The EM analysis of double-layered thick FSS structure with low-loss dielectric medium between the FSS layers has been carried out using MM-GSM technique. In this analysis, both evanescent and propagating modes are included that enhances the accuracy of the computation. This method provides less computational complexity in the formulation of FSS structures as compared to other numerical techniques. The cascaded FSS structure shows bandpass response (>95% transmission) over a frequency range from 8.84 GHz to 10.74 GHz. It is found that this FSS structure shows very good in-band transmission characteristics and excellent roll-off characteristics outside the band. Further, the dependence of transmission characteristics on the spacing between the FSS layers is also investigated. The optimum bandpass response is achieved for 0.3λ spacing between the layers. This FSS structure offers superior bandpass response and structural rigidity required for airborne radome applications.
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