Voltage Reflection Coefficient Question

In Wes Hayward's book "Introduction to Radio Frequency Design" on page

116, the voltage reflection coefficient is given as gamma = V-/V+ = (z-1)/(z+1) where z is the normalized impedance, Zin/Z_o. As an example, the author then takes a circuit comprised of a 2 volt source into a voltage divider to calculate the output voltage based on reflected voltage waves. For example, with a source resistance of 1 ohm and a load resistance of 0.5 ohm, gamma = (0.5 -1)/(0.5 +1) = -0.333. The forward wave is said to be 1 and the reverse wave is -0.333 leaving a sum of 0.667, which is the same thing you would get using the voltage divider equation: (2*0.5)/(0.5+1) = 0.667.

My point of confusion is that this example only seems to work with a source voltage of 2 volts. Why does a 2 volt supply cause the forward wave to be 1? I'm probably missing something obvious, but could use some insight.

Reply to
Bitrex
Loading thread data ...

If there's a voltage V across a matched resistive load R connected via a transmission line of characteristic impedance R to a generator with a source impedance R, the Thevenin equivalent of the generator is a voltage soure of e.m.f. 2*V in series with a source resistance R. The open-circuit voltage across the generator output would be 2*V if you disconnected the load.

Reply to
Andrew Holme

I don't have access to a copy of the book you quote, but, assuming that you've quoted correctly, I've never before seen such a poor "explanation".

The use of "gamma" for reflection coefficient, rather than the usual "rho", casts doubt over the author's familiarity with the subject.

Transmission lines can have reflections, resistive voltage dividers don't, and cannot have a reflection coefficient. The "example" is nonsense.

Reflection coefficient is simply the (complex) ratio of the reflected voltage to the forward voltage. It is always >=zero

Reply to
Fred Abse

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.