Wideband Four-Way Filtering Power Divider Based on Hybrid Spoof Surface Plasmon Polariton and Substrate Integrated Waveguide

In this paper, a four-way filtering power divider (FPD) based on hybrid spoof surface plasmon polariton (SSPP) and substrate integrated waveguide (SIW) is designed and fabricated. It is for the first time that a four-way FPD has been implemented by integrating SIW and SSPP structures. This combination can guarantee a wide bandwidth which would not be attainable by employing merely SIW or SSPP. The presented hybrid structure has been realized by etching some butterfly grooves on the upper metal surface of SIW and half-mode SIW. The lower and upper cutoff frequencies of this hybrid SIW-SSPP FPD can be adjusted independently by tuning the dimensions of SIW and SSPP unites, respectively. Employing butterfly-shaped SSPPs instead of typical rectangular SSPPs with the same length leads to a reduction in the circuit’s size, higher slow-wave effects, and shorter wavelength. To validate the proposed design procedure, the presented FPD is fabricated and measured. A good agreement between the simulated and measured results is achieved. What stands out from the measured results is that the proposed circuit achieves a 3-dB fractional bandwidth of 38% from 4.2 to 6.2 GHz, a return loss of higher than 13.5 dB, and a minimum insertion loss of 0.7 dB.