[SI-LIST] Re: reflection coeficient
- From: olaney@xxxxxxxx
- To: kpsubramani@xxxxxxxxx
- Date: Sun, 19 Aug 2007 08:43:42 -0700
Subbu:
The reflection coefficient describes the sign and magnitude of the
reflection that returns from an impedance discontinuity. The formula is
really simple if you break it into two parts. The formula that describes
a voltage divider is Volts out = Volts in times the voltage division
ratio, i.e. the fraction of the total resistance that volts out is
dropped across. The voltage division ratio, Zterm/(Z0 + Zterm) is what
matters here. The reflection coefficient computes this for two cases and
takes the difference between the two, namely the ideal case of Zterm =
Z0, and the case of what happens for the actual value of Zterm. The
difference between the ideal and the actual division ratios is rho. The
formula seems complicated only because we combine the two cases into a
single expression over the common denominator, which obscures the
reasoning.
Suffice to say, if Zterm actually does = Z0, the difference is zero and
no reflection occurs. As Zterm varies between 0 and inifinity, rho
varies between -1 and +1, and X volts sent into the transmission line
yields X volts times rho coming back (assuming a lossless line).
Orin Laney
On Sat, 18 Aug 2007 23:48:21 -0700 (PDT) sub mani <kpsubramani@xxxxxxxxx>
writes:
> Hello all,
> I was reading about signal reflections. I do not
> understand the formula rho = (zo-zterm)/(z0+zterm)
> Could anyone explain it/give some tech article, more
> detailed on the basics of reflection
>
> regards
> subbu
>
>
>
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