Design of substrate integrated plasmonicwaveguide bandpass filter with T-shaped spoof surface plasmon polaritons

A novel substrate integrated plasmonic waveguide (SIPW) filter with T-shaped slot line spoof surface plasmon polaritons (SSPPs) is proposed in this paper. By etching the SSPPs array between the two rows of the metal vias of the substrate integrated waveguide (SIW) structure, the SIPW bandpass filter can independently adjust the low cutoff frequency by changing the SIW geometric parameters and the high cutoff frequency by changing the SSPP geometric parameters, respectively. Comparing with the traditional SIPW filter with signal layer or double layers linear slot line SSPPs, the proposed SIPW filter with T-shaped SSPPs has smaller circuit size thanks to the better electromagnetic field confinement ability of the T-shaped SSPPs. The dispersion properties of the SIW unit and the T-shaped SSPPs are discussed and the parameters effect on filter's performance are numerically investigated. A bandpass SIPW filter with T-shaped SSPPs is designed and fabricated with the proposed design method. The measurement results show that its passband is at 5.6-7.3 GHz with the return loss higher than 10 dB and the maximal insertion loss 1.8 dB. Also, its out-of-band spurious rejection is higher than 40 dB at the bandwidth 8.1-14.8 GHz. The agreements between the simulated results and measured results demonstrate the effectiveness of the proposed SIPW filter with T-shaped SSPPs.