Low cost monotonic digital-to-analog converter
AssigneeRCA Corporation
InventorsTed N. Altman, Nicola J. Fedele
Life of this patent
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Abstract
A digital-to-analog converter generates an analog output signal which is subject to periodically occurring non-monotonic increments in response to consecutive increments of the value of a digital word. Apparatus in accordance with the present invention substantially reduces effects of the non-monotonic increments from disturbing the analog output signal by rapidly incrementing the value of the digital word after the occurrence of each of said non-monotonic increments.
Claims17
In a digital-to-analog converter which generates an analog output signal subject to periodically occurring non-monotonic increments in response to consecutive increments of the value of a digital word, apparatus for substantially reducing magnitude disturbances of said analog signal caused by said non-monotonic increments comprising:
- means for detecting the occurrence of each of said non-monotonic increments of said analog signal;
- means for rapidly changing the value of said digital word so as to rapidly change the magnitude of said analog signal in response to the detection of the occurrence of each of said non-monotonic increments;
- means for storing signals having magitudes related to the magnitudes of said analog signal prior to each of said non-monotonic increments;
- and
- sensing means having a first input responsive to the magnitude of said analog signal and a second input responsive to the magnitude of said stored signal for stopping said rapid changing of the value of said digital word when the magnitude of said analog signal corresponds to the magnitude of said stored signal.
Apparatus for converting a digital word including a plurality of bits to an analog signal comprising:
- first means for converting a first group of the most significant bits of said digital word to a first pulse signal having an incrementally variable duty factor;
- second means for converting a second group of the next most significant bits of said digital word to a second pulse signal having an incrementally variable duty factor;
- means for combining said first and second pulse signals to produce at its output an analog signal having periodically occurring non-monotonic increments in response to consecutive increments of the value of said digital word;
- means for detecting the occurrence of each of said non-monotonic increments of said analog signal;
- means for rapidly changing the value of said digital word so as to rapidly change the magnitude of said analog signal in response to the detection of the occurrence of each of said non-monotonic increments;
- means for storing signals having magnitudes related to the magnitudes of said analog signal prior to each of said non-monotonic increments;
- and
- sensing means having a first input responsive to the magnitudes of said analog signal and a second input responsive to the magnitude of said stored signal for stopping said rapid changing of the value of said said digital word when the magnitude of said analog signal corresponds to the magnitude of said stored signal.
In a television tuning system including an oscillator responsive to a tuning signal for generating a local oscillator signal, channel selector means for providing signals representative of a selected channel and a digital-to-analog converter responsive to said signals provided by said channel selector means for generating an analog signal from which said tuning signal is derived, said analog signal being subject to periodically occurring non-monotonic changes in response to consecutive changes of the value of a digital word, apparatus for substantially reducing magnitude disturbances of said analog signal caused by said non-monotonic changes comprising:
- means for detecting the occurrence of each of said non-monotonic changes of said analog signal;
- means for rapidly changing the value of said digital word so as to rapidly change the magnitude of said analog signal in response to the detection of the occurrence of each of said non-monotonic changes;
- means for storing signals having magnitudes related to the magnitude of said analog signal prior to each of said non-monotonic changes;
- and
- sensing means having a first input responsive to the magnitude of said analog signal and a second input responsive to the magnitude of said stored signal for stopping said rapid changing of the value of said digital word when the magnitude of said analog signal corresponds to the magnitude of said stored signal.
Dependencies are inferred from the claim text.