Q-factor and bandwidth of periodic antenna arrays over ground plane

TL;DR

This paper derives an efficient Q-factor expression for periodic antenna arrays over ground planes, linking it to the array's current distribution and validating it against full-wave simulations and existing formulas.

Contribution

It introduces a new Q-factor formula that accounts for element shape and simplifies numerical computation, improving bandwidth prediction accuracy for array designs.

Findings

Good agreement with full-wave simulations

Accurate bandwidth estimation for tilted dipoles

Validates against existing input-impedance formulas

Abstract

In this paper, the Q-factor expression for periodic arrays over a ground plane is determined in terms of the electric current density within the array's unit cell. The expression accounts for the exact shape of the array element. The Q-factor formula includes integration only over a volume of an element in a unit cell, and can thus be efficiently implemented numerically. The examples show good agreement between the proposed Q-factor, the full-wave-calculated tuned fractional bandwidth, and the input-impedance-based formula by Yaghjian and Best (2005) for the array of tilted dipoles and the loops array.