阵列天线自适应波束合成的光学实现

相控阵天线是雷达技术的重要发展方向之一。随着雷达信号带宽和阵列单元数目的增加,光学实延时技术的采用已成为一种趋势。介绍了一种基于受激光子回波的阵列天线实延时自适应波束合成的光学结构,从理论上详细分析了其工作原理,说明了波束合成的工作过程。     

高能光纤激光器光束合成技术

高能光纤激光器光束合成技术是近年来高能激光器尤其是定向能源应用中的研究热点,可突破单根单模光纤激光的输出功率限制,为高功率高光束质量的激光武器应用奠定了理论基础。介绍了光纤激光非相干合成和相干合成的国内外研究现状,给出了非相干合成技术中光束重叠和光谱合成的基本合成原理,重点介绍了国内外多家研究机构光谱合成近年来所达到的技术水平;介绍了国内外相干合成技术的最新研究进展,对相干合成等效大口径激光阵列输出中几种不同的透射式相干合成阵列输出和反射式相干合成阵列输出的关键合成装置,以及相干合成单一孔径输出中的核心光学元件进行详细分析。最后简要对比了高能光纤激光器光束相干合成技术和非相干合成技术的优缺点和应用范围。     

受激光子回波在阵列天线波束合成中的应用研究

由于孔径效应和孔径度越时间的限制,使得传统的相控阵雷达难以实现大角度扫描和大的信号瞬时带宽.把受激光子回波技术应用于波束合成,可以克服这一难题.介绍了基于受激光子回波的光学真实延时实现原理,并分析了其在阵列天线波束合成中的应用,阐述了波束合成的实现方法.     

阵列信号波束合成的光学实现技术

波束合成是阵列信号处理的一个重要内容,随着阵列单元数目的增加,传统电子学信号处理方法面临带宽、速度和功耗的挑战,光学处理技术由于其高度的并行性和超高的带宽,是未来此问题的理想解决方法之一.介绍了波束合成的四种光学处理方法,即纤维光学技术、空间光谱技术、光折变晶体技术和相干光学,分析了它们各自的工作原理和技术特点.     

相干光学多波束形成的原理及其理论分析

相干光学多波束形成技术是根据光学的干涉与衍射原理,利用光学傅里叶变换而实现的一种新型的宽带射频多波束形成技术.扼要介绍了其工作原理,并对其建立了较为完善的物理模型,通过详细的理论推导和软件仿真,表明此结构能够形成多波束,在空域覆盖、波瓣宽度、小体积、抗电磁干扰等方面具备重要的性能优势.     

宽带阵列波束合成信号载波相位连续性分析

针对宽带阵列信号波束合成过程中波束合成信号的载波相位连续性问题,在建立阵列天线模型的基础上,介绍了一种在实际工程中易于实现的宽带阵列波束合成处理流程,同时根据信号处理流程对宽带数字信号处理过程进行了理论分析和推导。根据分析和推导过程建立仿真模型,仿真结果充分验证了宽带阵列波束合成信号的载波相位连续性。     

基于液晶相控阵阵列的激光相干合成方法

结合相干合成理论与液晶相控阵波束控制技术,提出了一种基于液晶相控阵阵列的激光相干合成方法,可以获得一维方向上一定角度范围内具有任意波束指向的合成激光。阐明了相干合成理论,并从波束指向、合成光强和波束质量三方面对合成激光进行研究。研究发现,波束指向误差的产生原因是阵列干涉项的极大值非连续,提出了通过增大阵列间距减小波束指向误差的办法,筛选得到了使合成激光的峰值光强与理论值相符的特殊波束指向点,即电极干涉项与阵列干涉项的极大值重合点。仿真表明,这种相干合成方法对激光的波束质量有提高作用。最后通过基于1×3、2×2液晶相控阵阵列的相干合成实验得到了波束指向分别为0°、0.17°、0.34°的合成激光,证明了理论分析的正确性和基于液晶相控阵阵列的激光相干合成方法的可行性。     

基于微波光子相干接收的宽带射频前端技术（特邀）

提出了一种适用于电子战应用的宽带大动态微波光子射频前端方案,通过采用双边带抑制载波及微波光子相干接收技术,能够有效改善前端的噪声系数、无杂散动态范围等。在6~18 GHz工作频带内,该射频前端无杂散动态范围达到110 dB·Hz^(2/3)、噪声系数优于8 dB、多通道幅度一致性优于±1 dB、多通道相位一致性优于±10°,实现了宽带射频信号的高性能传输,同时满足阵列光学波束需求。     

一种用于双通道跳频技术的时间调制阵列系统

基于波束形成理论和时间调制阵列天线理论,围绕着规避噪声、干扰或者多用户情况下非重复的通道,提出了一种适用于跳频技术的时间调制阵列系统,通过控制天线阵列单元的工作状态对信号进行调制.在将第一边带的波束对准于目标方向的同时,在射频端对载频进行迁移,从而达到跳频通信的目的.仿真结果表明:该时间调制阵列系统在较低运算开销下实现了预期波束指向和实时载频迁移.此外,通过利用天线单元控制时序中的未使用间隙,系统被扩展为独立工作的双通道天线系统,并提供了时序冲突时的解决策略和实验证明.     

基于阵列平移的GPS相干干扰抑制技术

基于空间平滑预处理技术的波束形成算法虽可抑制相干干扰,但会损失阵列孔径且只适用于等间隔线阵.因此,提出一种适用于圆形天线阵列的抗相干干扰的波束形成预处理方法,该方法对真实阵列进行虚拟平移得到多个虚拟阵列,求多个虚拟阵列各自的信号协方差矩阵后求平均,得到预处理后的协方差矩阵.结合功率倒置波束形成算法仿真,其结果表明此方法对相干干扰具有良好的抑制效果,并且抑制深度与算法的收敛性受平移距离的影响.     

Beam Tracking Particle Filter for Hybrid Beamforming and Precoding Systems

Because millimeter wave (mmWave) systems can span notably wide spectral bands, mmWave systems are expected to dominate fifth-generation (5G) communication systems. Due to the short wave-length of mmWave radiation, multiple-input multiple-output (MIMO) systems can use massive antennas and precoding technology to overcome signal attenuation in mmWave channels. However, the cost and power consumption of radio frequency (RF) chains would increase substantially with the number of antennas. Hence, hybrid beamforming was proposed to reduce the number of RF chains in massive MIMO systems. Hybrid beamforming involves RF beamforming matrix construction and baseband precoding matrix derivation. This study focused on the design and implementation of an algorithm for the RF beamforming matrix construction for mobile environments. Accordingly, this study presents a mixture particle filter that exploits the temporal continuity of beam clusters in a mobile mmWave channel to reduce the computational complexity of RF beamforming matrix construction. Moreover, this beam-tracking particle filter is based on parallel processing architecture to support the tracking of multiple beam clusters in the mmWave channel. Finally, the beam-tracking particle filter was implemented on a field-programmable gate array platform and was verified in a hybrid beamforming system for mmWave MIMO systems. The particle filter processor achieved a maximal throughput of 9.198k matrices/s with a clock rate of 192 MHz, which could support a speed of up to 88.5 km/h for mobile users.

     

用于被动声纳微弱目标检测的宽带最大信噪比方法

本文尝试利用匹配场处理中的能量匹配思想，对阵列波束形成进行优化，用于解决水下目标被动声纳微弱信号检测问题。首先，本文对比了基于线性非相干、MVDR非相干、线性相干和MVDR相干四种匹配场处理器的检测方法的性能，之后分析推导了线性非相干处理器的输出信噪比和输出功率，得出了在声源频谱起伏增大时线性非相干处理器的检测能力会下降的结论。为了得到更高的输出信噪比，本文提出了最大信噪比处理器，在理想情况下可以在处理带宽上达到最高的输出信噪比。最大信噪比处理器没有通过归一化消除声源的影响，而是利用声源频谱的估计值和拷贝场直接对接收数据进行匹配。本文证明了最大信噪比处理器的检测能力优于线性非相干处理器，并且通过仿真实验进一步验证了这个结论。      

Hybrid Beamforming for Massive MIMO Using Rectangular Antenna Array Model in 5G Wireless Networks

Fifth and future generation (5G and B5G) wireless networks aim to serve users with higher data rates and lower latency. Data traffic due to the rapid growth in communication has motivated the study of Multiple Input Multiple Output (MIMO) systems. They utilize multiple antennas in both transmitter and receiver sides. It is necessary to improve the existing technology to achieve fast and reliable communication. In this research work, a rectangular array antenna based hybrid beamforming in a massive MIMO model has been proposed to improve the spectral efficiency of the system. Thus channel capacity with small RF chains is used. To achieve the high signal strength in the main lobe, Chebyshev tapering has been used to suppress the side lobes signals. In this manner, the proposed Hybrid Beamforming for Massive Output MIMO has been realized with a small complexity and higher spectral efficiency. In this research work, the spectral efficiency of both proposed Hybrid and fully-digital beamforming with a different number of RF chains for a various number of antennas at the transmitter, the receiver side has been analyzed. From the simulation results, it has been observed that the proposed rectangular array antenna based Hybrid beamforming in a massive MIMO system reduces the computational complexity up to 99% as compared with conventional fully digital beamforming to achieve the same spectral efficiencies, which is a productive model for 5G wireless networks.

     

基于IAA的协方差矩阵重构稳健波束形成方法

针对小样本背景下,存在相干信号、相位及阵元位置误差,传统波束形成方法性能不佳的问题,提出了基于迭代自适应法(IAA)的协方差矩阵重构稳健波束形成方法。该方法利用IAA估计出精确的功率谱,并进一步利用IAA估计的功率重构干扰协方差矩阵。重构过程中,将积分区域缩小到三维立体环域,减少无用信息的影响,提高了干扰协方差矩阵的重构精确度。最后通过波束形成抑制干扰信号。由于IAA不依赖于信号的非相干假设,解决了相干信号存在下的方位估计和功率估计。仿真表明,所提出的方法在相干信号、少快拍、相位及阵元位置误差同时存在的情况下,相对于其他波束形成方法,具有最优的信干噪比(SINR)输出,表明该方法具有优良的抑制干扰性能。     

A Novel Receiver Architecture for DBF Antenna Array

The developments of the high speed analog to digital converters （ADC） and advanced digital signal processors （DSP） make the smart antenna with digital beamforming （DBF） a reality. In conventional M-elements array antenna system, each element has its own receiving channel and ADCs. In this paper, a novel smart antenna receiver with digital beamforming is proposed. The essential idea is to realize the digital beamforming receiver based on bandpass sampling of multiple distinct intermediate frequency （IF） signals. The proposed system reduces receiver hardware from M IF channels and 2M ADCs to one IF channel and one ADC using a heterodyne radio frequency （RF） circuitry and a multiple bandpass sampling digital receiver. In this scheme, the sampling rate of the ADC is much higher than the summation of the M times of the signal bandwidth. The local oscillator produces different local frequency for each RF channel The receiver architecture is presented in detail, and the simulation of bandpass sampling of multiple signals and digital down conversion to baseband is given. The principle analysis and simulation results indicate the effectiveness of the new proposed receiver.     

Realizing an electronically tunable reflectarray using varactor diode-tuned elements

Electronically tunable reflectarrays hold significant promise as cost effective architectures for RF beamforming applications. The successful operation of these arrays depends on the phase agility of the cells used to realize the array. This letter describes the design of an electronically tunable reflectarray based on a novel cell architecture that provides a large degree of phase agility. Experimental results demonstrating the beamforming capabilities of the array at 5.8 GHz are presented.     

Photonic RF phase shifter and tunable photonic RF notch filter

A new photonic RF phase shifter structure for phased array antennas is presented. It is based on a single dual-output modulator and two optical switches and optical attenuators. This can realize continuous phase shifting of 0/spl deg/-360/spl deg/ without altering the signal amplitude. It has the advantages of wide bandwidth, fast response time, and fine tuning resolution. Experimental results demonstrate phase shifts over a 360/spl deg/ phase range, with RF signal power changes of less than 0.2 dB, which is in close agreement with predictions. A tunable photonic RF notch filter, which is based on the new phase shifter, is also presented. Experimental results demonstrate continuous tuning of the photonic notch filter over a wide tuning range, which covers the full free spectral range, which is in good agreement with predictions.     

Chirp强度调制与近红外激光合成孔径雷达距离向处理

合成孔径激光雷达是利用同一孔径(望远镜)与目标作相对运动并采用信号处理方法来模拟孔径阵列,获得高方位(横向)分辨率的相干成像雷达.采用窄线宽的单频光纤激光光源和相干探测方法;发射光波被啁啾信号作幅度调制,接收后进行距离向脉冲压缩;激光雷达和目标相对运动引起的回波相位变化,由相关运算实现相位补偿和累加(孔径合成),以提高方位向分辨率.提出了新的工作体制:距离向啁啾信号调制在发射光波振幅(强度)上,方位向多普勒频移反映在回波光波相位(频率)上,便于解决距离向与方位向之间的耦合模糊问题.报道了中期实验成果:Chirp 射频信号调制激光强度,实现合成孔径激光雷达距离向的压缩.     

A compact digital beamforming SMILE array for mobile communications

A compact spatial multiplexing of local elements (SMILE) scheme smart antenna array with adaptive beamforming is presented. Low-noise amplifiers are implemented as switching elements to maintain a low system noise figure and allow fast switching. The switching scheme effectively reduces N RF channels to one, reducing the amount of costly RF hardware by a factor of N. The sampling rate must be higher than the signal bandwidth based on the Nyquist criterion to ensure proper restoration of the original signal. Measured data for destination of arrival estimation, beamforming, and digital data recovery demonstrate the capability and benefits of digital beamforming with this architecture.     

Coherent interference suppression with complementally transformedadaptive beamformer

This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR). Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers