Digital Signal Processor-Based Broad Null Beamforming for Interference Reduction

Abstract

Shaping the radiation pattern of an antenna array to null the reception (or radiation in the case of transmitting antenna) in the direction of undesired interferences has become essential in the environment of electromagnetic interferences. This paper proposes a digital signal processor-based method using space-selective digital filter with Blackman window to nullify the broad interferences of a linear array along with its implementation. Convolution between array weight vector and filter coefficients of digital filter is performed to obtain the desired beam pattern. The cutoff points of the filter and hence the array weight vector are updated adaptively so as to obtain the desired attenuation in the vicinity $(\pm \Delta \varphi _{\mathrm{i}})$ of mean broad interfering direction $(\varphi _{\mathrm{i}})$. The even symmetry of the modified weight vector about its center is utilized to minimize the computational burden. The proposed model offers advantages such as more than 80-dB attenuation to broad interferences and lesser computational time with respect to conventional processor. Numerical results are presented to justify the performance of the proposed method for nullifying the interferences that are arriving over a nulling range between $[\varphi _{\mathrm{i}}-\Delta \varphi _{\mathrm{i}}]$ and $[\varphi _{\mathrm{i}}+\Delta \varphi _{\mathrm{i}}]$. The vicinity $(\pm \Delta \varphi _{\mathrm{i}})$ considered in the proposed model varies between $1^{\circ }$ and $8^{\circ }$. Exhaustive performance analysis is also provided with different directions of arrivals and desired attenuations for effective suppression of interference.