A novel feeding mechanism for realizing circular polarization characteristic is presented in this paper. Detailed theoretical analysis proves that a circular microstrip antenna, which is excited by three centrosymmetric feeds with equal amplitudes and relative 120° phase shifts, can obtain good circular polarization. This circular microstrip antenna is designed to work on TM_(11) mode. Good equal input powers with relative 120° phase shift for three feeds are provided by a Wilkinson power divider with three phase-adjusting transmission lines. Probe feeding for the radiating patch is accomplished by vertical via holes through the substrate material. The measured results show that the proposed antenna obtains a 10 dB return-loss impedance bandwidth of 22.3% and a 3 dB axial-ratio CP bandwidth of 18.9%, with the peak gain of 7.0 dBi. Additionally, the measured symmetrical radiation patterns are in good agreement with the simulated ones.
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