Lower Bounds on Q for Finite Size Antennas of Arbitrary Shape

TL;DR

This paper develops a new method to determine the fundamental lower bound on the radiation quality factor Q for arbitrarily shaped finite antennas by using equivalent electric and magnetic surface currents, ensuring no interior stored energy.

Contribution

It introduces a novel approach using combined electric and magnetic surface currents to accurately compute the lower bound on Q for arbitrary-shaped antennas.

Findings

Derived new expressions for stored energy, radiated power, and Q for coupled electric and magnetic currents.

Ensured no interior stored energy, leading to more accurate lower bounds on Q.

Applicable to antennas of arbitrary shape and size.

Abstract

The problem of the lower bound on the radiation Q for an arbitrarily shaped finite size antenna of non-zero volume is formulated in terms of equivalent electric and magnetic currents densities distributed on a closed surface coinciding with antenna exterior surface. When these equivalent currents radiate in free space, the magnetic current augments the electric current, so that the fields interior to the surface vanish. In contrast to approaches based solely on electric currents, the proposed technique ensures no stored energy interior to the antenna exterior surface, and thus, allows the fundamental lower bound on Q to be determined. To facilitate the computation of the bound, new expressions for the stored energy, radiated power, and Q of coupled electric and magnetic source currents in free space are derived.