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 . The calculated aperture efficiencies were 0.42, 0.40, 0.36, 0.25, 0.16, and 0.12 for equal to 0 , 20 , 30 , 40 , 45 , and 50 , respectively. For validation of the numerical simulations, three 277-element reflectarrays for fixed 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 equal to 0 , 20 , and 30 , respectively. Measured characteristics agreed satisfactorily with theoretical predictions.

A full-wave mathematical model was developed to analyze the radiation characteristics of a spiraphase-type finite reflectarray based on ring slot resonators with stubs controlled by p-i-n diodes. The scanning characteristics of the finite 289-element reflectarray with optimized elements were calculated. According to the simulated characteristics, the optimized reflectarray provides electronic scanning in the XOZ-plane for elevation angles up to 30 ı with a total aperture efficiency better than 0.22. The characteristics obtained with the developed mathematical model were compared with the simulated characteristics obtained with the mathematical model of the infinite array.

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