A circularly polarized (CP) patch antenna with a fractal structure that can be applied to the BeiDou navigation satellite system (BDS) is proposed. Etching two incomplete rings of different sizes with the antenna center as the center on the radiation patch generates CP. By adding a periodic structure based on the Sierpinski Carpet fractal around it, the size can be reduced while the gain is further improved. The dimension of the antenna is 0.35λo × 0.35λo × 0.03λo. Measured results manifest that the impedance bandwidth (S11 < -10 dB) is wider than 40 MHz at 1.561 GHz; the gain in 3-dB axial ratio (AR) bandwidth can reach 3.33 dBi; the beamwidth exceeds 140° in the 3-dB AR bandwidth.
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