Method and apparatus for clock recovery
A clock recovery system includes a rough clock generator, which yields a rough clock signal, based upon logic level transitions exhibited by a data signal. The rough clock signal is supplied to a phase locked loop having an adjustable order of frequency response, an adjustable corner frequency, an adjustable natural frequency, and/or an adjustable damping factor. The clock recovery system includes control parameters that, when properly adjusted, suppress non-ideal effects of components within the clock recovery system, and also permit the frequency response of the phase locked loop to be returned to a desired response.
1. A method of suppressing non-ideal effects in a clock recovery system exhibited by a rough clock generator of the clock recovery system configured to receive a data signal and to deliver a rough clock signal, the rough clock generator including control parameters affecting operation of the rough clock generator, the method comprising:
receiving the rough clock signal with the clock recovery system;
mixing down the rough clock signal in the clock recovery system to a lower frequency, yielding a replicant rough clock signal;
observing the replicant rough clock signal in the clock recovery system to identify energy in spectral bands not native to the replicant clock signal; and
adjusting at least one control parameter of the clock recovery system to reduce the energy in said spectral bands.
2. The method of claim 1 , wherein the mixed down frequency is approximately zero hertz.
3. The method of claim 1 , wherein the art of observing the replicant rough clock signal to identify energy in spectral bands not native thereto includes observing energy in sidebands of the mixed down frequency.
4. The method of claim 1 , wherein the act of adjusting at least one control parameter comprises adjusting a duty cycle exhibited by the rough clock signal.
5. The method of claim 1 , wherein the act of adjusting at least one control parameter comprises adjusting timing or amplitude of logic level transitions exhibited by the rough clock signal.
6. The method of claim 1 , wherein the act of adjusting at least one control parameter comprises adjusting a resonant frequency of a resonator included within the rough clock generator.