An effective method to reduce grating lobes in linear scanning phased array antennas with large element spacing of one wavelength is presented. The proposed technique is based on employing self-nulling antenna elements by simultaneously exciting the first two modes in a circular microstrip patch antenna to partially nullify the grating lobes. More importantly, a modified amplitude tapering is optimized in the array level to facilitate the grating lobe reduction for relatively wide scan angles up to ±60°. Analytical results of a 21-element linear array are fully presented, and a -22.5 dB grating lobe reduction for up to ±60° scan angles is reported using the proposed method, followed by the results of a smaller array for validation purposes.
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