Tri-Band Circularly Polarized Annular Slot Antenna for GPS and CNSS Applications

A single-feed tri-band circularly polarized (CP) annular slot antenna is presented. The antenna structure is composed of two non-concentric annular slots that are fed by an L-shaped series step impedance microstrip line configuration. The proposed antenna is designed to operate at the L1 & L2 bands of the Global Positioning System (GPS) and the frequency band of the Compass Navigation Satellite System (CNSS). The measured results show that the impedance bandwidths are good for all bands. And the radiation patterns with good CP characteristics are obtained at the three resonant frequencies.