A Low-Loss High-Speed SIW Cavity SPDT Switch Architecture

In this paper, a novel low-loss high-speed substrate integrated waveguide (SIW) single-pole double-throw (SPDT) switch is presented. It consists of a circular cavity resonator with four centered capacitive posts. By controlling the capacitances between adjacent posts, the cavity excites three evanescent modes at the same resonant frequency, one main mode, and two switchable differential modes. Switching between the two differential modes will change the positions at which the fields will add up constructively or destructively with the main mode. PIN-diodes are placed between the posts for switching the modes. The three ports are positioned in a way that high transmission and good isolation are achieved. The SIW-SPDT switch has a low measured insertion loss of 1.6 dB and a measured isolation of 18 dB at 8 GHz. The measurements show an ON-switching time (Ton) less than 40 ns and an OFF-switching time (Toff) less than 80 ns.