Study Of Adaptive Beamforming Algorithm

An adaptive antenna is a collection of sensor elements whose outputs are combined by an iteratively adjusted weight vector so as to pass a desired signal with minimum distortion while rejecting interfering signals. In particular, a key assumption is that the interfering signals are not coherent with the desired signal. But in practice, coherent interference can arise when multipath propagation or "smart" jammers is present. The coherent interfering signals can cause "signal cancellation" phenomena, which can make many excellent adaptive beamforming algorithm ineffective. The aim of the paper is to reject the coherent interfering signals.Firstly, the paper discusses the essential problems of the adaptive antenna. Then, we study a new faster adaptive beamforming algorithm under the base of the analysis for the conventional adaptive beamforming algorithm. We put the emphases of the paper in the rejecting of coherent interfering signals. The paper analyses the conventional method rejecting coherent interfering signals, which is spatial smoothing technique. It includes forward spatial smoothing technique and forward/backward spatial smoothing technique. Combining the faster adaptive beamforming algorithm, we study the application under coherent and noncoherent interfering signals. Lastly, we discuss two new techniques which can reject coherent interfering signals,that is, the random weighted combining technique and the array correlation matrix reconstruction technique. Combining the faster adaptive beamforming algorithm, the paper gives the applications of the two new techniques. The computer simulation show the preferable result. And, we also compare the three techniques by the computer simulation.