Electronic proximity switch
First Claim
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1. An electronic proximity switch comprising:
- an oscillator providing an electrical signal;
a signal strength comparator;
a sensor antenna providing for a free space transmission of the electrical signal;
a first and second transmission path between the oscillator and the signal strength comparator, the first transmission path communicating with the sensor antenna for a free space transmission of the electrical signal in a sensor region and the second transmission path being shielded from the sensor region;
wherein the signal strength comparator further provides a switch output determined by a relative strength of the electrical signal received over the first and second transmission paths.
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Abstract
An electronic proximity switch employs two oscillators coupled through two electrical paths, one associated with an antenna serving as a proximity switch sensor. Absorption by an object near the antenna changes the coupling between the oscillators producing a dramatic phase shift that may be detected and used for switching purposes.
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Citations
12 Claims
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1. An electronic proximity switch comprising:
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an oscillator providing an electrical signal; a signal strength comparator; a sensor antenna providing for a free space transmission of the electrical signal; a first and second transmission path between the oscillator and the signal strength comparator, the first transmission path communicating with the sensor antenna for a free space transmission of the electrical signal in a sensor region and the second transmission path being shielded from the sensor region; wherein the signal strength comparator further provides a switch output determined by a relative strength of the electrical signal received over the first and second transmission paths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A proximity detector comprising:
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an oscillator; a phase and frequency sensitive detector; a first and second transmission path between the oscillator and the phase and frequency sensitive detector, the first transmission path providing a predetermined first phase shift, and the second transmission path providing a predetermined second phase shift; an antenna structure causing a shift of a relative strength of signals along the first and second transmission paths; and a switch circuit communicating with the phase and frequency sensitive detector to detect a dominant signal along one of the first and second transmission paths according to a phase and frequency detected by the phase and frequency sensitive detector, and to switch when the dominant signal changes between the first and second transmission paths.
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Specification