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

A method for miniaturization of microstrip patch antennas without degrading radiation characteristics is investigated. It involves perforating the patch to form a microstrip square-ring antenna, which is investigated numerically and experimentally. The ring geometry introduces additional parameters to the antenna that can be used to control its impedance, resonance frequency, and bandwidth. For a single square ring increasing the size of perforation increases its input impedance, but decreases the resonance frequency and bandwidth. It has a small effect on directivity of the antenna. To match the antenna to a transmission line and also enhance its bandwidth, the ring is stacked by a square patch or another square ring. The computed results are compared with experimental data and again good agreement is obtained.

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