Wideband True-Time-Delay Dual-Polarized Reflectarray Antenna for Satellite Applications

A wideband dual-polarized offset reflectarray antenna (RA) using a novel wideband true-time-delay (TTD) unit cell is presented. This element is designed to accommodate large-size wideband dual-polarized RAs for satellite communications in the range of 10.7–14.5 GHz. The element, consisting of stacked microstrip circular patches coupled with an hourglass-shaped aperture and an embedded fork-shaped feed network, is designed to enhance both the bandwidth and phase range. A new arrangement for the elements is presented, which minimizes coupling between different elements and improves cross-polarization and element loss. For two polarizations, the linear phase range bandwidth exceeds 32% at the center frequency of 12.6 GHz (10.6–14.6 GHz). Exhibiting a linear phase range of over 800° at the center frequency (12.6 GHz) and maintaining an error of less than 45° across various frequencies compared to the TTD model, this element showcases exceptional dual-polarized wideband reflectarray performance. Measurement results show a maximum gain of 31.2 dBi at 12.6 GHz and 31 dBi at 13.5 GHz for vertical and horizontal polarizations (H-Pol), respectively. A 1-dB gain bandwidth of approximately 21% and a 3-dB gain bandwidth of around 31% are achieved for the vertical and H-Pols in an offset feed configuration. Sidelobe levels (SLLs) are maintained below −13 dB, while cross-polarization in vertical polarization (V-Pol) is kept under −30 dB across the entire band. For H-Pol, cross-polarization is maintained below −29 dB across the band, while SLLs remain better than −16 dB. Aperture efficiency measurements indicate values up to 57% and not less than 28% over the band.