www.microwavejournal.com/articles/36875-vna-frequency-extenders
VNA Frequency Extenders
October 5, 2021
VNA frequency extenders cover waveguide bands from 50 to 220 GHz. They are compatible with many VNAs that provide external LO and IF signal access. Standard models come as a pair to support full 2-port S-parameter testing. RF test power is adjustable over a 20-dB range. Typical measurement dynamic range is 110 dB.
https://www.eravant.com/products/vector-network-analyzer-extenders