I am preforming an experiment that involves a transmitter, material target, and two receivers (as a baseline). The goal is to record the RF reflectivity of the target. How can I calculate/measure this from the received signal, and can it be done in GNUradio-companion?
Any help is appreciated. Thank You.
You can do that, in many ways. In the end, chances are you'll send some predefined signal, e.g., precomputed white pseudorandom noise from a "vector source", record that (e.g. using a "file sink" or a "vector sink") and build a correlation estimator that processes that data offline.
Of course, a correlation is just convolution with the (conjugate) time-inverse, so you can also (conjugate if complex and) time-reverse your reference signal, and use it as filter taps.
Note that in general, SDR devices are nice and linear, but not calibrated – you can only compare received signal powers, but you cannot attribute an absolute power to them – unless you know the strength of some reference reception.