Circulator Based on Spoof Surface Plasmon Polaritons

Abstract

In the letter, we propose the design of circulators based on spoof surface plasmon polaritons (SSPP). Rather than striplines, the center conductor is replaced with a blade structure that supports the SSPP mode and exhibits a shorter wavelength and larger wave vector. To enhance the efficiency, a matching transition is employed between the coplanar waveguide and the blade structure. With biased ferrites attached on both the top and bottom sides, the blade structure shows good nonreciprocal properties. The simulation results indicate that in the 5.0-6.6 GHz frequency range, the isolation and return loss reaches 15 dB and the insertion loss is less than 0.5 dB. Since the circulator utilizes the SSPP mode, which exhibits a shorter wavelength than its analogous stripline mode, the size of ferrites, and thus the size of the circulator, can be reduced. Our work provides an effective route to the design of compact, broadband circulators.