Programmable Hybrid Circuit Based on Reconfigurable SPP and Spatial Waveguide Modes

A programmable hybrid circuit is proposed, which is composed of two reconfigurable spoof surface plasmon polariton (SPP) waveguides loaded with varactor diodes and a substrate integrated waveguide (SIW). By manipulating their dispersion behaviors, the band-pass effect is achieved in the hybrid circuit, in which the upper and lower cutoff frequencies are determined by the SPP waveguide and SIW, respectively. When two SPP waveguides are configured to have the same cutoff frequency that is higher than the SIW's cutoff, the proposed circuit can realize a power division; when one SPP waveguide is reconfigured to reject the waves from SIW, this circuit will be a band-pass filter. As a typical application, a logic OR gate with 2-bit coding is designed by programming the bias voltages applied to the varactor diodes loaded on the unit structures of the SPP waveguides. All functions are demonstrated by measurement results that agree with numerical simulations very well. The work provides more potential applications in multifunctional integrated circuits and digital communication systems.