Analysis of noise in repetitive waveforms

An apparatus for measuring low frequency jitter of a test device waveform, including:

• a measurement initiating circuit for initiating timing measurements of a waveform at an actual measurement rate that varies about a nominal measurement rate between a maximum rate;
• a test device waveform measuring circuit, operating in response to the measurement initiating circuit, for timing a duration of a series of “n” consecutive periods of the test device waveform during a measuring episode using hardware-based event counters, wherein n is an integer of at least two, to generate a multiple period time value;
• and
• a processing circuit for dividing the multiple period time values by n to generate average single-period time values, wherein single-period time values describe jitter for the test device waveform.

A process for generating a function with characteristics of an auto-correlation function indicating periodic jitter in a repetitive waveform, including:

• a. timing a duration of a series of “n” consecutive periods in a repetitive waveform a plurality of times for a given “n,” where “n” is an integer, to generate a set of time values associated with the given “n;”
• b. determining a variance value for the set of time values;
• c. repeating steps (a) and (b) for a plurality of different values of n;
• and
• d. generating an array of the variance values as a function of the values of “n.”

A process for characterizing an angle modulating component in an angle modulated signal, including:

• measuring a waveform multiple times at a measurement rate that varies about a nominal measurement rate between a maximum measurement rate and a minimum measurement rate;
• based on said measuring, timing a duration of “n” consecutive periods of the waveform during each episode of said measuring, where n is an integer, to provide an array of time values, one time value associated with each measuring episode;
• and
• processing the array of time values to generate an array of the time values as a function of frequency.

A process for characterizing an angle modulating component in an angle modulated signal, including:

• (a) timing a series of “n” consecutive periods in a repetitive waveform for a plurality of times for a given “n” where n is an integer, to generate a set of measured time values associated with the given n;
• (b) generating a range value indicating a difference between the maximum measured time value and the minimum measured time value for the set of measured time values;
• (c) repeating steps (a) and (b) for a plurality of different values of n;
• (d) using the range values obtained in step (c) to generate a range array depicting the range of values as a function of the values of n;
• (e) differentiating the range array with respect to n;
• and
• (f) reconstructing the differentiated range array symmetrically around a designated location to provide a reordered array.