How to Characterize TDR Impedance

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Modular Sampling Oscilloscope
+ Modular Sampling Oscilloscope
Modular Sampling Oscilloscope
+ Modular Sampling Oscilloscope

Characterize Interconnect Impedance with a Sampling Oscilloscope

Time-domain reflectometry (TDR) is used to characterize impedance uniformity and locate discontinuities in high-speed interconnects such as printed circuit board traces, packages, connectors, and cables used in 400G, 800G, and 1.6T systems. Engineers rely on TDR measurements to identify impedance mismatches, reflections, and propagation delay that degrade signal integrity, but accurate analysis requires a fast-edge stimulus, a well-defined reference plane, and high-fidelity acquisition of reflected signals.

The measurement is performed with a sampling oscilloscope and TDR/TDT module that generates a calibrated step stimulus and captures reflected signals. Reflections are converted into impedance versus time or distance, allowing engineers to locate discontinuities and determine whether features exhibit inductive or capacitive behavior. This requires precise control of the stimulus edge, consistent reference-plane definition, and sufficient temporal resolution to resolve closely spaced physical structures.

TDR Impedance Characterization Solution

Characterizing time-domain reflectometry impedance requires launching a fast calibrated step into the interconnect and measuring reflections to determine impedance variations versus time or distance. Keysight’s TDR impedance characterization solution includes a modular sampling oscilloscope with a TDR/TDT remote sampling head and signal integrity software for impedance profile analysis. The workflow enables engineers to identify discontinuities, measure propagation delay, and isolate physical features within the interconnect while maintaining high measurement resolution through close-to-device signal access.
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