Research On Low Interception Directional Modulation Technology Of Transmitting Arra

Recently,the directional modulation(DM)technique for wireless communication physical layer security has received extensive attention and research.In this paper,The DM methods for three kinds of arrays are researched to realize information security of low intercept probability in physical layer by modulation constellation maintaining in desired position and distorting in other undesired positions.Firstly,research on phased array DM is carried out.In order to solve the problems of large computational complexity and fixed constellation distortion in existing algorithms,a fast DM algorithm based on independent optimization of dual beams is proposed.The algorithm divides the weight coefficient vector into two parts,beam control vector and interference beam vector,which can be optimized and designed respectively and adjusted by the power utilization factor.The proposed algorithm can quickly and flexibly make tradeoffs between the link gain of the communication area and the dynamic distortion degree of the constellation diagram in the non-communication area.Then,research of frequency diverse array DM is carried out.Aiming at the problem that the phased array DM cannot realize the distortion of the modulated signal constellation diagram at the same angles and different distances,an application based on frequency diverse array transmit beamforming for secure communication is given.The method makes full use of the dependence characteristic of the angle-distance of the frequency diverse array to optimize the distance-direction modulation.Simulation results verify the feasibility of constellation maintaining in angle and distance dimensions.In addition,in view of the serious coupling problem in distance-angle for the frequency diverse array with uniform stepped frequency,two frequency nonlinear stepped schemes are given to improve the precise control capability of the desired communication area and energy utilization of the system.Finally,research of DM based on low-cost switch array is carried out.A method for generating a DM spread-spectrum signal based on switches is proposed by combining the modulation of the spread spectrum signal with the switched antenna array.The array can be realized by only one phase shifter and one transmitter.The correct spread spectrum signal is synthesized in the desired direction and the spread spectrum sequence is distorted in undesired directions by simply swithing swiches.Thus,the information cannot be demodulated even if the spread spectrum sequence is known previously.