A Broadband Waveguide Calorimeter in the Frequency Range From 50 to 110 GHz

A new broadband rectangular waveguide calorimeter for radio-frequency (RF) power meter calibration in the millimeter-wave region is reported. The calorimeter has a quasi-twin structure exploiting the WR-10 and WR-15 rectangular waveguides, and its operational frequency ranges from 50 to 110 GHz. This calorimeter is characterized by its high measuring speed and sensitivity. A thermal feedback control system reduces the typical reading time per frequency to less than 10 min, and the minimum measurable incident RF power is 0.2 mW. A new technique for reducing the equivalence error by utilizing a flat millimeter-wave absorber is also discussed.