US 7,480,329 B2 · Method of finding data dependent timing and voltage jitter for different bits in an arbitrary digital signal in accordance with selected surrounding bits

Abstract

Separation and analysis of measured Total Jitter (TJ) begins with a suitably long arbitrary digital test pattern, from which an Acquisition Record is made. A Time Interval Error (TIE) or Voltage Level Error (VLE) Record is made of the Acquisition Record. A Template defines a collection of associated bit value or transitions that are nearby or otherwise related to a bit location of interest, and has associated therewith a collection of Descriptors and their respective Metrics. Each Descriptor identifies one of the various different patterns of bit value or transitions that fit the Template. The TIE/VLE Record is examined, and a parameter is measured for each instance of each Descriptor for the Template. The collection of measured parameters for each particular Descriptor are combined (e.g., averaging) to produce the Metric for that Descriptor. A Look-Up Table (LUT) addressed by the different possible Descriptors is loaded with the associated discovered Metric, which is a plausible value for Data Dependent Jitter (DDJ) at that bit. DDJ separates from TJ because DDJ is correlated with the Descriptors, while Periodic Jitter (PJ) and Random Jitter (RJ) can be expected to average to near zero over a sufficient number of instances of a given Descriptor. Identified instances of DDJ are individually removed from corresponding locations of TJ found for the entire waveform (the original TIE/VLE Record) to leave an Adjusted TIE/VLE Record that is PJ convolved with RJ.

Claims11

Dependent claims

A method of measuring Data Dependent Jitter for a digital signal in a System Under Test, comprising the steps of:

(a) processing consecutively sampled values of an instance of an arbitrary Test Pattern in the digital signal to produce an Acquisition Record;
(b) measuring times of occurrence of consecutive edges in the Acquisition Record to form a corresponding Original Time Interval Error Record;
(c) specifying, via a Template, a collection of Descriptors of digital signal behaviors with which amounts of Data Dependent Jitter are to be associated, the Template specifying at least one bit position or signal value transition that is both A) not adjacent to a reference bit location or signal value transition of the Template, and B) not contiguous with a set of bit positions or signal value transitions of the Template that include a bit position or signal value transition that is adjacent to the reference bit location or signal value transition of the Template;
(d) inspecting the Acquisition Record of Step (a) to find instances of a selected Descriptor chosen from among those specified in Step (c);
(e) identifying in the Original Time Interval Error Record a respective Time Interval Error value associated with each instance of the selected Descriptor found in Step (d);
(f) subsequent to an instance of Step (e), finding a Metric that is the average of the Time Interval Errors values associated with the found instances of the selected Descriptor in Step (d);
(g) repeating Steps (d), (e) and (f) for a different selected Descriptor until Steps (d), (e) and (f) have been performed for at least two Descriptors in the collection thereof specified in Step (c);
and
(h) storing each Metric found in Step (f) in a table indexed by the selected Descriptor for which it was found.

6 more elements

A method of measuring Data Dependent Jitter for a digital signal in a System Under Test, comprising the steps of:

(a) specifying a collection of Descriptors of digital signal behaviors with which amounts of Data Dependent Jitter are to be associated;
(b) processing consecutively sampled values of an instance of a first Arbitrary Pattern in the digital signal to produce a first Acquisition Record;
(c) measuring times of occurrence of consecutive edges in the first Acquisition Record to form a corresponding first Original Time Interval Error Record;
(d) inspecting the first Acquisition Record of Step (b) to find instances of a first selected Descriptor chosen from among those specified in Step (a);
(e) identifying in the first Original Time Interval Error Record a respective Time Interval Error value associated with each instance of the first selected Descriptor found in Step (d);
(f) subsequent to an instance of Step (e), finding a first Metric that is the average of the Time Interval Errors values associated with the found instances of the first selected Descriptor in Step (d);
(g) repeating Steps (d), (e) and (f) for a different first selected Descriptor until Steps (d), (e) and (f) have been performed for all Descriptors in the collection thereof specified in Step (a);
(h) processing consecutively sampled values of an instance of a second Arbitrary Pattern in the digital signal to produce a second Acquisition Record;
(i) measuring times of occurrence of consecutive edges in the second Acquisition Record to form a corresponding second Original Time Interval Error Record;
(j) inspecting the second Acquisition Record of Step (h) to find instances of a second selected Descriptor chosen from among those specified in Step (a);
(k) identifying in the second Original Time Interval Error Record a respective Time Interval Error value associated with each instance of the second selected Descriptor found in Step (j);
(l) subsequent to an instance of Step (k), finding a second Metric that is the average of the Time Interval Errors values associated with the found instances of the second selected Descriptor in Step (j);
(m) repeating Steps (j), (k) and (l) for a different second selected Descriptor until Steps (j), (k) and (l) have been performed for all Descriptors in the collection thereof specified in Step (a);
(n) for each Descriptor, averaging the first Metric associated with that each Descriptor with a the second Metric associated with that same each Descriptor, to generate an average of Metrics for that same each Descriptor;
and
(o) storing each average of Metrics found in Step (n) in a table indexed by an associated Descriptor for which it was found.

13 more elements

Dependencies are inferred from the claim text.

Method of finding data dependent timing and voltage jitter for different bits in an arbitrary digital signal in accordance with selected surrounding bits

Life of this patent

Method of finding data dependent timing and voltage jitter for different bits in an arbitrary digital signal in accordance with selected surrounding bits

Life of this patent

Abstract

Claims11