A Crossbar Mixer up to 120 GHz Based on the SISL Platform

This letter reports a crossbar mixer based on the substrate-integrated suspended line (SISL) platform, with two contributions below. First, multistage stepped double-ridge waveguides are designed for the radio frequency (RF) signal coupling to the Schottky diode pair directly, with low-RF path loss as well as easier wideband matching. Furthermore, the surface roughness of the waveguide sidewall plating layer is measured to analyze the additional metal loss. Measurements show that the results are in reliable agreement with the simulation after considering the practical factors, including surface roughness and dielectric frequency properties. The conversion loss of this mixer is 6.16–9.84 dB within the RF range of 104–118.5 GHz, which is competitive with those in the similar frequency band that adopt advanced processing technology, yielding a good balance between the cost, weight, and performance of the circuits.