What does a complex reflection coefficient signify?

A reflection coefficient (Г) of 0 means that all power is absorbed by load. This happens when both source and load impedance are equal.
A reflection coefficient (Г) of 1 means that all power is reflected by load. This happens if the load is open circuit.

What does a complex value of reflection coefficient mean?

I do understand that the reflection coefficient can be positive or negative, if the reflection is inverted signal relative to the source, then the reflection coefficient must be negative. What I don't understand is what does a complex reflection coefficient mean. I wonder if it has something to do with phase difference, but that really will be even more confusing if it really is the case.

Gamma=Zin-Zs/(Zin+Zs)

Zs and Zin are complex so the reflection coefficient is also complex.

Magnitude of the Reflection Coefficient cannot be negative.It's always between 0 and 1.

Read about Smith chart. It's an intuitive way to understand complex reflection coefficients.

In addition to the above comments -- similar (and related) to a complex impedance, a complex reflection coefficient means that reflection is caused by a load that has both real and imaginary components. As you indicated, this results in a reflection phase that is not 0 or 180 degrees.

All the above is right (except for a missing pair of parenthesis for (Zin-Zs) in post #2), but the essential concept should be emphasized:

The reflection coefficient is the ratio reflected_wave/incident_wave. Both waves are complex magnitudes (phasors).

Its modulus is the ratio of amplitudes (real and positive).
Its phase can be viewed as the angle between both phasors.

Regards

Z

I was not talking about the magnitude of the reflection coefficient. The coefficient iteslf which is Г=Zin-Zs/(Zin+Zs), can be both positive or negative. It can be purely imanigery as well and in this case it can be positive imaginary as well as negative imaginary.

Please read my post #5:

a) Don't miss parenthesis in Г=(Zin-Zs)/(Zin+Zs)

b) Г is the quotient of two complex numbers (representing reflected and incident waves), so it is a complex number. It has modulus and phase. It has both real and imaginary part, and both of them can be positive or negative.

Z