A Wideband Transmitarray Using Dual-Resonant Double Square Rings

A four-layer transmitarray operating at 30 GHz is designed using a dual-resonant double square ring as the unit cell element. The two resonances of the double ring are used to increase the per-layer phase variation while maintaining a wide transmission magnitude bandwidth of the unit cell. The design procedure for both the single-layer unit cell and the cascaded connection of four layers is described and it leads to a 50% increase in the dB gain bandwidth over that of previous transmitarrays. Results of a 7.5%-1 dB gain bandwidth and 47% radiation efficiency are reported.