A 20–40 GHz quasi-optical network analyzer

A 20-40 GHz 2-port quasi-optical scalar network analyzer consisting of a transmitter and receiver both built in planar technology is presented. The network analyzer is based on a Schottky-diode mixer integrated inside a double-slot antenna and fed differentially by a CPW transmission line. The antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The LO signal is swept from 3-5 GHz and high-order harmonic mixing in both up- and down- conversion mode is used to realize the 20-40 GHz RF bandwidth. The network analyzer resulted in a dynamic range of greater than 30 dB and was successfully used to measure a frequency selective surface designed to give a band-pass response at 30 GHz. Furthermore, the system was built with circuits and components for easy scaling to millimeter-wave frequencies which is the primary motivation for this work. The application areas for a millimeter-wave network analyzer include material characterization and art diagnostics.