Jitter estimation in phase-locked loops
AssigneeAltera Corporation
InventorsDaniel Tun Lai Chow, San Wong, Vincent K. Tsui, Lik Huay Lim, Man On Wong
Life of this patent
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Abstract
A phase-locked loop is characterized by analyzing phase noise in its output signal while known levels of input phase noise are provided. The resulting data provides intrinsic phase noise and gain of the phase-locked loop. These values provide a general relationship between input phase noise and output phase noise for the phase-locked loop, which allows estimation of output phase noise corresponding to a given level of input phase noise, and allows estimation of input phase noise corresponding to a given level of output phase noise.
Claims17
A method, comprising:
- providing a reference clock signal to a phase-locked loop circuit, the reference clock signal having variable phase noise PRef;
- varying the phase noise PRef of the reference clock signal;
- analyzing an output signal of the phase-locked loop circuit to obtain a measurement of phase noise POut in the output signal as the phase noise PRef of the reference clock signal is varied;
- and
- from the measurement, quantifying a relationship between the phase noise PRef of the reference clock signal and the phase noise POut of the output signal by obtaining a value for a gain factor G and a value for an intrinsic phase noise factor PInt in the equation POut=PRef×G+PInt.
A method of characterizing phase noise of a phase-locked loop circuit, comprising:
- providing a reference clock signal to an input of the phase-locked loop circuit;
- introducing input phase noise PRef(f) into the reference clock signal over a range of frequency f, the input phase noise PRef(f) introduced at two or more phase noise levels;
- measuring output phase noise POut(f) over a range of frequency f, at the output of the phase-locked loop circuit as the input phase noise PRef(f) is introduced at the two or more phase noise levels;
- and
- from the input phase noise PRef(f) and the output phase noise POut(f), calculating a value for an intrinsic phase noise PInt(f) of the phase-locked loop as a function of frequency f, and a value for a noise gain G(f) of the phase-locked loop, according to the equation Pout(f)=PRef(f)×G(f)+PInt(f).
A non-transitory computer readable medium having computer code embodied therein, the non-transitory computer readable medium comprising:
- computer code for accepting an input representing one of (i) phase noise PRef(f) in an input signal provided to a phase-locked loop and (ii) phase noise POut(f) in an output signal of the phase-locked loop;
- and
- computer code for calculating the other one of (i) phase noise PRef(f) in the input signal provided to the phase-locked loop and (ii) phase noise POut(f) in the output signal of the phase-locked loop according to the equation POut(f)=PRef(f)×G(f)+PInt(f), where G(f) is an experimentally-obtained gain factor and PInt(f) is an experimentally-obtained intrinsic phase noise factor.
Dependencies are inferred from the claim text.