US 4,308,524 AGranted

Fast high resolution predictive analog-to-digital converter with error correction

AssigneeHarrison Systems, Inc.

InventorsWilliam D. Harrison, Henry H. Martin

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Abstract

An analog-to-digital conversion system uses a fast analog-to-digital converter having a resolution less than the system resolution to convert the difference between a previously predicted value and the current analog value. The converted difference is summed with the predicted value to compute the actual value of the analog input signal to a resolution greater than that of the fast analog-to-digital converter. The high resolution digital value thus obtained becomes the predicted value for the next conversion. This predicted value is converted by a digital-to-analog converter having the same accuracy but not the same resolution as the system output to an analog signal which is compared with the input analog signal to obtain a difference signal. This difference signal is sampled and held to provide the input to the fast analog-to-digital converter. The system includes a gain scaling and switching circuit to compensate for errors which would occur when the difference between the true analog input and the prediction exceeds the range of the low resolution, fast analog-to-digital converter.

Claims12

Dependent claims

An analog-to-digital converter system for converting a rapidly changing analog signal to a very high resolution quantized digital output value, comprising:

differencing means connected to receive said analog input signal and a predicted analog signal for producing an analog error signal proportional to the difference between said analog input signal and said predicted analog signal;
first sample and hold means connected to receive said analog error signal and providing a sampled output error signal;
a first analog-to-digital converter connected to receive said sampled output error signal and having a resolution of N bits, the resolution of said analog-to-digital converter system being M bits where M is greater than N;
prediction and computation logic means connected to the output of said analog-to-digital converter and including accumulator means, said digital prediction and computation logic means combining the output of said analog-to-digital converter with a value previously stored in said accumulator means, said accumulator means providing an M bit output;
and
digital-to-analog converter means connected to receive the R highest order bit outputs but less than the M bit outputs of said accumulator means for generating said predicted analog signal.

3 more elements

Dependencies are inferred from the claim text.