Use of I/Q representation for unmodulated Rx Signal
If you are &quot;observing&quot; the source, this implies there is some sort of information you are looking to get out of it, whether it be the total background noise, interference levels etc.
Do you find &quot;value and use&quot; in the RF signal's magnitude versus time? What about the RF signal's phase versus time? The IQ representation gives us both of these and it simply is another way to represent complex numbers:
$$Ae^{j\theta} = A\cos(\theta)+jA\sin(\theta) = I + jQ$$
One reason complex numbers (I/Q representation) for RF signals are useful is that for real signals, the positive and negative frequency spectrums are complex conjugate symmetric as complex numbers. This means we can represent any real RF signal using just the positive (or negative) spectrum as an analytic baseband signal, describing the signal independently from the carrier frequency.