Dual-band circularly polarized rotated patch antenna with a parasitic circular patch loading

A dual-band circularly polarized (CP) rotated patch antenna is proposed in this letter. Dual-band CP operation of the proposed antenna is achieved by adopting a circular patch below the rotated rectangular patch. The extra circular patch not only provides a higher band, but is also employed to tune the operating frequency of the lower band, which is generated by the rotated rectangular patch. The rectangular patch and the circular patch can be arranged on the front and back of a thin substrate and fed by a single slot. The dual CP operating bands can be tuned separately with a small frequency ratio of 1.18. A prototype of the proposed antenna is built to validate the design strategy. The measured 3-dB axial-ratio (AR) bandwidth is 2.1% (2.238-2.285 GHz) for the lower band and 2.0% (2.645-2.695 GHz) for the higher band, with the reflection coefficient being lower than $-$10 dB. The radiation pattern and gain are also measured and compared to the simulated ones.