A Broadband Circularly Polarized Slot Antenna with Ferrite Substrate for CNSS Application

Abstract

A single-feed wideband circularly polarized (CP) antenna that consists of a rectangular patch and a slotted ground was designed based on a magneto-dielectric ferrite substrate. The radiation patch is excited by a microstrip line that mounted on the ferrite substrate $(\varepsilon=9.5, \tan\delta_{\varepsilon}=0.005, \mu=6, \tan\delta_{\mu}=0.03)$ . The designed antenna is compared with the antenna that has the same structure while using a dielectric ceramic substrate. The comparison reveals that the ferrite substrate with magnetic permeability can make the antenna operate in a much lower frequency band that means a good miniaturization effect. The circular polarization is realized by the coupling between the edges of asymmetrical slot on the ground and the rectangular radiation patch. And the wide slot floor structure is conducive to expand the impedance bandwidth. The simulation results show that the impedance bandwidth $(S_{11} and 3-dB axialratio bandwidth achieve 43.6% (0.93-1.66 GHz) and 41.3% (0.98-1.49 GHz) respectively. The gain of this antenna is maintained at about 3dBi in the B2 (1.166-1.217GHz) and B3 (1.251-1.286GHz) bands of the compass navigation satellite system (CNSS). The radiation pattern shows the proposed antenna has good directionality. In the direction of principal axis (Z+), the designed antenna radiates righthand CP wave required by the CNSS at the center frequency of the B2 and B3 bands. The proposed antenna has a low profile with the overall size of $100\times 100\times 1.35 \text{mm}^{3}$ . The wide working bandwidth, good circular polarization performance, and simple structure make the proposed antenna a suitable candidate for CNSS application.