Studies On The Radiation Manipulation Mechanism And Information Perception Application Fundamentals Of Four-dimensional Antenna Arrays

Array antennas are widely used in various wireless systems due to their high gain and flexible beamforming capability.With the increasingly complex electromagnetic environment,modern wireless systems have put forward more and more stringent requirements to antenna array design.Conventional phased arrays can only manipulate the radiation distribution in space domain by adjusting the amplitude and phase excitation of each radiation element,but cannot manipulate the radiation distribution in the time-frequency domain.Therefore,conventional phased arrays are more and more difficult to be used to cope with radiation manipulation problems in complex electromagnetic environments.On the other hand,the complex electromagnetic environment have also driven the wireless systems to develop towards the multi-functional integration of radar,communication,electronic countermeasure,etc.While focusing on the front end of a wireless system,it is not difficult to find that the performance of separated multi-antenna systems is usually mutually restricted with limited reliability,huge volumes,and high costs,etc.Therefore,it is an urgent requirement of modern electronic systems to increase the design degrees of freedom(Do Fs)of antenna arrays so that a signle array can simultaneously perform functions such as radar,communication,electronic countermeasure,etc.By introducing “time” as the design degree of freedom of the fourth dimension,the four-dimensional(4-D)antenna arrays can be used to regulate radiation in the space,time and frequency domains,simultaneously.Through joint space-time modulation signals,4-D arrays are able to realize simultaneous multi-beam scanning which cannot be achieved by traditional phased arrays.In addition,they can also reconstruct the electromagnetic characteristics in real-time according to specific application scenarios.In this way,4-D antenna arrays can meet the requirements of modern electronic systems,such as the miniaturization,intelligence,and multi-function integration of the antenna systems.This dissertation is focused on the radiation manipulation mechanism and the application of information perception of 4-D antenna arrays,promoting the basic research of the 4-D antenna arrays in the radar,communication,and integrated radar-communication systems.The main contents and innovation points are summarized as follows:1.The radiation manipulation mechanism and time-varying characteristics of the4-D antenna arrays through the space propagation are analyzed.In this dissertation,the radiation manipulation nature of 4-D antenna arrays to space,time,and frequency domains is described in detail.The radiation characteristics of 4-D antenna arrays are revealed,which are related to time,range and angle.In addition,based on the 4-D antenna theory,the time-modulated frequency diverse arrays(FDAs),which have attracted much attention in recent years,are introduced through time-modulated frequencies.Then,the propagation mechanism of radiation under typical conditions is analyzed in detail,and the accurate signal models are established.It is of great significance to understand the radiation nature of 4-D antenna arrays and promote their practical applications.2.The high-efficiency radiation control capability of 4-D antenna array is used to effectively improve the anti-interception and detection capability of the low probability of intercept(LPI)radar system.Traditional phased array radars cannot effectively regulate the radiation in free space to deal with the interception by the adversary.Aimed at this issue,this dissertation firstly proposes an LPI signal transmission approach by pseudo-randomly modulating the antenna elements,thereby pseudo-randomly distorting the radiation in the undesired directions.In this way,it is difficult for the adversary to recognize the original signals in undesired directions.On the other hand,traditional phased arrays can only generate a single beam for scanning a single target at the same time.When multiple targets are needed to be dealt with,the phased array needs to scan the beam between multiple targets at high speed.Therefore,this approach is difficult to deal with high-speed maneuvering targets or weak targets effectively.To solve this problem,based on the LPI signal transmission approach of 4-D arrays,a simultaneous multi-target detection method is further proposed in this dissertation,which can be used to generate multiple beams simultaneously to deal with multiple radar targets in space on the premise of maintaining good LPI capability.Finally,an experimental platform was built to verify the effectiveness of the proposed approach.3.The application of 4-D antenna arrays in wireless physical layer security communication has been systematically studied,which further improves the security and transmission efficiency of the wireless communication system.It is difficult for the traditional directional modulation techniques to manipulate the spatial distribution of radiated energy while maintaining the directional modulation capability.To solve this problem,a hybrid beamforming and directional modulation approach based on 4-D antenna arrays is proposed in this dissertation.This approach can be used to effectively control the spatial distribution of the radiated energy while distorting the radiation characteristics in undesired directions.Consequently,it is difficult for eavesdroppers to detect and identify the signals,which greatly improves the physical layer security in the wireless communication systems.On the other hand,aiming at the low radiation efficiency of traditional directional modulation techniques,a physical layer secure communication approach based on joint space-time modulation is proposed in this dissertation.The approach makes full use of the space-time freedom of the antenna arrays.Thus,it can be used to improve the radiated signal gain of the antenna system in the desired direction,while maintaining good physical layer transmission security.In addition to numerical simulations,the experimental platforms are fabricated to verify the effectiveness of the two proposed approaches in this dissertation.4.Based on the multi-dimensional radiation control capability of the 4-D antenna array,the approach of integrating radar sensing and wireless communication functions is deeply studied.The performance of separate radar and communication systems usually restricts each other with the relatively large quality/volume/power consumption,the difficult maintenance,and the insufficient LPI performance.By combining 4-D antenna array design and integrated radar-communication waveform design,a radar communication integrated approach based on 4-D antenna arrays is proposed.Through this approach,radar sensing and wireless communication have been integrated into a single 4-D antenna array simultaneously.In addition,with the high design degrees of freedom of the 4-D antenna arrays,the proposed approach can also provide an excellent LPI capability.Finally,through numerical simulation and experimental measurement,the rationality and feasibility of the proposed approach are verified.