Phase-locked loop with sigma-delta modulator having feedback path representing complex transmission function in Laplace plane

摘要

The phase-locked loop has a phase comparator (1) with 2 inputs and an output coupled to the control input of a voltage-controlled oscillator (4), a variable frequency divider (9) receiving the oscillator output and a sigma-delta modulator (11) coupled to the control input of the frequency divider. The sigma-delta modulator has a feedback path (16) for combining the output of a summation element (15) with an input so that the feedback path represents a complex transmission function in the Laplace plane.