Design of Compact TM21 Higher Order Mode Circular Patch Antennas with Shorting Pins

Abstract

In this thesis, I proposed a miniaturized TM21 higher order mode circular patch antenna and a dual-band semi-circular half-mode patch antenna for water utility Advanced Metering Infrastructure (AMI). The miniaturized TM21 higher order mode circular patch antenna composed of a coaxially center-fed circular ground and a circular patch with two shorting pins to generate the TM21 higher order mode. The radius of the circular ground and patch is 140 mm and the overall antenna height is 30 mm. The measured 10-dB return loss bandwidth is 8.5 MHz (260 MHz – 268.5 MHz). The measured radiation pattern has a monopole-like radiation characteristic with a maximum gain of 0.96 dBi. The dual-band semi-circular half-mode patch antenna consists of a semi-circular ground and a semi-circular patch with two shorting plates to generate the TM21 higher order mode. In order to reduce the size in half, the proposed antenna adopts a half-mode concept. The radius of the semi-circular ground and patch is 245 mm and the height of the antenna is 30 mm. The measured 10-dB return loss bandwidths are 9.5 MHz (265 MHz – 274.5 MHz) at the low band and 29 MHz (897 MHz - 926 MHz) at the high band. The measured results show that the proposed antenna has an omni-directional radiation characteristic with a maximum gain of 1.51 dBi at the low band and a directional radiation pattern with a maximum gain of 6.44 dBi at the high band.