空时编码阵波束域超分辨角度估计方法

空时编码阵(space time coding array,STCA)雷达通过在相邻阵元间引入时间延迟,在发射单一波形的条件下可实现全向空域的有效覆盖,工程上易于实现。针对STCA雷达体制,提出了一种基于发射维空间自由度的波束域超分辨角度估计方法。通过分析STCA多维模糊函数,设计了接收端的角度时间二维匹配滤波器,因而在接收端等效形成发射多波束,获得发射维空间自由度,进而设计相应的波束域搜索导向矢量,基于波束域多重信号分类 (multiple signal classification, MUSIC)算法实现了STCA等效发射端的超分辨角度估计。仿真结果验证所提方法的有效性。     

相关瑞利信道环境下空时编码系统性能分析

主要研究了空时编码系统在相关瑞利衰落信道和高斯噪声环境下的性能。基于Karhunen Loeve去相关变换,将相关的系统子信道系数向量投影到另一组元素间不相关的系数向量。根据所得的去相关的系数向量,得到了系统误码率的解析表达式。同时,将误码率公式表示为有利于数值计算的一元有限积分形式,推广了熟知的不相关瑞利衰落环境下的系统误码率公式。对所得理论结果进行数值仿真,结果表明相关性使系统编码增益降低1～2dB。     

基于Frobenius范数的正交空时多格形编码设计

基于Frobenius范数理论,提出了正交空时多格形编码(OST-MTCM)方法.新方法通过在编码网格图中的每个网格传输分支上引入正交码字矩阵,并采用Ungerboeck的星座图扩展和集分割思想,从而在获得满分集增益的同时,也获得优秀的编码增益.仿真结果表明,相对于原有的空时多格形编码方法,在相同的码速率和编码状态数的情况下,新方法可以获得大约1.5 dB左右的性能改善;并且,网格分支上传输码字矩阵正交性的确定极大简化了好码的搜寻过程,无需针对不同的信道衰落条件设计不同的编码方案.     

基于空时分组编码的水声MIMO通信系统仿真研究

为了提高水声信道的信道容量,将多输入多输出（MIMO）技术用于水声信道,提出一种基于空时分组编码（STBC）的MIMO通信系统。为了抵抗水声多径传播造成的频率选择性衰落,接收机采用MIMO判决反馈均衡器,结合二阶锁相环路补偿载波相位偏移,将水声信道转换为频率非选择性信道。通过计算机仿真证明了该方法的有效性,并与单输入单输出（SISO）系统以及采用空时网格编码（STTC）的MIMO系统进行了性能对比,结果表明STBC和STTC可以获得两倍于SISO的频带利用率和较低的误码率,STBC系统的误码率性能比STTC略差,但编译码计算量远低于STTC系统,更适于实际应用。     

多用户条件下利用信道信息结合发送分集的空时编码

给出了多用户条件下利用扩频结合空时编码传输信号的系统模型,然后利用多用户与基站之间的信道冗余,通过提出的天线优选模型对信道进行选择,经优选后的系统,从整体上提高了误码率性能。理论分析和仿真结果表明,该方法具有较好的性能和较强的实用性。     

空时分组编码的MC-CDMA下行链路性能分析

将MC-CDMA和空时分组编码相结合,构建出一种新的MCCDMA系统下行链路方案(ST-MC-CD-MA).该方案利用MC-CDMA中固有的频率分集和空时分组码的空间分集来抵抗多径,提高系统性能.详细分析了该方案的信号变换形式和处理过程,从理论上给出了系统采用最大比合并时的误码率性能.仿真结果表明,在瑞利衰落信道和较多用户条件下,该系统较传统MCCDMA具有明显的性能改善.     

空时频分组码的设计和GLRT解码算法

基于多输入多输出(MIMO)天线和正交频分多路复用(OFDM),提出了空时频分组编码方法,发射端的编码和接收端的解码都不需要信道状态信息(CSI)。利用广义似然比检验(GLRT)解码算法,导出了成对符号错误概率(PEP)上限和码的设计准则。分析表明,在频率选择性MIMO信道中,这种码能充分利用空间分集和频率分集,而且只有较低的编解码复杂性。仿真结果证实,在频率选择性MIMO信道中,提出的非相干空时频码相对空时分组码性能有很大提高。     

机载前视阵列雷达俯仰慢时间空时自适应处理

针对机载前视平面阵列雷达杂波抑制问题,提出了一种利用阵列俯仰维自由度和慢时间自由度进行空时二维自适应处理的方法。分析了该模型中杂波在俯仰多普勒平面的分布规律,通过采用多普勒频移方法补偿了杂波的距离非均匀性,与常规方位多普勒空时二维自适应处理方法不同,所提方法可以同时补偿杂波的主瓣和旁瓣。最后通过仿真实验将所提方法与三维空时自适应处理、传统方位慢时间二维自适应处理作了对比,证明了所提方法的优越性。     

利用空时二维编码抑制MIMO雷达波形互相关能量

分析了常规时域编码信号用于多输入多输出(multiple-input multiple-output,MIMO)雷达发射信号无法获得良好的波形分集性能.提出了将空时二维编码技术用于MIMO雷达发射波形设计,理论分析得出该技术能有效抑制波形的互相关能量,提高回波信号的信杂比,可获得良好的波形分集性能,并分析了空时编码技术...     

多输入多输出阵列目标方位估计方法

提出了一种主动阵列目标定向空时编码新构型,即多输入多输出(multi-input multi-output,MIMO)阵列。MIMO阵列发射不相关信号(正交信号),扫描向量是常规相控阵发射扫描向量与接收扫描向量的卷积,从而产生了虚拟阵元,扩展了阵列孔径,形成的波束图是常规发射阵波束图与接收阵波束图的乘积,因此主瓣更窄,旁瓣更低。两目标高分辨统计性能的仿真分析和实验研究表明,与常规相控阵相比,MIMO阵列具有更高的目标角度分辨率和检测性能。     

Power control scheme for multiple antenna systems with space-time coding in Rayleigh fading channels

Two optimal power control(PC) schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information(CSI) are presented.One is based on the minimization of a bit error rate(BER),and the other is based on the maximization of a fuzzy signal-to-noise ratio.In these schemes,different powers are allocated to individual transmit antennas rather than equal power in the conventional one.For the first scheme,the optimal PC procedure is developed.It is shown that the Lagrange multiplier for the constrained optimization in the power control does exist and is unique.A practical iterative algorithm based on Newton’s method for finding the Lagrange multiplier is proposed.In the second scheme,some existing schemes are included,and a suboptimal PC procedure is developed by means of the asymptotic performance analysis.With this suboptimal scheme,a simple PC calculation formula is provided,and thus the calculation of the PC will be straightforward.Moreover,the suboptimal scheme has the BER performance close to the optimal scheme.Simulation results show that the two PC schemes can provide BER lower than the equal PC and antenna selection scheme under the imperfect CSI.     

Efficient spread space-time block coding scheme in multiple antenna systems

1 .INTRODUCTIONRecently ,an intense interest has focused on wire-less systems that can provide good quality and highdata rate .Space-ti me coding is an i mportant tech-nique that can i mprove system performance at fa-ding environments by obtaining diversity gains andcoding gains in multiple antenna systems .To make multiple antenna system practical ,methods that can obtain diversity gains with mod-erate complexity and provide acceptable bit errorrate ( BER) performance are investigated i…     

空时分层结构码分多址系统的上行多用户检测

针对目前已提出的空时编码结构大多只研究单用户检测这一现状,研究了频率选择性信道下多输入多输出(MIMO)的多用户结构,并提出了一种采用V BLAST空时编码结构码分多址系统的多用户检测算法。基于发射符号的旋转不变特性和奇异值分解,得到了矢量信道冲激响应(VCIR)的盲估计,进而提出了上行信号的多用户检测器。该方法在满足系统对多用户检测性能期望的同时,还能很容易地对算法复杂度进行有效控制。仿真结果表明了该方法的有效性。     

Improved scheme with cooperative diversity based on distributed space-time block coding

An improved scheme with cooperative diversity based on distributed space-time block coding (WCD-DSTBC) is proposed, which effectively achieves diversity gains and improves the performance of the system by sharing some single-antenna users' antennas to form a virtual antenna array and combining with distributed space-time block coding (DSTBC) mode. Then the relation between the system BER and the interuser BER for WCD-DSTBC scheme is theoretically derived and the closed-form expression of BER for WCD-DSTBC system is obtained. The simulation results show that the proposed WCD-DSTBC scheme achieves distinct gains over the non-cooperative multi-carrier CDMA (MC-CDMA) system. When system BER is le-3 and interuser BER is le-3, about 2.5 dB gain can be gotten. When interuser channel state information (CSI) outgoes the users' individual CSI, about 3 dB gain is also achieved.     

Differential modulation based on space-time block codes

A differential modulation scheme using space-time block codes is put forward. Compared with other schemes, our scheme has lower computational complexity and has a simpler decoder. In the case of three or four transmitter antennas, our scheme has a higher rate a higher coding gain and a lower bit error rate for a given rate. Then we made simulations for space-time block codes as well as group codes in the case of two, three, four and five transmit antennas. The simulations prove that using two transmit antennas, one receive antenna and code rate of 4 bits/s/Hz, the differential STBC method outperform the differential group codes method by 4 dB. Useing three, four and five transmit antennas, one receive antenna, and code rate of 3 bits/s/Hz are adopted, the differential STBC method outperform the differential group codes method by 5 dB, 6. 5 dB and 7 dB, respectively. In other words, the differential modulation scheme based on space-time block code is better than the corresponding differential modulation     

基于单元位置误差的有源相控阵天线辐射和散射性能综合分析

针对有源相控阵天线雷达散射截面积(radar cross section, RCS)计算复杂,及天线单元位置误差对其RCS的影响难以估计的问题,基于天线单元的相位误差分析,建立了有源相控阵天线的结构与散射阵因子耦合模型,极大简化了有源相控阵天线RCS计算的复杂度,并在此基础上研究了天线单元位置误差对增益及RCS的综合影响。结果表明,合理降低天线单元的位置精度可以抑制有源相控阵天线的RCS。工程人员可基于此权衡辐射和散射性能,适当放宽有源相控阵天线加工及安装公差,在保证天线综合性能前提下有效减轻加工难度,降低加工成本。     

基于模拟退火算法校正天线阵列方向性误差

针对天线阵列方向性误差的校正问题,基于信号子空间的基本原理,结合模拟退火算法,提出了一种精确估计天线阵方向性的方法。该方法使用校正源少,稳定性好,即使在雷达工作、并且存在其它未知信号时,也能准确估计出天线阵的方向性。给出了应用该方法的具体步骤,通过仿真实验证明该方法的有效性。