Combined and simplified multiplexing and dithered analog to digital converter
AssigneeHewlett-Packard Company
InventorDonald R. Hiller
Life of this patent
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Abstract
A circuit for analog-to-digital conversion is disclosed comprising multiplexed ADCs. Dithering is introduced into the circuit before conversion and subtracted out of the resulting digital output stream. Gain control feedback loops are employed to eliminate non-unity gain error of the dither signal and multiplexed ADC differential gain errors. Correlation between the digital output stream and the dither signal is used to detect a non-unity condition and derive gain control feedback. Correlation with the dither signal is also used to detect gain differences between multiplexed ADCs and generate corrective feedback.
Claims25
A method of dynamically correcting gain errors occurring during analog-to-digital conversion of an input analog signal comprising the steps:
- generating a dither signal with a digital pseudo-random noise generator;
- converting the dither signal to analog form with a digital-to-analog converter;
- summing the dither signal and the input analog signal to yield a summed signal;
- converting the summed signal into a digital output stream corresponding thereto;
- subtracting the dither signal from the digital output stream;
- correlating the dither signal to the digital output stream to detect residue of the dither signal remaining in the digital output stream indicative of non-unity gain of the dither signal;
- and
- adjusting the gain of the dither signal to remove the residue.
An electronic circuit for converting an analog input signal into a digital output stream without analog-to-digital converter gain errors, comprising:
- an input for receiving the analog input signal;
- a noise source for generating a stream of digital noise words;
- a digital-to-analog converter (DAC) coupled to the noise source for converting the stream of digital noise words into a dither signal;
- an analog summation circuit connected to the DAC and the input for adding the dither signal and the analog input signal to produce a summed signal;
- at least one analog-to-digital converter for converting the summed signal into a digital output stream;
- a subtraction circuit for subtracting the stream of digital noise words from the digital output stream;
- a correlator connected to the subtraction circuit for detecting residue of the dither signal in the digital outputs stream and for controlling the gain of the dither signal responsive to the amount of the residue detected in the digital output stream.
In a method of converting an input analog signal to an output digital signal, the method including adding and subsequently removing a dither signal to improve conversion accuracy, an improvement comprising:
- generating a control signal related to a correlation between the output digital signal and the dither signal;
- and
- controlling the gain of a circuit sage through which the dither signal passes in response to the control signal;
- wherein dither residue in the digital output signal due to gain error is minimized.
Dependencies are inferred from the claim text.