The Radiation Efficiency Cost of Resonance Tuning

TL;DR

This paper investigates how realistic material properties in resonance tuning affect the radiation efficiency bounds of small antennas, revealing that practical dissipation factors scale more severely than idealized models suggest.

Contribution

It demonstrates that accounting for realistic material losses significantly alters the predicted radiation efficiency bounds for small antennas.

Findings

Dissipation factors scale as (ka)^-4 with realistic materials.

Lossy tuning networks reduce the maximum achievable efficiency.

Previous models assuming lossless tuning overestimate efficiency bounds.

Abstract

Existing optimization methods are used to calculate the upper-bounds on radiation efficiency with and without the constraint on self-resonance. These bounds are used for the design and assessment of small electric-dipole-type antennas. We demonstrate that the assumption of lossless, lumped, external tuning skews the true nature of radiation efficiency bounds when practical material characteristics are used in the tuning network. A major result is that, when realistic (e.g., finite conductivity) materials are used, small antenna systems exhibit dissipation factors which scale as $(ka)^{-4}$, rather than $(ka)^{-2}$ as previously predicted under the assumption of lossless external tuning.