A method (and apparatus) of receiving (and transmitting) a wanted modulated radio frequency signal and of demodulating it to recover the wanted modulating signal (131,132) therefrom, the method comprising the steps of receiving a radio frequency signal (99); generating a high frequency local oscillator signal (71,72), which can be mathematically described as having a fixed frequency ω RF corresponding to the frequency of the carrier wave of the wanted modulated radio frequency signal and a phase φ ss which varies in time according to a predetermined phase function; mixing the received radio frequency signal (99) with the high frequency local oscillator signal (71,72) to generate a mixed signal (111,116); converting the mixed signal from an analogue signal into a digital signal (121,122); generating a low frequency local oscillator signal (61,62,63,64), which can be mathematically described as having a fixed frequency of zero and a phase φ ss which varies in time according to the predetermined phase function when delayed by a predetermined delay corresponding to the time taken for the signal to propagate between the first mixing step (110,115) and the second mixing step (300); and mixing the mixed signal with the low frequency local oscillator signal to recover a recovered signal (131,132) including both a wanted base-band signal whose phase is not dependent on the predetermined phase function and a noise signal whose phase is dependent upon the predetermined phase function.