Circuit for measuring variations in the capacitance of a variable capacitor using a continuously rebalanced detection bridge
First Claim
1. A circuit for measuring variations in the capacitance of a variable capacitor, wherein the circuit comprises:
- an oscillator generating an alternating signal;
a detection bridge comprising first and second branches connected to the oscillator, the first branch including the variable capacitor connected in series with a variable capacitance diode, while the second branch comprises a capacitor connected in series with a variable capacitance diode;
a differential stage having its inputs connected to respective ones of the branches at their common points between their capacitors and their variable capacitance diodes;
a DC bias circuit for biasing the common point of the second branch;
synchronous demodulation means following the differential stage and connected to the oscillator for delivering a DC unbalance signal; and
a feedback line injecting the unbalance signal to the common point of the first branch to continuously rebalance the detection bridge.
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Accused Products
Abstract
A circuit for measuring variations in the capacitance of a variable capacr forming part of a sensor includes an oscillator which generates an alternating signal which is supplied to two branches of a detection bridge. The first branch includes the variable capacitor connected in series with a variable capacitance diode. The second branch includes a capacitor connected in series with a variable capacitance diode. A differential stage has each of its in puts connected to the common point of a respective one of the branches. Synchronous demodulation means connected to the oscillator, are connected to the output of the differential stage for delivering a DC unbalance voltage Ve which is injected by a feedback line to the common point of the first branch, thereby continuously balancing the detection bridge.
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Citations
14 Claims
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1. A circuit for measuring variations in the capacitance of a variable capacitor, wherein the circuit comprises:
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an oscillator generating an alternating signal; a detection bridge comprising first and second branches connected to the oscillator, the first branch including the variable capacitor connected in series with a variable capacitance diode, while the second branch comprises a capacitor connected in series with a variable capacitance diode; a differential stage having its inputs connected to respective ones of the branches at their common points between their capacitors and their variable capacitance diodes; a DC bias circuit for biasing the common point of the second branch; synchronous demodulation means following the differential stage and connected to the oscillator for delivering a DC unbalance signal; and a feedback line injecting the unbalance signal to the common point of the first branch to continuously rebalance the detection bridge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification