Research On Secure Communication Technology Based On Frequency Diversity Array

Traditional phased arrays are known for their excellent electronically controlled beam capabilities,and the concept of Frequency Diversity Array(FDA)was first proposed by P.Antonik.By introducing a tiny frequency offset between the elements of a traditional phased array,a distance-dependent transmission beam is generated,which has a higher degree of freedom.Because of the distance-angle dependence of the FDA,it has potential application prospects in radar,target recognition,and secure communications,which has caused widespread concern.With the commercialization of 5G,more application scenarios cannot be separated from wireless communication technology,so secure communication technology has attracted increasing attention.Different from the application layer encryption technology,it is of great research significance to realize the secure transmission of information at the physical layer.Firstly,we studied the range-angle dependence of FDA beam pattern,and then the implement errors of FDA and its impact on beam forming was investigated,and finally focused on the modulation physical layer secure communication techniques based on FDA.The main work of this paper is as follows:1.The main characteristics of the FDA beam: range-angle dependence,periodicity,"S" shaped beam and other characteristics are studied.Aiming at the study of the distance-angle coupling of the frequency diversity array beam,this paper proposes a distance-angle decoupling of the beam pattern based on the nonlinear frequency offset of the Chebyshev polynomial.2.Considering that the radiation characteristics of the array antenna are affected by various engineering implementation errors,which will affect the performance of the communication system.This paper analyzes the possible errors in the implementation of the FDA arrays,such as amplitude and phase errors,frequency offset errors,and array element position errors,then a mathematical model of the FDA beam pattern with errors was established.The effects of those random errors on the FDA radiation pattern and beamforming performance are statistically analyzed.Simulation results agrees well with the theoretical derivation,which demonstrates the effectiveness of the proposed derivation.3.Based on a typical FDA directional modulation communication system,this paper studies the effect of FDA array implementation errors on the performance of a directional modulation system.The effects of different errors on the performance of the communication system are studied in the range and angle dimensions,respectively,which has guiding significance for the design and implementation of directional modulation communication systems.4.The switched antenna direction modulation and spread spectrum technology is researched,and it is found that there are problems with the leakage range and the angle position of the technology.The study found that there are two reasons for the information leakage: First,the serial number of the antenna selection is related to the spreading code,which results in a despreading effect at some locations;Secondly,the existing researches on directional modulation technology based on FDA are based on linear frequency offset,which leads to directional modulation system information leakage due to the periodicity of its beam in the distance dimension.This paper proposes a new type of spread spectrum dynamic direction modulation communication system,which realizes more secure information transmission.