Agilent Attenuation Measurement of Step Attenuators 5991-1268EN c20140520 [10] free download

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Keysight Technologies High Attenuation Measurement of Step Attenuators White Paper Abstract 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 @ 18 GHz is less than 0.8 dB and 110 dB @ 18 GHz is less than 1.0 dB. Introduction There was a need to verify the accuracy of an attenuator in a new synthesizer product. This method provides a simpler procedure for Calibration Lab using an automatic measurement system to perform high attenuation measurement of step attenuators. This T-matrix method was originally suggested by the project manager, and finally implemented by software engineer. The author of this report, as metrologist of the project, provided principle verification, experimenta- tion results review and measurement uncertainty analysis. This method was also approved by expert from Keysight Technologies Component Test Division. This measurement system has been used to calibrate a large number of step attenuators for many years. This paper describes the T-matrix mea- surement method for achieving high accuracy, and will introduce details of using cascade parameters to represent each thru-line and attenuator section based on attenuator physical structure of step attenuator. Sulan Zhang, Keysight Technologies T-matrix Description The following discussion in general applies to a cascade of N-port networks. For the sake of simplicity, however, we limited our analysis to two-port networks only. When cascading a number of two-port network in series, a more useful network representation is needed to facilitate the calculation of the overall network parameters. This representation should relate the output quantities in terms of input quanti-