Compact High-isolation Sub-THz Micro-electromechanical SPST Switch

This paper presents a novel single-pole-single-throw wideband microelectromechanical switch circuit operating in the 220 to 290 GHz frequency band. The switching operation is based on short-circuiting the dominant TE10 mode of the rectangular waveguide by micro-electromechanically reconfigurable surfaces. The improved performance of this switch circuit comes from utilizing two such reconfigurable surfaces and taking advantage of the interference between them to achieve improved RF performance, in particular in terms of return loss and isolation. The switch has a compact design with dimensions of $2 \times 3.5 \times 1.2$ mm3. Due to its axial port arrangement, it can be mounted directly between two standard waveguide flanges. The insertion loss, measured between the two standard waveguide flange interfaces and including all internal circuit routing and E-plane bends, is between 0.7-1.2 dB. The measured return loss is better than 17 dB in the entire frequency band of 220 to 290 GHz. Reference waveguide measurements of the same prototype fabrication run showed that 0.2-0.5 dB of the measured insertion loss comes from the waveguide itself. The measured isolation of the switch is very uniform in the whole 220-290 GHz waveguide band and between 28.5-32.5 dB. The measured fractional bandwidth of 27.5% has been achieved, which is almost equal to a full waveguide band performance.