Synthesis of Adaptive Interpolated Beamformer

Abstract

In this paper, synthesis of Adaptive Interpolated Beamformer (AIB) which is an adaptive version of Spatially Interpolated Beamformer is introduced. The AIB consists of a sparse beamformer whose weights are updated using Steepest Descent Constant Modulus Algorithm (SD-CMA). The spatial interpolation produces grating lobes which are eliminated using a spatial masking filter. Two forms of AIB are synthesized, one uses Chebyshev spatial masking filter and the other uses Type-I spatial masking filter. Update expression for weight vector of AIB is derived. AIB achieves superior adaptability and spatial discrimination with narrow beamwidth and produces deeper nulls in the direction of interferences with fewer physical antenna elements compared to conventional SD-CMA adaptive beamformer. Simulation studies demonstrate AIB using Type-I spatial masking filter offers better nulling of interferences because of its superior tapering sidelobe characteristics compared to Chebyshev masking filter. AIB is suitable in beamforming applications where very narrow beam is required employing less number of antenna elements.