software defined radio
In SDR, all basic processing is done on digital hardware, including modulation/demodulation (AM/PM/FM)... The output of the digital unit, is usually an N-bit word, which represents the waveform sample, which feeds a DAC and Power amp. for transmit....
In Rx. side, ADC digitizes the signal as close as possible to the antenna... Digitization at RF is very tough... So IF digitization is usually carried out... Then baseband demodulation is carried out...