An Analytical Approach to Null Broadening

The adaptive beamforming algorithm can be used to automatically form nulls to the direction of interferences, while the incident angle will variate because of the movement of the aerocraft, which make the Signal to Interference and Noise Ratio (SINR) drop dramatically. Take linear array as example, any movement of the aerocraft will result in the variation of the incident angle. So the incident angle is modeled as a variable in uniform distribution around its center. Through analyzing with optimization theory, the null broadening weight in explicit form is obtained, which includes the deduction of a so called average matrix and calculation of a Lagrange constant. The obtained weight can be used to confront the variation of incident angle. This method is certified in simulation to be effective. As applying the weight on the array, the SINR dropping caused by variation of incident angle is avoided, which improves the robustness of anti-jam algorithm.