Grating Lobe Reduction in a Phased Array of Limited Scanning

Amplitude and phase weighting at the subarray outputs alone causes grating lobes (GLs) in the array factor. A combined approach to disrupt the periodicity in the array is proposed to reduce the GLs. In this approach, three measures are simultaneously used. They are: (1) the optimized amplitude weighting at the subarray ports; (2) using the random subarray; and (3) the random staggering of the rows. The optimization was carried out by using genetic algorithms (GAs). The 24 (along X) times 32 (along Y) phased array was designed to verify the proposed approach. Along Y, the scan range is (-10deg, +10deg) and the subarrays are used. Along X, the scan range is (-45deg, +45deg) without using the subarrays. The comparison was done through array factor. In the whole two dimensional scan space, the simulated results show that the GL is -3.77 dB when using the conventional array, -4.28 dB when using (1) alone, -11 dB when using (2) alone, -14 dB when using (3) alone, -20 dB when using the combined approach proposed in this paper. This approach can be used for a phased array with limited scanning and for the digital beamforming antenna array with adaptive nulling.