An FSS-Backed 20/30-GHz Dual-Band Circularly Polarized Reflectarray With Suppressed Mutual Coupling and Enhanced Performance

A high-efficiency wideband frequency selective surface (FSS)-backed 20/30-GHz dual-band circularly polarized reflectarray antenna is presented. In order to effectively suppress the mutual coupling between the different element sets and improve the aperture efficiency, the variable element size and the element rotation angle phasing techniques are utilized in the multilayer reflectarray element designs at the Ka receive and transmit bands, respectively. Furthermore, a double-layer FSS with double concentric square loops is employed between the 20- and 30-GHz element layers. Thus, the uncoupled 20/30-GHz phase responses can significantly reduce the phase errors and simplify the dual-band reflectarray design process. To experimentally validate the performance of the proposed FSS-backed element configuration, an offset-fed 20/30-GHz dual-band circularly polarized reflectarray with a circular aperture of 400 mm is designed, fabricated, and measured. The measured gains are 36.7 dBic with aperture efficiency of 64.1% at 20.4 GHz and 40.2 dBic with aperture efficiency of 65.4% at 30.2 GHz, respectively. The measured aperture efficiencies exceed 47% within the whole receiving band (19.6-21.2 GHz) and 59% within the whole transmitting band (29.4-31 GHz), respectively. The proposed dual-band circularly polarized reflectarray antenna can be used for satellite communication applications at Ka-band.