High frequency measurements for circuits such as MMICs and high speed digital circuits are made using some kind of Vector Network Analyzer ( VNA) or some kind of TDR instrument. In most cases the DUT ( device under test) is mounted on a test fixture which probably has an input connector and microstrip and an output connector and microstrip. The measurements are to be made on the characteristics of the DUT. To do this the test fixtures have to be de-embedded. This technique and its basics form the subject of the latest brief paper from the technical team at Signal Processing Group Inc. It can be found at http://www.signalpro.biz in the Engineer’s Corner.