Three-Dimensional Frequency Selective Surface with Multiple Transmission Zeros for Wide Stopband

A new bandpass three-dimensional frequency-selective surface (3-D FSS) based on the square coaxial waveguide (SCW) with wide stopband is proposed. By utilizing parallel-plate waveguide (PPW) as foundation of one propagation path in the unit cell, two transmission poles can be generated, resulting in a passband. Multiple transmission zeros are obtained by counteraction between paths based on SCWs and reflection in all paths. For this property, a wide stopband is generated for good frequency selectivity. The E-field analysis is presented to offer operating principle of the proposed 3-D FSS. The simulated results exhibit high frequency selectivity, dual polarizations and stable response characteristics under a variation of the incidence angle.