Clock noise canceling circuit
In a clock noise canceling circuit, a coupler extracts a signal from a clock signal. A filter selects a harmonic component of a preset frequency in the extraction signal from the coupler. A phase shifter phase inverts the harmonic component of the preset frequency from the filter. An AGC amplifier amplifies the phase-inverted harmonic component from the phase shifter. Also, a combiner combines the amplified component from the phase shifter with the clock signal to eliminate the harmonic component of the preset frequency from the clock signal. A power detector detects a power level of the harmonic component of the preset frequency in an output signal of the combiner. Additionally, a controller controls gain of the automatic gain control amplifier based on the power level of the harmonic component detected by the power detector, thereby canceling noises.
1. A clock noise canceling circuit comprising:
a coupler for extracting a signal from a clock signal;
a filter for selecting a harmonic component of a preset frequency in the extraction signal from the coupler;
a phase shifter for phase inverting the harmonic component of the preset frequency from the filter;
an automatic gain control amplifier for amplifying the phase-inverted harmonic component from the phase shifter;
a combiner for combining the amplified component from the phase shifter with the clock signal to eliminate the harmonic component of the preset frequency from the clock signal;
a power detector for detecting a power level of the harmonic component of the preset frequency in an output signal of the combiner; and
a controller for controlling gain of the automatic gain control amplifier based on the power level of the harmonic component detected by the power detector, thereby canceling noises.
2. The clock noise canceling circuit according to claim 1 , wherein the controller is adapted to monitor the power level of the harmonic component from the power detector while varying the phase-inverted frequency from the phase shifter in order to control phase shifting at a frequency where the power level of the harmonic component is at a minimum.
3. The clock noise canceling circuit according to claim 1 , wherein the controller is adapted to control harmonic selection and phase shifting based on the harmonic component of the preset frequency.
4. The clock noise canceling circuit according to claim 3 , wherein the filter comprises a tunable filter for setting a pass band having the harmonic component as a center frequency under control of the controller.
5. The clock noise canceling circuit according to claim 3 , wherein the phase shifter is adapted to invert a phase of a frequency signal corresponding to the harmonic component from the filter under control of the controller.
6. The clock noise canceling circuit according to claim 1 , wherein the clock signal is generated by a clock signal generator and provided to an image sensor module.