空时编码联合波束形成技术研究现状分析

通过采取适当策略把空时编码和波束形成技术结合起来,可同时获得波束形成增益和分集增益,进一步改善系统性能、提高系统容量.文中分别从不同算法和天线配置结构上,分析介绍了两技术相结合的原理及特点,讨论了几个典型的空时分组码与波束形成的结合技术,分析了它们的内在机理及其优缺点,最后对该结合技术的发展趋势进行了展望.     

一种动态子信道分配MIMO-OFDM波束成形系统的信号检测算法

基于动态子信道分配的MIMO-OFDM波束成形系统可以获得比传统系统更好的误码率性能。但由于处理或者反馈时延的影响,会使得发射机利用不准确的信道状态信息发射数据,从而在数据流之间引入干扰,导致系统性能下降。通过分析时延对系统的影响,该文提出了一种改进的检测算法:通过构建等效MIMO系统模型,采用最小均方误差MIMO检测算法抑制数据流之间的干扰,并利用等效MIMO信道矩阵的特征值分解白化噪声获得等效高斯信道模型,计算编码比特的对数似然比。仿真表明,该算法相对于现有算法有2.5～4 dB的性能增益。     

多维正交天线的鲁棒波束成形算法分析

将服务质量(QoS)概念引入码分多址(CDMA)系统鲁棒波束成形(BF)的分析,通过对基站端天线阵元空间排列的调整,使接收信号同时在三维空间进行处理,使用凸优化算法对各维信号进行多目标约束优化,最终形成所需的合成发射波束模式。文中最后给出了仿真结果,并与WUSIC及MMSE算法进行了性能比较。     

An improved cyclic beamforming method for signal DOA estimation

Modulated signals used in telecommunication are cyclostationary. This property can be exploited to improve the direction of arrival (DOA) estimation performance. In this work, we propose an improved cyclic beamforming algorithm exploiting cyclostationarity. The proposed method exploits the information of both cyclic correlation matrix and cyclic conjugate correlation matrix with different cyclic frequencies. Compared with the existing methods, the simulation results show that proposed method improves substantially the signal selectivity; also it allows an increase in resolution power.     

A dual phase genetic algorithm for improved initial access in 5G millimeter wave communication

Initial access (IA) in 5G millimeter wave (mmWave) communication is the problem of establishing a directional link between the base station (BS) and the user equipment (UE). For a multiple-input multiple-output (MIMO) system, where both the BS and UE have many antennas, finding the optimal beams can be prohibitively expensive in terms of delay and computation. In this work, we propose a meta-heuristic approach which is a modified dual-phase genetic algorithm. Since it is a meta-heuristic approach, it is generic and hence does not require extensive modifications to apply to different scenarios, it also does not require context information such as prior knowledge of channel state or statistics of user behavior. The proposed method is using iterative search for the optimal beams, but switch to a different fine-grained search phase on later iterations in order to quickly converge to the local optimum. The effect of this approach is analyzed in terms of capacity achieved vs number of transmit and receive antennas at BS and UE, codebook size, outage probability, total transmitted power, and other parameters specific to this particular dual-phase method. The proposed work has shown improved performance when compared to the existing similar work done in Souto et al. (2019) in terms of capacity achieved (2.12%), reduced power consumption (8.57%), and reduced IA delay (35% to 50%).     

基于多速率滤波器组的UWB脉冲波束形成方法

在UWB脉冲信号的角度分集接收中,通常的空时处理中通道时延不易精确地控制。该文提出一种适合UWB脉冲信号的基于多速率滤波器组的波束形成方法,避开了时域处理中延迟控制的问题,同时实现了大带宽范围内的均匀一致的频率不变阵列响应。本文具体分析了进行多速率滤波的方式,其优点是滤波器设计简单,运算量与子带数目无关,同时UWB脉冲信号处理的不连续性使得其可以采用比较简单的时域插值算法。仿真实验结果证明了该文方法的可行性和有效性。     

Frequency Downconverting Fiber Grating-Based Beamformers for High-Capacity Phased Arrays

A technique is presented to remove the beat noise limitation in multibeam beam formers using a simple all-optical microwave frequency downconversion technique prior to performing the true-time delay equalization in the optical domain. The frequency conversion concept enables a significant increase in beam-number capac ity to be achieved due to the elimination of beat noise limits, and also effectively removes the power penalty due to chromatic dispersion limitations of the chirped grating units in the beamformer. The Bragg grating requirements for the frequency converting beamforming network are analyzed and show that tanh-profile apodized gratings can meet the isolation, reflectivity, and narrow bandwidth requirements. For an X-band phased array, more than a twofold increase in beam capacity is shown through the use of the frequency conversion technique with the grating-based beamformer, and the resulting beamformer has the minimum number of optical interconnects with true-time delay operation.     

Photonic Architectures for Broadband Adaptive Nulling with Linear and Conformal Phased Array Antennas

This paper presents several photonic architectures for independently steering multiple broadband nulls for linear and conformal phased array antennas. Analytic expres sions that quantify bandwidth requirements are developed and both experimental and simulation results which demonstrate the antenna system performance are presented. In a fully integrated, optimized system, null depths in excess of 50 dB across a multigigahertz bandwidth are anticipated and the critical factors that influence this performance are examined.     

恒定束宽波束形成器的设计和仿真研究

宽带恒定束宽波束形成器是基阵信号处理中的难点。本文提出一种基于均匀一致性旁瓣级的设计方法,在求出宽带信号实现恒定束宽所须的频率响应后,通过一组FIR滤波器来拟合该频率响应。该方法不仅能用于一般的等间隔直线阵,而且当阵元存在指向性且位置不精确时,也能较好地实现恒定束宽。计算机仿真表明了该方法的可行性。     

分布式卫星SAR的波束形成和多视处理成像

针对分布式卫星SAR的正侧视工作模式,该文建立了雷达信号的回波模型,提出了分布式卫星SAR中单个星载SAR的成像算法和利用波束形成和多视处理合成分布式卫星SAR图像的算法。理论分析和仿真结果表明:该算法能在不改变图像分辨力的情况下提高图像的信噪比和抑制相干斑,改善图像质量。