Achievable Rate of Near-Field Communications Based on Physically Consistent Models

TL;DR

This paper develops a physically consistent information-theoretic model to analyze how mutual coupling affects the achievable rate in near-field SISO communications with size-constrained antennas.

Contribution

It introduces a novel approach combining Chu's theory and scattering assumptions to derive mutual impedance and establish an upper bound on system performance.

Findings

Mutual coupling significantly impacts the achievable rate in near-field communications.

Derived explicit expressions for self and mutual impedances based on physical antenna models.

Provided insights into the limits of near-field communication performance with compact antennas.

Abstract

This paper introduces a novel information-theoretic approach for studying the effects of mutual coupling (MC), between the transmit and receive antennas, on the overall performance of single-input-single-output (SISO) near-field communications. By incorporating the finite antenna size constraint using Chu's theory and under the assumption of canonical-minimum scattering, we derive the MC between two radiating volumes of fixed sizes. Expressions for the self and mutual impedances are obtained by the use of the reciprocity theorem. Based on a circuit-theoretic two-port model for SISO radio communication systems, we establish the achievable rate for a given pair of transmit and receive antenna sizes, thereby providing an upper bound on the system performance under physical size constraints. Through the lens of these findings, we shed new light on the influence of MC on the information-theoretic limits of near-field communications using compact antennas.