Bolometric Microwave Power Calibration Techniques at the National Bureau of Standards

A bolometric method of calibrating low-level microwave power measuring devices is currently employed at the National Bureau of Standards in Boulder, Colo. The technique is one of direct comparison between the standard and the unknown, and utilizes NBS working standard bolometer units and self-balancing dc bridges. In general, the unknown is calibrated to an accuracy of one per cent. The following quantities are defined and the associated errors are discussed: 1) Calibration factor of a bolometer unit in combination with a directional coupler, 2) Calibration factor of a bolometer unit, and 3) Effective efficiency of a bolometer unit.