【作者】 熊杰；

【导师】 王文钦；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2018， 博士

【摘要】 与传统的相控阵雷达(Phased Array,PA)相比,频控阵(Frequency Diverse Array,FDA)雷达在每个天线上使用不同的发射频率,每个频率之间有一个固定的频率间隔。由于这个频率间隔的存在,频控阵波束的能量分布不再只与角度有关,同时也与距离有关,从而形成了距离和角度双重依赖的波束方向图。因此,拥有较高自由度的频控阵雷达在目标识别、抑制干扰和射频隐身等方面有较大潜力。本文基于频控阵距离和角度依赖的波束图,对频控阵发射波束形成及其应用方法进行深入研究,主要包括基于频控阵的距离-角度去耦合发射波束形成方法以及频控阵发射波束形成在安全通信、低截获雷达以及雷达通信一体化中的应用方法等。具体研究内容和创新点如下:(1)距离-角度去耦合发射波束形成方法:针对频控阵波束图的距离角度耦合问题,本文主要提出了两种频控阵去耦合方法,第一种方法采用了单载波发射模型,通过对每个阵元上的频率偏移重新编码,打乱其原有线性递增关系,利用优化算法得到新的频率偏移矢量,使频控阵形成点型波束图。第二种方法是采用了多载波发射模型,每个阵元不再发射单一的载波,而是发射多个载波,进一步提高了频率上的自由度,通过每个频率上设计的加权矢量综合得到点型波束图,从而达到去耦合的目的。(2)频控阵发射波束形成在安全通信中的应用方法:针对传统安全通信方法只能在角度维到达安全性能,本文提出了三种基于频控阵的距离-角度维安全通信波束形成方法,第一种方法通过将频控阵代替相控阵应用于方向调制,由于频控阵带新的距离维自由度,可以增加距离维的安全性,使得传统只具备角度维调制的阵列也同时具备了距离维调制,增强了通信安全。第二种方法将频控阵结合时间调制阵列,提出了一种时间频率调制阵列,这种阵列可以通过优化射频开关时间形成距离角度依赖性的调制性能,从而实现安全通信。第三种方法将正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号与频控阵相结合,使OFDM中各个子载波将通过不同的频控阵天线发送,通过优化各个子载波的加权系数,得到了一种基于OFDM的频控阵安全通信方法。(3)频控阵发射波束形成在低截获雷达中的应用方法:针对传统相控阵雷达发射的高增益波束容易受到反雷达设备监听的安全问题,本文提出了三种基于频控阵的低截获雷达发射波束形成方法。第一种方法借鉴了LAWRENCE提出的低截获思想,利用一系列低增益的波形做时间累积得到原来高增益的波形,从而达到实现低截获雷达的目的。由于时间积累会浪费宝贵战场时间,又提出了第二种基于多个方向合成的低截获雷达发射波束形成方法,此方法可以在同一时刻发射不同方向的低增益波形,利用多径反射得到原来高增益波形。最后一种方法利用了频控阵距离依赖性特点,通过控制波束图的能量分布,使得目标处能量最小化,而接收机处能量最大化,从而达到在目标处雷达低截获性的目的。(4)频控阵发射波束形成在雷达通信一体化中的应用方法:针对雷达设备和通信设备如何有效结合的问题,本文提出了一种基于频控阵MIMO的雷达通信一体化设计方法,首先利用非线性频偏的频控阵形成去耦合的点型波束图,又利用MIMO技术发送正交波形来嵌入不同的通信符号,通过优化阵列加权矢量,使得发送不同波形时得到的波束图主瓣恒定(作为雷达功能),旁瓣随着发送波形不同而不同(作为通信功能)。由于主瓣与旁瓣的分开应用,该系统能够实现雷达通信一体化功能。更多还原

【Abstract】 Compared with conventional phased-array,frequency diverse array(FDA)transmits different carrier frequencies with a frequency increment across the array elements.Due to the frequency increment,FDA beampattern is not only related with the angle,but also related with the range.Therefore,more Degrees of Freedom(DoFs)are applied in the FDA which can provide promising potential applications in interferences suppressing,target resolution,low probability of intercept and so on.This paper introduces several transmit beamforming applications of FDA range-angle dependent beampattern,including range-angle beampattern decoupling,secure communications,low probability of radar interception,radar-communications and so on.The main contributions of this paper are summarized as follows:(1)Since the traditional FDA produces range and angle coupled beampattern,two kinds of methods are proposed to decouple it in this thesis.The first method uses a single carrier for each element to destroy the original linear frequency increments as binary codes,and then use the genetic algorithm(GA)to optimize their values to achieve a dot-shape beampattern.Multiple carriers for each element is used in the second method,and different weights are adopted to different carriers.Due to the additional DoF,a better dot-shape beampattern is achieved for the multiple carriers.(2)Since traditional secure communications can only guarantee the security in angle dimension,three methods for FDA secure communications are proposed in this thesis.The first method uses FDA instead of phased-array for directional modulation.It can enhance the range dimensional security.Time-modulation array(TMA)and FDA is combined in the second method to achieve secure communications,where radio frequency switches are used to control each element for on-off selection.Finally,orthogonal frequency division multiplexing(OFDM)and FDA are compared in the third method.By putting different OFDM subcarriers to different elements for transmitting and then using optimal weight on each subcarrier,range-angle dependent secure communications are achieved.(3)Since high-gain beam is accessible for anti-radar device to monitor,three methods for low probability of intercept(LPI)beamforming are proposed in this thesis.The first method is inspired by LAWRENCE’s idea and replaces traditional high-gain beam by a series of low-gain beams with nonlinear frequency increments via FDA antenna.It can reduce the system visibility and achieve the same performance as the original high-gain beam.The second method uses low-gain beams from multiple directions instead of one high-gain beam from a single direction to illuminate the targets.Compared with the first method,it can save valuable time to synthesize the original high-gain beampattern.Finally,in the third method,the range-angle dependent characteristics are utilized for generating the distinct distribution for the beam power to result in the high power for desired receiver,but low power for target.The simulation results show that these methods can effectively reduce the probability of radar interception.(4)An adaptive flexible sidelobe control method using FDA and multiple-input multiple-output(MIMO)is presented for joint radar-communications.This flexible beamforming control method uses mainlobe for radar function and sidelobe for communication function.It enables communication links to use the same pulse radar spectrum.Multiple orthogonal waveforms are used to embed communication information bits during a radar pulse at each scanning.The simulation results show that the system is effective and efficient for joint radar-communcations更多还原