De-embedding errors due to inaccurate test fixture characterization

Making high quality vector network analyzer (VNA) measurement is relatively easy with standard coaxial connectors. However, in RF or high speed interconnect applications, test fixtures are usually required to connect the standard coaxial connectors to the device under test (DUT). The test fixtures need to be characterized first and then de-embedded to reveal the measured S parameters of the DUT. A good test fixture design is critical to the measurement accuracy of DUT. In this paper, the de-embedding error due to in-accurate fixture characterization is analyzed. Examples are given to show that for test fixtures with large insertion loss and return loss, a small error in the fixture characterization can lead to significantly larger error in the deembedded result of the DUT.