MIMO雷达正交多相编码信号优化

为获得较好的波形分集增益与避免波形间串扰,MIMO（Multi-Input Multi-Output）雷达一般要求发射正交信号。已有的正交相位编码信号对多普勒偏移敏感,制约了其在MIMO雷达中的应用。提出一种具有较好多普勒容限的正交多相编码信号优化设计方法,联合考虑目标静止、匀速运动和匀加速运动场景下MIMO雷达脉压输出,并将其转化为一个多目标优化问题,基于自适应克隆选择算法进行求解。最后,进行仿真实验。结果表明,相比典型的Deng编码和Khan编码,设计的多相编码信号具有更好的正交性能、更大的速度、加速度容限,更适合MIMO雷达系统应用。     

混沌理论在MIMO雷达波形设计中的应用

针对多输入多输出(MIMO)雷达波形设计的特殊要求,本文将混沌理论应用于MIMO雷达的波形设计中,设计了基于混沌序列的跳频编码波形.该编码方式省略了波形序列寻优过程,使雷达波形设计问题得到了很大程度的简化.仿真结果表明,基于混沌编码的MIMO雷达波形具备良好的正交性,并具有类似图钉形的模糊特性,是一种理想的雷达信号.     

基于混沌的调频调相的多输入多输出雷达正交波形设计

针对混沌序列单一调频或调相波形存在波形复杂度低,限制了混沌信号可预测的概率、雷达的截获概率和抗干扰性能的问题,提出了基于混沌序列将频率和相位联合调制用于波形设计的方法。首先,对雷达信号进行混沌频率编码,即将一个脉冲分成一系列子脉冲,对不同子脉冲进行不同的频率调制。同时,在每个频率编码子脉冲内对波形的每个周期使用随机产生的初始相位。仿真结果表明,联合调频调相混沌雷达信号的自相关旁瓣峰值最大值达到-24.71 dB,相比调频混沌信号或调相混沌信号,其相关性性能有所提高。实验结果表明,联合调频调相混沌雷达波形结合调相和调频的优点,既具有调相信号的功率谱平坦的特性,又具有调频信号抗噪声干扰特性,为非常理想的探测信号。     

基于FPGA的雷达目标回波模拟器的设计与分析

现代脉冲体制雷达广泛采用线性调频、非线性调频和相位编码等脉冲信号调制方式;雷达目标回波作为一种脉冲调制信号,主要与调制方式、斜率、带宽和编码形式有关;通过分析雷达目标回波特点和雷达目标回波模拟器的实现方式,提出了一种基于FPGA的雷达目标回波信号模拟器方案;该方案采用DDS模拟器方法,利用EP2C8Q208C8N实现DDS功能;仿真结果表明该方案可便捷地生成频率范围为5～40MHz相位可控的常规波形、线性调频、非线性调频和相位编码脉冲调制信号。     

数字子阵级MIMO雷达设计方法

设计并实现了一种集中式数字子阵级MIMO雷达实验系统,该系统在子阵间实现正交二相相位编码信号发射,接收端实现了子阵级发射数字多波束合成与接收数字多波束合成,有效完成了对民航飞机的观测。子阵多波束与子阵正交波形发射成倍简化了系统设计复杂度,具有良好的工程应用价值,使得MIMO雷达功能可作为数字相控阵雷达的典型工作模式在数字阵中推广应用。     

MIMO阵列正交频分发射波形模糊函数分析

多输入多输出(Multiple-Input Multiple-Output,MIMO)阵列因具有的优越性能在通信技术研究中成为信号处理界研究的热点,对发射波形设计是MIMO阵列应用的关键.建立了MIMO阵列的发射、接收信号模型,针对MIMO阵列及发射信号正交的特点,在远场窄带情况下对MIMO模糊度函数进行简化.从目标分辨力的角度出发,利用仿真分析了MIMO阵列不同发射阵元数正交频分线性调频(LFM)信号的模糊函数特点.仿真结果表明MIMO阵列的分辨能力优于常规相控阵,随着发射阵元数目的增大,系统的距离和角度分辨力有显著提高,多普勒分辨力保持不变.     

基于改进飞蛾扑火优化算法的MIMO雷达相位编码信号集设计

提出一种MIMO雷达相位编码信号集设计方法，该方法对飞蛾扑火优化算法进行改进，利用改进的飞蛾扑火算法优化相位编码信号集，提高其正交性.在改进方法中，增加对火焰的更新过程，使火焰不仅能够保存最优飞蛾位置还具有搜索最优解的功能.优化过程以自相关函数旁瓣峰值和、互相关函数峰值和，以及自相关函数旁瓣能量、互相关函数能量作为算法适应度函数.仿真实验结果表明，改进方法明显提高了飞蛾扑火优化算法的收敛速度和收敛精度，且优化得到的信号集具有较低的自相关旁瓣值和互相关值.     

多发多收SAR编码正交信号设计及性能分析

多发多收(MIMO)雷达是一种新的雷达体制,具有许多突出的优点.将MIMO技术应用于对地观测的SAR系统,将为高性能地完成高分辨率、宽测绘带成像和GMTI等功能提供有效途径.正交波形优化设计是MIMO雷达研究中的基础性关键问题.首先针对SAR应用的特点,考虑同频编码正交信号之间互相关能量影响,提出了综合积分旁瓣比指标定义.然后通过理论分析和一维数值仿真论证了同频编码正交信号综合积分旁瓣比性能无法满足SAR成像的要求;再通过数值仿真验证了失配滤波处理仍然无法改善同频编码正交信号的综合积分旁瓣比性能.最后优化设计了一组相位编码正交信号作为MIMO-SAR发射信号,通过MIMO-SAR成像和InSAR仿真试验,进一步验证了分析结论的有效性.     

噪声-相位编码复合调制一体化信号设计方法

提出了一种新型的雷达/干扰机一体化共享信号——噪声-相位编码调制一体化信号。结合高斯白噪声良好的干扰特性以及相位编码信号良好的自相关特性,在高斯白噪声的基础上,调制相位编码信号,采用二相编码信号,二者有机结合生成一种混合噪声-二相编码复合相位调制一体化信号。仿真实验结果表明,该信号既具有雷达的目标探测定位性能,同时具备干扰机的压制干扰性能,与其他一体化信号体制相比,噪声-二相编码复合相位调制波形对二相编码信号的压制干扰作用尤为明显,效果更好。     

二相编码探地雷达信号的误差分析与补偿

针对探测电雷达中产生的干扰和向位误差,研究了二相编码信号是常用的脉压雷达信号,可有效地解决雷达探测深度和距离分辨率之间的矛盾。在数学推导的基础上用探地雷达的二相编码信号以及衡量其脉压波形优劣的各项指标;分别对二相编码信号存在饱和失真和信号频谱失真的情况进行了仿真,实验数据表明二相编码信号具有良好的抗干扰性能;通过仿真分析了各种相位误差对于信号脉压波形的影响,并对探地雷达所采集的实际回波信号进行了相位误差补偿,取得了良好的补偿效果。     

Total ionizing radiation effects of 2-T SONOS for 130 nm/4 Mb NOR flash memory technology

In this paper,we have studied the total ionizing dose(TID)radiation response up to 2 Mrad(Si)of silicon-oxide-nitride-oxide-silicon(SONOS)memory cells and memory circuits,fabricated in a 130 nm complimentary metal-oxide-semiconductor(CMOS)SONOS technology.We explored the threshold voltage(VT)degradation mechanism and found that the VT shifts of SONOS cells depend on the charge state;simply programming the cell to a higher VT cannot compensate for the radiation induced VT loss.The off-state current(Ioff)increase in the SONOS cell is also studied in this paper.Both VT and Ioffdegradation would affect the memory system.Read data failures are mainly caused by VT shifts under irradiation,and program and erase failures are mainly caused by increased Ioff,which overloads the charge pumping circuit.By varying the reference current,our 4 Mb NOR flash chip has the potential to survive a radiation dose of 1 Mrad(Si)in read mode.     

An improved OFDM chirp waveform used for MIMO SAR system

Special attention has been devoted to multi-input multi-output(MIMO)synthetic aperture radar(SAR)systems in recent years.The applications of MIMO SAR systems which involve 3D imaging,highresolution wide-swath remote sensing,and multi-baseline interferometry are seriously limited to the orthogonal waveforms.Although orthogonal frequency division multiplexing(OFDM)chirp waveforms can be used for MIMO SAR systems to avoid intra-pulse interferences,there is a small frequency shift between the transmitted OFDM pulses.This vulnerable shift,which can not only affect the waveform orthogonality,but also introduce residual phase error,renders the OFDM waveforms impractical.In this paper,an improved OFDM chirp waveform which works without the mentioned shift is presented,along with the novel modulation and efficient demodulation procedures.Comparison between the improved and the conventional OFDM chirp waveforms is detailed.The influence of random noise,quantization error,and Doppler shift on the orthogonality of OFDM waveform is also investigated in this paper.Theoretical analysis and simulation results illustrate the feasibility of this waveform scheme.     

陈-Mobius多路载波数字通信系统及性能仿真

将几种常用数字波形的陈-Mobius逆变换作为多路载波数字通信系统数字输入信号的编码波形函数族,由其对二进制输入信号进行调制后直接叠加在一起在一个物理信道上进行传输;在接收端,用与各调制编码波形对应的正交的数字波形对各路信号进行同步相干解调,从而构成新的相干调制解调系统;而调制编码波形与解调波形函数族这两个函数族内部本身却是非正交的;而后应用MATALAB平台对这种新型多路载波数字通信系统进行性能仿真,在大量仿真平均的基础上,绘出了使用各函数族的系统的位错率对信噪比曲线,并与传统的相干调制解调系统的仿真结果相比较;结果表明,该系统具有更优异的抗强噪声与干扰的性能,可实现多路载波数字通信的直接叠加,节约系统的初始投资与运行费用.     

Design and performance analysis of orthogonal coding signal in MIMO-SAR

Multi-input multi-output (MIMO) radar which has evident advantages in many applications is a new radar system.Applying the MIMO technique to the earth observing synthetic aperture radar (SAR) system offers effective ways for the improvement of high resolution and wide swath imaging and ground moving target indication (GMTI) systems.Designing the optimal orthogonal waveform is a crucial problem in the research on MIMO radar.First,the index definition of synthetic integrated side-lobe level ratio (ISLR) is pr...     

基于波形分集的雷达抗欺骗干扰

提出一种基于波形分集技术的雷达抗距离欺骗式干扰方法.该方法采用Alamouti空时码的思想,利用干扰机对雷达信号的转发,通过构造一组具有频域正交性的发射波形,从而实现距离波门拖引下假目标的对消.文中分析了欺骗式干扰下回波信号模型,推导了停拖期和拖引期假目标对消的原理,最后进行了仿真实验.理论和仿真结果表明,该方法正确可行.     

OFDM wavefroms designed with piecewise nonlinear frequency modulation pulse for MIMO radar

ABSTRACT

Multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) waveform diversity design has drawn extensive attention since it has a great potential in remote sensing. The orthogonal frequency-division multiplexing (OFDM) waveform designing becomes one of the most significant tasks in MIMO SAR system. In this article, a novel piecewise nonlinear frequency modulation (NLFM) waveform is proposed. The OFDM waveform is composed of the piecewise NLFM waveforms as its subpulses, and each subpulse has a different subcarrier beginning frequency. The subpulse is centre symmetrical and can be divided into three segments. The first and third segments of the subpulse are linear frequency modulation waveforms, and the second segment of the subpulse is an NLFM waveform. A few parameters are used to control the duration and bandwidth of each segment in the subpulse. Genetic algorithm is used for the OFDM waveforms to optimize the sidelobes of autocorrelation and cross-correlation function. Compared with other OFDM waveform design methods, the proposed method is more flexible and has higher degrees of freedom and thus can yield waveforms with a better autocorrelation and cross-correlation properties. The performances of ambiguity function and cross ambiguity function are analysed to have low time delay and Doppler correlation peaks. Simulation results demonstrate the validity of the proposed method.     

Target models and waveform design for detection in MIMO radar

In this paper,we propose a general target model for multiple-input multiple-output(MIMO)radar.Two types of targets are presented.For each type of target,we develop a corresponding optimum waveform designing method to optimize detection performance.Based on Chernof-Stein lemma,we use relative entropy as the performance measure.We show that the optimum waveform designing method can obtain better detection performance than traditional orthogonal waveform designing method.     

MIMO SAR OFDM chirp waveform design and GMTI with RPCA based method

Multiple-input multiple-output synthetic aperture radar (MIMO SAR) has drawn wide attention for its increased degrees of freedom (DOFs) compared to the traditional multi-channel SAR (MC-SAR) system. The MIMO SAR system, which makes each antenna illuminate one subswath, can widen the range swath without decreasing PRF. One of the foremost tasks involved in the MIMO SAR system is the waveform design at the transmitter. Moreover, at the receiver, how to accurately separate the auto-correlation signal from the cross-correlation interferences is the other important issue. In this paper, an orthogonal frequency division multiplexing (OFDM) chirp signal designing method is firstly proposed, which is based on low cross-correlation interferences and good peak-to-sidelobe ratio (PSLR) rules. Using the designed OFDM chirp signals, the focused signal of MIMO SAR system matched the robust principal component analysis (RPCA) basic model. The moving target (sparse signal), clutter (low-rank signal) and noise (noise signal) can be separated directly. Hence, RPCA based method can be employed for ground moving target indication (GMTI) with no need for extracting the matched signal or suppressing the unmatched interferences. Extensive simulations demonstrate the effectiveness of the waveform designing method and GMTI with RPCA based method for MIMO SAR system.