Modulation noise estimation mechanism
First Claim
1. A method of testing an oscillator within a phase locked loop, said method comprising the steps of:
- averaging phase error samples produced by said phase locked loop, wherein said phase error samples correspond to the phase noise of said oscillator;
subtracting said average from a current phase error sample to yield a normalized phase error;
generating an exception event if said normalized phase error exceeds a threshold, thereby indicating that the level of oscillator phase noise is not acceptable; and
repeating said steps of averaging, subtracting and generating over a period of time and outputting a test failure indication if the number of exception events exceeds a maximum criterion and a test pass indication otherwise.
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Abstract
An on-chip reduced complexity modulation noise estimation mechanism for performing nonlinear signal processing to analyze modulation noise to determine whether a semiconductor device under test complies with the performance criteria set by specifications or a standard corresponding thereto. When used in a two-point transmitter modulation architecture, the mechanism relies on the fact that the noise statistics at the output of the transmitter can be determined by observing the phase error output of the phase detector within the phase locked loop. In the digital embodiment of the mechanism, the phase error signal is compared to a configurable threshold value to generate an exception event. If the number of exception events exceeds a configurable max_fail value after comparisons of a configurable number of phase error samples, the test fails. A pass/fail signal is output reflecting the result of the test. The test comprises a configurable number of test samples to permit flexibility in the tradeoff between the time required to complete the test versus the statistical reliability of the test result, i.e. the probability of it correctly determining whether the tested device complies with target specifications.
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Citations
37 Claims
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1. A method of testing an oscillator within a phase locked loop, said method comprising the steps of:
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averaging phase error samples produced by said phase locked loop, wherein said phase error samples correspond to the phase noise of said oscillator; subtracting said average from a current phase error sample to yield a normalized phase error; generating an exception event if said normalized phase error exceeds a threshold, thereby indicating that the level of oscillator phase noise is not acceptable; and repeating said steps of averaging, subtracting and generating over a period of time and outputting a test failure indication if the number of exception events exceeds a maximum criterion and a test pass indication otherwise. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for testing an oscillator in a phase locked loop having a phase locked loop, comprising:
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means for averaging phase error samples produced by said phase locked loop; means for subtracting said average from a current phase error sample to yield a normalized phase error, wherein said normalized phase error corresponds to the phase modulation noise of said oscillator; means for generating an exception event if said normalized phase error exceeds a threshold; and means for repeating said functions of averaging, subtracting and generating over a period of time and outputting a test failure indication if the number of exception events exceeds a maximum criterion and a test pass indication otherwise. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An apparatus for testing an oscillator in a phase locked loop, comprising:
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first means for measuring a phase error signal within said phase locked loop, wherein said phase error signal corresponds to the phase noise of said oscillator; second means for comparing a plurality of phase error signal samples over a period of time to a threshold and generating an exception event each time a phase error signal sample exceeds said threshold; and generating a test failure indication if the number of exception events exceeds a defined limit and generating a test pass indication otherwise. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A method of testing an oscillator in a phase locked loop, said method comprising the steps of:
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generating a normalized phase error signal from a plurality of phase error samples generated by said phase locked loop; and counting the number of times said normalized phase error signal crosses a threshold within a predefined period of time, wherein the count represents an estimate of the phase modulation noise of said oscillator; and failing said oscillator if said count exceeds a predefined maximum, and passing said oscillator otherwise. - View Dependent Claims (37)
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Specification