Abstract
A substrate integrated waveguide (SIW) based spoof surface plasmon polariton (SSPP) is proposed for the design of bandpass filter (BPF). The left and right edge cutoff frequencies of the passband can be easily adjusted by changing the parameters of SIW and ring slot embedded into the SIW. Then, four half-wavelength circular slots are added on two sides of the SSPP located at the center of the circuit to introduce a high-selectivity notch band. In order to make the notch band switchable, four full-wavelength circular slots and four PIN diodes are applied instead of the four half-wavelength circular slots. As the PIN diodes are under the ON state, the notch band will be generated within the passband of BPF. On the contrary, as the PIN diodes are under the OFF state, the notch band will disappear. To validate the design idea, two BPF examples are fabricated and measured, whose simulation and measurement results are both in reasonably good agreement.
Highlights
Surface plasmon polaritons (SPPs) are surface waves in the optical frequency band that propagate along the metal-dielectric interface but decay fast in the vertical direction [1]
It indicates that the left- and right-edge cutoff frequencies of the passband can be independently adjusted by changing the width of substrate integrated waveguide (SIW) walls and radius of ring slot embedded into the SIW, respectively, when this spoof surface plasmon polariton (SSPP) unit cell is used for the design of bandpass filter (BPF)
As the PIN diodes are under the ON state, the closed-loop ring slot resonators will be equivalent to the halfwavelength circular slots as shown in Figure 2, and the notch band will be generated within the passband of BPF
Summary
Surface plasmon polaritons (SPPs) are surface waves in the optical frequency band that propagate along the metal-dielectric interface but decay fast in the vertical direction [1]. It indicates that the left- and right-edge cutoff frequencies of the passband can be independently adjusted by changing the width of SIW walls and radius of ring slot embedded into the SIW, respectively, when this SSPP unit cell is used for the design of BPF. Based on the above analysis, a corresponding BPF using the proposed SSPPs is designed It consists of the following parts: microstrip lines as the input and output ports for connecting with the SMA connectors to measure the filter performance, a transition part by using a trapezoidal microstrip line and a smaller ring slot for the transition from microstrip line to SSPP waveguide, and a SSPP waveguide with seven periodic unit cells.
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