EMC Question of the Week: September 14, 2026
Which of the following is a visual aid that is useful for analyzing certain transmission line problems in the frequency domain?
- Bounce Diagram
- Triboelectric Series
- Smith Chart
- Bob Smith Termination
Answer
The best answer is “c.” A Smith chart (partially depicted on the right side of the figure) maps the real and imaginary components of complex reflection coefficient values to a magnitude and phase on a unit circle. It is useful for visualizing how the magnitude of the reflection coefficient and the standing wave ratio vary as a function of frequency. It can be particularly helpful for determining the length and location of matching stubs in a microwave circuit.
A bounce diagram (depicted on the left side of the figure) is a visual aid for analyzing transmission line problems in the time domain. It visually represents a wavefront and its reflections as they propagate and is useful for determining what the voltage and/or current on the line will be at any point as a function of time.
A triboelectric series is a listing of materials ranked according to their affinity for charge. It is useful for understanding the likelihood of triboelectric charging when two dielectric materials make and break contact.
A Bob Smith termination is a pair of 75-Ω resistors and a capacitor used to terminate certain high-speed differential interfaces.
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