What is de-embedding in RF measurement?
De-embedding removes the effects of fixtures, probes or launches between the instrument’s calibration plane and the device. If the fixture halves are known two-ports A and B, the device’s cascade matrix is TDUT = TA−1 · Tmeas · TB−1. The accuracy of the result depends entirely on how well the fixture is characterized.[1][2]
What de-embedding methods exist?
- Port extension: removes a delay and optionally loss; simple, assumes a matched uniform line.
- Fixture models: simulated or measured S-parameter files of each fixture half.
- 2x-thru: measures two fixture halves connected back-to-back and splits them; standardized in IEEE P370 for interconnect characterization.
- In-fixture calibration: TRL or multiline TRL standards built on the same board moves the calibration plane to the device.[3]
- Open-short methods for on-wafer transistor pads.
When is calibration better than de-embedding?
When the fixture is poorly matched or lossy, measuring calibration standards in the same medium (TRL on the PCB) directly corrects to the device plane and is generally more accurate than a model.[3][1]
What can go wrong?
- Non-identical fixture halves produce errors at frequencies where the fixture is mismatched.
- Noise in measured fixtures amplifies when inverted.
- Resulting data can be non-causal or non-passive; check before using in simulation.
Frequently asked questions
Is port extension de-embedding?
A simple form; it assumes the fixture is a matched lossless or lossy line.
What is TRL?
Thru-Reflect-Line, a calibration using a thru, a high reflect and a delay line, introduced by Engen and Hoer in 1979.
Can de-embedding make data non-passive?
Yes, if fixture data are inaccurate.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “Understanding the Fundamental Principles of Vector Network Analysis (Application Note 1287-1)”. Keysight Technologies. application note.
- “Microwave Engineering, 4th ed.”. D. M. Pozar, Wiley. 2012.
- “Thru-Reflect-Line: An Improved Technique for Calibrating the Dual Six-Port Automatic Network Analyzer”. G. F. Engen and C. A. Hoer, IEEE Transactions on Microwave Theory and Techniques, vol. 27, no. 12, pp. 987-993. December 1979.