Equivalent time pseudorandom sampling system
AssigneeTektronix, Inc.
InventorAgoston Agoston
Life of this patent
Estimating the term…
Abstract
An equivalent time pseudorandom sampling system samples a repetitive waveform within each of several narrow acquisition windows bounding repetitive sections of the waveform in order to obtain equivalent time sample data characterizing the shape of the waveform included within the acquisition windows. The period between successive triggering events is measured and sampling is delayed following an initiating triggering event by delay time adjusted according to the measured period so as to maximize the probability that sampling will occur within an acquisition window. The time difference between samples and subsequent triggering event is measured with high accuracy and resolution utilizing a time interval measurement system based on a dual vernier interpolation.
Claims13
A method for measuring a time interval between first and second events comprising the steps of:
- periodically generating a reference signal;
- triggering first and second periodic signals on occurrence of said first and second events, respectively;
- sampling said first and second periodic signals on each occurrence of said reference signal and determining the magnitude of each signal sample;
- counting cycles of said first periodic signal occurring after triggering said first periodic signal and before the sampled magnitude of said first periodic signal crosses a predetermined level, thereby producing a first count;
- counting cycles of said second periodic signal occurring after triggering said second periodic signal and before the sampled magnitude of said second periodic signal crosses said predetermined level, thereby producing a second count;
- and
- counting occurrences of said reference signal generated between a first moment when said sampled magnitude of said first periodic signal crosses said predetermined level and a second moment when said sampled magnitude of said second periodic signal crosses said predetermined level, thereby producing a third count.
A method for sampling a repetitive waveform, the method comprising the steps of:
- measuring a first time interval between first and second triggering events in said repetitive waveform;
- and
- generating in delayed response to a third triggering event in said repetitive waveform a strobe signal for initiating sampling of said repetitive waveform, the delay between said third triggering event and generation of said strobe signal being adjusted according to said measured time interval.
An apparatus for measuring a time interval between first and second events comprising:
- a reference oscillator for periodically generating a reference signal;
- a first triggerable oscillator for generating a first periodic signal triggered by said first event;
- a second triggerable oscillator for generating a second periodic signal triggered by said second event;
- means for sampling said first and second periodic signals on each occurrence of said reference signal;
- means for counting cycles of said first periodic signal occurring before the sampled magnitude of said first periodic signal crosses a predetermined level;
- means for counting cycles of said second periodic signal occurring before the sampled magnitude of said second periodic signal crosses a predetermined level;
- and
- means for counting occurrences of said reference signal generated between a first moment when said sampled magnitude of said first periodic signal crosses said predetermined level and a second moment when said sampled magnitude of said second periodic signal crosses said predetermined level.
An apparatus for timing sampling of a repetitive waveform comprising:
- means for measuring a first time interval between first and second triggering events in said repetitive waveform;
- and
- means for generating in delayed response to a third triggering event in said repetitive waveform a strobe signal for initiating sampling of said repetitive waveform, the delay between said third triggering event and generation of said strobe signal being set according to said measured first time interval.
Dependencies are inferred from the claim text.