Characteristics of single- and double-layer microstrip square-ring antennas

A method for miniaturization of microstrip patch antenna without degrading its radiation characteristics is investigated, It involves perforating the patch to form a microstrip square-ring antenna, which is investigated numer ically and experimentally, The ring geometry introduces additional paramete rs to the antenna that can be used to control its impedance, resonance freq uency, and bandwidth. For a single square ring increasing the size of perfo ration increases its input impedance, but decreases the resonance frequency and bandwidth. It has a small effect on directivity of the antenna. To mat ch the antenna to a transmission line and also enhance its bandwidth, the r ing is stacked by a square patch or another square ring. The computed resul ts are compared with experimental data and again good agreement is obtained .