An Electronically Tunable Single-Layer Reflectarray Antenna Element With Improved Bandwidth

This letter presents a varactor diode-tuned reflectarray element that achieves an improved element phase bandwidth relative to designs that employ a single resonance for phase tuning. This is accomplished by introducing two resonances in the element while maintaining a single-layer structure. Simulation results based on full-wave simulations compare favorably to experimental measurements inside a waveguide. The unit cell exhibits over 380° of phase agility, 3.5 dB of peak cell loss, and a 2.4% phase bandwidth at 5.4 GHz. In addition, it has the attractive features of using only a single control voltage as well as having a quasi-linear phase versus voltage characteristic.