Broadband Reflectarray Using Circular Cosine Curve Elements

An automated design methodology of large-aperture broadband reflectarray is proposed by exploiting the unique properties of circular cosine curve elements with the slope of frequency-phase (F-P) response that can be changed by adjusting two degrees of freedom. The single-layer miniaturized element (0.3λ) with quadrantal symmetry provides the phase range coverage of 360° and negligible reflection loss for either dual-linear or dual-circular polarization. The variable slope of the F-P response facilitates the optimal arrangement of reflectarray elements minimizing spatial dispersion over the wideband. A 60 × 60 offset-fed reflectarray prototype with dimensions of 960 × 960 mm is designed and fabricated. The measured 33.6 dB of peak gain, 20% of the 1-dB bandwidth, and a 52.9% aperture efficiency are achieved, exhibiting excellent radiation performance. In addition, a 26 × 26 center-fed reflectarray was designed for comparison with a simulated 1-dB bandwidth of more than 35%, which is regarded as a highly acceptable result.