Sinewave generating circuit and amplitude demodulator
First Claim
1. Apparatus for generating a low-distortion sinewave and amplitude demodulating an input time-varying signal derived from the generated sinewave or an external source and producing an output proportional to the amplitude demodulated signal with said apparatus comprising:
- a) activation circuitry for generating and driving a low-distortion sinewave with said activation circuitry including an oscillator first means, a second means for selecting frequency and a third means driving the sinewave with an amplitude that is proportional to an input reference level; and
b) monitoring circuity coupleable to said time-varying signal to achieve said amplitude demodulation including a means to detect the amplitude of the time-varying signal and a second means to provide a signal proportional to the amplitude with an adjustable scale of proportion.
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Accused Products
Abstract
An integrated circuit for driving a sensor includes an oscillator for providing a first clock signal synchronized to a periodic waveform supplied by an external source. A second clock signal in the form of a uni-polar square wave is derived from the first clock signal. A sinewave signal is generated by consecutively selecting voltage steps from a resistor ladder under control of the second clock signal. A low-pass filter removes from the sinewave signal higher frequency harmonics generated by switching through the steps of the resistor ladder. A linear amplifier utilizes an external capacitor to couple the filtered sinewave signal to the sensor. Temperature compensation is provided by comparing the voltage of the sinewave signal supplied to the sensor with an external temperature stable reference voltage. The integrated circuit also includes circuitry for amplitude demodulating a signal returned from the sensor to provide a sensor output signal.
7 Citations
26 Claims
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1. Apparatus for generating a low-distortion sinewave and amplitude demodulating an input time-varying signal derived from the generated sinewave or an external source and producing an output proportional to the amplitude demodulated signal with said apparatus comprising:
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a) activation circuitry for generating and driving a low-distortion sinewave with said activation circuitry including an oscillator first means, a second means for selecting frequency and a third means driving the sinewave with an amplitude that is proportional to an input reference level; and b) monitoring circuity coupleable to said time-varying signal to achieve said amplitude demodulation including a means to detect the amplitude of the time-varying signal and a second means to provide a signal proportional to the amplitude with an adjustable scale of proportion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification