Context: I am doing a project where I have to sample a video signal from a monitor with an SDR. The data is coming in for each pixel left to right top to bottom. Since my receiver doesn't have a very wide bandwidth (25MHz) and the signal I am trying to receive is very wideband (+100MHz), I have tried to set my centre frequency to equally spaced intervals within this wideband and sampled the signal at each interval. The frequency "bins" have been demodulated to baseband and I have lined up the images.
Question I want to now combine these different sub-bands together again to attempt to recreate the original wideband signal. Would I just shift the FFTs of the images and average them together? I have tried to do this but I am getting additional frequency components that are corrupting the image.
What is the theory of combining sub-bands together called? I have tried to do some research but I have been unsuccessful.