High accuracy radio frequency analogue to digital converter

摘要

A radio frequency analogue to digital converter achieving high accuracy over a limited band-width comprises high gain amplifiers 12,13,14 incorporating bandpass filters in the form of single tunable resonators 15,16 tuned so that their resonant frequencies are at substantially the signal frequency, connected to perform the band-pass equivalent of integrators in the forward path of a delta sigma analogue to digital converter. A tuning arrangement comprises means to make the resonator oscillate and for adjusting a variable reactance within the resonators to tune the resonant circuits, together with digital circuitry to implement a phase locked loop to set the resonator frequency to that of the signal which it is desired to receive. Such an analogue to digital converter circuit may be used to digitize signals up to the microwave region with very high precision. This enables a radio receiver to be implemented on an integrated circuit with almost all filtering and the frequency conversion performed digitally.