Research On Anti-interference And Low Interception Technology Of Smart Antenna Beam Forming

As a key technique of wireless transceiver systems,the digital array based smart antennas,which have attracted much attention in recent years,provides many effective solutions in solving the problem of anti-interference and low-probability-of-interception caused by the openness of wireless channels.Aiming at suppressing interferences of smart antenna receiving systems in space domain,a weighted subspace based approach to adaptive beamforming with sidelobe control is developed.The method employs a subspace constraint for adaptive weight to accurately control the peak sidelobe level(PSL).By weighting the subspace,it's feasible to further achieve complex sidelobe distribution.Numerical results demonstrate that the algorithm proposed outperforms existing ones in terms of beampattern control capability and computational complexity.Then,the idea of subspace is extended to adaptive beamforming with wide-angle coverage,and an adaptive algorithm for sidelobe control under arbitrarily shaped mainlobe maintaining is proposed.At last,the mainlobe maintenance performance,the sidelobe control performance and the interference suppression performance are verified on a 19-element triangular grid smart antenna array.Aiming at lowering the probability of interception of smart antenna transmitting systems in space and time domain,two kinds of physical layer directional modulation methods are studied.Firstly,the genetic algorithm(GA)based directional modulation technique for phased array is introduced.This technique uses GA to synthesize the required phase shift of each array element to ensure that the standard constellation pattern is formed only along the desired communication direction,and the constellation patterns along all other directions are distorted.So it's difficult for eavesdroppers to recover information;Then,a transmitting multi-beamforming approach for the analysis and synthesis of directional modulation is proposed.The transmitter simultaneously emits two beams: beamsteering beam and interference beam.The beamsteering beam is directed to the desired receiver for conveying modulated symbols,and the interference beam is orthogonal to the desired direction and randomly varies in modulation rate to distort the symbols along undesired directions.Bit error rate simulations indicate that the directional modulation array possesses superior security than the conventional beamforming array.