Pre-interpolation adaptive filter
AssigneeTektronix, Inc.
InventorsCharles L. Saxe, Daniel E. Milliron
Life of this patent
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Abstract
An adaptive filtering procedure reduces overshoot which may be present on a waveform having infinite slopes displayed on a digital oscilloscope as a result of interpolation between samples at the location of the infinite slopes. An adaptive filtering procedure identifies sampled points adjacent the infinite slope and moves the points closer to each other to avoid ringing or overshoot on the display. Before modification, a straightness test relative to the waveform before and after a discontinuity and a test for sudden changes in the waveform before and after the discontinuity are performed.
Claims9
In a digital oscilloscope having means for sampling an input signal and providing sample related values for presentation by graphic display, a method of altering said samples comprising:
- detecting a series of said samples that correspond to a rapid change in the value of said input signal,
- altering the values of ones of said samples to reduce said rapid change, and
- interpolating between said series of altered samples.
In a digital oscilloscope having means for sampling an input signal and providing sample related values for presentation by graphic display, a method of altering said samples comprising:
- determining the slope of said signal according to changes in value between successive samples,
- detecting an array of samples having a change in slope as between successive pairs of samples, which change is less than a predetermined standard, followed by a large slope as represented by a large change in value between a further pair of samples, which change is greater than a second predetermined standard, followed by a change in slope between further successive pairs of samples, which is less than a predetermined standard, and
- in response to said detection altering the value of at least one of said further pair of samples to bring it closer to the remaining sample of said further pair of samples.
A digital oscilloscope circuit having means for sampling an input signal and providing sample related variables for presentation on graphic display means, comprising:
- input means for storing a plurality of time related samples of an input signal,
- means for detecting an array of stored samples having rapid rise or fall times between a pair of said array of stored samples,
- means for altering at least one of said pair of samples for bringing its value closer to the other of said pair of samples and
- interpolation means for receiving said altered samples and producing interpolation between ones of said altered samples according to a predetermined approximation.
Dependencies are inferred from the claim text.