Synthetic Aperture Radar (SAR). How to do Range Compression?
What format is your input data in? It sounds like you have a phase history signal as it's often called. Assuming that the transmitted waveform was a linear FM chirp, has it already been deramped? Some receivers perform deramp-on-receive processing, which removes the chirped nature of the waveform. In that case, range compression is as simple as performing a 1-D FFT on each pulse return (which appears to be one per column in your example).

If you instead have a raw collection from the receiver that hasn't been deramped, then you expect to have an input signal that consists of many reflections of the transmitted waveform, separated in time according to the round-trip delay to the various reflectors in your scene. In this case, in order to perform range compression, you need to generate and apply a matched filter to each pulse return (again, a 1-D convolution of each column of your dataset with the matched filter).