Performance of broadband adaptive digital beamforming in communication

In this paper the bandwidth performance of a broadband adaptive array is investigated. We carry out simulations based on a linear array with K elements, where each element is followed by a tapped delay-line with L taps. It is shown that by using multi-frequency constraints with the method of Minimum Variance Distortionless Response (MVDR), we get a plateau in the frequency response (relative bandwidth ¿ 20%) at signal direction and adaptive nulling of the wideband interference. We present a bandwidth controllable signal and interference model for carrying out simulations and discuss the method for choosing the frequencies to obtain a distortionless response. Graphs showing array gain and interference attenuation versus INR (interferenceto-noise ratio ) are given, which show the feature of adaptive rejection of interference. Theoretically we prove that any full rank transform between tap samples and weights is not able to improve the bandwidth performance of MVDR. The comparison is made between the bandwidth related characteristics for wideband and narrowband adaptive beamforming.