Modeling of nonlinearities and their effects on digital beamforming

The simulation of a 32 element digital beamforming array with a 30-dB Dolph-Chebyshev weighting and including nonlinearities showed degradation in the beam pattern when third-order intermodulation products are present at the receivers\´ outputs due to both the desired signal and the interference signal. When the interference source levels are much stronger than the desired signal, the beam pattern is not severely degraded. This seems to be valid regardless of the type of interference source present. The most important degradations in the beam pattern are seen when the interference source power level is close to the signal power level. In the case of single tone signal and interference sources, "phantom" interferences appear in the beam pattern as a consequence of the nonlinearities. The saturation or compression in receivers due to high signal levels further enhance the magnitude of the phantom lobes relative to the major or principal lobes. In the case of broadband noise interference, the beam pattern is degraded but without the appearance of definite phantom lobes.<>