星载双站SAR地面场景回波仿真

双站SAR回波仿真利用小面单元模型和Kirchhoff双站后向散射模型,给出了地面场景后向散射系数的计算方法;为了保证双站SAR精确的相位信息,在时域中模拟双站SAR回波。根据实际的DEM数据进行了计算机仿真,对仿真数据进行成像和干涉处理,结果表明,该方法能够逼真地模拟地面场景的双站散射特性和相位信息。     

基于双波长解调的光纤干涉型传声器研究

提出了一种基于双波长解调的光纤法布里-珀罗(Fabry-Perot,FP)干涉型传声器,采用归一化算法和微分交叉相乘处理(DCM)算法,实现了声信号的准确还原.在归一化算法中,利用椭圆拟合,实现了两路波长光信号的归一化,减小了激光器输出波动对光纤FP干涉型传声器输出特性的影响;在DCM算法中,通过信号处理及滤波,实现了声信号的准确输出,减小了温度等环境因素对光纤FP干涉型传声器输出特性的影响.在实验中,采用对比法,测试了基于双波长解调的光纤FP干涉型传声器的特性,结果显示器件实现了灵敏度为210 mV/Pa、频率响应为100～3 15 0 H z的声信号测量,能够很好地应用于语音识别、噪声测量、空气声探测等领域.     

一种特殊构型的双站SAR的CS实现

针对发射机位于地球同步卫星的双站SAR这种新型成像雷达体制,建立了信号的回波模型,并推导了在这一模型下的Chirp Scaling算法实现.通过大场景点阵目标的仿真证明,该算法处理速度快,无需插值即可实现对SAR原始数据的二维匹配滤波操作进而实现良好的SAR图像效果,可适用于高精度发射机位于同步卫星的双站SAR的成像处理.     

发射机固定的斜视双基地SAR的NLCS算法

针对发射机固定的斜视双基地SAR新成像雷达体制，建立了雷达信号的回波模型，推导了此模型下的非线性Chirp Scaling算法（NLCSA）。仿真证明，该算法可对双基地SAR在较大的斜视角下，不进行插值操作而实现精确的距离徙动枝正，得到聚焦良好的SAR图像，其处理速度快，非常适合斜视双基地SAR的高速并行信号处理。     

Mobile direct-sequence spread-spectrum underwater acoustic communication based on improved differential energy detector

A Doppler estimation method based on the structural features of spread spectrum signal was proposed,which could achieve real-time Doppler estimation for received spread spectrum signals by energy detecting the result of matching correlation calculation of adjacent received spreading symbols.In addition,this method made full use of the spread spectrum processing gain and could do Doppler estimation under low SNR condition.Improved differential energy detector was further proposed,which can effectively deal with the rapid carrier phase fluctuation interference caused by Doppler effect and time-varying multi-path interference by detecting the output energy of two correlators.Simulation verified the robustness of improved differential energy detector algorithm and the Doppler estimation method based on spread spectrum signal.At-sea data shows that improved differential energy detector combined with the proposed Doppler estimation method can achieve low bit error rate communication for direct-sequence spread spectrum underwater acoustic communication with large time-varying Doppler interference when SNR is ?10 dB.     

GSM辐射源雷达干扰抑制技术

全球移动通信（Global System for Mobile communication,GSM）信号已经被很多文献证明可以作为外辐射源雷达的机会照射源信号,但是在以往的研究中主要考虑抑制主基站的直达波和多径干扰.而实际上,GSM辐射源雷达不仅受到主基站的干扰,还受到其它同频基站的干扰.为了消除主基站干扰,同时抑制其它同频基站的干扰,本文提出首先利用扩展相消算法（Extensive Cancellation Algorithm,ECA）在时域上消除主基站的干扰,然后利用基于最差性能最优准则的稳健自适应波束形成在空域上对其它同频基站干扰进行抑制.最后仿真分析表明本文提出的杂波抑制方法的有效性.     

基于声表面波技术的变压器无线温度传感器信号处理方法

目前配电变压器的状态监测迫切需要一种无线无源的传感监测方式,而声表面波(SAW)传感器是满足此需求的重要技术手段之一。该文以用于变压器出线端测温的SAW传感器为研究对象,提出了一种SAW传感器回波信号处理流程,设计了信号去噪、频谱分析等信号处理环节。为解决同频信号对传感器测量带来的干扰问题,研究了基于奇异谱分析和独立分量分析的单通道盲源分离算法对SAW传感器的抗干扰作用,利用搭建的信号采集平台验证了该算法在信号分离和干扰抑制上的有效性。     

一种实用的DS信号抗干扰技术

研究了DS信号的相位谱接收方法,给出了基于加窗DFT的迭代实现算法,讨论了该算法在DS系统抑制窄带干扰中的应用。给出了该算法与常规DS信号接收方法及未加窗情况下,在不同干扰下的对比数值仿真结果。     

基于双时域傅里叶变换的相位测量算法

提出了一种双时域傅里叶变换相位提取算法。通过把一段具有两个干涉周期的时域光强信号分成多段一个周期的子段,通过两次使用傅里叶变换把相移器引入的相移频率和其他干扰频率分离出来,模拟和实验结果都证明了该算法在不提高系统复杂性和大幅度减少数据获取量的前提下显著提高了系统抗干扰能力,该方法从采集到待测物体相位的提取,完全无须人工干预,有利于实现自动化。     

非合作连续波雷达中存在强直达波和多径杂波的运动目标检测方法

研究了利用非合作商用调频照射信号的收发分置连续波无源雷达系统运动目标的检测技术.针对该系统中强直达波及多径杂波对动目标检测的干扰,提出了一种直达波和多径到达时间为整数采样迟延的杂波抑制方法和利用分数内插提高杂波对消性能的算法.在杂波对消的基础上,通过对回波信号作长时间相干匹配滤波实现对微弱运动目标的检测.基于实测数据及实时系统的处理结果验证了方法的有效性.     

Parameter estimation of weak space-based ADS-B signals using genetic algorithm

Space-based automatic dependent surveillance-broadcast (ADS-B) is an important emerging augmentation of existing ground-based ADS-B systems. In this paper, the problem of space-based ultra-long-range reception processing of ADS-B signals is described. We first introduce a header detection method for accurately determining the pulse position of a weak ADS-B signal. We designed a signal encoding method, shaping method, and fitness function. We then employed a genetic algorithm to perform high-precision frequency and phase estimations of the detected weak signal. The advantage of this algorithm is that it can simultaneously estimate the frequency and phase, meaning a direct coherent demodulation can be implemented. To address the computational complexity of the genetic algorithm, we improved the ratio algorithm for frequency estimation and raised the accuracy beyond that of the original ratio algorithm with only a slight increase in the computational complexity using relatively few sampling points.     

Automatic aircraft landing using interferometric inverse syntheticaperture radar imaging

This paper presents an interferometric processing of an aircraft's monostatic and bistatic inverse synthetic aperture radar (ISAR) signatures for automatic landing. The aircraft's squint angle in this ISAR imaging problem is near 90 degrees . We show that this extreme squint angle does not pose any problem for the ISAR Fourier-based (wavefront) reconstruction algorithm. In fact, the aircraft can be imaged accurately, and without any erroneous shifts in the cross-range domain, within the imposed theoretical resolution. Moreover, the algorithm is accurate enough such that one can utilize the phase of the ISAR monostatic and bistatic measurements for interferometric processing. The resultant interferometric ISAR image is used to detect undesirable rotations in the aircraft's orientation.     

Interaction of electromagnetic and acoustic waves in a stochastic atmosphere

In the Stanford radio acoustic sounding system (RASS) an electromagnetic signal is made to scatter from a moving acoustic pulse train. Under a Bragg-scatter condition maximum electromagnetic scattering occurs. The scattered radio signal contains temperature and wind information as a function of the acoustic-pulse position. In this investigation RASS performance is assessed in an atmosphere characterized by the presence of turbulence and mean atmospheric parameters. The only assumption made is that the electromagnetic wave is not affected by stochastic perturbations in the atmosphere. It is concluded that the received radio signal depends strongly on the intensity of turbulence for altitudes of the acoustic pulse greater than the coherence length of propagation. The effect of mean vertical wind and mean temperature on the strength of the received signal is also demonstrated to be insignificant. Mean horizontal winds, however, shift the focus of the reflected electromagnetic energy from its origin, resulting in a decrease in received signal level when a monostatic radio-frequency (RF) system is used. For a bistatic radar configuration with space-diversified receiving antennas, the shifting of the acoustic pulse makes possible the remote measurement of the horizontal wind component.     

相位解调实现低频水表面声波振幅探测

为了实现低频水表面声波振幅准确探测和时变声信号的跟踪识别,提出了一种基于相位解调的激光干涉探测方法。该方法在参考光路中引入高频载波,利用相位生成载波技术的反正切解调算法,并结合高频载波初相位和调制深度的测定,可实现水表面声波的准确识别。在实验室环境下搭建了一套水表面声波探测系统,实验结果表明:该方法对水表面声波微振幅的测量重复性不超过1 nm。同时该系统能够实时跟踪水下声源的变化,对幅度受到正弦调制的水下声源信号进行了水表面声波振幅检测,实验结果证明了该方法识别时变声信号的正确性。     

Interference alignment scheme for massive MIMO system

The performance of massive multiple-input multiple-output （MIMO） system is limited by pilot contamination. To reduce the pilot contamination, uplink and downlink precoding algorithms are put forward based on interference alignment criterion. In the uplink receiving processing, the target function aligns the pilot contamination and the interference signals to the same null space and acquires the maximal space degree of the desired signals. The uplink receiving precoding matrix is solved on maximal signal to interference plus noise ratio （SINR） criterion considering the impact of the pilot contamination on channel estimations. The uplink receiving precoding matrix is used as the downlink transmitting precoding matrix. Exploiting the channel reciprocity, it is proved that, if the uplink receiving precoding matrix achieves maximal S1NR, the identical precoding matrix can be used in the downlink transmission and acquires maximal signal to leakage plus noise ratio （SLNR）. Simulations show that the spectrum efficiency of the proposed algorithm can reach about 1.5 times higher than that of popular matched filtering （MF） precoding algorithm, and about 1.1 times higher than multi-cell minimum mean square error （MMSE） precoding algorithm. The performance of the proposed algorithm can be improved approximately linearly with the increasing of the number of antennas.     

发射阵列互耦及幅相误差校正

该文研究了基于发射方向图综合的双基地高频地波超视距雷达发射天线阵互耦、幅度及相位误差模型。根据误差模型的特点,提出一种发射天线阵列误差校正的方法。该方法利用收、发天线之间的直达波信号,采用迭代最小二乘法对发射天线阵误差进行估计。仿真结果验证了该方法的有效性。     

Rain side-scatter interference in the satellite links of the 1990s

In addition to inducing attenuation and depolarization in satellite links, scattering by rain can create intersystem interference. This type of interference was investigated extensively in the 1970s for terrestrial paths, but little has been done to study its effects on modern and future satellite links. Studies of the potential interference created by the scattering of an uplink signal into an adjacent satellite and the inverse case where a downlink signal is scattered into the earth station of an adjacent satellite system are reported. Two computation methods for the interfering power are presented. The first, based on the bistatic radar equation, takes only the first-order multiple scattering into account, whereas the second method, based on the radiative transfer equation, includes higher orders of multiple scattering     

基于复倒谱技术的无源雷达直达波提纯方法

利用民用FM广播信号为无源雷达的外辐射源时，由于信号在空间传输时产生严重的多径干扰，导致接收站获取的直达波参考信号与目标反射的回波在后继匹配滤波时出现失配现象，严重影响了雷达的目标检测性能。文中首先建立了基于FM广播外辐射源的双基地雷达模型；然后提出了一种在复倒谱域对直达波参考信号进行提纯处理后再进行匹配滤波的方法；最后给出了一个基于FM广播的外辐射源雷达实验系统，通过该实验系统采集的数据进行仿真，其结果表明了该方法与未提纯时相比，输出信噪比约有6dB的改善，在工程上有参考价值。     

稳健的宽带多径干扰抑制波束形成算法

针对传统宽带多径干扰抑制波束形成算法计算量大、稳健性差的问题,提出一种基于均匀直线阵的稳健宽带多径干扰抑制波束形成算法。当期望信号垂直入射时,该算法首先在波束旁瓣区域引入虚拟干扰源构造能量聚焦矩阵,通过主瓣宽度的迭代处理,整体控制输出波束的旁瓣级,将旁瓣区域能量聚焦到主瓣区域,实现多径干扰条件下的宽带波束形成;然后对期望信号和辅助方位角施加相位响应约束,将其扩展至期望信号非垂直入射和存在指向误差的情况,与传统宽带多径干扰抑制波束形成算法相比,在提高算法稳健性的同时大大降低了计算复杂度;最后仿真分析与实际数据验证表明,该算法能够有效的抑制多径干扰,稳健性较好且具有较高的输出信干噪比。      

非对称MIMO双向中继干扰信道的干扰对齐算法

针对非对称的多用户MIMO双向中继干扰信道,本文提出了一种简化的基于最大信干噪比的干扰对齐算法,给出了干扰对齐的可行性条件和干扰抑制方案,并分析了系统容量和自由度。本文算法的中继节点不必做复杂的信号处理,大大降低了整个系统的信号处理复杂度;同时,本文算法是基于最大信干噪比方案,与现有文献的中继迫零方案比较,大大提高了系统在中低信噪比时的容量;进一步,通过仿真验证表明,基于本文算法的K用户对双向中继干扰网络可以达到。