Mismatch uncertainty in radiofrequency connections

Mismatch uncertainty originates from mismatch at both the generator and load side of a radiofrequency connection. Error correction for mismatch is a well-known practice by radiofrequency power calibration laboratories [1]. Nowadays the evaluation of mismatch uncertainty is an issue also for Electromagnetic Compatibility (EMC) testing laboratories compliant with, accredited or working towards accreditation to ISO/IEC 17025 since they must evaluate and declare uncertainty of testing and internal calibration results. The recent developments of receivers’ technology, mainly due to the motion of analog-to-digital conversion towards the input of the receiver (from the output of the envelope detection circuit to the output of the last intermediate frequency stage), have dramatically enhanced the performances in terms of amplitude measurement accuracy [2]. Hence mismatch uncertainty has become a significant (if not dominant) contribution to many measurement uncertainty budgets. The scope here is to introduce the reader to mismatch uncertainty, giving the basic theoretical background and formulas. A simple and practical example is also illustrated.