Field disturbance type motion detection system

• US 3,925,774 A
• Filed: 03/24/1975
• Issued: 12/09/1975
• Est. Priority Date: 03/24/1975
• Status: Expired due to Term

• Current Assignee: Clifford L. Amlung
• Original Assignee: Clifford L. Amlung
• Inventors: Amlung, Clifford L.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/561,229
• Time in Patent Office: 260 Days
• Field of Search: 340/258A,258B 343/5PD,7.7,1AM,818,908,702,795 325/19,119,352
• US Class Current: 340/553
• CPC Class Codes: G01V 3/102 by measuring amplitude

Abstract

A field disturbance proximity motion sensor apparatus includes a printed circuit board mounted in a plastic housing one-quarter wavelength from a metal backplate which serves as a reflector as well as providing antenna gain for a printed circuit half-wave dipole antenna fabricated on the printed circuit board. A single transistor oscillator/detector circuit is fabricated on the printed circuit board and forms a transceiver which is located adjacent to and coupled to the dipole antenna. Collector current change of the oscillator/detector transistor is sensed in response to any field disturbance whereupon an audio signal is produced which is amplified, filtered and fed to a comparator whose output activates an instrusion alarm device. All of the circuitry is mounted on the printed circuit board containing the antenna.

Claims

1. A field disturbance motion detection system generating an electromagnetic wave pattern which is radiated to a selected location and being responsive to a predetermined disturbance of said wave pattern thereat to activate an alarm device, comprising in combination:

a housing having a front portion adapted to pass electromagnetic waves therethrough without substantial attenuation;

a printed circuit board in said housing adjacently behind said front portion;

said printed circuit board including thereon a single transceiver antenna comprised of a pair of opposing quarter wave antenna elements including a spacing therebetween forming a half-wave dipole antenna, and tuning control means located in said spacing coupled between said opposing elements;

an electromagnetic wave reflecting plate attached to said housing substantially one quarter wavelength behind said printed circuit board thereby providing a predetermined antenna gain and directional sensitivity;

a transceiver oscillator/detector circuit located immediately adjacent and coupled to said pair of antenna elements on said printed circuit board and including a single transistor having an emitter, base and collector, and additionally including a direct circuit connection of said base to one of said pair of antenna elements, first circuit means coupling said base to a point of reference potential, second circuit means coupling said emitter to said point of reference potential, third circuit means coupling said collector to said one antenna element, fourth circuit means coupling said collector to the other of said pair of antenna elements, and fifth circuit means coupling said collector to a supply potential, whereby said circuit is energized to provide oscillations which are coupled to said antenna whereupon electromagnetic signals of a predetermined frequency are radiated to a localized area which when a field disturbance occurs a change in collector current of said transistor results providing a relatively low level output signal of another predetermined frequency across said fifth circuit means;

bandpass filter-amplifier means coupled to said collector and being responsive to said output signal occurring across said fifth circuit means and being adapted to increase the amplitude of said output signal by a predetermined gain;

comparator circuit means having first and second input means respectively coupled to the output of said bandpass filteramplifier means and A reference potential whereby a control signal is generated in response to a field disturbance for initiating an alarm when the amplitude of said output signal from said bandpass amplifier exceeds said reference potential.

2. The system as defined by claim 1 wherein said first, third and fifth circuit means comprises means of a first type electrical impedance, said fourth circuit means comprises means of a second type electrical impedance and said second circuit means comprises means of a third type electrical impedance.

3. The system as defined by claim 2 wherein said first type of electrical impedance comprises resistive impedance means, said second type electrical impedance comprises capacitive type impedance means and said third type electrical impedance comprises inductance means.

4. The system as defined by claim 3 wherein said pair of opposing quarter wave antenna elements comprise printed circuit elements of a generally trapezoidal configuration each having a pair of relatively longer parallel sides of unequal length greater than a pair of associated non-parallel sides, and wherein the mutually opposing shorter non-parallel sides of said pair of elements diverge with respect to the location of said single transistor and wherein said tuning control means is coupled between said mutually opposing shorter non-parallel sides.

5. The system as defined by claim 4 wherein said tuning control means comprises feedback control means in the form of a ladder type structure of printed circuit material.

6. The system as defined by claim 5 wherein said ladder type structure is comprised of a pair of parallely disposed printed circuit line elements adjacent said mutually opposing non-parallel sides and a plurality of spaced apart printed circuit line elments interconnecting said pair of parallely disposed line elments.

7. The system as defined by claim 4 wherein the other non-parallel shorter side of said trapezoidal configuration is substantially at right angles to the pair of parallel sides.

8. The system as defined by claim 7 wherein each of said pair of antenna elements have a predetermined width substantially less than the length of either of said parallel sides, said width providing a predetermined antenna impedance.

9. The system as defined by claim 1 wherein said comparator circuit means comprises a differential amplifier.

10. The system as defined by claim 9 and additionally including an output circuit adapted to activate said alarm device coupled to the output of said differential amplifier, said output circuit including a transistor having an emitter, base and collector and wherein said base is coupled to the output of said differential amplifier, said emitter is coupled to said point of reference potential, and the collector is adapted to be coupled to said alarm device.