Impedance of Coaxial Cable
Just as a mechanical wave may be inverted when traveling through different medium, electric waves can be inverted when traveling through conductors of different impedance. A fundamental equation for coaxial cables which describes this phenomena is:
Vreflected / Vincident = (Zload - Zcable) / (Zload + Zcable)
Where Zload is the impedance of a component placed at the end of the cable, and Zcable is the impedance of the coaxial cable. Using this equation, we know that Vreflected will equal zero, when Zload equals Zcable .
Click to see examples of how load resistance affects the reflected pulse.
To experimentally calculate the coax cable's impedance, we made a graph of (Vr / Vi) vs. Load Impedance.
Thus our experimental value of 55.4 ohms was very close to the accepted value of 53.5 ohms.
Introduction | Cable Info | Lab Procedure and Results | Conclusions