Microwave proximity sensor
First Claim
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1. A microwave proximity sensor system comprising:
- oscillator means having a resonance frequency determining element in the form of folded dipole antenna means, said folded dipole antenna means being adapted to serve as transmitting and receiving antenna means;
capacitor means connected to said oscillator means such that the capacitor means are alternately chargeable and dischargeable through said oscillator means by triggering said oscillator means into operation, until the voltage across said oscillator means drops to a selected level such that oscillation ceases and the capacitor means again can become charged;
negative peak follower means connected to the capacitor means for converting the minimum voltage across the capacitor means into DC voltage; and
comparator means connected to the negative peak follower means for detecting changes in the output voltage of the negative peak follower means caused by the approach of a person or object to the antenna means.
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Abstract
Microwave oscillator means wherein the resonant frequency determining element is a 1/2 or 1/4-wavelength folded dipole antenna that also serves as the transmitting and receiving antenna, capacitor means that is alternately charged and then discharged through said oscillator means until the voltage drops so low that oscillation ceases at which point the capacitor is charged again, negative peak follower means to convert the minimum voltage across the capacitor into a DC voltage, and comparator means to detect changes in the output voltage of the peak follower caused by the approach of a person or object to the 1/2 or 1/4-wavelength antenna.
19 Citations
7 Claims
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1. A microwave proximity sensor system comprising:
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oscillator means having a resonance frequency determining element in the form of folded dipole antenna means, said folded dipole antenna means being adapted to serve as transmitting and receiving antenna means; capacitor means connected to said oscillator means such that the capacitor means are alternately chargeable and dischargeable through said oscillator means by triggering said oscillator means into operation, until the voltage across said oscillator means drops to a selected level such that oscillation ceases and the capacitor means again can become charged; negative peak follower means connected to the capacitor means for converting the minimum voltage across the capacitor means into DC voltage; and comparator means connected to the negative peak follower means for detecting changes in the output voltage of the negative peak follower means caused by the approach of a person or object to the antenna means. - View Dependent Claims (2, 3, 4)
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5. A method for detecting the movement of a person or object comprising the steps of:
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providing oscillator means having a resonance frequency determining element in the form of folded dipole antenna means, said folded dipole antenna means being adapted to serve as transmitting and receiving antenna means; providing capacitor means connected to said oscillator means such that said capacitor means are chargeable and dischargeable through said oscillator means; charging said capacitor to a predetermined voltage; triggering said oscillator means into oscillation when said predetermined voltage has been reached; discharging said capacitor means until oscillation of said oscillator means ceases; charging said capacitor means after cessation of oscillation by said oscillator means; and detecting changes in the minimum voltage across the capacitor caused by the approach of a person or object to the antenna means. - View Dependent Claims (6, 7)
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Specification