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AWR Version 13
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Linear TDR Measurements
This project demonstrates how to use the linear TDR measurement capability of MWO. This capability is the same as using a Vector Network Analyzer to do TDR measurements, so the frequency span and frequency steps should match lab equipment when comparing results to measured data. It also demonstrates the use of equations to convert simulated reflection coefficient to impedance.
A simple circuit has been employed to study the standard TDR measurement problem when a length of transmission line is terminated with a resistance. The resistance is coupled to the transmission line using two reactive elements that can represent discontinuities. For example, these discontinuities could be found in a typical coaxial to microstrip transition. Other elements can be added to suit the needs of the designer.
The primary elements, R, L and C can be tuned (Simulate > Tune). The terminating resistance is defined using the vector equation capability of MWO. Here we see that the resistance has a fixed set of values, ranging from 0 - 200W. If required, this list (or vector) can be edited and other resistance values can be added or removed. The equations for the resistance values are found in the main schematic window. The equations used to collect the reflection coefficient and convert this to impedance are found in the output equations window.
This graph displays the results from the TDR measurement directly. The reflection coefficient vs. time is being displayed. The two traces show the TDR measurements for step (blue) and impulse (magenta) response.
This graph displays the results from the equation used to convert between reflection coefficient and impedance.
Schematic - Reflection
Graph - Impedance TDR
Graph - Reflection TDR