Sine wave synthesizer
First Claim
1. A sine wave synthesizer circuit, comprising:
- an integrator;
a plurality of selectable integration constant capacitors;
decoder means, coupled to said selectable integration constant capacitors, for sequential selection of an integration constant capacitor from among said selectable integration constant capacitors at a rate corresponding to a desired sine wave frequency; and
switch means for alternately coupling said selected integration constant capacitor between a reference source and said integrator at the same time to produce a first sine wave transition direction and 180°
out-of-phase to produce a second opposite sine wave transition direction;
whereby coordinated operation of said decoder means and said switch means operates said integrator to produce a sine wave output signal.
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Abstract
A sine wave synthesizer is employed in an analog signal processing integrated circuit. The circuit includes an integrator driven from a plurality of integration constant capacitors which are sequentially selected by a clocked decoder. Each capacitor is selected by coupling it between the integrator and a switched reference source. The capacitors are selected so that their sequential selection produces a sine wave approximating current in four increments. A first increment of a sine wave is produced according to an ascending selection of integration constant capacitors. Thereafter, the capacitors are selected in reverse in a descending manner to produce a second increment of the sine wave. The switched capacitor phasing circuit is then operated to invert the sine wave signal to produce the third and fourth increments having a negative instead of a positive excursion. The frequency of the sine wave is controlled by the decoder clock input. An output filter stage converts the digitally produced sine wave increments into a smooth sine wave output. This filter is provided with selectable time constants to allow operation at different selected frequencies.
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Citations
13 Claims
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1. A sine wave synthesizer circuit, comprising:
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an integrator; a plurality of selectable integration constant capacitors; decoder means, coupled to said selectable integration constant capacitors, for sequential selection of an integration constant capacitor from among said selectable integration constant capacitors at a rate corresponding to a desired sine wave frequency; and switch means for alternately coupling said selected integration constant capacitor between a reference source and said integrator at the same time to produce a first sine wave transition direction and 180°
out-of-phase to produce a second opposite sine wave transition direction;whereby coordinated operation of said decoder means and said switch means operates said integrator to produce a sine wave output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In an integrated circuit, a sine wave synthesizer circuit, comprising:
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an integrator; at least two selectable integration constant capacitors; a reference source; at least two switches, one of each coupled in a series with a corresponding one of said integration constant capacitors and operable to select said integration constant capacitor; decoder means, coupled to said switches, for sequential operation of said switches to select an integration constant capacitor from among said selectable integration constant capacitors in a sequence and at a rate corresponding to a desired sine wave frequency; and means for effecting switched capacitor phasing of said integration constant capacitors, including; a first phase switch for alternately coupling a first terminal of a selected integration constant capacitor between a reference source and a circuit ground; and a second phase switch, for alternately coupling a second terminal of said selected integration constant capacitor between an integrator input and said circuit ground; whereby operation of said first and second phase switches at the same time produces transition of said sine wave in a first direction; and whereby operation of said first and second phase switches 180°
out-of-phase produces transition of said sine wave in a second, opposite direction, such that coordinated operation of said first and second phase switches and said decoder operates said circuit to produce a sloped line approximation of a sine wave output signal. - View Dependent Claims (10, 11, 12, 13)
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Specification