Patent ID: 6782038
Filing Date: 2004-08-24
Classification: H03C,H03D,H04B,H04L

Abstract:
A method of receiving a wanted modulated radio frequency signal and of demodulating it to recover the wanted modulating signal therefrom, the method comprising the steps of receiving a radio frequency signal; generating a high frequency local oscillator signal, which can be mathematically described as having a fixed frequency corresponding substantially to the frequency of the carrier wave of the wanted modulated radio frequency signal and a phase which varies progressively in time according to a predetermined local progressively-varying phase function; mixing the received radio frequency signal in a first mixing step with the high frequency local oscillator signal so as to down-convert and phase-spread locally the band-width of the signal with which it is mixed and generate a mixed base-band signal; converting the mixed base-band signal from an analogue signal into a digital signal; generating a low frequency local oscillator signal, and mixing the mixed base-band signal with the low frequency local oscillator signal in a second mixing step, said low frequency local oscillator signal being, mathematically describable, as having a fixed frequency of substantially zero and a phase which varies progressively in time according to the predetermined local progressively-varying phase function when delayed by a predetermined delay corresponding to the time taken for the signal to propagate between the first mixing step and the second mixing step; and wherein mixing the mixed base-band signal with the low frequency local oscillator signal in the second mixing step, recovers a recovered signal including both a wanted base-band signal whose phase is not dependent on the predetermined local progressively-varying phase function and a noise signal whose phase is dependent upon the predetermined local progressively-varying phase function.