High Attenuation Measurement of Step Attenuators
Application Notes
This paper introduces a solution for high attenuation measurement of step attenuators. Fundamentally, this high attention measurement method is based on the cascaded 2-port network and S-parameter theory; this method is to compute S-parameters of high attenuation (> 80 dB) using the measured S-parameters of lower attenuation (≤ 80 dB) settings, and the calculations depend on attenuator card sequence and physical structure of step attenuator. This method can measure the attenuation high as 120 dB.
This is NOT a straight dB addition, this solution can offer considerable accuracy only using VNA (Vector Network Analyzer), and it uses T-matrix (as known as transmission parameter or cascade parameter) method which can make the calculations easier. Measurement uncertainties are derived from uncertainties of cascaded S-parameters, for example, measurement uncertainty for 80 dB at 18 GHz is less than 0.8 dB and 110 dB at 18 GHz is less than 1.0 dB.