An ultra-wideband out-of-phase power divider based on odd-mode spoof surface plasmon polariton

In this article, a feasible design of an ultra-wideband power divider (PD) based on spoof surface plasmon polariton (SSPP) is proposed. A quasi T-junction transmission structure is composed of the sub-wavelength corrugated grooves drilled on the up metal layer, realizing the wideband and low loss for the propagation of the odd-mode SSPP wave. The consistency of the dispersion curves between the H-shaped and the U-shaped unit cells under the same dimension parameters ensures the smooth transition at the bifurcation point and out-of-phase property further. The odd-mode SSPP is effectively excited by using the microstrip-to-slotline convertor. Some design details like gradient corrugations and stepped slotlines are employed to achieve high-coupling efficiency from the input electromagnetic energy. The simulated and measured results show that the proposed PD achieves 180 degrees +/- 5 degrees phase difference over an ultra-wideband from 3.3 to 9.8 GHz (a relative bandwidth of 99.24%) with high-transmission efficiency. The ultra-wideband out-of-phase property of this design has potential applications in the differential feed network.