Narrowband SIW-SSPP Hybrid Bandpass Filter With Compact Profile at Ka-Band

Narrowband SIW-SSPP Hybrid Bandpass Filter With Compact Profile at Ka-Band

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In this paper, a narrowband bandpass filter comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs) is proposed, achieving miniaturization and low insertion loss at Ka-band.SIWs and Washer SSPPs exhibit low and high cut-off responses, respectively, which can be combined for filtering functionalities.By designing I-shaped SSPP structures with large effective length, the cut-off frequencies of SIW and SSPPs can be tailed to converge at a certain frequency for the narrowband filter, where the SIW mode functions as a quasi-evanescent mode, and the mode impedance ramps fast.A sharp funnel-shaped transition is designed to connect SIW with a large impedance and 50- $Omega $ microstrip line for low insertion loss and a compact profile.In addition, no transitional SSPP structures are desired in the proposed devices, which further shortens the profile dimension.

To verify our design, a hybrid filter at 30 GHz is fabricated and characterized.The measured insertion loss is as low as 1.5 dB, and the 3-dB bandwidth is as narrow as 3%, which shows good consistency with the simulation.The proposed SIW-SSPP device Lids has a low profile of $0.70,,lambda imes 0.

38,,lambda $ and may find important applications in frequency division multiplexing.