Up one level (Radio (RF))
Software Defined Radio (SDR)
Software defined radio is the technique which concerns demodulation of information from radio waves entirely in software. The most important part of the SDR-system is a good AD (Analog-Digital converter). This digitalizes a radio signal so that a computer can work with it.
For experimenting with Software defined radio there is a GNU project called GNU Radio. Take a look at this if you are interested.