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Broadband Polarization-Reconfigurable Slot Antenna and Array With Compact Feed Network

A broadband polarization-reconfigurable slot antenna and 2 × 2 array with compact feed network are proposed in this letter. The wide circle slot, etched on the ground, serves as the radiation aperture with a wideband characteristic. A novel compact microstrip (MS)–slot line–coplanar waveguide feed network on the top side is proposed to realize reconfigurable-polarization senses. Three p-i-n diodes are loaded on the MS for generating the linear polarization (LP), left- and right-hand circular polarizations (CPs) in the wide circular slot. Based on the compact feed network, a 2 × 2 polarization-reconfigurable antenna array with two dielectric layers is suggested. The feed networks are printed on the bottom and top metal planes, while the wide slots are on the middle one. To further improve the directivity, a reflector is loaded at the back of the array. A prototype operating at S-band is fabricated and measured. The measured 10 dB impedance bandwidth is 10.8% for the LP operation. The overlapped 10 dB impedance and 3 dB axial-ratio bandwidths are 14.5% for the CP operations. The peak gain reaches 14.7 dBi, which comes from the low loss and compactness of the novel feed network. The design can be extended to a larger array without increasing the structure complexity.