A Compact Dual Circularly Polarized Antenna With Wideband Operation and High Isolation

This paper presents a dual-sense circularly polarized (CP) antenna with compact size, high isolation, and wideband characteristics. The antenna consists of a microstrip patch, an array of parasitic metal plates positioned around the patch, and a 90° branch line coupler as feeding structure. Unlike the conventional design method, we demonstrate that the wide isolation bandwidth can be achieved with an imperfect coupler and imperfect matching at the radiating element. The final design with overall dimensions of 0.59λc× 0.59λc × 0.06λc (λc is the free-space wavelength at center operating frequency) was fabricated and tested. Measurements on the fabricated prototype show that the antenna has a bandwidth of 16.5% (5.0-5.9 GHz) with port isolation of better than 15 dB. In addition, a peak broadside gain of about 6.6 dBic is attained. In comparison with other related works in literature, this antenna has advantages of wide operating bandwidth with high isolation while possessing a compact footprint.