Data-directed scrambler for multi-bit noise shaping D/A converters
First Claim
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1. For use in apparatus for converting digital signals to analog signals, wherein a multi-bit digital signal is transformed to a thermometer code which passes through a scrambler to a D/A converter to produce an analog output signal;
- an improved scrambler comprising;
input means and output means;
a plurality of switchable scrambler devices configured as swapper cells interconnected to provide a number of mutually-exclusive selectable signal paths from said input means to said output means;
each of said swapper cells including;
two input terminals to receive respective signal bits and two output terminals to produce corresponding output bits;
means within each swapper cell for controllably connecting the two input terminals to the two output terminals either directly or reversely;
select terminal means for receiving an activating signal designating whether the swapper cell is to effect said direct connection or said reverse connection;
logic means for producing said activating signal;
said logic means including means for storing the integrated difference of past swapper output signals;
said logic means further including means for computing the new value of the activating signal based on the current two input values to said swapper cell and said stored integrated difference signal and for updating the value of the stored difference signal.
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Abstract
A scrambler for use with thermometer-code digital signals and having a number of interconnected identical switching cells in the form of swapper cells with two inputs and two outputs. A control signal determines whether the inputs are connected directly or reversely to the outputs. The control signal is developed by logic circuitry which receives as inputs the two swapper cell input bits and a state bit representing the integrated difference of past swapper output signals.
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Citations
12 Claims
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1. For use in apparatus for converting digital signals to analog signals, wherein a multi-bit digital signal is transformed to a thermometer code which passes through a scrambler to a D/A converter to produce an analog output signal;
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an improved scrambler comprising; input means and output means; a plurality of switchable scrambler devices configured as swapper cells interconnected to provide a number of mutually-exclusive selectable signal paths from said input means to said output means; each of said swapper cells including; two input terminals to receive respective signal bits and two output terminals to produce corresponding output bits; means within each swapper cell for controllably connecting the two input terminals to the two output terminals either directly or reversely; select terminal means for receiving an activating signal designating whether the swapper cell is to effect said direct connection or said reverse connection; logic means for producing said activating signal; said logic means including means for storing the integrated difference of past swapper output signals; said logic means further including means for computing the new value of the activating signal based on the current two input values to said swapper cell and said stored integrated difference signal and for updating the value of the stored difference signal. - View Dependent Claims (2, 3, 4)
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5. In a digital-to-analog conversion system wherein a digital thermometer code signal is passed through scrambler apparatus of the type comprising means definable as a plurality of swapper cells each having two inputs and two outputs and including means operable by a control signal for establishing either a direct connection between each input and a corresponding output or a reverse connection between said inputs and outputs, said plurality of swapper cells being interconnected to provide a number of mutually-exclusive signal paths selectable in accordance with the states of the control signals for the individual swapper cells;
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the method of developing the control signal for each swapper cell which comprises; storing a signal representing the integrated difference of past output signals of the swapper cell; and operating logically on the state of the two input signals for the swapper cell and said integrated difference to produce said control signal for the swapper cell. - View Dependent Claims (6, 7, 8, 9)
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10. In a digital-to-analog conversion system wherein a digital thermometer code signal is passed through scrambler apparatus of the type comprising means definable as a plurality of swapper cells each having two inputs and two outputs and including means operable by a control signal for establishing either a direct connection between each input and a corresponding output or a reverse connection between said inputs and outputs, said plurality of swapper cells being interconnected to provide a number of mutually-exclusive signal paths selectable in accordance with the states of the control signals for the individual swapper cells;
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the method of developing the control signal for each swapper cell which comprises; operating logically on the states of the two swapper input signals for the respective swapper cell; including in said logical operation the states of the output signals of the swapper; and producing said control signal from the results of said logical operation. - View Dependent Claims (11, 12)
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Specification