A Novel Annular Slotted Center-Fed BeiDou Antenna With a Stable Phase Center

A novel annular slotted center-fed circularly polarized (CP) antenna with a stable phase center is proposed in this letter. Two symmetric annular slots with tabs are embedded onto a square microstrip patch for CP radiation. Good CP radiation and impedance matching is achieved by reasonably adjusting the radii of the annular slots and the position of the tabs. The symmetric structure brings about a very stable phase center. The proposed antenna can work in the compass satellite navigation system B1 band (1561.098 +/- 2.046 MHz). The measured results show that the 10 dB return-loss bandwidth is 148 MHz, 9.24%, and the 3 dB axial-ratio (AR) bandwidth is 39.9 MHz, 2.5%. Moreover, the antenna has a wide 3 dB AR beam width of around 210 degrees. The deviation of the phase center is about 0.91 mm at the central frequency. The measured results agree well with the simulated results.