A Fast and Sensitive Submillimeter Waveguide Power Meter

A sensitive, fast and stable power meter has been developed which responds over a frequency range emending from 75 GHz up to the THz range. The method of measurement is essentially calorimetric, but with feedback circuitry added to speed up the response. The measurement time constant is 0.5 sec for power levels from 2-100 mW, but increases to 9 sec below 50 W. The drift level is 2-5 [LW in a typical measurement, while accuracy is better than 3%.