Patent ID: 11846661

Abstract:
Determining the ratio between two frequencies can be a useful electronic building block in different electronic circuits with very divers functionalities. The invention comprises a circuit for determining a frequency ratio between a first input signal having a first frequency and a second input signal having a second frequency, wherein the circuit comprises: a controlled fractional frequency divider arranged for generating a divided signal having a divided frequency being substantially the first frequency divided by a control signal; a frequency phase detector arranged for generating a phase difference signal based on a frequency phase difference between the divided frequency of the divided signal and the second frequency of the second input signal; and a loop filter arranged for generating the control signal based on the phase difference signal; wherein a loop is formed by the controlled fractional frequency divider, the divided signal, the frequency phase detector, the phase difference signal, the loop filter and the control signal; wherein the loop filter filters the phase difference signal such that instability of the loop is prevented; and wherein the control signal, preferably the magnitude of the control signal, is indicative of the frequency ratio.