Wideband Circularly Polarized Dielectric Resonator Antenna With Bandpass Filtering and Wide Harmonics Suppression Response

A wideband circularly polarized (CP) dielectric resonator antenna (DRA) with filtering response was proposed in this communication. To combine additional filtering and harmonic suppression functions within an antenna while realizing circular polarization, a new wideband filtering quadrature coupler was implemented to feed a hollow DRA. The filtering quadrature coupler was based on a snowflake shaped patch, whose operating modes can be flexibly controlled by the loading slots. Quarter wavelength coupled line sections were introduced to the coupler, realizing simultaneously wide bandwidth, excellent bandpass filtering, and wide harmonics suppression characteristics. For demonstration, a filtering CP antenna operating at 1.8 GHz was designed, fabricated, and measured. Reasonable agreement between simulated and measured results was observed. The prototype exhibited excellent bandpass filtering characteristics together with a wide overlapping bandwidth of 27.8%, within which the axial ratio value was less than 3 dB, and return loss was better than 12.4 dB. Over the same band, an average gain of 6 dBic with a variation less than 1 dB was achieved. A rejection level larger than 19 dB was found within the suppression band up to the third harmonic.