Parasitic Scatterer Radiation Field Analysis Method for ESPAR Antennas

In this letter, an electronically steerable parasitic array radiator (ESPAR) antenna design method is proposed. This method achieves beam steering by analyzing the radiation field of the parasitic scatterer within the ESPAR antenna and determining the amplitude and phase of the parasitic scatterer with respect to the active element. At this time, the dc bias and varactor operating parameters are also considered adequately because they are comprised in the radiation field. A 9-element ESPAR antenna with a maximum steering angle of −47° in the E-plane, 36° in the H-plane, and −48° in the D-plane is fabricated and measured to validate the proposed method, where the fractional bandwidth reaches 8.3%, and the aperture efficiency attains 40%. Furthermore, the proposed analysis from the perspective of the radiation field of scatterers can also provide valuable insights for the design of other structures featuring active components and parasitic scatterers.

I. Introduction

Presently, the integration of Internet of Things (IoT) frameworks, including smart homes and Industry 4.0, requires antennas with beam steering capabilities to facilitate the connection of numerous wireless sensor networks (WSNs) to the Internet [1]. The beam steering antenna (BSA) enhances IoT framework efficiency by steering the radiated beam to achieve spatial division multiplexing, suppress interference, mitigate multipath fading, and improve direction-of-arrival (DoA) estimation accuracy [2]. BSAs with phased-array regimes can lead to excessive cost, energy consumption, and weight due to too many active RF channels, which can cause adjustments to IoT frameworks [3]. Therefore, pattern-reconfigurable antennas (PRAs) have emerged to simplify the number of steerable beams while significantly addressing the challenges above.