A Simple RF Attenuation Measurement Technique With a Small Mismatch Uncertainty

An accurate radio frequency (RF) and microwave attenuation measurement method is described, where source and load do not have to be matched to the line impedance and where the contribution of a mismatch effect to the uncertainty is reduced to about 0.002 dB. From loss measurements carried out for variable attenuators, as well as for attenuators of fixed attenuation values as devices under test, which are fitted to quarter-wavelength lines in three different configurations, the attenuation is simply obtained and is unrelated to the source and load reflection coefficients of Gamma_G and Gamma_L, respectively. Experimental results on a 10-dB step attenuator measurement at frequencies from 1 to 17 GHz show good agreement with measurements where the source and load are impedance matched. The technique is effective even with Gamma_G and Gamma_L higher than 0.1.