A novel design methodology for single-layer dual-band reflectarray antennas with wide frequency ratios is proposed by exploiting the unique reflection phase properties of Phoenix elements. Full 360° phase ranges at both frequency bands are achieved simultaneously by using only one element set. Compared to conventional approaches that use two sets of elements for dual-band operation, physical and electromagnetic mutual interferences between the elements operating at different frequency bands can be completely avoided. A detailed design procedure for single-layer dual-band reflectarrays with a wide frequency ratio up to 2.5 is presented, and a set of three center-fed dual-band reflectarrays operating at 15/10, 20/10, and 25/10 GHz, respectively, are designed and numerically verified using full-wave simulations. Furthermore, an offset-fed single-layer dual-band reflectarray operating at 20/10 GHz with a circular aperture of 400 mm in diameter is designed, fabricated, and tested for experimental verification. The measured gains are 36.1 dBi with an aperture efficiency of 58.0% at 20 GHz and 30.3 dBi with an aperture efficiency of 61.1% at 10 GHz, respectively. The measured 1-dB gain bandwidth is 9.1% and 14.0% at the upper and lower bands, respectively. Both the simulated and measured results successfully demonstrate the effectiveness of the proposed design methodology.
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