Circularly polarized antenna using ground-mode tuning technique for small-sized IoT devices

This study focuses on the generation of circular polarization (CP) in a small-sized ground plane by using ground-mode tuning (GMT) technique. The proposed antenna is composed of two branches, so that it can simultaneously excite two orthogonal modes of the ground plane for radiation. Two metal strips at the ends of the ground plane are adopted as GMT structures, and the dominant modes along the length and width of the ground plane can be controlled by tuning the property of the shorting pins, conveniently. Both simulation and measurement results indicate that the proposed technique can achieve a wideband impedance bandwidth and a sufficient AR bandwidth. Furthermore, the proposed CP antenna provides a less directive radiation pattern compared to a linearly-polarized antenna, which can be attractive in receiving performance.