Dithering apparatus to properly represent aliased signals for high speed signal sampling
AssigneeTektronix, Inc.
InventorsForrest A. Edwards, Eric P. Etheridge
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Abstract
The subject invention addresses the problem of aliasing in subsampled data by adding dither to the timing of the subsampling of the data. The subject invention solves a speed problem caused by delays in modifying (i.e., dithering) the A/D converter sampling clock. It is herein recognized that to maintain a high acquisition rate one should randomly select (i.e., dither) samples after demultiplexing the data into a wider and slower stream of samples, rather than attempting to modify the high speed A/D converter sampling clock.
Claims16
A dithering arrangement for a digital oscilloscope, comprising:
- an A/D converter for providing samples of a waveform to be analyzed;
- a demultiplexer having an input coupled to an output of said A/D converter for receiving and demultiplexing said samples;
- a sample shifter having a first input coupled to an output of said demultiplexer for producing one of a plurality of a samples of said waveform within a given range of samples;
- programmable control signal generation circuitry responsive to predetermined dither characteristics and to a pseudo-randomly generated number for producing a range control signal relating to said range of samples;
- and
- sample selection circuitry coupled to said sample shifter and to said programmable control signal generation circuitry, and responsive to said one sample of said plurality of samples and to said range control signal for selecting a particular sample from a group of N samples for producing a dithering about an Nth sample.
A dithering arrangement, comprising:
- source of digital signal samples;
- a demultiplexer having an input coupled to an output of said digital signal sample source for receiving and demultiplexing said samples;
- a sample shifter having a first input coupled to an output of said demultiplexer for producing one of a plurality of said samples within a given range of samples;
- programmable control signal generation circuitry responsive to predetermined dither characteristics and to a pseudo-randomly generated number for producing a range control signal relating to said range of samples;
- and
- sample selection circuitry coupled to said sample shifter and to said programmable control signal generation circuitry, and responsive to said one sample of said plurality of samples and to said range control signal for selecting a particular sample from a group of N samples for producing a dithering about an Nth sample.
A dithering arrangement, comprising:
- source of digital signal samples;
- a demultiplexer having an input coupled to an output of said digital signal sample source for receiving and demultiplexing said samples;
- programmable control signal generation circuitry responsive to predetermined dither characteristics and to a pseudo-randomly generated number for producing a range control signal relating to a range of samples;
- and
- one of a sample shifter having a first input coupled to an output of said demultiplexer for producing one of a plurality of said samples within said range of samples;
- and a sample selection circuit coupled to an output of said demultiplexer and to said programmable control signal generation circuitry, and responsive to said range control signal for selecting a particular sample from a group of N samples for producing a dithering about an Nth sample.
Dependencies are inferred from the claim text.