Developing High-Quality Test Fixtures for De-embedding of S-Parameters

Extracting high-quality S-parameters for a DUT from measurements inherently involves de-embedding them from a total structure that includes test fixture lead-ins. These lead-ins typically include probes or connectors, and potentially some length of non-coaxial transmission-line, e.g., stripline or microstrip on a PCB, as well as via transitions, in addition to the DUT. A common current de-embedding approach often used for DUTs on printed circuit boards, packages, and cabling for example, utilizes a 2X Thru, or 1X Open together with the total structure to extract the DUT Sparameters.
For many current high-speed and high-frequency applications it is necessary to do 3D full-wave electromagnetic simulation in order to develop a high-quality test fixture from which successful de-embedding can result. The features that comprise good lead-in test fixturing from which DUT S-parameters can be extracted will be detailed in this presentation. EM simulation for developing test fixtures will be discussed and examples provided. This presentation will also briefly discuss making quality S-parameter measurements with a VNA and provide comparison results. Examples for de-embedding to 50 GHz will be presented.