Studies on Novel Anti-jamming Technique of Unmanned Aerial Vehicle Data Link

Based on the M-ary spread spectrum （M-ary-SS）, direct sequence spread spectrum （DS-SS）, and orthogonal frequency division multiplex （OFDM）, a novel anti-jamming scheme, named orthogonal code time division multi-subchannels spread spectrum modulation （OC-TDMSCSSM）, is proposed to enhance the anti-jamming ability of the unmanned aerial vehicle （UAV） data link. The anti-jamming system with its mathematical model is presented first, and then the signal formats of transmitter and receiver are derived. The receiver＇s bit error rate （BER） is demonstrated and anti-jamming performance analysis is carded out in an additive white Ganssian noise （AWGN） channel. Theoretical research and simulation results show the anti-jamming performance of the proposed scheme better than that of the hybrid direct sequence frequency hopping spread spectrum （DS/FH SS） system. The jamming margin of the OC-TDMSCSSM system is 5 dB higher than that of DS/FH SS system under the condition of Rician channel and full-band jamming, and 6 dB higher under the condition of Rician channel environment and partial-band jamming.

Pattern recognitionbased method for radar antideceptive jamming

In order to make the effective ECCM to the deceptive jamming, especially the angle deceptive jamming, this paper establishes a signal-processing model for anti-deceptive jamming firstly, in which two feature-extracting algorithms, i.e. the statistical algorithm and the neural network （NN） algorithm are presented, then uses the RBF NN as the classitier in the processing model. Finally the two algorithms are validated and compared through some simulations.

Cognitive anti-jamming receiver under phase noise in high frequency bands

This paper investigates the jamming sensing performance of the simultaneous transmit and receive based cognitive anti-jamming(SCAJ) receiver impaired by phase noise in local oscillators(LO) over fading channels. Firstly, energy detection(ED)based on the jamming to noise ratio(JNR) of the high frequency bands SCAJ receiver with phase noise under different channels is analyzed. Then, the probabilities of jamming detection and false alarm in closed-form for the SCAJ receiver are derived. Finally,the modified Bayesian Cramer-Rao bound(BCRB) of jamming sensing for the SCAJ receiver is presented. Simulation results show that the performance degradation of the SCAJ system due to phase noise is more severe than that due to the channel fading in the circumstances where the signal bandwidth(BW) is kept a constant. Moreover, the signal BW has an effect on the phase noise in LO, and the jamming detection probability of the wideband SCAJ receiver with lower phase noise outperforms that of the narrowband receiver using the same center frequency. Furthermore,an accurate phase noise estimation and compensation scheme can improve the jamming detection capability of the SCAJ receiver in high frequency bands and approach to the upper bound.

Combined algorithm of acquisition and anti-jamming based on SFT

A communication and navigation receiver is required to remove hostile jamming signals and synchronize receiving signals effectively especially for satellite communication and navigation whose resources are becoming more and more limited. This paper proposes a novel signal receiving method by combining the pro- cesses of anti-jamming and synchronization to reduce the overall computationa~ complexity at the expense of slightly affecting the detection probability, which is analyzed in detail by derivations. Furthermore, this paper introduces sparse Fourier transformation （SFT） into the proposed algorithm to replace fast Fourier transfor- mation （FFT） so as to further reduce the calculation time especially in large frequency offset environments.

Space-borne antenna adaptive anti-jamming method based on gradient-genetic algorithm

A novel space-borne antenna adaptive anti-jamming method based on the genetic algorithm （GA）, which is combined with gradient-like reproduction operators is presented, to search for the best weight for pattern synthesis in radio frequency （RF）. Combined, the GA＇s the capability of the whole searching is, but not limited by selection of the initial parameter, with the gradient algorithm＇s advantage of fast searching. The proposed method requires a smaller sized initial population and lower computational complexity. Therefore, it is flexible to implement this method in the real-time systems. By using the proposed algorithm, the designer can efficiently control both main-lobe shaping and side-lobe level. Simulation results based on the spot survey data show that the algorithm proposed is efficient and feasible.

Comparison of the Radar Receiver Anti-Jamming Circuits Performance

This paper researches on some key technologies of anti-jamming of an air-borne radar receiver, the automatic testing of AGC, IAGC and multi-filtering under one million noisy pulses by the computer simulation system. The system tests the width of the jamming pulse whose width is 100% bigger, 60% bigger and 100% smaller than the Radar signal’s respectively and show the SNR curve.

EFFICIENT DESIGN OF ANTI-JAMMING RATELESS CODING IN COGNITIVE OFDM

Efficient anti-jamming rateless coding based on cognitive Orthogonal Frequency Division Multiplexing (OFDM) modulation in Cognitive Radio Network (CRN) is mainly discussed. Rateless coding with small redundancy and low complexity is presented, and the optimal design methods of building rateless codes are also proposed. In CRN, anti-jamming rateless coding could recover the lost packets in parallel channels of cognitive OFDM, thus it protects Secondary Users (SUs) from the in-terference by Primary Users (PUs) efficiently. Frame Error Rate (FER) and throughput performance of SU employing anti-jamming rateless coding are analyzed in detail. Performance comparison between rateless coding and piecewise coding are also presented. It is shown that, anti-jamming rateless coding provides low FER and Word Error Rate (WER) performance with uniform sub-channel selection. Meanwhile, it is also verified that, in higher jamming rate and longer code redundancy scenario, rateless coding method could achieve better FER and throughput performance than another anti-jamming coding schemes.

Performance of Luby transform coded frequency hopping systems in partial-band jamming

Luby transform （LT） codes are proposed to suppress the effect of partial band noise jam- ming in frequency hopping （FH） communication systems. A decoding scheme for joint erasures of severely jammed symbols and error correction is proposed. If an uncorrectable error is detected, the receiver erases the jammed symbols and uses incremental redundancy to increase the error-correcting capability. The performance of LT codes, under power-oppressive partial band noise jamming （ PB- N J） with the additive white Gaussian noise （AWGN）, is evaluated via simulation. Even if the jam- mer spreads its high power over half of the hopping bandwidth, LT codes are shown to achieve a tar- get bit error probability of 10 -5, demonstrating their effectiveness as high-performance codes to im- prove the ability of FH systems to combat varying partial band noise jamming.

Chaff Jamming Recognition of Radar

A modified chaff jamming recognition method of radar is investigated using grey relational analysis（ GRA） based on the difference in echo correlation characteristics between a complex rigid target and chaff cloud in time domain. Slice method（ SM）,a novel modeling approach,is proposed to construct an electromagnetic scattering model of chaff cloud in a scenario with slowly moving platform that is targeted. The diffusion characteristics and echo characteristics of the chaff cloud are analyzed. The GRA of a real target and chaff cloud shows that the adjacent return waves have a good correlation for the target but a weak correlation for chaff cloud. Since the correlation degree of chaff cloud＇s echo is far lower than that of a complex rigid target＇s,the chaff jamming can be identified by setting a reasonable threshold. Simulation results are presented to verify the effectiveness of this method.

JAM-C单抗对小鼠急性坏死性胰腺炎的抑制作用

目的:观察JAM-C单克隆抗体对小鼠急性坏死性胰腺炎(ANP)模型胰腺和全身炎症的抑制作用.方法:采用雨蛙素和脂多糖联合腹腔注射的方法建立小鼠重症急性胰腺炎模型.生理盐水对照组(NS组):小鼠给予腹腔注射无菌生理盐水(10mLkg),共注射6次,间隔1h;ANP模型组(ANP组):小鼠给予腹腔注射雨蛙素(50μgkg)6次,间隔1h,末次注射后立即给予腹腔注射内毒素(10mgkg);抗小鼠JAM-C单抗处理组(anti-JAM-CmAb组):小鼠给予腹腔注射雨蛙素(50μgkg)6次,间隔1h,在首次注射30min时,予每只小鼠腹腔内注射anti-JAM-CmAb0.3mL(300μg),末次雨蛙素注射后予腹腔内注射内毒素(10mgkg).在末次注射3h后,收集血液检测血清淀粉酶和血TNF-α浓度,并收集胰腺组织称胰腺湿质量和进行组织积分分析.结果:与ANP组小鼠比较,anti-JAM-CmAb的使用明显减轻了小鼠胰腺的水肿,炎症细胞浸润,坏死和出血,病理学评分明显降低(1.9±0.1vs2.4±0.3;1.5±0.2vs2.4±0.2;1.1±0.2vs2.0±0.2;1.0±0.2vs1.8±0.2,均P<0.05).此外,ANP组小鼠的胰腺湿质量、血清淀粉酶含量和血清TNF-α浓度明显高于NS组和anti-JAM-C组(348mg±27mgvs235mg±24mg,286mg±36mg;17985UL±1064ULvs1876UL±245UL,13870UL±988UL;628ngL±48ngLvs320ngL±23ngL,58ngL±13ngL,均P<0.05).结论:anti-JAM-CmAb能有效缓解小鼠ANP模型的胰腺炎症损伤和全身炎症反应.

智能反射面辅助的抗干扰安全通信系统鲁棒资源分配算法

为了解决恶意干扰攻击、窃听和不完美信道状态信息造成的通信质量降低和安全性差等问题,该文提出一种智能反射面(IRS)辅助的抗干扰安全通信系统鲁棒资源分配算法。首先,基于合法用户的最小安全速率约束、最大发射功率约束和IRS相移约束,在非法节点不完美信道状态信息、干扰器波束成形向量未知的情况下,构建了一个联合优化基站的波束成形向量、人工噪声的协方差矩阵和IRS的相移矩阵的鲁棒资源分配问题。其次,为了求解该非凸问题,利用交替优化、Cauchy-Schwarz不等式、连续凸逼近和泰勒级数展开等方法,将原问题转化为易于求解的凸优化问题。仿真结果表明,与传统算法相比所提算法能有效提高系统安全性、降低功率开销、提高抗干扰裕度,且在一定信道误差范围内能够减低约35%的保密中断概率,具有较强的鲁棒性。

资源块间跳频的高可靠SCMA系统设计与分析

传统稀疏码分多址(Sparse Code Division Multiple Access,SCMA)系统在固定时频资源块(Resource Block,RB)上传输信息,系统性能易受到信道污染(外在干扰和信道衰落)的影响。为了解决这一问题,提出一种基于资源块间跳频(Frequency Hopping,FH)的SCMA系统(FH-SCMA系统)。借助跳频技术实现动态SCMA码字复用,使得各用户能够均匀、随机地使用所有资源块。同时,基于素数序列设计了一种动态码字正交复用的跳频策略(跳频码),提升了FH-SCMA系统容量以及抗干扰能力。该系统接收端采用对数域消息传递(MAX-log-MPA)多用户检测算法,推导了该FH-SCMA系统的理论误码率上界。对比传统的SCMA系统,该资源块间FH-SCMA系统能均匀化资源块被污染对用户性能的影响,使得每个用户的传输误码率达到可接受的程度;相比传统SCMA系统和采用完全随机跳频策略的FH-SCMA系统(干扰时频资源占比η=25%时),设计的跳频策略及FH-SCMA系统在误码平层处分别获得4 dB和8 dB的信噪比增益。

反装甲导弹导引头抗干扰能力与关键技术发展

针对反装甲导弹面临的复杂战场环境、多样化作战目标和复杂干扰环境,分析其抗干扰能力和关键技术需求。分析反装甲导弹导引头面临的干扰威胁、抗干扰特点和不足,以科学高效提升反装甲导弹导引头抗干扰能力为目标,给出相关措施与建议。结果表明,该分析可为提升反装甲导引头抗干扰能力提供参考。

高对抗强博弈场景下雷达波形设计思路

未来陆域突击作战中高对抗强博弈场景使得雷达与目标间博弈日趋激烈,雷达波形作为雷达装备的核心和基础特征,将是提高雷达对目标检测性能的关键因素。该文首先梳理高对抗强博弈场景下的军事需求和发展现状,然后从波形产生与处理、目标和环境信息参数化建模、波形博弈方法等方面展开讨论,可为雷达在复杂电磁环境下如何提升装备作战效能提供设计参考。

基于现场可编程门阵列的矩阵求逆算法设计

由于自适应抗干扰算法在更新最优权值时存在时间延时,导致很难满足动态环境下的权值更新率要求。针对该情况已有学者对如何实现快速采样矩阵求逆算法进行研究,但仍存在只适用于低维矩阵,且权值更新率慢的问题。为解决上述问题,提出了一种基于Cholesky分解的采样矩阵求逆算法实现架构。该实现架构主要包括协方差矩阵计算模块、Cholesky分解模块、计算下三角矩阵L的逆矩阵模块、三角矩阵相乘和权值计算模块。设计采用流水线加状态机实现结构有效地解决了因高阶采样矩阵求逆运算量大产生的权值更新率慢的问题。仿真结果表明,在现场可编程门阵列(field programmable gate array,FPGA)的硬件平台上,对于56阶采样矩阵,在100 MHz工作频率下,一次权值的更新时间仅需要1.2 ms。本文所提的实现架构为自适应抗干扰快速求解权值提供了一种切实可行的解决方案,对存在类似需求的权值求解系统具有一定的参考价值。

空天基合成孔径雷达多域抗干扰技术综述

合成孔径雷达(Synthetic Aperture Radar,SAR)是现代雷达技术发展的主要成就之一,具有全天候、全天时、高分辨率的特性,广泛应用于空基及天基各类平台。现代战场电磁环境日趋恶劣,电子战装备可以在多维度产生高强度、多样式和有针对性的电子干扰,极大制约了SAR作战效能的发挥,如何提高SAR抗干扰能力已成为当前国内外该领域研究热点。本文探讨了SAR常规抗干扰思路和优缺点,并以雷达信号发射和信号接收两个方面为主线,围绕空域、时域、频域、能量域、极化域以及数据处理域等多域,结合仿真和试验数据分析了典型空天基SAR抗干扰方法的实施效果,最后分析其未来的发展趋势,为以后的相关技术研究提供参考。

对瞬时测频干扰机理的研究

瞬时测频(instantaneous frequency measurement,IFM)接收机是电子侦察中非常重要的测频资源,其结构简单、灵敏度高、侦察频带宽、分辨率高,可以快速测定被测信号的频率,在现代电子战中得到广泛应用。基于IFM微波鉴相器在某一瞬间只能响应一个信号的特性,结合IFM工作原理,研究了一种新的(超过2个信号)对IFM干扰策略,并分析了干扰机理,通过模拟仿真对IFM的干扰效果进行了评估。仿真结果表明:多信号交叠可以对IFM系统产生明显的干扰效果,可以使得其无法测得正确频率,并错误地输出同时到达信号指示。

基于KM算法的转发式干扰辨识与抑制方法

转发式干扰是对截获的雷达信号进行调制后发射出去的干扰信号,它在空时频多域与目标回波存在强相关性。当雷达接收端进行信号处理时,此类干扰能够获得匹配滤波增益,形成若干个虚假目标,同时实现欺骗和压制2种干扰效果。联合频率捷变技术,利用聚类思想在脉压域实现干扰辨识与抑制。仿真实验表明,所提方法能够有效抑制干扰,且当干扰功率较大时,依然具有良好的抗干扰效果。

频率分组编码信号的相参积累算法

针对捷变频信号的相参积累处理进行研究,提出了一种基于频率分组编码信号的相参积累算法。以线性调频(Linear frequency modulation,LFM)信号为基础,构建了频率分组编码信号,使得发射信号的脉冲载频序列具有一定随机性,保证了波形的抗干扰能力。同时针对频率捷变信号相位非相参带来的主瓣展宽和旁瓣抬高问题,设计了对应编码信号的相参处理方法。首先对回波脉压后的信号进行高分辨距离补偿,然后通过速度遍历插值和距离一致性校正实现脉组内相参处理,最后利用编码信号载频序列的优势实现脉组间相参处理。在仿真实验中,对构建的编码信号相较于LFM信号在抗干扰方面的优越性进行了验证,同时验证了所提相参处理方法相较于基于压缩感知的稀疏重构算法的有效性。

散射通信自适应选频分集抗干扰性能分析

针对选频分集散射通信抗干扰性能评估准确性提升,提出了一种自适应选频分集抗干扰性能分析方法,基于抗衰落分集接收解调算法建立了选频抗干扰分析模型。通过仿真分析可获得选频分集准确的抗干扰性能,并根据不同的干扰特性得到了量化的分析结果。仿真结果表明,该自适应选频分集抗干扰分析方法优于现有的散射通信抗干扰分析方法,便捷有效,能够显著提升抗干扰性能评估的准确性。