Transmission Lines - Signal Transmission and Reflection
Why Electrical Engineering Stack Exchange recommends it
Electrical Engineering Stack Exchange users link it when they need an intuitive picture of wave propagation, reflection and why transmission lines need termination.
Recommended by 3 people across 4 different months, 2019 to 2024.
What it is
A short animated explainer by Eugene Khutoryansky that visualizes voltage and current waves travelling along a transmission line, modeled as a chain of inductors and capacitors. It shows how a step signal propagates and reflects from open, shorted and terminated ends.
What people said
Recommends techSultan · 2019-06 · Electrical Engineering Stack Exchange · on “Do I need to measure impedance before every CAN termination?”
Background : I need to set up a CAN bus between different components of an electric UAV (battery management system, motor inverter, autopilot, etc.). My avionics/networking experience up to now includes home networking, RC hobby servos (PWM), and "smart" hobby servos (serial), so I'm familiar with the general process I have to follow in terms of network software (device IDs, baud rates, etc). Problem : I've never dealt with the idea of "termination". I keep reading something along the lines of "CAN needs 120Ω termination at each device". This video [this video] helps me understand why I need termination, but I'm not sure how to implement that. Am I supposed to slap a 120c resistor parallel to the
Recommends hacktastical · 2019-08 · Electrical Engineering Stack Exchange · on “Voltage propagation along a wire”
tl; dr version: The voltage step propagates as a wave along the wire. Yes, your scheme will work if you take care of termination on the line so you don't get unwanted reflections. The speed of the voltage-step wave propagation is some fraction of the speed of light, C . For a low-loss coax cable, the speed will be about 0.8 C . For a microstrip PCB trace it's more like 0.5 ~ 0.6 C (about 140-170ps/inch.) You can take advantage of this fact to create a delay line, assuming you take care of signal integrity issues to ensure the waveforms you pick off are clean. Here's a video with a visualization of wave propagation on a wire, unterminated and terminated: [this video] In this video, the wire (or, m
Recommends hacktastical · 2021-08 · Electrical Engineering Stack Exchange · on “Trace impedance ohm meaning”
All circuits have resistance (R), inductance (L) and capacitance (C). Taken together, these form the overall impedance of a circuit. Regardless, the unit of impedance is still Ohms. Expressed another way, DC resistance is a special case of impedance where there is only the resistive element and no reactive elements (L and C) in play. Transmission lines have an additional element: signal flight time. They are modeled as a series of L-C unit impedances which determine the net impedance of the line. The trick is, with a transmission line the signal flies down the wire as a wave. But the driver only ‘sees’ a net unit impedance at the driven end, not the whole lumped L and C of the line. Here's a
Recommends Bruno Pimenta · 2024-07 · Electrical Engineering Stack Exchange · on “Why does the voltage double at the end of line in a open transmission line (physical explanation)”
I'm seaching a way to explain physically what happens in a wave reflection in a transmission line, if we apply a DC voltage in a open circuit transmission line, the voltage at the doubled. I saw this video presentation [this video] , but I would like to understand physically the reflection that is represented in the video. In the first moment of the signal travel it's charging the capacitors that are in between the conductors, but according to the video (minute 2:08) after a reach a few capacitors the first capacitor started to discharge, why does the voltage decrease? When the current reaches the last capacitor, the voltage in the last capacitor almost doubled its value. I would like to know wha