协同多点传输中迫零预编码和天线选择技术

MIMO无线传输技术极大地提高了系统的容量，在实际通信系统中，整个网络是一个干扰受限的系统，小区间干扰对MIMO系统传输的影响是显著的，每个相邻小区的基站天线都可以看成一个干扰源．由于基站端数据处理能力的提升和回程容量的增加，多个小区协同多点传输技术引起了人们的广泛关注．目前的大部分工作都是集中于研究系统的容量（吞吐量），而在实际系统中，每个用户的接收等效信噪比（即公平性）对系统的性能如误帧率等有重要的影响．对于每个用户为单天线的情形，研究了总功率受限和每天线功率受限下采用迫零预编码的系统容量和公平性．对两种功率约束条件下的公平性进行了分析，得到了公平性算法的闭式表达式．当每个用户为多天线的情形，为了降低计算的复杂度，引入了信道范数最大的接收天线选择算法，把每个用户为多天线的情形转化成等效的每个用户单天线情形，推导的每用户为单天线的公平性算法仍然适用．仿真结果显示，采用迫零预编码的多小区协作可以使系统性能显著提升．在相同的迫零预编码下，不同的功率分配策略对系统的容量和公平性有显著的影响．和用户为单天线相比，采用天线选择算法可以提升系统的容量和公平性．考虑了用户公平性时的吞吐量和最大系统吞吐量之间的折中关系，并给出了仿真结果．     

Transmit Antenna Selection in MIMO-OFDM System Based on CO-SFBC Schemes

A transmit antenna selection (TAS) multi-input multi-output orthogonal frequency-division multiplexing (MIMO-OFDM) system based on channel-orthogonalized space-frequency block coding (CO-SFBC) schemes was proposed for better performance. Firstly,the principles and criterions for designing CO-STBC/SFBC schemes with angle feedback were proposed,and then the effect of quantization for the feedback angle information within such schemes was discussed. Meanwhile,the TAS scheme was applied to the system to further improve the overall performance.Simulation results show that the combination of the proposed CO-STBC and TAS schemes can significantly improve the system performance,which is much larger than only applying them to systems individually.     

基于压缩感知的多角度合成孔径雷达成像

多角度合成孔径雷达（syntheticapertureradar，SAR）成像是实现多SAR信息融合的重要方式．对提高成像分辨率．重构目标轮廓进而提高雷达目标检测或分类性能具有基础性价值．由于各传感器发射信号和测量位置的多样性，实现多角度SAR成像具有挑战性．如何在噪声干扰情况下快速实现多角度SAR成像是一个新问题．本文建立了基于压缩感知的多角度SAR测量模型．通过对测量矩阵的分析，证明多角度SAR测量角度范围、发射信号载频和空间采样位置是影响成像性能的关键因素，研究了目标空间离散间隔对成像质量和分辨率的影响．以上述分析为基础，本文对多角度SAR发射信号载频和测量位置进行设计，构建满足约束等距性的测量矩阵．针对测量矩阵阶次较高的问题，文章提出用分段正交匹配追踪（stagewiseorthogonalmatchingpursuit，STOMP）进行模型求解，在测量矩阵欠定严重的情况下，该算法可以迅速求得模型最优稀疏解．在实验环节．通过分析多角度SAR参数对成像性能的影响，进一步验证了本文结论．实验验证了模型和相应求解算法的有效性和鲁棒性．     

TD-HSPA+系统级的双极化天线建模及仿真分析

提出一种双极化天线的系统级建模方法,以解决TD-HSPA+系统中极化性能研究无准确天线模型的问题。并通过结合多天线方案中的PARC和S-PARC方案,对TD-HSPA+下行系统性能进行了仿真分析和研究,重点对比了市区宏小区和郊区宏小区等场景下的双极化天线配置和传统线阵天线配置性能差异。系统级仿真结果表明,在覆盖半径较小的市区,利用双极化天线组网能提供良好的系统性能,提高小区容量。     

Nonlinear RCMC method for spaceborne/airborne forward-looking bistatic SAR

In the spaceborne/airborne forward-looking bistatic synthetic aperture radar (SA-FBSAR),due to the system platforms’ remarkable velocity difference and the forward-looking mode,the range cell migration (RCM) not only depends on the target’s twodimensional location,but also varies with the range location nonlinearly.And the nonlinearity is not just the slight deviation from the linear part,but exhibits evident nonlinear departure in the RCM trajectory.If the RCM is not properly corrected,nonlinear image distortions would occur.Based on the RCM model,a modified two-step RCM compensation (RCMC) method for SA-FBSAR is proposed.In this method,firstly the azimuth-dependent RCM is compensated by the scaling Fourier transform and the phase multiplication.And then the range-dependent RCM is removed through interpolation.The effectiveness of the proposed RCMC method is verified by the simulation results of both point scatterers and area targets.     

Application of improved equivalent edge currents in synthetic aperture radar imaging

Target modeling and scattering function calculating are important prerequisites and groundwork for the synthetic aperture radar (SAR) imaging simulation. According to the difficult problems that normal methods cannot calculate the scattering function of electrically large object under the condition to wideband, an effective method of improved equivalent edge currents is presented and applied to SAR imaging simulation for the first time. This method improves calculating velocity and has relatively high precision. The concrete steps of applying the method are given. By way of the simulation experiment, the effectiveness of the method is verified.     

急倾斜煤层采空区结构特征GPR探测

急倾斜煤岩体结构和地质缺陷具有隐蔽性。历史性无序开采形成的采空区分布的不规则性严重影响安全开采。以神新小红沟煤矿急倾斜煤层开采区域空区分布规律预测与参数确定为目标。通过理论分析、GPR地面与地下立体联合探测,分析了+522水平B3和B6开采扰动范围内采空区结构特征。+522水平距五一煤矿巷道垂直距离约为35.0～35.5 m.B3巷1 214～1 232m范围内空区覆岩破坏严重,多处出现破碎区。空区下部近似椭圆,上部似半椭球体结构,且空区已联通。1 232～1 250 m范围空区及覆岩破坏严重,局部区域积水量大,为现场开采设计与灾害防治提供科学依据。     

组网雷达探测能力的并行计算与可视化方法研究

深入研究了并行计算与并行绘制相结合的并行框架构建问题。针对组网雷达探测能力的计算与可视化特点,在(PC)集群的基础上,构建了一个并行计算与可视化运行框架。该框架在并行计算中,采用八叉树分割的方法对组网雷达计算区域进行任务分配；在并行绘制中,采用sort-last的并行绘制机制。仿真试验结果表明,该运行框架能够有效地满足大规模组网雷达探测能力计算与可视化的应用需要。     

Pre-processing for time domain image formation in SS-BSAR system

A pre-processing procedure is designed for a space-surface bistatic synthetic aperture radar (SS-BSAR) system when a time domain image formation algorithm is employed. Three crucial technical issues relating to the procedure are fully discussed. Firstly, unlike image formation algorithms operating in the frequency domain, a time domain algorithm requires the accurate global navigation satellite system (GNSS) time and position. This paper proposes acquisition of this information using a time-and-spatial transfer with precise ephemeris and interpolation. Secondly, synchronization errors and compensation methods in SS-BSAR are analyzed. Finally, taking the non-ideal factors in the echo and the compatibility of image formation algorithms into account, a matched filter based on the minimum delay is constructed. Experimental result using real data suggest the pre-processing is functioning properly.     

Range walk and array rotation in space-time adaptive processing: effects and compensations

This paper proposes a unified clutter model incorporating the effects of range walk and array rotation for space-time adaptive processing (STAP) in airborne multi-channel early-warning radar. Based on this clutter model, STAP performance is then analyzed from the perspective of covariance matrix tapering (CMT). For STAP performance degradation due to array rotation, a determinate compensation method is proposed based on the CMT method. Numerical examples are provided to verify the analysis and the proposed compensation method.