A compact circularly polarized microstrip ring antenna is presented for Global Navigation Satellite systems (GNSS) application in this paper. The antenna consists of a ring-shaped slotted ground and a radiation patch which is fed by a T-like coupling feedline. The radiation patch is a square ring strip embedded within two inverted L-shaped strips and a rectangular strip. The overall size of the proposed antenna is 0.38×0.38×0.038λg3 (λg is the guide wavelength at the frequency of 1575 MHz). The measured -15 dB |S11| bandwidth, 3 dB axial ratio (AR) bandwidth, and gain bandwidth of larger than 5 dBi are in the frequency range of 1552-1623 MHz, which can fully cover the operating frequency band of BDS B1, GPS L1, and GLONASS L1.
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