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%.

I. Introduction

Phased array antennas represent a cutting-edge technology in the field of wireless communication and radar systems. They are characterized by their ability to electronically steer and shape antenna beams, offering a versatile and efficient means of achieving beam scanning in various application contexts. Despite their numerous advantages, phased array antennas come with certain drawbacks, primarily associated with the utilization of phase shifters. The key limitations linked to the use of phase shifters include increased complexity and cost, especially at higher frequencies where the integration of phase shifters becomes expensive. Additionally, there are higher losses attributed to the insertion loss of the phase shifters. Moreover, the phase shifters' phase range and resolution can impact the steering performance of the antenna, particularly when attempting to scan over a wide angular range with finer beam control. Additionally, phased array antennas, especially those used in high-power applications, can generate substantial heat. Managing the thermal effects of phase shifters becomes crucial to maintain system performance and reliability.