Time Domain Reflectometry

Time Domain Reflectometry in EMWORKS?

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 

• Impedance profile along the line - Compute the characteristic impedance versus distance to spot steps, dips, and mismatches.

• Signal integrity assessment - See reflections, overshoot and ringing caused by vias, connectors, layer transitions and stubs.

• Fault and discontinuity location - Convert time to distance to pinpoint where an open, short or defect is located on the structure.

• Time-domain waveforms -Plot incident and reflected voltage/current versus time for different excitation pulses.

• 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 – Board-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.