Ultra-Wideband Absorber Based on Printed Resonance Frequency-Selective Surfaces with Lumped Losses

A method of creating thin and ultra-wideband radio absorbers based on use of frequency-selective surfaces with lumped losses was presented. It was found that shape of the frequency dependence of the reflection coefficient is determined by the geometry of the double square frame of absorber. The number of resonances is determined by the frequency-selective surfaces geometry only if thickness of the dielectric substrate is less than 0.08 $\lambda$. An increase in thickness of the substrate to a value of 0.1$\lambda$ leads to appearance of an additional resonance in the reflection characteristic due to the excitation of surface wave. Influence of material parameters of the substrate on the absorbing properties of a radio absorber based on double square frames was researched.