STC-20-28-S1 is a Ka-Band down-converter that converts millimeterwave signals from a frequency range of 26.5 to 40 GHz to the baseband at 10 MHz to 1.6 GHz. The down-converter requires 13.25 to 20 GHz at +3 dBm input power as its LO, which can be obtained from a standard 20 GHz synthesizer, such as Eravant models STL-SG-022403-S1 or SOT-02220313200-SF-B6. The down-converter has low harmonic levels and excellent gain flatness, making it a good candidate to extend low frequency test equipment for millimeterwave testing purposes.