Time Domain Reflectometry
TDR in EMWorks simulates how a fast edge travels along transmission lines, PCB traces, cables and connectors, and how it reflects from impedance changes. From a single 3D model, you can visualize the TDR waveform, extract the impedance profile versus distance, and quickly locate discontinuities, stubs, opens, shorts or poorly matched transitions.
Key Capabilities
1
Impedance profile along the line: Compute the characteristic impedance versus distance to spot steps, dips, and mismatches.
2
Signal integrity assessment: See reflections, overshoot and ringing caused by vias, connectors, layer transitions and stubs.
3
Fault and discontinuity location: Convert time to distance to pinpoint where an open, short or defect is located on the structure.
4
Time-domain waveforms: Plot incident and reflected voltage/current versus time for different excitation pulses.
5
Design and layout verification: Compare TDR results before and after geometry changes to validate stackup, trace width and launch design.
Devices and Structures Commonly Analyzed
High-speed PCB traces and vias – Single-ended and differential lines with launches and layer transitions.
Connectors and interconnects – WBoard-to-board, cable, and RF connectors in their real 3D environment.
Cables and harness segments – Coax and high-speed copper links with bends, splices and junctions.
Packages and sockets – BGA breakouts, chip packages and sockets where discontinuities are critical.
Backplane and mezzanine links – Long multi-connector paths in networking and telecom systems.
Output of EMWORKS' TDR Analysis
TDR analysis generates a wealth of valuable information about the tested transmission line or cable. The key output parameters obtained from a TDR analysis include:
Reflection waveform (TDR trace) - Voltage or reflection coefficient versus time, showing where and how strongly reflections occur.
Impedance vs. distance profile -Extracted impedance along the line, derived from the TDR response.
Return loss / reflection metrics - Quantitative measures of mismatch at critical interfaces.
Attenuation and loss behavior -Estimation of how much the signal is attenuated along the path.
Propagation velocity / effective dielectric -Effective propagation speed and dielectric constant inferred from the TDR response.
These outputs let you quickly check whether a high-speed path meets its impedance and SI targets, and where to adjust geometry, stackup or connectors if it doesn’t.