Multiband frequency selective surface with multiring patch elements

Theoretical discussions and experimental verifications are presented for a multiband frequency selective surface (FSS) with perfectly conducting multiring patch elements. It is found that the narrow-ring approximation is valid for a ring width less than 0.025λ with λ being the wavelength of the FSS´s resonant frequency. A single screen double-ring element FSS is demonstrated for (1) a low-pass FSS that reflects the Ka-band signal while passing the S-, X-, and Ku-band signals, and (2) a tri-band system that reflects the X-band signal while transmitting through the S- and Ku-band signals. In addition, a double screen four-band FSS with non-similar double-ring elements is developed by cascading the above mentioned two single screens. The good agreement obtained between the measured and the computed results verified the computer codes and the approaches of the paper