Loss Extraction
Comparison of signal attenuation across two distinct trace lengths allows for the extraction of per-unit losses. This delta l method removes the effects of connectors and measurement probes to isolate the properties of the board material. It provides an accurate decibel-per-inch figure for high-speed signal routing.
Material Analysis
Dielectric constant and dissipation factor are the primary variables influenced by the results of this measurement. By comparing a short line to a long line, the constant losses associated with the transitions at each end are subtracted. The remaining difference represents the purely resistive and dielectric losses of the trace itself.
High-frequency designs rely on these extracted values to verify that the laminate meets the specified performance targets. Engineers use the resulting data to calibrate simulation models, ensuring that the predicted reach of a serial link aligns with the physical reality of the manufactured board.
Coupon Geometry
Fabrication of specialized test coupons on the panel border is necessary to execute this test accurately. These coupons must match the stackup and impedance of the functional traces on the main board. Accurate results require the two lines to be long enough to produce a measurable difference that exceeds the noise floor of the vector network analyzer.
