An absolute method for calibrating microwave attenuators

This method of calibrating a variable attenuator is based on the attenuation through a 3 dB coupler; an iterative process is used to take into account the absorption loss and the unequal power split of the coupler. Details are given of the procedure used for calibrating a particular attenuator, and the method of calibration at intervals of attenuation closer than the nominal 3 dB of the coupler is described. An estimate is made of the possible accuracy of the calibration, which, in the case described, was ±0.4 dB in 40 dB at a frequency of 6.2 Gc/s.