Grating lobe reduction of phased array antennas using bed of nails structure
The periodic phased array antennas are popular due to their ability to steer the main beam over angle. However, after a certain angle of beam steering a grating lobe start to appear when the distance between the elements is larger than half wavelength. In many cases, these certain conditions are unavoidable. Thus, this paper presents a solution to reduce the grating lobe of phased array antennas. The proposed solution is the bed of nails (BON) structure placed along the E-plane of the antenna array where the grating lobe mainly occurs. The BON is designed and used in this paper to minimize the electric field components that produce the grating lobe. Simultaneously, it enhances the gain at the main beam direction while it is steered off-zenith. This extends the scanning ability of the antenna array over angle. The proposed solution has been implemented in this paper on an antenna array that consists of 20 elements of patch antennas placed along the E-plane with separation distance of 0.6 l. The simulation results show that the grating lobe has been attenuated by 11 dB when the main beam is steered at 40°. On the other hand, the main lobe gain has been enhanced by 2 dB.