信号的协方差矩阵,从而能够在空间匹配理想的方向图,接着建立了一组恒模的二相离散序列来匹配已有的协方差矩阵,并将这种方法推广到多相码设计中,并对实验结果进行了详细分析。     

Probability distribution of pseudorandom waveforms obtained from msequences

The letter discusses the probability distribution of pseudorandom waveforms obtained from m sequences by summing the digits stored in the feedback shift register which generates the sequence. A recurrence relation is given, valid for both the binary and nonbinary cases, which enables the probability distribution to be determined easily.     

Partitioning of spreading sequences for increased minimum distanceusing CPFSK modulation

By using continuous-phase frequency shift keying (CPFSK) in a direct-sequence code-division multiple-access (DS-CDMA) system, and by partitioning the spreading sequence so that differing patterns of plus and minus chips are multiplied onto successive data bits, the net phase change will differ from bit to bit, giving an apparent variation in modulation index similar to multi-h CPFSK. This gives similar coding gain effects as multi-h CPFSK when maximum-likelihood sequence detection is used. Improved probability of error performance in terms of increased minimum distance has been demonstrated when the spreading sequence of a CDMA system is properly overlaid on outgoing data bits in the CPFSK modulation scheme. At the best modulation index observed, h=5/7, a computer search shows ~1.4-dB advantage over binary phase shift keying, and a ~0.6-dB advantage over the best fixed-h CPFSK