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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Like, how do you define characteristic impedance? What is the relationship between the wave and the impedance of the medium that it is travelling 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 betwen 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.