Design of a Miniaturized Wideband Circularly Polarized Patch Antenna Using Characteristic Mode Analysis

A miniaturized wideband Circularly-polarized (CP) antenna based on coupled orthogonal patches is proposed in this paper. Three triangular patches with shorting pins are placed perpendicular to each other. Triple characteristic modes can be produced based on the three triangular patches, and they are orthogonal to each adjacent mode. Besides, by manipulating the coupling strength between adjacent patches, wideband phase shift around 90° can be produced for circularly-polarized radiation. Therefore, two axial-radio (AR) minima can be constructed to broaden the AR bandwidth. Furthermore, both the pin loading and the triangular patches play a great role in miniaturization. Finally, the proposed antenna realizes 8.4% (1.48 GHz-1.61 GHz) 3-dB AR bandwidth, while the overall size of the antenna is merely <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.34 \lambda_0 \times 0.35 \lambda_0 \times 0.045 \lambda_0$</tex> .