Periodical Measurement Error With Respect to the Length of Thru in TRL Technique
This paper investigates the impact of imperfect connection on measurement results in thru-reflect-line (TRL) calibration technique while the devices under test are lumped resistors, capacitors, and inductors. First, a simplified error-transfer model is proposed for theoretically analyzing the effects of imperfect connection. Then, the simulation and measurement procedure is numerically carried out a sufficient number of times to statistically testify the results from analytical derivation. To get further verification, simulation by commercial software to mimic real scenarios and measurements with microstrip test fixtures at around 0.9 GHz are performed. Analytical derivation, simulation, and measurement all show that the length of the thru periodically reduces the effects of connection errors on the measurement results. Since test fixtures are often artificially embedded in or de-embedded from the ports of the vector network analyzer, random errors are inevitably introduced to different TRL standards and most of the time these errors are the main error contributors. Thanks to the periodical property of the measurement error, the measurement precision can be improved by choosing a thru of a particular length.