Calibration of a Terahertz Attenuator by a DC Power Substitution Method

An attenuation calibration system is developed using an isothermal temperature control-type calorimeter for a terahertz (THz) attenuator. This system is based on a power ratio measurement by dc power substitution. A highly sensitive calorimeter achieves a simple and accurate attenuation calibration at room temperature. Calibration is performed for metalized-film attenuators at 1 THz using a photomixer as the THz source. The measurement uncertainties in the system are evaluated, and the expanded uncertainty is found to be 0.19-0.84 dB (k = 2) for an attenuation measurement range up to 12 dB.