A broad-band annular-ring microstrip antenna

Abstract

A heuristic discussion of the radiation properties of the transverse magnetic (TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> ) and (TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> ) modes of the annular-ring microstrip antenna is presented, indicating the possibility of the TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> mode as a superior microstrip antenna. Rigorous analyses of the resonant frequency characteristics of the antenna are then performed with the matched asymptotic expansions technique and the perturbation approach. The analyses show that the TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> mode is decidedly the best mode for microstrip antenna applications while the TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> mode, having a high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -factor, is best reserved for resonator applications. The analyses include the study of the resonant frequencies, bandwidths, and radiation pattern of the antenna. The matched asymptotic expansions technique and the perturbation approach are also shown to agree excellently with each other within their domain of validity.