Defected Ground Structure Multiple Input-Output Antenna For Wireless Applications

In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Electromagnetic Radiation Structures(ERS)is composed of multiple radiating elements.These MIMO antennas are designed and analyzed with and without DGS.The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size,which is 60×40×1 mm.The high directivity and divergence characteristics are attained by introducing the microstripfed lines perpendicular to each other.And the projected MIMO antenna structures are compared with others by using parameters like Return Loss(RL),Voltage Standing Wave Ratio(VSWR),Radiation Pattern(RP),radiation efficiency,and directivity.The same MIMO set-up is redesigned with DGS,and the resultant parameters are compared.Finally,the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL,VSWR,RP,radiation efficiency,and directivity.This projected antenna displays an omnidirectional RP with moderate gain,which is highly recommended for human healthcare applications.By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3,4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications.The proposed design covers numerous well-known wireless standards,along with dual-function DGS slots,and it can be easily integrated into Wireless Body Area Networks(WBAN)in medical applications.This WBAN links the autonomous nodes that may be situated either in the clothes,on-body or beneath the skin of a person.This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.

Direction-of-arrival estimation for co-located multiple-input multiple-output radar using structural sparsity Bayesian learning

This paper addresses the direction of arrival （DOA） estimation problem for the co-located multiple-input multiple- output （MIMO） radar with random arrays. The spatially distributed sparsity of the targets in the background makes com- pressive sensing （CS） desirable for DOA estimation. A spatial CS framework is presented, which links the DOA estimation problem to support recovery from a known over-complete dictionary. A modified statistical model is developed to ac- curately represent the intra-block correlation of the received signal. A structural sparsity Bayesian learning algorithm is proposed for the sparse recovery problem. The proposed algorithm, which exploits intra-signal correlation, is capable being applied to limited data support and low signal-to-noise ratio （SNR） scene. Furthermore, the proposed algorithm has less computation load compared to the classical Bayesian algorithm. Simulation results show that the proposed algorithm has a more accurate DOA estimation than the traditional multiple signal classification （MUSIC） algorithm and other CS recovery algorithms.

Target estimation using MIMO radar with multiple subcarriers

This paper analyzes the effect of waveform parame- ters on the joint target location and velocity estimation by a non- coherent multiple input multiple output （MIMO） radar transmitting multiple subcarriers signals. How the number of subcarriers in- fluences the estimation accuracy is illustrated by considering the joint Cramer-Rao bound and the mean square error of the maxi- mum likelihood estimate. The non-coherent MIMO radar ambiguity function with multiple subcarriers is developed and investigated by changing the number of subcarriers, the pulse width and the frequency spacing between adjacent subcarriers. The numerical results show that more subcarriers mean more accurate estimates, higher localization resolution, and larger pulse width results in a worse performance of target location estimation, while the fre- quency spacing affects target location estimation little.

ANALYSIS OF TRANSMIT BEAMFORMING PERFORMANCE ON MULTIPLE-TRANSMIT BINARY ZCZ WAVEFORMS

The Transmit BeamForming (TBF) technology, applied in a multiple-transmit radar system, is studied in this paper, where multiple elements of antenna array transmit binary Zero Correlation Zones Orthogonal Signals (ZCZ-OS) independently. For each Direction Of Arrival (DOA) with respect to the transmitting array, the analysis on the gain and sidelobe level of TBF output is presented. This paper focuses on the range sidelobes performance within the main beam (in angle domain). For the normal direction, due to the inherent phase property of ZCZ-OS, the TBF output has part zero sidelobes area, of which the distribution is discussed. For the other directions, a systematic search algorithm to optimize the transmission order of signals is proposed for an optimal relationship chart of DOA and transmission order. The range sidelobe performance within the main beam can be improved as the optimal transmission order is adopted.

Design of integrated radar and communication system based on MIMO-OFDM waveform

Orthogonal frequency division multiplexing (OFDM) waveform enables radar and communication functions simultaneously, which encounters low angle resolution and poor data rate for traditional single input single output (SISO) systems. To solve these problems, an integrated radar and communication system (IRCS) with multiple input multiple output (MIMO) OFDM waveform is proposed. The different limitations of radar and communication in designing such a system are investigated. Then, an optimization problem is devised to obtain suitable system parameters, including the number of subcarriers, subcarrier spacing, number of symbols, pulse repetition frequency (PRF) and length of cyclic prefix (CP). Finally, to satisfy the requirements of both radar and communication, the IRCS parameters are derived in three typical cases. Several numerical results are presented to illustrate the demands of radar and communication, inconsistent or consistent, for the IRCS parameters and the superiority of the proposed system.

User Assisted Cooperative Relaying in Beamspace Massive MIMO NOMA Based Systems for Millimeter Wave Communications

A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy efficiency for millimeter wave(mmWave)communications.A downlink system for M users,where base station(BS)is equipped with beamforming lens antenna structure having NRF radio frequency(RF)chains,has been considered.A dynamic cluster of users is formed within a beam and the intermediate users(in that cluster)between beam source and destination(user)act as relaying stations.By the use of successive interference cancellation(SIC)technique of NOMA within a cluster,the relaying stations relay the symbols with improved power to the destination.For maximizing achievable sum rate,transmit precoding and dynamic power allocation for both intra and inter beam power optimization are implemented.Simulations for performance evaluation are carried out to validate that the proposed system outperforms the conventional beamspace M-MIMO NOMA system for mmWave communications in terms of spectrum and energy efficiency.

ORTHOGONAL DISCRETE FREQUENCY-CODING WAVEFORM DESIGN FOR MIMO RADAR

Design of orthogonal code sets with ideal correlation properties is crucial for orthogonalMultiple Input Multiple Output(MIMO)radar.A modified Genetic Algorithm(GA)is proposed tonumerically design orthogonal Discrete Frequency-Coding Waveforms(DFCWs)with good correlationproperties for MIMO radar.Some of the designed results are presented,and their correlation propertiesare better than those presented in literatures.The effect of Doppler frequency shift on the performanceof these signals is simply investigated.Simulation results and comparisons show that the proposedalgorithm is more effective for the design of DFCWs with superior aperiodic correlation properties.

Adaptive time-space resource and waveform control for collocated MIMO radar with simultaneous multi-beam

Collocated multiple input multiple output(MIMO)radar,which has agile multi-beam working mode,can offer enhanced multiple targets tracking(MTT)ability.In detail,it can illuminate different targets simultaneously with multi-beam or one wide beam among multi-beam,providing greater degree of freedom in system resource control.An adaptive time-space resource and waveform control optimization model for the collocated MIMO radar with simultaneous multi-beam is proposed in this paper.The aim of the proposed scheme is to improve the overall tracking accuracy and meanwhile minimize the resource consumption under the guarantee of effective targets detection.A resource and waveform control algorithm which integrates the genetic algorithm(GA)is proposed to solve the optimization problem.The optimal transmitting waveform parameters,system sampling period,sub-array number,binary radar tracking parameterχ_i(t_k),transmitting energy and multi-beam direction vector combination are chosen adaptively,where the first one realizes the waveform control and the latter five realize the timespace resource allocation.Simulation results demonstrate the effectiveness of the proposed control method.

Fast multi-parameter estimation and localization for MIMO radar

This paper addresses the problem of four-dimensional angle and Doppler frequency estimation for bistatic multiple-input multiple-output （MIMO） radar with arbitrary arrays in spatial co- lored noise. A novel method for joint estimation of Doppler fre- quency, two-dimensional （2D） direction of departure and 2D direc- tion of arrival based on the propagator method （PM） for arbitrary arrays is discussed. A special matrix is constructed to eliminate the influence of spatial colored noise. The four-dimensional （4D） angle and Doppler frequency are extracted from the matrix and the three- dimensional （3D） coordinates of the targets are then calculated on the basis of these angles. The proposed algorithm provides a lower computational complexity and has a parameter estimation very close to that of the ESPRIT algorithm and the DOA-matrix al- gorithm in the high signal to noise ratio and the Cramer-Rao bound （CRB） is given. Furthermore, multi-dimensional parameters can be automatically paired by this algorithm to avoid performance degra- dation resulting from wrong pairing. Simulation results demonstrate the effectiveness of the proposed method.

Wideband MIMO Radar Waveform Optimization Based on Range Profile

Aiming at the signal bandwidth design problem for multi-target imaging task,a kind of multiple input multiple output(MIMO)radar waveform design method is proposed.At first,the closed-loop feedback between the range profile and the signal bandwidth,which can design the minimum bandwidth of a transmitting signal that can distinguish each scatterer of the target in range direction,is established.Then,considering the request of beam pattern and the bandwidth limitation,a waveform optimization model is established and solved.Therefore,the multi-target observation and the dynamic adjustment of the signal bandwidth are accomplished.In the end,the simulation results prove the performance of the algorithm in a low SNR circumstance.

COMPLETE PARAMETER MEASUREMENT FOR MIMO BISTATIC RADAR WITHOUT SYNCHRONIZATION

In order to measure the range, angle, and Doppler frequency of the target without any synchronization in the bistatic radar, a novel complete parameter estimation method based on separability of a pair of Linear Frequency Modulation (LFM) signal is presented. The Doppler fre-quency is measured by the time difference between two peak positions corresponding to the positive and the negative LFM return signal respectively. Direction Of Departures (DODs) and Direction Of Arrivals (DOAs) of the target are estimated by constructing a special eigenmatrix in which the es-timated angles can be extracted from the eigenvalue or the eigenvector. The target position can be located in the presence of the estimated DODs, DOAs and the signal delay difference between the echo and the directive wave signal in Multiple Input Multiple Output (MIMO) bistatic radar without any synchronization. The correctness and effectiveness of the proposed method are verified by the computer simulation.

Adaptive waveform design based on Morlet wavelet for ultra-wideband MIMO radar

For the issue of deterioration in detection performance caused by dynamically changing environment in ultra-wideband（UWB） multiple input multiple output（MIMO） radar, this paper proposes a novel adaptive waveform design which is aimed to improve the ability of discriminating target and clutter from the radar scene. Firstly, a sequence of Morlet wavelet pulses with frequency hopping and pulse position modulation by Welch-Costas array is designed. Then a waveform optimization solution is proposed which is achieved by applying the minimization mutual-information（MI） strategy. After that, with subsequent iterations of the algorithm, simulation results demonstrate that the optimal waveform design method brings an improvement in the target detection ability in the presence of noise and clutter.

MIMO雷达分组正交波形集优化设计方法

在现代电子对抗中,数字射频存储(DRFM)设备能够快速截获机载脉冲多普勒雷达信号,能够实现对多输入多输出(MIMO)雷达的干扰。MIMO雷达可基于多组相互正交的波形集来对抗DRFM干扰。同时,为最大化MIMO雷达波形分集增益,每个脉冲内发射的波形也需要正交。为了平衡组内和组间的正交性,文中建立了一种分组正交波形集优化模型,其目标函数为组内和组间相关函数性能评估指标值的加权和;为了求解该优化问题,提出了一种分组正交波形集设计方法。所提方法将原优化问题简化为p-范数优化问题,基于MM算法导出了最小化目标函数的迭代求解表达式。仿真结果表明,所提方法可通过改变权重系数来灵活平衡MIMO雷达的干扰抑制性能和距离压缩性能。

一种基于稀疏重构的多视角MIMO雷达关联成像算法研究

为改善复杂目标的成像表现、提升雷达图像的视觉效果,提出一种基于稀疏重构的多视角多输入多输出(multiple input multiple output,MIMO)雷达关联成像方法,设计了多视角雷达散射面积(radar cross section,RCS)起伏的稀疏重构关联成像模型。所提算法能提高辐射场信号随机性,改善复杂目标雷达关联成像参考信号与回波之间相关性退化的情况,减小多视角RCS起伏对相关性的影响,提升多视角下的关联成像质量。最后,通过仿真验证了所提方法的有效性。

基于延迟线组合调相的高能效自适应混合预编码方案

针对毫米波大规模多输入多输出系统采用混合预编码技术所带来的高功耗影响,基于延迟线组合调相器件设计了一种间接全连接型混合预编码系统结构,并提出一种自适应连接的混合预编码方案,可大幅减少与天线直连的调相器数量从而降低硬件造成的功耗损失。方案将编码矩阵的求解分为数字编码矩阵、模拟编码矩阵和开关组成的连接交换矩阵3个部分进行交替优化;提出一种基于互补正交投影矩阵的算法来解决模拟编码矩阵的优化;利用功率约束条件和最小二乘算法简化数字编码矩阵的求解;针对连接交换矩阵的离散组合优化问题,利用低复杂度的交叉熵算法进行优化。仿真结果表明,所提方案可以保证系统性能在接近纯数字预编码方案的同时有效提高系统的能量效率。

具有无线携能技术的MIMO-NOMA系统

用户干扰降低了毫米波大规模多输入多输出(MIMO)非正交多址接入(NOMA)系统的频谱效率和能量效率,针对这一问题,提出将无线携能技术(SWIPT)引入基于混合预编码(HP)的MIMO-NOMA系统,并设计了用户分组、混合预编码以及功率分配方案。首先,提出了簇头选择算法,以设计模拟预编码,基于等效信道相关性进行用户分组,并最大化等效信道增益设计数字预编码;其次,为追求用户间的公平性,提出一种基于二分的功率分配方案,以实现最小可达速率最大化。理论分析和仿真结果表明,信噪比(SNR)为5dB时,相较于现有的具有无限携能的正交多址方案,所提方案在全连接架构下频谱效率提升约24.8%,在子连接架构下能量效率提升约24.6%。

重叠阵元时分复用MIMO雷达多目标参数估计方法研究

针对多普勒-角度耦合和速度模糊问题,该文提出一种基于重叠阵元MIMO阵列的多目标参数估计方法。该方法基于虚拟孔径原理,在传统MIMO天线阵列中引入重叠阵元,构建重叠阵元MIMO天线阵列。通过在角度快速傅里叶变换(FFT)算法中引入循环迭代的方法估计阵列位置参数,利用重叠阵元回波信号的相位差值进行频率估计。同时,引入频谱搬移方法对速度区间进行转换,实现多目标的距离和速度估计。通过蒙特卡罗仿真实验,信噪比15 dB的条件下,解模糊正确率为100%,速度误差为0.1 m/s,角度误差为0.1°。基于城市交通场景采集的车辆数据集进行测试,测试结果表明,该方法能够实现对车辆目标的速度和角度精确估计,可满足交通雷达对车辆信息监测的实时性和准确性需求。

基于频率分集阵列小埋体检测三维形貌成像方法

频率分集阵列(Frequency Diverse Array,简称FDA)在埋体管线的探测识别与成像中具有很大优势,利用其灵活的波束控制和信号处理性能,能够摆脱传统阵列发射信号限制,灵活接收和处理复杂信号。通过发出窄带信号进而获得宽带信号探测参数,大大降低操作成本,实现高效率、高精度、高性价比三维立体成像。现如今埋体管线探测成为城市发展中不可避免的痛点,小埋藏体检测成像更是难点问题。文章提出一种基于多进多出技术(Multiple-Input Multiple-Output,简称MIMO)的频率分集阵列三维合成孔径雷达(3D-FDA-MAR)成像方法,并将MIMO阵列引入频率分集阵列实现三维成像,建立了MIMO-FDA三维形貌成像模型。该多进多出频率分集阵列在三维空间中能够随平台运动而运动,在沿航向处得到综合孔径,根据切航向阵列能够获得仿真频率分集阵列平面,从而得到目标物成像的三维立体效果,实现精准定位,全空间透视探测,智能3D成像,小埋藏体的精准检测诊断。

GDS-MIMO-OFDM雷达通信一体化波形设计

针对正交频分复用(OFDM)雷达通信一体化波形存在的通信速率较低、自相关旁瓣较高的问题,提出了一种基于Gold码扩频的多输入多输出-正交频分复用(MIMO-OFDM)雷达通信一体化波形。将MIMO-OFDM与扩频序列相结合,利用相关性较好的Gold码对通信信息进行扩频,再与OFDM脉冲符号进行调制,进而设计出一种既能提高通信速率又能改善雷达性能的一体化波形。仿真实验证明,较相同仿真条件下的Gold-OFDM、脉冲压缩-正交频分复用(PC-OFDM)一体化波形而言,所设计的一体化波形的通信速率能够倍数提高且可以在不影响通信性能的前提下降低信号模糊函数的旁瓣,从而改善一体化系统的雷达性能。

存在幅相误差时二维稳健超分辨测角算法

针对4D车载毫米波雷达在俯仰与方位维角度分辨力较低、阵列存在幅相误差时测角有偏的问题,提出一种基于快速稀疏贝叶斯学习的稳健二维超分辨测角方法。首先,利用空域稀疏性特点,对角度域空间进行栅格划分,构建了存在幅相误差时的二维超分辨测角信号模型;然后,通过固定点更新的MacKay SBL重构算法实现了多个邻近目标二维角度估计,并利用基于向量点乘的自校正算法对相位误差进行估计,以对有偏的角度估计进行修正;最后,给出了多输入多输出虚拟阵列下的二维角度估计的克拉美-罗界,并分析了所提算法的计算复杂度。仿真结果表明,在大陆ARS548雷达实际12发16收天线布局下,通过对比6种超分辨测角算法,所提方法在低信噪比、少量快拍下和幅相误差较小时,具有较高的角度分辨力与较低的均方根误差。