Ultra-Wide Bandstop Frequency Selective Structure Using Stepped-Impedance Parallel-Plate Waveguides

A three-dimensional (3-D) bandstop frequency selective structure (FSS) with an ultra-wide stop-band is presented in this paper. It is comprised of two stepped-impedance parallel-plate waveguide (PPW) channels, which are stacked along the E-field direction. Simulated results show that the proposed FSS achieves a wide stop band (|S
11
|≥–1dB) with a fractional bandwidth of 138.8%, ranging from 3.17 GHz to 17.55 GHz. Moreover, the stop-band is quite flat, across which the fluctuation is less than 0.4 dB. The simulated reflection coefficients of the FSS under the oblique incidence up to 60° are also given, which indicate good stability of the frequency response. The proposed band-stop FSS has potential in radomes of radars to suppress the higher order harmonics of certain communication systems.