Antenna bandwidth engineering through time-varying resistance

TL;DR

This paper introduces a novel method of bandwidth engineering for small antennas by using slow time modulation of resistive elements, creating a virtual impedance to enhance multi-frequency matching and radiation.

Contribution

The paper presents a new technique of using time-varying resistance to control virtual impedance, overcoming traditional size limitations for antenna bandwidth.

Findings

Enhanced antenna bandwidth through time-varying resistance.

Experimental validation shows improved radiation of broadband signals.

Virtual impedance control enables multi-frequency matching.

Abstract

Operational bandwidth of resonant circuits is limited by the resonator's size, which is known as the Chu limit. This limit restricts miniaturization of antennas, as the antenna bandwidth is inversely proportional to its size. Here, we propose slow time modulation of resistive elements to engineer bandwidth of small antennas. The temporal modulation of resistance induces virtual impedance that is fully controlled by the modulation parameters. We show how the virtual impedance can be used to optimize the frequency response of a resonant circuit, leading to enhanced matching at multiple frequencies simultaneously. We experimentally verify the proposed technique, demonstrating enhancement of radiation of a broadband modulated signal radiated by a small antenna.