基于截获因子评价的双基前视SAR成像LPI设计

降低雷达辐射信号被截获概率,是保障机载平台战场生存与作战效能发挥的重要方面。本文结合双基雷达在低截获（LPI）方面的优势,提出了基于截获因子评价的移不变双基前视条带合成孔径雷达（SAR）成像LPI探测设计方法。考虑利用截获因子评价双基SAR成像的LPI性能,针对移不变双基前视条带SAR成像模式,简要分析了成像分辨率,推导了截获因子表达式,在保证成像性能前提下,以降低截获因子为目标设计了LPI探测方法,并进行了仿真验证。实验结果表明,本文提出的方法能明显改善机载火控雷达SAR模式的抗截获性能。     

机间数据链核心问题的分析与探讨

指出了机间数据链的重要性,阐述了低传输延迟特性、高数据传输率、低截获率、高抗干扰能力、动态组网等特征对系统的要求.对频率选择、窄带多波束天线设计、信道接入协议等核心问题进行了较深入的分析,指出了解决方案和途径,并讨论了建立网络协议开发平台的意义及方法.     

Wireless field trial results of a high hopping rate FHSS-FSK testbed

This paper presents a complete study and characterization of a real-time frequency-hopped, frequency shift-keyed testbed capable of transmitting data at 160 kb/s, with hopping rates of up to 80 Khops/s operating in the 900 MHz band. The system provides the highest hopping rate reported to date and sets a new trend for FHSS communications with superior low probability of interception/detection and anti-jamming (LPI/LPD/AJ) capabilities. The architecture features a direct digital frequency synthesizer to enable high-rate hopping, and a frequency correlator-based demodulator, plus all digital timing and frequency recovery algorithms to minimize complexity. Furthermore, single sideband modulation was used to achieve spectral efficiency. The testbed is software configured and provides the user with full control over the diversity combining techniques, symbol interleaving, packet structure, and acquisition protocols. A total of 5850 independent experiments were carried out under various receiver configurations and wireless environments. The results underscore the dramatic potential for a system that optimally combines high-rate hopping, interleaving, and equal gain combining to combat severe propagation conditions, including multipath fading and intentional jamming.     

Adaptive resource management algorithm for target tracking in radar network based on low probability of intercept

In this paper, a low probability of intercept (LPI) performance driven adaptive resource management algorithm for target tracking in a radar network is presented, where the radar network consists of a dedicated radar transmitter and multiple receivers. Firstly, the intercept probability for radar network systems is derived. Then, an adaptive resource management scheme based on LPI is proposed, in which a novel objective function for LPI performance is defined and minimized by optimizing the revisit interval, dwell time, and transmit power in radar networks to guarantee a specific target tracking accuracy with passive time difference of arrival and frequency difference of arrival cooperation. Numerical simulations demonstrate the superior performance of the proposed adaptive resource management scheme over other methods via Monte Carlo simulations.     

低截获概率火控系统的设计

反辐射导弹技术的快速发展,给防空系统中的各种辐射源造成极大的威胁,火控系统采用低截获概率技术可以极大的提高武器系统的作战有效性和生存能力.该文论述低截获概率的原理和关键技术,探讨了一种新型火控系统的低截获概率设计方法.     

基于LPI的双基地雷达

针对当前雷达面临的四大威胁，提出了构建基于低截获概率（LPI）的双基地雷达，介绍了该雷达的系统组成和工作原理，对其LPI性能和反隐身性能进行了分析。分析结果表明该雷达体制具有良好的综合对抗能力，是雷达发展的新趋势。     

基于PWHT的LFM-PRBC雷达信号截获与特征提取

线性调频-伪随机二相编码调相复合调制雷达信号(LFM-PRBC)融合了两者的优点,弥补了单一信号的不足,是一种性能较好的低截获概率雷达信号,给传统雷达截获接收机带来挑战。提出了将周期Wigner Hough变换(PWHT)与相关检测相结合的方法,通过在信号的周期WignerHough域搜索峰值,检测复合调制雷达信号并实现其特征提取。通过理论分析和计算机仿真验证,该方法能实现高斯白噪声背景下低信噪比复合调制信号的截获与特征提取。     

圆极化捷变LFM脉冲压缩信号分析

针对极化捷变雷达体制，提出一种脉内线性调频、脉间圆极化编码的新型复合体制雷达信号。其信号采用脉内线性调频信号的脉冲压缩来提高距离分辨率，采用脉间圆极化编码的相关检测来提高对电子干扰的抑制能力。建立了信号的数学模型并给出具体的信号处理方案，研究了一种基于Poincare极化球上空间距离的极化解码方法。仿真结果表明，该信号体制不但具有LFM脉冲压缩信号的特点，而且伪随机编码技术和极化调制技术的结合，使其具有低截获概率，并且抗干扰性能有所提高。     

低截获概率雷达在反ESM系统中的应用

通过对低截获概率（LPI）雷达和电子支援措施（ESM）系统性能的比较,得出了LPI雷达在反雷达侦察方面存在优势,阐明了LPI雷达的定义,分析了雷达各参数对截获因子的影响,最后提出了实现LPI雷达的7种途径和国内外LPI雷达的发展趋势。     

Mutual information–based LPI optimisation for radar network

Radar network can offer significant performance improvement for target detection and information extraction employing spatial diversity. For a fixed number of radars, the achievable mutual information (MI) for estimating the target parameters may extend beyond a predefined threshold with full power transmission. In this paper, an effective low probability of intercept (LPI) optimisation algorithm is presented to improve LPI performance for radar network. Based on radar network system model, we first provide Schleher intercept factor for radar network as an optimisation metric for LPI performance. Then, a novel LPI optimisation algorithm is presented, where for a predefined MI threshold, Schleher intercept factor for radar network is minimised by optimising the transmission power allocation among radars in the network such that the enhanced LPI performance for radar network can be achieved. The genetic algorithm based on nonlinear programming (GA-NP) is employed to solve the resulting nonconvex and nonlinear optimisation problem. Some simulations demonstrate that the proposed algorithm is valuable and effective to improve the LPI performance for radar network.     

一种毫米波调频连续波探测器的研制

与传统的脉冲雷达相比,毫米波调频连续波雷达具有发射功率低、信号时宽带宽积大、距离分辨率高、无近距离盲区、低截获性等显著优点,在精确制导领域占有重要地位.本文介绍一种毫米波调频连续波探测器的研制和试验结果.该探测器采用小型化和集成化设计,具有方案设计简单合理、结构精巧、体积小、重量轻等特点,其性能指标满足系统要求.     

ESM系统与低截获概率雷达之争

阐述了低截获概率(LPI)雷达和ESM系统截获接收机的现状,讨论了ESM系统如何增加灵敏度和截获距离,以及如何采取措施使得ESM系统对雷达信号的截获更加困难。结论为任何一方都不可能长期占有优势。     

编码跳频信号的低截获性能分析

结合截获接收技术的发展,在低截获概率的基础上阐述了低利用概率的新概念,并定义了雷达信号截获利用因子.分析了目前截获接收机最为常用的解线性调频和循环谱分析2种截获处理方法,在此基础上,通过仿真对比了编码跳频信号以及其他4种低截获雷达信号的截获处理增益和截获利用因子.仿真结果表明,编码跳频信号由于其大的时带积和波形的随机性,对于解线调与循环谱两种截获处理方法,都具有良好的抗截获性能.     

Blind estimation of direct sequence spread spectrum signals inmultipath

Self-recovering receivers for direct-sequence spread-spectrum signals with unknown spreading codes are discussed in this paper. Applications include signal interception, jamming, and low probability of intercept (LPI) communications. A multirate/multichannel, discrete-time model of the spread spectrum signal is introduced, which establishes links with array processing techniques. Borrowing blind channel estimation ideas, which were originally developed in the context of fractionally spaced equalizers or receivers with multiple antennas, linear solutions are obtained that are independent of the input distribution. The signal interception problem is further studied, and a zero-forcing (ZF) receiver/equalizer is proposed to recover the transmitted data. Its performance is analyzed, and some illustrative simulations are presented     

改进灰色关联分析法在雷达低截获性能评估中的应用

针对灰色关联分析方法在计算关联度时客观性不足的问题,首先对传统灰色关联分析法进行简单介绍,通过分析提出改进方法。然后将改进方法应用于低截获雷达评估中。实际应用表明,该改进方法可为雷达低截获性能这种多指标系统的评估问题提供科学可行的方法。     

基于跳频和调制跳变的无线通信抗截获新技术研究与展望

基于跳频和调制跳交的无线通信技术,是一种有效的低截获概率通信新技术.针对通信对抗技术发展的现状,即对跳频信号的截获接收、识别技术研究已经比较成熟,为保证信息的安全传输,提出了跳频和调制跳变相结合的思想.基于软件无线电的平台,提出了完整的跳频与调制跳变系统实现方案,从体制上减少了被截获识别的概率.并通过对其关键技术的深入研究,提出了调制星座图集分割方法和插入前导序列的同步算法,提高了系统的抗截获性能并且易于工程实现.最后对该技术的发展前景与趋势进行了展望.     

一种抗扩频参数测量的低截获波形设计

针对传统通信扩频体制在统计学上具有较强的规律性而易被敌方侦测设备发现的缺点,提出了一种抗扩频参数测量的低截获波形方案.从抑制和消除通信信号中存在的可检测、可攻击统计特征的思路出发,通过引入随机过程对跳码扩频序列和码速率进行随机化控制,使输出的码速率和扩频周期时间具有非平稳统计特征和非各态历经性质,以增强低截获波形抗扩频参数测量的能力.仿真结果表明,相比于固定增益定码扩频体制,所提出的低截获波形具备码速率和扩频周期时间测量精度低的特点,且在高信噪比条件下存在较高的相对稳态误差.     

一种新的低截获概率雷达信号的设计与分析

从信号频谱、模糊函数等方面对二相编码信号、步进频率信号两种典型的低截获概率雷达信号进行了分析,提出一种脉内二相编码——脉间步进频率复合调制雷达信号,并对其优缺点进行了比较。研究结果表明,复合调制信号既能克服步进频率信号较严重的距离——多普勒耦合和相位编码信号的多普勒频移敏感的缺点,同时又具备相位编码信号的大带宽特性和步进频率信号的高距离分辨率特性,是一种较理想的低截获概率雷达信号。     

米波圆接收阵雷达

全面地介绍了一种新体制米波雷达——米波圆接收阵雷达。重点分析了该体制雷达的特点、优势，如技术体制先进，抗干扰能力强，低截获性能好等，并与萁他体制的雷达进行了比较；同时阐明了需要解决的关键技术，如圆形天线阵的设计及收、发天线的布置，数字波束形成技术，检测与跟踪，信号波形设计等。最后指出其潜在的推广应用前景。     

A distributed differentially encoded OFDM scheme for asynchronous cooperative systems with low probability of interception

Recently, Li, Hwu and Ratazzi have proposed a physical-layer security design to guarantee low probability of interception (LPI) for MIMO systems without relying on upperlayer data encryption. The proposed scheme utilizes antenna array redundancy to deliberately randomize the transmitted signals to prevent eavesdropping. Motivated by their idea, in this paper we design a physical-layer transmission scheme to achieve LPI in cooperative systems. There are two major differences in cooperative systems: 1) each relay node may have only one antenna that can not provide antenna array redundancy for signal randomization; 2) there may exist timing errors due to the asynchronous nature of cooperative systems. Considering the two differences, we propose a distributed differentially encoded OFDMtransmission scheme with deliberate signal randomization to prevent eavesdropping and exploit the available spatial and frequency diversities in asynchronous cooperative systems. We use diagonal unitary codes to perform the differential encoding in the frequency domain over subcarriers within each OFDM block, or we use general (not necessarily diagonal) unitary codes to perform the differential encoding in the frequency domain across several OFDM blocks. By some deliberate signal randomization, the eavesdropper can not detect the transmitted symbols, while the authorized receiver can perform differential decoding successfully without the knowledge of the channels or the timing errors.