Title:
Field disturbance type motion detection system
United States Patent 3925774
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.
US Patent References:
Television antenna
Schlesinger - August 1953 - 2650304
Fm transistor transceiver
Carroll - June 1961 - 2989745
DETECTION OF MOVEMENT IN CONFINED SPACES
Bloice - September 1972 - 3691556
INTRUSION DETECTION SYSTEM
Cheal - April 1974 - 3806941
Television antenna
Schlesinger - August 1953 - 2650304
Fm transistor transceiver
Carroll - June 1961 - 2989745
DETECTION OF MOVEMENT IN CONFINED SPACES
Bloice - September 1972 - 3691556
INTRUSION DETECTION SYSTEM
Cheal - April 1974 - 3806941
Application Number:
05/561229
Publication Date:
12/09/1975
Filing Date:
03/24/1975
View Patent Images:
Export Citation:
Assignee:
Security Devices Corporation (Pompton Lakes, NJ)
Primary Class:
Other Classes:
343/908, 455/128, 343/795
International Classes:
G01V3/10; G08B13/18
Field of Search:
340/258A,258B 343/5PD,7.7,1AM,818,908,702,795 325/19,119,352
Primary Examiner:
Swann III, Glen R.
Attorney, Agent or Firm:
Brady, O'Boyle & Gates
Claims:
Having thus described what is at present considered to be the preferred embodiment of the subject invention, I claim
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:
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.
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:
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.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to proximity or motion detection systems and more particularly to the class including field disturbance devices which generate a directional antenna pattern around an area to be monitored and accordingly generate a signal in response to any change in the field due to motion of an object or person in the area.
2. Description of the Prior Art
Motion detection or intruder alarm systems are well known in the art. Generally these systems may be classified into two classes, one of which includes means which operate on the principle of the Doppler effect and the other includes means which operate on the disturbed field principle.
Examples of Doppler type systems of which the applicant is aware are disclosed in: U.S. Pat. 3,813,699, L. T. Saunders, May 28, 1974; U.S. Pat. 3,665,448, H. A. McGlinchey, et al., May 23, 1972; and U.S. Pat. 3,376,507, A. H. McEuen, et al., Apr. 2, 1968. Examples of field disturbance type systems of which the applicant is aware is shown in: U.S. Pat. 3,839,709, K. Sugiura, Oct. 1, 1974; U.S. Pat. 3,747,012, R. Buck, July 17, 1973; and U.S. Pat. 3,483,437, J. J. Coyne, Dec. 9, 1969.
Additionally, such systems require some type of antenna as utilized in combination with electronic circuitry for radiating waves of radio frequency energy through the space under surveillance. One such antenna which is adapted to be utilized with electronic detection systems is disclosed in U.S. Pat. 3,239,838, K. S. Kelleher, Mar. 8, 1966. Other known antenna structures are disclosed, for example, in U.S. Pat. 2,990,574, J. R. McDougal, June 27, 1961; U.S. Pat. 2,724,772, D. E. Bridges et al., Nov. 22, 1955; U.S. Pat. 2,492,358, T. H. Clark, Dec. 27, 1949; and finally U.S. Pat. 2,418,084, B. E. Montgomery, Mar. 25, 1947.
SUMMARY
Briefly, the subject invention is directed to an improved field disturbance type of proximity sensing system comprised of a printed circuit half-wave dipole antenna coupled across the base-collector junction of a single transistor oscillator/detector which operates as a transceiver. Both the antenna and transceiver circuitry as well as a bandpass filter-amplifier and comparator circuit are incorporated on a printed circuit board which is mounted immediately behind the front face of a plastic housing which has a metal backplate secured thereto a quarter wavelength away from the printed circuit board including the antenna. The base-collector connection of the transistor to the antenna results in feedback through the antenna such that any change in the radiated field is detected as a change in the transistor's collector current. A signal of audio frequency is thus provided and is fed to the bandpass filter-amplifier which provides a gain in the order of 2 × 10 4 . The output of the amplifier is fed to one input of a comparator circuit having a reference level signal applied to the other input. The output of the comparator is coupled to an output transistor which operates as a DC switch to control the operation of a sonic alarm device or relay which is adapted to control other external circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspectivve view of the plastic housing for the subject invention, being partially cut away to illustrate the physical relationship of a printed circuit board located immediately behind the front face thereof;
FIG. 2 is a central vertical cross-section of the arrangement shown in FIG. 1;
FIG. 3 is illustrative of the metallization layout fabricated on the printed circuit board shown in FIGS. 1 and 2;
FIG. 4 is an electrical schematic diagram illustrative of the electrical power supply circuitry and voltage regulator located on the printed circuit board for powering the subject invention; and
FIG. 5 is an electrical schematic diagram illustrative of the preferred embodiment of the subject invention also located on the printed circuit board.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and more particularly to FIGS. 1 and 2, reference numeral 10 denotes a generally rectangular box-like housing made of plastic or the like, so that radio frequency electromagnetic waves pass therethrough without appreciable attenuation. Immediately behind the front face 12 of the housing 10, is affixed a substantially flat printed circuit board 14 well known in the art, upon which is mounted the required electrical circuit components, forming the subject invention. One of the components comprises a printed circuit half-wave dipole antenna 16 adapted for operation in the UHF range and more particularly at a frequency of 915± 5MHz (megaHertz). The antenna 16 is comprised of two generally trapezoidal printed circuit elements (FIG. 1) 18 and 20 having a small spacing therebetween. A printed circuit ladderlike structure 22 bridges the elements in the spacing for providing tuning i.e. feedback control. The printed circuit elements 18, 20 and 22 are fabricated in a common plane on the front face 24 of the printed circuit board 14. A metal backplate 26 is adapted to be fastened to the housing 10 such that it is substantially parallel to the printed circuit board 14 containing the antenna 16, being separated therefrom by one-fourth wavelength. The metal backplate 26 serves as a reflector for the antenna 16 for providing a directional radiated antenna pattern as well as providing an antenna gain of 3db (decibels) when utilized in combination with the circuitry to be described.
The antenna 16 is shown in greater detail in FIG. 3. The elements 18 and 20 each have the same mean length (1/4λ) and width W (for providing a predetermined antenna impedance) and are substantially identical with the exception that element 20 additionally includes an appendage or tab 28, at the lower edge which is closer to element 18 and which includes the junction of the tuning structure 22. The element 20 also includes an inclined inner side portion 30 which diverges away from a like opposing side portion 32 of the element 18. Adjacent the tab 28 is a triangular shaped printed circuit land portion 34 which has an apex directed to the lower corner of the element 18 to which the tuning structure 22 is attached. The tab 28 and the land 34 are adapted to accommodate the connection of the base and collector leads, respectively, of a transistor, not shown, at location 35 whose emitter is connected to the printed circuit line element 36 so as to be positioned as closely as possible to the antenna 16 for operation as a single transistor oscillator/detector circuit of a transceiver.
Adjacent the land 34 and the printed circuit element 36 is a relatively large encircling printed circuit area of metallization 38, which is adapted to act as a point of common reference potential, commonly referred to as "ground". The location 40 of the printed circuit board 14 is adapted to accommodate circuit means shown in FIG. 4 for providing a suitable DC power supply potential from a 115 volt AC line source. The location 42, adjacent location 40, is adapted to accommodate solid state voltage regulator means also shown in FIG. 4 for providing a regulated DC supply potential +V at the metallization element 44 which element is coupled to the inner metallization region 46 by means of a jumper lead 48. The location 50 of the printed circuit board 14 is adapted to accommodate solid state circuitry shown in FIG. 5 by reference numeral 52 for providing an active bandpass filter-amplifier combination and a differential amplifier comparator circuit configured from an integrated circuit module package having a plurality of operational amplifiers included therein. A typical example is identified as a 34-10E manufactured by RCA. The location 54 of the printed circuit board 14 is also designed to accommodate a transistor switch, not shown, which is adapted to be coupled to an external sonic alarm device or other alarm circuitry via a terminal land 56.
Referring now to the electrical circuitry embodying the subject invention, attention is directed to FIG. 4 which discloses the means for supplying power for operating the circuitry shown in FIG. 5. A power transformer 58 has its primary winding coupled to a 115 VAC power line while the secondary winding is connected to full-wave diode rectifier 60, whose output is coupled to a voltage regulator 62. The voltage regulator typcially comprises an integrated circuit configuration such as a CA 723 CE manufactured by RCA. The capacitors 64 and 66 act as filter capacitors and a regulated DC power supply potential appears on printed circuit lead 44 shown in FIG. 3. Such circuits are well known to those skilled in the art.
Turning attention now to FIG. 5, it discloses, inter alia, a single N-P-N transistor 68 which has its base, collector, and emitter respectively connected to the metallization tab 28, metallization land portion 34 and printed circuit element 36. Since the base is connected to the tab 28, it is directly connected to the λ/4 antenna element 20 and one side of the ladder tuning structure 22 which bridges elements 18 and 20. The base is also connected to a resistor 70 which is returned to ground 38. The emitter is returned to ground 38 through an inductance coil 72. The collector of transistor 68 is commonly connected to a resistor 74 and a capacitor 76 whose opposite ends are respectively connected to the antenna elements 18 and 20 at the location of the connection of the tuning structure 22 thereacross. Physically, the resistor 74 is connected between the metallization land portion 34 and the tab 28, while the capacitor 76 is connected between the apex of the land portion 34 and the lower corner of the side portion 32 (FIG. 3) common to the tuning structure 22. A collector load resistor 78 having the +V supply potential applied via metallization region 46 is connected to the collector of transistor 68 by means of the metallization land 34.
A bandpass filter/amplifier comprised of three operational amplifier portions 80, 82 and 84 of the integrated circuit module 52 is connected to the collector of transistor 68. This is provided by means of resistor 86 and capacitor 88 connected in series to the input of operational amplifier 80. The positive power supply potential V+ on metallization portion 46 (FIG. 3) is applied to the operational amplifier 80 by means of a resistor 90. A parallel combination of a capacitor 92 and resistor 94 is coupled between the output and input of the operational amplifier 80 to provide feedback required to partially implement a bandpass filter characteristic. The output of operational amplifier 80 is coupled to the input of operational amplifier 82 by means of a resistor 96. The positive supply potential V+ is also applied to the operational amplifier 82 by means of resistor 98. As in the case for the first operational amplifier 80, operational amplifier 82 also includes a feedback network comprised of the parallel combination of capacitor 100 and resistor 102. The output of operational amplifier 82 is capacitively coupled to the third operational amplifier 84 by means of the series combination of capacitor 104 and resistor 106. The positive power supply potential V+ is adapted to be coupled to the operational amplifier 84 by means of resistor 108. A single feedback element comprising resistor 110, however, is connected between the input and output of operational amplifier 84.
It is to be noted that the capacitance values of capacitors 92 and 100 of the feedback networks for operational amplifiers 80 and 82 determine the high frequency cut-off of the desired filter characteristic whereas the capacitance values of the series coupling capacitors 88 and 104 at the input of operational amplifier 80 and the input of operational amplifier 84, determine the low frequency cut-off. The high frequency cut-off is selected to be in the order of 15Hz to prevent the 60Hz AC line frequency from affecting the operation of the subject invention whereas the low frequency cut-off is selected to be in the order of 1.8Hz or lower and thus provides a bandpass for audio frequencies appearing at the collector of transistor 68. The output of the operational amplifier 84 is fed to one input of a fourth operational amplifier portion 112 of the integrated circuit module 52 and is configured to operate as a comparator and more particularly a differential amplifier. Accordingly, one input of operational amplifier 112 is coupled to the output of operational amplifier 84 by means of the resistor 114. The other input of the operational amplifier 112 is connected to a selectable DC reference voltage which is provided by a potentiometer 116 coupled between the positive supply potential V+ and ground 38 and a fixed resistor 118 connected to the potentiometer's slider element. The output of the differential amplifier comprised of operational amplifier 112 is connected to the base of a second N-P-N transistor 120 by means of a resistor which transistor comprises the switch transistor referred to above located at location 54 on the printed circuit board shown in FIG. 2. As shown in FIG. 5, the emitter is directly connected to the ground metallization 38, while the collector is connected to the terminal 56 shown in FIG. 3. A sonic alarm device 122 or other desired device or circuitry is adapted to be connected to terminal 56.
In operation, the transceiver circuit including the single transistor 68 coupled to the antenna 16 is adapted to operate as an oscillator having a frequency of operation in the UHF range and more particularly at a frequency of 915± 5MHz. These oscillations are coupled to the dipole elements 18 and 20 which in combination with the tuning structure 22 and the metal backplate 26 positioned a one-fourth wavelength away from the antenna 16 generates a highly directional localized radiation pattern which is transmitted to the area under surveillance. The coupling of the base-collector junction of the transistor 68 across the antenna elements 18 and 20, as shown in FIG. 5, provides a unique feedback through the antenna system under the control of the ladder structure 22 whereby any change of the localized field results in a change in collector current of the transistor 68, thus operating as the detector as well as the oscillator. Accordingly, any movement within the radiated field will be detected as an audio signal of very low level at the collector of transistor 68. The combination of the operational amplifier 80, 82, and 84, and the circuitry associated therewith provides a bandpass filter-amplifier having a gain in the order of 2 × 10 4 which when compared against a reference voltage set by potentiometer 116 for controlling system sensitivity, causes a DC output voltage from the comparator amplifier 112 to turn the transistor 120 "on" if the reference level is exceeded and thereby drive any type of an appropriate alarm device.
In summation then, what has been shown and described is a single transistor oscillator/detector forming a transceiver which is coupled to a single printed circuit half-wave dipole antenna mounted a quarter wavelength in front of a reflector formed of the back mounting plate of the plastic housing. The collector current change occurring as a result of field disturbance of the highly directional antenna pattern is sensed, amplified, filtered and fed to a comparator whose output is adapted to initiate an alarm.
1. Field of the Invention
The present invention is directed generally to proximity or motion detection systems and more particularly to the class including field disturbance devices which generate a directional antenna pattern around an area to be monitored and accordingly generate a signal in response to any change in the field due to motion of an object or person in the area.
2. Description of the Prior Art
Motion detection or intruder alarm systems are well known in the art. Generally these systems may be classified into two classes, one of which includes means which operate on the principle of the Doppler effect and the other includes means which operate on the disturbed field principle.
Examples of Doppler type systems of which the applicant is aware are disclosed in: U.S. Pat. 3,813,699, L. T. Saunders, May 28, 1974; U.S. Pat. 3,665,448, H. A. McGlinchey, et al., May 23, 1972; and U.S. Pat. 3,376,507, A. H. McEuen, et al., Apr. 2, 1968. Examples of field disturbance type systems of which the applicant is aware is shown in: U.S. Pat. 3,839,709, K. Sugiura, Oct. 1, 1974; U.S. Pat. 3,747,012, R. Buck, July 17, 1973; and U.S. Pat. 3,483,437, J. J. Coyne, Dec. 9, 1969.
Additionally, such systems require some type of antenna as utilized in combination with electronic circuitry for radiating waves of radio frequency energy through the space under surveillance. One such antenna which is adapted to be utilized with electronic detection systems is disclosed in U.S. Pat. 3,239,838, K. S. Kelleher, Mar. 8, 1966. Other known antenna structures are disclosed, for example, in U.S. Pat. 2,990,574, J. R. McDougal, June 27, 1961; U.S. Pat. 2,724,772, D. E. Bridges et al., Nov. 22, 1955; U.S. Pat. 2,492,358, T. H. Clark, Dec. 27, 1949; and finally U.S. Pat. 2,418,084, B. E. Montgomery, Mar. 25, 1947.
SUMMARY
Briefly, the subject invention is directed to an improved field disturbance type of proximity sensing system comprised of a printed circuit half-wave dipole antenna coupled across the base-collector junction of a single transistor oscillator/detector which operates as a transceiver. Both the antenna and transceiver circuitry as well as a bandpass filter-amplifier and comparator circuit are incorporated on a printed circuit board which is mounted immediately behind the front face of a plastic housing which has a metal backplate secured thereto a quarter wavelength away from the printed circuit board including the antenna. The base-collector connection of the transistor to the antenna results in feedback through the antenna such that any change in the radiated field is detected as a change in the transistor's collector current. A signal of audio frequency is thus provided and is fed to the bandpass filter-amplifier which provides a gain in the order of 2 × 10 4 . The output of the amplifier is fed to one input of a comparator circuit having a reference level signal applied to the other input. The output of the comparator is coupled to an output transistor which operates as a DC switch to control the operation of a sonic alarm device or relay which is adapted to control other external circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspectivve view of the plastic housing for the subject invention, being partially cut away to illustrate the physical relationship of a printed circuit board located immediately behind the front face thereof;
FIG. 2 is a central vertical cross-section of the arrangement shown in FIG. 1;
FIG. 3 is illustrative of the metallization layout fabricated on the printed circuit board shown in FIGS. 1 and 2;
FIG. 4 is an electrical schematic diagram illustrative of the electrical power supply circuitry and voltage regulator located on the printed circuit board for powering the subject invention; and
FIG. 5 is an electrical schematic diagram illustrative of the preferred embodiment of the subject invention also located on the printed circuit board.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and more particularly to FIGS. 1 and 2, reference numeral 10 denotes a generally rectangular box-like housing made of plastic or the like, so that radio frequency electromagnetic waves pass therethrough without appreciable attenuation. Immediately behind the front face 12 of the housing 10, is affixed a substantially flat printed circuit board 14 well known in the art, upon which is mounted the required electrical circuit components, forming the subject invention. One of the components comprises a printed circuit half-wave dipole antenna 16 adapted for operation in the UHF range and more particularly at a frequency of 915± 5MHz (megaHertz). The antenna 16 is comprised of two generally trapezoidal printed circuit elements (FIG. 1) 18 and 20 having a small spacing therebetween. A printed circuit ladderlike structure 22 bridges the elements in the spacing for providing tuning i.e. feedback control. The printed circuit elements 18, 20 and 22 are fabricated in a common plane on the front face 24 of the printed circuit board 14. A metal backplate 26 is adapted to be fastened to the housing 10 such that it is substantially parallel to the printed circuit board 14 containing the antenna 16, being separated therefrom by one-fourth wavelength. The metal backplate 26 serves as a reflector for the antenna 16 for providing a directional radiated antenna pattern as well as providing an antenna gain of 3db (decibels) when utilized in combination with the circuitry to be described.
The antenna 16 is shown in greater detail in FIG. 3. The elements 18 and 20 each have the same mean length (1/4λ) and width W (for providing a predetermined antenna impedance) and are substantially identical with the exception that element 20 additionally includes an appendage or tab 28, at the lower edge which is closer to element 18 and which includes the junction of the tuning structure 22. The element 20 also includes an inclined inner side portion 30 which diverges away from a like opposing side portion 32 of the element 18. Adjacent the tab 28 is a triangular shaped printed circuit land portion 34 which has an apex directed to the lower corner of the element 18 to which the tuning structure 22 is attached. The tab 28 and the land 34 are adapted to accommodate the connection of the base and collector leads, respectively, of a transistor, not shown, at location 35 whose emitter is connected to the printed circuit line element 36 so as to be positioned as closely as possible to the antenna 16 for operation as a single transistor oscillator/detector circuit of a transceiver.
Adjacent the land 34 and the printed circuit element 36 is a relatively large encircling printed circuit area of metallization 38, which is adapted to act as a point of common reference potential, commonly referred to as "ground". The location 40 of the printed circuit board 14 is adapted to accommodate circuit means shown in FIG. 4 for providing a suitable DC power supply potential from a 115 volt AC line source. The location 42, adjacent location 40, is adapted to accommodate solid state voltage regulator means also shown in FIG. 4 for providing a regulated DC supply potential +V at the metallization element 44 which element is coupled to the inner metallization region 46 by means of a jumper lead 48. The location 50 of the printed circuit board 14 is adapted to accommodate solid state circuitry shown in FIG. 5 by reference numeral 52 for providing an active bandpass filter-amplifier combination and a differential amplifier comparator circuit configured from an integrated circuit module package having a plurality of operational amplifiers included therein. A typical example is identified as a 34-10E manufactured by RCA. The location 54 of the printed circuit board 14 is also designed to accommodate a transistor switch, not shown, which is adapted to be coupled to an external sonic alarm device or other alarm circuitry via a terminal land 56.
Referring now to the electrical circuitry embodying the subject invention, attention is directed to FIG. 4 which discloses the means for supplying power for operating the circuitry shown in FIG. 5. A power transformer 58 has its primary winding coupled to a 115 VAC power line while the secondary winding is connected to full-wave diode rectifier 60, whose output is coupled to a voltage regulator 62. The voltage regulator typcially comprises an integrated circuit configuration such as a CA 723 CE manufactured by RCA. The capacitors 64 and 66 act as filter capacitors and a regulated DC power supply potential appears on printed circuit lead 44 shown in FIG. 3. Such circuits are well known to those skilled in the art.
Turning attention now to FIG. 5, it discloses, inter alia, a single N-P-N transistor 68 which has its base, collector, and emitter respectively connected to the metallization tab 28, metallization land portion 34 and printed circuit element 36. Since the base is connected to the tab 28, it is directly connected to the λ/4 antenna element 20 and one side of the ladder tuning structure 22 which bridges elements 18 and 20. The base is also connected to a resistor 70 which is returned to ground 38. The emitter is returned to ground 38 through an inductance coil 72. The collector of transistor 68 is commonly connected to a resistor 74 and a capacitor 76 whose opposite ends are respectively connected to the antenna elements 18 and 20 at the location of the connection of the tuning structure 22 thereacross. Physically, the resistor 74 is connected between the metallization land portion 34 and the tab 28, while the capacitor 76 is connected between the apex of the land portion 34 and the lower corner of the side portion 32 (FIG. 3) common to the tuning structure 22. A collector load resistor 78 having the +V supply potential applied via metallization region 46 is connected to the collector of transistor 68 by means of the metallization land 34.
A bandpass filter/amplifier comprised of three operational amplifier portions 80, 82 and 84 of the integrated circuit module 52 is connected to the collector of transistor 68. This is provided by means of resistor 86 and capacitor 88 connected in series to the input of operational amplifier 80. The positive power supply potential V+ on metallization portion 46 (FIG. 3) is applied to the operational amplifier 80 by means of a resistor 90. A parallel combination of a capacitor 92 and resistor 94 is coupled between the output and input of the operational amplifier 80 to provide feedback required to partially implement a bandpass filter characteristic. The output of operational amplifier 80 is coupled to the input of operational amplifier 82 by means of a resistor 96. The positive supply potential V+ is also applied to the operational amplifier 82 by means of resistor 98. As in the case for the first operational amplifier 80, operational amplifier 82 also includes a feedback network comprised of the parallel combination of capacitor 100 and resistor 102. The output of operational amplifier 82 is capacitively coupled to the third operational amplifier 84 by means of the series combination of capacitor 104 and resistor 106. The positive power supply potential V+ is adapted to be coupled to the operational amplifier 84 by means of resistor 108. A single feedback element comprising resistor 110, however, is connected between the input and output of operational amplifier 84.
It is to be noted that the capacitance values of capacitors 92 and 100 of the feedback networks for operational amplifiers 80 and 82 determine the high frequency cut-off of the desired filter characteristic whereas the capacitance values of the series coupling capacitors 88 and 104 at the input of operational amplifier 80 and the input of operational amplifier 84, determine the low frequency cut-off. The high frequency cut-off is selected to be in the order of 15Hz to prevent the 60Hz AC line frequency from affecting the operation of the subject invention whereas the low frequency cut-off is selected to be in the order of 1.8Hz or lower and thus provides a bandpass for audio frequencies appearing at the collector of transistor 68. The output of the operational amplifier 84 is fed to one input of a fourth operational amplifier portion 112 of the integrated circuit module 52 and is configured to operate as a comparator and more particularly a differential amplifier. Accordingly, one input of operational amplifier 112 is coupled to the output of operational amplifier 84 by means of the resistor 114. The other input of the operational amplifier 112 is connected to a selectable DC reference voltage which is provided by a potentiometer 116 coupled between the positive supply potential V+ and ground 38 and a fixed resistor 118 connected to the potentiometer's slider element. The output of the differential amplifier comprised of operational amplifier 112 is connected to the base of a second N-P-N transistor 120 by means of a resistor which transistor comprises the switch transistor referred to above located at location 54 on the printed circuit board shown in FIG. 2. As shown in FIG. 5, the emitter is directly connected to the ground metallization 38, while the collector is connected to the terminal 56 shown in FIG. 3. A sonic alarm device 122 or other desired device or circuitry is adapted to be connected to terminal 56.
In operation, the transceiver circuit including the single transistor 68 coupled to the antenna 16 is adapted to operate as an oscillator having a frequency of operation in the UHF range and more particularly at a frequency of 915± 5MHz. These oscillations are coupled to the dipole elements 18 and 20 which in combination with the tuning structure 22 and the metal backplate 26 positioned a one-fourth wavelength away from the antenna 16 generates a highly directional localized radiation pattern which is transmitted to the area under surveillance. The coupling of the base-collector junction of the transistor 68 across the antenna elements 18 and 20, as shown in FIG. 5, provides a unique feedback through the antenna system under the control of the ladder structure 22 whereby any change of the localized field results in a change in collector current of the transistor 68, thus operating as the detector as well as the oscillator. Accordingly, any movement within the radiated field will be detected as an audio signal of very low level at the collector of transistor 68. The combination of the operational amplifier 80, 82, and 84, and the circuitry associated therewith provides a bandpass filter-amplifier having a gain in the order of 2 × 10 4 which when compared against a reference voltage set by potentiometer 116 for controlling system sensitivity, causes a DC output voltage from the comparator amplifier 112 to turn the transistor 120 "on" if the reference level is exceeded and thereby drive any type of an appropriate alarm device.
In summation then, what has been shown and described is a single transistor oscillator/detector forming a transceiver which is coupled to a single printed circuit half-wave dipole antenna mounted a quarter wavelength in front of a reflector formed of the back mounting plate of the plastic housing. The collector current change occurring as a result of field disturbance of the highly directional antenna pattern is sensed, amplified, filtered and fed to a comparator whose output is adapted to initiate an alarm.