Comparison of Cross-Polarization Characteristics of Frequency-Selective Surfaces Composed of Square Split-Ring and Spiral Resonators

This paper reports on the design, measurement and modeling of frequency-selective surfaces in the microwave regime using arrays of spiral resonators. A distinct and unusual variation in the transmission properties of the frequency-selective surface composed of spiral resonators was observed. This variation may be a function of the geometry of the spiral resonator used and/or the use of slant/cross-polarization characterization. The cross-polarization results obtained for both orientations imply that the spiral resonators behave differently than the circular split-ring resonators. These results may be explained by an approximately 50deg shift in electromagnetic axis, reflecting the differences in the geometries of the two structures