Cascade A/D converter
First Claim
1. A cascade A/D converter comprising:
- first comparator means for converting an analog input signal into a first digital signal latch means for holding said first digital signal;
D/A converter means for converting said first digital signal to a first analog signal;
subtractor means for subtracting said first analog signal from said analog input signal and for outputting a subtract output signal;
waveform composition means for composing code changing waveforms of said analog input signal utilizing said subtract output signal;
window comparator means for detecting each vicinity of code changing points of said analog input signal for one stage and of said changing waveforms in other stages and for outputting an output signal; and
error correction means for rejecting noise generated at said code changing points based on first digital signal and on output signals from said waveform composition means and from said window comparing means.
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Abstract
A cascade A/D converter configured by connecting in cascade two or more stages of electronic circuits, each stage comprising a comparator to convert an analog input signal to a digital signal, a latch circuit to hold the output of the comparator, a D/A converter to convert the output of the comparator to an analog signal, and a subtractor to subtract the output of the D/A converter from the analog input signal; wherein are provided a waveform composition circuit to compose code changing waveforms in the comparators, a plurality of detecting devices for detecting each vicinity of code changing points for detecting the code changes in the comparators by receiving the changing waveforms in the waveform composition circuit as inputs, and an error correction circuit that rejects noise generated at the code changing points based on the outputs of the detecting devices; whereby errors due to noise are substantially eliminated.
37 Citations
18 Claims
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1. A cascade A/D converter comprising:
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first comparator means for converting an analog input signal into a first digital signal latch means for holding said first digital signal;
D/A converter means for converting said first digital signal to a first analog signal;
subtractor means for subtracting said first analog signal from said analog input signal and for outputting a subtract output signal;
waveform composition means for composing code changing waveforms of said analog input signal utilizing said subtract output signal;
window comparator means for detecting each vicinity of code changing points of said analog input signal for one stage and of said changing waveforms in other stages and for outputting an output signal; and
error correction means for rejecting noise generated at said code changing points based on first digital signal and on output signals from said waveform composition means and from said window comparing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A cascade A/D converter comprising:
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first comparator means for comparing an analog input signal with a first analog signal for all upper bits and for outputting a first digital signal;
latch means for holding said first digital signal outputted from said first comparator means;
D/A converter means for converting said first digital signal outputted from said first comparator means to a second analog signal;
waveform composition means for composing code changing waveforms from said first digital signal outputted from said D/A converter means;
window comparator means for detecting each vicinity of code changing points of said code changing waveforms; and
error correction means for rejecting noise generated at code changing points based on output signals from said first digital signal, said waveform composition means and said window comparing means. - View Dependent Claims (12, 13, 14)
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15. A cascade A/D converter configured by connecting in cascade a plurality of stages, each stage comprising:
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a first comparator means for converting an analog input signal into a first digital signal;
latch means for holding said first digital signal;
D/A converter means for converting said first digital signal from said first comparator into a first analog signal;
subtractor means for subtracting said first analog signal from said analog input signal and for outputting a subtracted output signal;
window comparator means for detecting each vicinity of code changing points to detect code changes of said analog input signal during a particular time duration in two or more stages; and
error correction means for rejecting noise generated at code changing points based on output signals from said first digital signal, said subtractor means and said window comparator means. - View Dependent Claims (16, 17, 18)
absolute value means for receiving each changing waveform in said waveform composition means as an input signal and for obtaining an absolut value; and
second comparator means for using the absolute value from said absolute value means for comparison.
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17. The converter of claim 15, wherein said time duration during which said window comparator means detects said analog input signal in one stage is wider in time duration than said particular time duration in two or more stages.
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18. The converter of claim 17, wherein said detecting to window comparing means for detecting comprises:
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absolute value means for receiving each changing waveform in said waveform composition means as an input signal and for obtaining an absolute value; and
second comparator means for using the absolute value from said absolute value means for comparison.
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Specification