A broadband circularly polarized microstrip antenna with stable phase center is proposed for multi-mode GNSS applications. The proposed antenna consists of two crossed slots on one side of PCB and a Γ-shaped microstrip feeding structure on the other side of PCB. Measurement of the designed antenna demonstrates a -10-dB impedance bandwidth of 76.7% and a 3-dB axial ratio bandwidth of 64% are realized, which cover all GPS, BeiDou, Galileo, and GLONASS bands ranging from 1.164 GHz to 1.612 GHz. In addition, stable phase center for orientation in the region above 10˚ elevation is realized for high-precision positioning. For each GNSS band, phase center variation with respect to its own mean phase center can be retained within 5˚. Over the whole GNSS bands, phase center variation with respect to the common mean phase center is retained within 6˚.
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