Reconfigurable Reflectarrays Based on Optimized Spiraphase-Type Elements

Reconfigurable spiraphase-type reflectarrays based on ring slot resonators with switchable radial stubs are presented. The mathematical model of the infinite array was used to optimize the spiraphase-type element at 36.5 GHz. The optimization goals were to minimize the dissipative loss in the p-i-n diode switches and to reduce the cross-polarization radiation. The mathematical model of the finite array was then used to simulate the radiation characteristics of a reconfigurable reflectarray with 277 optimized elements for different scanning elevation angles θ_ο. The calculated aperture efficiencies were 0.42, 0.40, 0.36, 0.25, 0.16, and 0.12 for θ_ο equal to 0°, 20°, 30°, 40°, 45°, and 50°, respectively. For validation of the numerical simulations, three 277-element reflectarrays for fixed θ_ο of 0°, 20°, and 30° were designed. Metal strips and open circuits were used instead of the forward and reverse p-i-n diode states, respectively. These reflectarrays were then fabricated and tested, demonstrating aperture efficiencies equal to 0.41, 0.40, and 0.28 for θ_ο equal to 0°, 20°, and 30°, respectively. Measured characteristics agreed satisfactorily with theoretical predictions.