I/Q Signal Power Calculation I am trying to understand the basics of IQ modulation. The amplitude of a demodulated IQ signal is given as $\sqrt{I^2 + Q^2}$ which is easy to understand from the phasor diagram. 

Yet, I don't understand the IQ power: ${I^2 + Q^2}$ . Where is the load impedance in this expression ? I'd expect something like 

$Z_{load} = 50 \Omega $

$P = \frac{I^2 + Q^2}{Z_{load}}$

What is missing in my understanding ?
Nothing is missing in your understanding. When we calculate power that way, it is assuming a $1 \Omega$ load and that amplitudes are given in volt, but almost nobody ever says that even in textbooks. Unless it is explicitly stated otherwise, I think it is safe to assume this.