In Plane Permittivity Extraction Using Multiline Thru Reflect Line Test Vehicles
Multiline TRL stripline vehicles isolate in-plane permittivity by extracting propagation constants directly, bypassing transition discontinuities and z-axis bias.
Microstrip De Embedding
Fixture Removal
A mathematical calibration procedure removes the parasitic electrical effects of test fixtures from measured high-frequency signal data. During radio frequency characterization, microstrip de embedding isolates the scattering parameters of the actual device under test by subtracting the influence of the launching pads and lead-in traces. This extraction ensures that the recorded return loss and insertion loss belong solely to the component.
Designers rely on this technique to obtain clean measurements of sub-millimeter components mounted on planar substrates.
Calibration Strategy
Execution of this process requires the fabrication of specific calibration standards alongside the main circuitry on the test board. Common methods include measuring a through line, a reflect standard, and a line of known electrical length to characterize the fixture behavior. The resulting error terms are converted into matrix representations and mathematically inverted to strip away the fixture response from the raw measurements.
This subtraction yields the true performance of the trace under test.
Extraction Boundary
Accuracy of the correction diminishes when the transition from the coaxial connector to the microstrip trace is highly non-linear or produces severe radiation losses. If the test fixtures on the calibration coupon do not match the physical layout of the device board, the correction becomes invalid. Fixture symmetry governs measurement accuracy.