Low-loss K-band Photoconductive Switches in SIW Technology

A design approach for mmWave switches in substrate integrated waveguide (SIW) technology is demonstrated. The switch is based on a photoconductive element (PE) which represents a piece of an intrinsic silicon wafer with light modulated conductivity. Using both dielectric (high-resistivity) and conductive states of the PE, we can design a low-loss mmWave switching element. Owing to the light actuation, the control circuitry of the photoconductive switch (PS) is electrically separated from the high-frequency elements of the device. This solves the bottleneck of conventional mmWave switches based on PIN diodes, MOSFETs, MEMS, etc., which are bulky and lossy due to decoupling filters and matching elements of control and biasing circuits. The proposed approach is generic and can be applied to many mmWave applications within 10 - 100 GHz such as 5G, WiGig, automotive radars, and others.