Time-varying components for enhancing wireless transfer of power and information

TL;DR

This paper develops a theory for time-varying electromagnetic components and demonstrates how temporal modulation can improve wireless power transfer and antenna performance across a broad frequency spectrum.

Contribution

It introduces a comprehensive theory for physical models of time-varying circuit elements and applies it to enhance wireless power transfer and antenna systems.

Findings

Periodic modulation of mutual inductance surpasses classical transfer limits.

Time modulation improves electrically small dipole antenna performance.

Theory applicable from radio to optical frequencies.

Abstract

Temporal modulation of components of electromagnetic systems provides an exceptional opportunity to engineer the response of those systems in a desired fashion, both in the time and frequency domains. For engineering time-modulated systems, one needs to thoroughly study the basic concepts and understand the salient characteristics of temporal modulation. In this paper, we carefully study physical models of basic bulk circuit elements -- capacitors, inductors, and resistors -- as frequency dispersive and time-varying components and study their effects in the case of periodical time modulations. We develop a solid theory for understanding these elements, and apply it to two important applications: wireless power transfer and antennas. For the first application, we show that by periodically modulating the mutual inductance between the transmitter and receiver, the fundamental limits of classical wireless power transfer systems can be overcome. Regarding the second application, we consider a time-varying source for electrically small dipole antennas and show how time modulation can enhance the antenna performance. The developed theory of electromagnetic systems engineered by temporal modulation is applicable from radio frequencies to optical wavelengths.