All-digital phase-locked loop system for producing oscillator output signal under control of digital reference input signal, has sigma delta modulator for producing additional digital one-bit-control signals

摘要

The all-digital phase-locked loop system has a sigma delta modulator for producing additional digital 1-bit-control signals for a digitally controlled oscillator. A digital adder is provided with an additive input, on which a digital reference input signal is set, and another subtractive input, on which a divided digital signal is set. The digital adder makes available the digital output signal, whose most significant bits are set on an input of a digital loop filter (12), and whose least significant bits are set on an input of the sigma delta modulator.