Frequency selective surfaces based on ring slots loaded with monolithically integrated capacitors

Monolithic integration of loading capacitors into the X-band frequency selective surfaces (FSSs) based on ring slots is investigated as a means to control the frequency response of the FSS. Ring slots and integrated capacitors are formed on a microwave-friendly substrate using multistep thin-film deposition and patterning. Numerical simulations and experimental measurements are performed to extract the capacitance values and quality factors of the fabricated capacitors. It is proven that these capacitors in the range of 0-120-fF shift congruently the resonant frequency of the ring slot FSS from 11.8 to 8.14-GHz. Quality factors of the fabricated capacitors are estimated to be within the range of 50-150.