Fixture De-Embedding Challenges for Short 2xThru Structure

Fixture de-embedding represents a procedure developed to eliminate undesirable fixture effects from the initial measurements, allowing us to isolate and obtain the S-parameters solely for the device under test. Currently one of the most popular methods for fixture de-embedding, that is used in most commercial tools, is 2xThru de-embedding. The main advantage of 2xThru de-embedding is that it significantly reduces required number of measurements and is much easier to implement compared to other traditional methods. “IEEE Standard for Electrical Characterization of Printed Circuit Board and Related Interconnects at Frequencies up to 50 GHz” provides requirements for fixture design. Based on the requirements 2xThru should have long enough transmission line in the middle. In the present paper will be analyzed the case, when 2xThru does not satisfy requirements of the standard. Particularly, will be considered the case when 2xThru is very short and discontinuity in the fixture is not vanished before it reaches middle point of the structure. We will show in which cases existing de-embedding tools will be able to still extract accurately left and right fixtures from short 2xThru structure.