An Error Analysis for the RF-Attenuation Measuring Equipment of the PTB Applying the Power Method

Abstract

After a short review on the different attenuation measuring techniques, some special points of view in the application of the power method are described. By employing exactly measured standard attenuators in cascade, the modified measuring equipment can be used over a range of more than 100dB. An error analysis is given considering all essential sources of systematical errors the limits of which are calculated.It is shown that the systematical error of the system described is less than 1 10-4 dB for very small attenuation values. It is in the order of ISAI = 1 10-4 (1 + A ) dB over the whole range, when A is the numerical value of the attenuation (in dB) being measured.

Error model for insertion loss measurement in testing of balanced twisted-pair cabling: A complete expression and its simplification

“…A 30-m link is used in the comparison. Figure 4 presents the calculated performance limits for insertion loss measurements using the current error model (1) and the newly proposed error model (6). From the results, it is clearly observed that the calculated results using the new error model are higher than those from the current error model, and their difference is increasing correspondingly when the operating frequency increases.…”

“…The worst case for the measurement error (maximum possible error by an ignorance of the phase relations as in [6]) should be considered and can approach to be, where ‫ܧ‬ ோ,௧௦௧ = −20log ଵ ሺ|Γ ୗ |ሻ is the residual source/load return loss of a tester in dB, ‫ܧ‬ ோ, = −20log ଵ ሺ|S ୢୢଵଵ |ሻ is the return loss of the link in dB, and ‫ܧ‬ ூ, = −20log ଵ ሺ|S ୢୢଶଵ |ሻ is the insertion loss of the link in dB. Comparing to (1) in the current IEC standard [1][2], an additional contribution from ‫ܧ‬ ூ, is introduced in the newly proposed error model (6).…”

Importance and estimation of mismatch uncertainty for RF parameters in calibration laboratories

“…So, instead of performing the accurate measurements to have imprecise knowledge of this system used, adding a further term to uncertainty budget as mismatch uncertainty is recommended. Formulas for estimating mismatch uncertainty are derived in terms of reflection coefficients, VSWRs and S-parameters and evaluated earlier in [19][20][21][22][23]. These formulas were developed in accordance to the measurement parameter, its measuring system and the system for measuring the components of formulas.…”

“…If S 11, S 22, Γ G and Γ L are extremely small, i.e. 1, in dB for almost the matched conditions, the maximum mismatch uncertainty for attenuation would be evaluated by [20],…”

“…If the reflection coefficient measurements are performed in terms of magnitude and phase by VNA systems and the phase of Γ G is unknown, the mismatch uncertainty can be evaluated in dB (applicable for high attenuation values, >10 dB) given in [20,21,24].…”