Up to 50 GHz Microwave Frequency Measurement Using Down-Convert Technique at Telecommunication Laboratories, Taiwan

TL has established its microwave frequency measurement capability by using a microwave signal synthesizer (~40 GHz) and a microwave counter (~46 GHz) from 2010. Our initial setup of microwave frequency measurement system, utilized direct frequency measurement, couldn't meet the requirement for calibrating a Device under test(DUT) with high frequency accuracy. Therefore, an indirect measuring way utilizing down-convert technique has been used for microwave frequency measurement with enough resolution. In 2012, a HP 83630L signal generator (served as a DUT, ~26.5 GHz ) was used to output a nominal frequency signal to be measured, and the Agilent E8257D synthesizer was then adjusted accordingly to keep a constant difference frequency output (10 MHz) from the mixer. The SR620 time interval counter was popularly used in T&F measurement and which has been adopted in our indirect measurement since 2012. In 2014, an amplified doubler was used to extend the DUT's output to the upper frequency limit provided by the E8257D (40 GHz). The measurement capability of our system was then changed to 40 GHz. In this study, we will follow our previse scheme of 2014 and upgrade the measurement range up to 50GHz. The uncertainty budget will also be discussed.