let's consider a coaxial cable of length L and see what happens at port 1 when port 2 is left open. Let's consider what is written on these slides:
1) I do not understand the reason of this graph. In fact I thought that the absolute value of input reflection coefficient should be always equal to 1 (or 0 in dB) since for a transmission line we have total reflection if at the end it is left open. Why is there this curve that decreases with frequency?
2) Now let's consider the following slide:
It is written that in resonance the absolute value of the input reflection coefficient shows a periodic dependence of frequency. I do not understand:
what is exactly the resonance condition
why is the curve oscillating
why is the curve different from that seen in 1) and in general from |ᴦ|dB = 0