Meaning
Mathematical correction algorithms remove the electrical effects of test fixtures from measured S-parameters to isolate the device under test. Process engineers use de-embedding to shift the measurement reference plane directly to the pins of a transceiver module soldered to a test board.
Mathematical Subtraction
Probe transitions and trace losses are measured separately using dedicated calibration structures on the same panel. This calibration data is represented as a matrix and inverted to subtract the fixture behavior from the total system measurement. The remaining data represents the isolated component as if it were connected directly to the coaxial cables, enabling the validation of specific board components against supplier data sheets.
Reference Plane
Shifted boundaries allow for accurate comparisons between simulation models and physical board measurements. Without this shift, the loss of the launch trace would make the component appear to have worse return loss than its actual specifications.
Measurement Accuracy
High frequency boards require precise models of transitions to avoid introducing mathematical artifacts during the subtraction step. Any mismatch between the calibration trace and the actual fixture trace will generate non-physical gain or phase ripples in the final data. This sensitivity limits the method to clean transmission structures with highly repeatable connections.
