Beamforming with hybrid reconfigurable parasitic antenna arrays

TL;DR

This paper introduces a circuit-theoretic model for hybrid reconfigurable parasitic antenna arrays, addressing physical realizability and mutual coupling challenges, and proposes a closed-form solution for beamforming weights that enhances energy efficiency.

Contribution

It develops a comprehensive model and optimization method for reconfigurable parasitic arrays, overcoming non-linearity issues and enabling practical, energy-efficient beamforming.

Findings

The model is validated through electromagnetic simulations.

The closed-form solution simplifies parasitic reactance tuning.

Hybrid arrays outperform conventional architectures in energy efficiency.

Abstract

A parasitic reconfigurable antenna array is a low-power approach for beamforming using passive tunable elements. Prior work on reconfigurable antennas in communication theory is based on ideal radiation pattern abstractions. It does not address the problem of physical realizability. Beamforming with parasitic elements is inherently difficult because mutual coupling creates non-linearity in the beamforming gain objective. We develop a multi-port circuit-theoretic model of the hybrid array with parasitic elements and antennas with active RF chain validated through electromagnetic simulations with a dipole array. We then derive the beamforming weight of the parasitic element using the theoretical beam pattern expression for the case of a single active antenna and multiple parasitic elements. We show that the parasitic beamforming is challenging because the weights are subject to coupled magnitude and phase constraints. We simplify the beamforming optimization problem using a shift-of-origin transformation to the typical unit-modulus beamforming weight. With this transformation, we derive a closed-form solution for the reconfigurable parasitic reactance. We generalize this solution to the multi-active multi-parasitic hybrid array operating in a multi-path channel. Our proposed hybrid architecture with parasitic elements outperforms conventional architectures in terms of energy efficiency.