A Method of Frequency-Invariant Array Pattern Nulling by Fourier Transform

In this paper, fixed beamforming methods are discussed. We propose a way to extend existing fixed narrowband method to frequency-invariant beam pattern nulling. The narrowband method is based on a property of adaptive array, i.e. beam pattern is the sum of the weighted patterns of the array. The proposed approach is implemented as follows: we represent the frequency response of the finite impulse response filter as a function of frequency and main lobe direction of the beam pattern, next we apply the Fourier transform to find the frequency-invariant beamforming coefficients. The proposed method of pattern nulling can be implemented using real filters with finite impulse responses, as shown by numerical experiments.