K-band Microstrip ESPAR Antenna Integrated into Large Array

This study introduces a novel design for a microstrip electronically steerable parasitic array radiator (ESPAR), specifically employing a 5-element cluster configuration. Each cluster is composed of a single active element and four varactor-loaded parasitic elements, enabling beam steering in the E-plane and H-plane. The reported results show a continuous steering range of 50 degrees along the E-plane, spanning from -25° to +25°. While on the H-plane the steering range goes from -40° to +40°. The operational bandwidth is approximately 13%, including the bandwidth reduction due to the beam scanning operation. The simulated peak gain of the subarray reaches 7.85 dB, corresponding to an aperture efficiency of 65%. The proposed subarray is integrated into a large array design comprising nine subarrays arranged in an interleaved triangular lattice. Notably, for each 5-element subarray, only one element necessitates phase control, leading to an 80% reduction in the number of required phase shifters compared to a standard phased array. The outcomes demonstrate a maximum scanning range of approximately 70 degrees on both E and H planes, with a maximum efficiency of 43%.