Triband Circularly Polarized Antenna Using a Single Patch

A single-feed single-patch triband antenna with different senses of circular polarization in different operating bands is presented in this letter. The first three pairs of the orthogonal modes of a single patch, TM10/TM01, TM20/TM02, and TM30/TM03 modes, are excited to serve the triband circularly polarized operation, by loading stubs and etching slots in both x- and y- directions. Benefited from the asymmetrical radiating patch and aperture coupling on the diagonal line, the orthogonal modes can be well excited and controlled to realize the different senses of circular polarization in different operation bands by tuning the stubs and slots. A patch antenna prototype has been designed and fabricated for experimental validation. The measured 3 dB axial ratios (ARs) of the three bands are 2.439-2.452 GHz, 3.343-3.365 GHz, and 4.342-4.378 GHz, respectively, and the corresponding polarizations are left-hand circularly polarized (LHCP), right-hand circularly polarized (RHCP), and RHCP, respectively.