Why Does Wave Reflect at Impedance Discontinuity?

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SUMMARY

The discussion centers on the reflection of waves at impedance discontinuities, specifically addressing the 180-degree phase shift observed when a transmission line terminates in a short circuit, compared to no phase shift when terminated in an open circuit. The characteristic impedance of coaxial cables is defined as the ratio of voltage to current at high frequencies, influenced by the cable's series of LC cells and inherent resistance. Additionally, the wave's velocity is directly related to the medium's permittivity, which varies with the frequency of the wave.

PREREQUISITES
  • Understanding of characteristic impedance in coaxial cables
  • Knowledge of wave propagation and impedance relationships
  • Familiarity with transmission line theory
  • Basic concepts of LC circuits and their behavior
NEXT STEPS
  • Research the mathematical definition of characteristic impedance in transmission lines
  • Study the effects of impedance mismatches on wave reflection
  • Learn about the relationship between wave velocity and medium permittivity
  • Explore the principles of wave behavior in LC circuits
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Electrical engineers, physics students, and professionals involved in telecommunications and signal processing will benefit from this discussion, particularly those interested in wave behavior and transmission line characteristics.

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Why does a wave reflect when it meets an impedance discontinuity? And why is there a 180 degrees phase shift of the reflected wave when the transmission line finished with short circuit and no phase shift when the far end of the line is opened?
 
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Tell us what you know so far about these questions, so that we can help you. We do not provide solutions to homework and coursework questions here on the PF (that's against our rules), but we are more than willing to help if you show us what your thoughts are so far.

Like, how do you define characteristic impedance? What is the relationship between the wave and the impedance of the medium that it is traveling through?
 
The characteristic impedance of a cable (it was coaxial cable I was interested in) is, as far as i know, its high frequency impedance (if we supply the line with some signal, the line draws some current from the source and the ratio voltage/current defines the characteristic impedance of the cable. (the cable acts as a series of LC cells, and is lossy because of its resistance)
As regards the relation between wave and medium impedance, I don't know if there is a general formula to characterize this. I know that the wave's velocity depends on medium permitivity which in turn is dependendent on waves' frequency.
 

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