Design and Validation of Flexible Multilayer Frequency Selective Surface With Transmission Zeros

The design, analysis, and validation of a flexible multilayer frequency selective surface (MFSS) with two transmission zeros at the upper side of the passband is presented. The MFSS unit cell is composed of two metallic quasi-Jerusalem-cross patterns on the top and the bottom layers, a metallic slot coupling aperture on the middle layer, and two flexible polyimide-Teflon supported substrates. The equivalent circuit is derived to explain the principle of transmission poles and zeros. This MFSS exhibits a good resonance stability for different polarization and incident angles. A prototype flexible MFSS centered at 21.6 GHz is fabricated and measured, which shows an insertion loss of 1.3 dB and a fractional bandwidth of 15.7%. The stable performances of the MFSS at oblique incidences and under different bent conditions for TE and TM polarization are demonstrated as well.