Analyzing Time Domain properties of cables and circuits

February 7, 2023

TDR and DTF with a Vector Network Analyzer (VNA)

A VNA measures impedance and gain over a frequency sweep. There are math functions, the Fourier Transform, that can convert this frequency information to the Time Domain, to analyze the properties over time and distance.

Time Domain measurements

The TDR functions of the MegiQ VNA software make it possible to measure the impedance of a cable or circuit as a function of the time, or distance, in the network.

This allows analysis of the impedance at certain spots in a cable or a PCB trace.
 

Distance To Fault detection

In the TDR graph it is easy to see if there are impedance jumps, like a short or open in the cable, and how far from the VNA they are.

A damaged coax can show a slight or large impedance variation along its length.
 

Time Gating

With the TDR functionality it is possible to ‘filter’ the gain-frequency graph with a filter in time.
 

Analyzing PCB traces

With the TDR functions we can determine the impedance at a specific point in a circuit. This makes it possible to evaluate the impedance of traces on a PCB.

Learn more: VNA-0460e, 400MHz to 6GHz, 2 1/2 port