De-Embedded Measurements Using the HP 8510 Microwave Network Analyzer

It is often difficult to directly measure components and devices at microwave frequencies. Transistors and other active devices must be mounted in some type of fixture in order to be measured by an automatic network analyzer (ANA). Because suitable in-fixture calibration standards are often not available to calibrate the ANA it becomes necessary to have a method to correct errors in the measured data caused by the fixture. This paper demonstrates how to modify the HP8510 error correction process so that the HP 8510 can make direct real time measurements of fixtured devices by correcting for fixture errors. In addition, an extension of this basic technique is presented which uses the built-in error correction ability of the HP 8510 to display the response of a real device in a hypothetical circuit. Overall circuit performance relative to device parameter or type changes can be observed. An example is presented which shows a packaged microwave transistor measured as though it were part of a matched bandpass amplifier circuit. Amplifier performance as a function of bias conditions is shown. This technique, called embedding, offers a powerful blend of real time circuit analysis and measurement.