Adaptive beamforming system for radio-frequency interference rejection

Results from an experimental antenna array that is processed adaptively to cancel external radio-frequency interference are presented. The eight-element array has been tested in a far-field anechoic chamber. The adaptive beamformer rejects sidelobe and main-lobe interference by up to 37 dB. A conventional Fourier beamformer rejects interference only in the sidelobes by between 13 and 30 dB depending on the location of the interference within the array´s sidelobes. The adaptive beamformer does not need any a priori knowledge about the interfering signals such as the number of interferers or their direction of arrival. The adaptive beamformer also has superior angular resolution to the Fourier beamformer. With an aperture of 4.4 wavelengths and an input signal-to-noise ratio of 37 dB, the adaptive beamformer´s resolution is as low as 0.28° while the Fourier beamformer´s resolution is 8.8