Millimeter-Wave Bandpass Filter Using Rectangular Waveguide and SSPP with a Notched Band

A millimeter-wave bandpass filter for Ka-band applications is proposed, which uses a rectangular waveguide and spoof surface plasmon polariton (SSPP) with a notched band. This filter incorporates SSPP, and double grating (DG) combined with two coupled split ring resonators (SRRs). The proposed SSPP and DG can provide the lower and upper cut-off frequencies of the bandpass filter (BPF). Two coupled SRRs are embedded into the waveguide to form a notched band, whose center frequency and bandwidth can be independently tuned by adjusting the parameters of SRRs. The dispersion curves of the SSPP and DG are calculated to determine the lower and upper cut-off frequencies. The bandwidth and notched band of the proposed filter can be controlled by varying the geometric parameters of SSPP, DG, and SRR. For demonstration, a Ka-band BPF with a notched band was fabricated and characterized. The measurement results agree well with the simulation, verifying the feasibility of the proposed design.