RADIO FREQUENCY BURGLAR ALARM SYSTEM

• US 3,696,368 A
• Filed: 04/15/1969
• Issued: 10/03/1972
• Est. Priority Date: 04/15/1969
• Status: Expired due to Term

• Current Assignee: Ray B. Kauffman
• Original Assignee: Ray B. Kauffman
• Inventors: Kauffman, Ray B.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Slobasky, Michael
• Application Number:
  US04/816,320
• Time in Patent Office: 1,267 Days
• Field of Search: 340/258A,258B 325/29,131
• US Class Current: 340/553
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

The burglar alarm system utilizes a transmitter that transmits an RF signal which is both amplitude modulated and frequency modulated. The signal is received by a receiver which is capable of sensing increases or decreases in the received energy due to movement through or into the energy field which is generated and radiated by the transmitter. This change in energy level causes the receiver to trigger an alarm.

Claims

1. An intrusion detection system for detecting the intrusion of a moving object, comprising:

means for generating a frequency modulated signal of a first frequency band which continuously sweeps from a first to a second frequency having its amplitude modulated by a second frequency, means for radiating said frequency mOdulated and amplitude modulated signal connected to said generating means, and means for receiving said frequency modulated and amplitude modulated signal containing means for detecting amplitude changes in said received frequency modulated and amplitude modulated signal, said signal amplitude changes at the receiving means indicating the intrusion of a foreign object, said means for generating a frequency modulated signal having its amplitude modulated by a second frequency comprising an oscillator including an electronic valve whose bias is gradually being built up to cause said electronic valve to cut off whereby the building up of said bias causing said electronic valve to become less conductive thereby amplitude modulating the frequency modulated signal.

2. An intrusion detection system as defined in claim 1, but further characterized by said receiver means having means for automatically controlling the level of received frequency modulated signal so that the relative position of said radiating means and said receiving means does not affect the operation of said receiver.

3. An intrusion detection system as defined in claim 2, but further characterized by having means responsive to said means for detecting amplitude changes for triggering an alarm indicating means.

4. An intrusion detection system having a receiver for detecting directly radiated frequency modulated and amplitude modulated radio frequency wave from a transmitting antenna and a radio frequency wave which is reflected from an intruder, the intruder affecting the amplitude of the received signal, comprising:

a transmitter means for generating said frequency modulated and amplitude modulated wave comprising an oscillator including an electronic valve whose bias is gradually being built up to cause said electronic valve to cut off whereby the building up of said bias causes said electronic valve to become less conductive thereby amplitude modulating the frequency modulated signal, means for receiving said frequency modulated and amplitude modulated radio frequency wave energy, means for detecting said radio frequency modulated wave connected to said receiving means, means for amplifying said detected frequency modulated signal connected to said detecting means, said amplifier means having an output, means for detecting both positive and negative changes in amplitude of said frequency modulated detected signal on said output of said amplifier means, and detector means responsive to said both positive and negative detected amplitude changes of said frequency modulated detected signal for triggering an alarm means whereby both positive and negative changes in said detected signal cause said alarm to be triggered.

5. An intrusion detection system as defined in claim 4, but further characterized by having an automatic level control means for controlling the level of the detected signal connected to said means for detecting said radio frequency wave energy.

6. An intrusion detecting system as defined in claim 1, but further characterized by said receiving means having an antenna, a tuned circuit means tuned to said frequency modulated signal having an input and an output, said means for detecting amplitude changes having an input and an output, said antenna connected to said tuned circuit input, said output of said tuned circuit connected to said input of said means for detecting amplitude changes, and an amplifier means having a tuned bandpass filter, said amplifier means having an input and an output, said amplifier input being connected to said output of said means for detecting amplitude changes and said amplifier output having a signal which is indicative of the amplitude of the received frequency modulated signal.

7. An intrusion detecting system as defined in claim 6, but further characterized by said receiving means having a second detector having an input and an output, a second amplifier having an input and an output, said second detector input connecTed to said output of said amplifier having a bandpass filter, said output of said second detector being connected to said input of said second amplifier, an automatic level control means having an input and an output, said automatic level control means input connected to said output of said second amplifier and said output of said automatic level control connected to said means for detecting amplitude changes in said frequency modulated signal, means for detecting positive and negative changes of signal level having an input and an output, said input of said means for detecting positive and negative changes being connected to said output of said second amplifier, and an alarm indicating means having an input connected to said output of said means for detecting positive and negative changes in said signal level whereby changes in said signal level trigger an alarm indicating the presence of an intruder.

8. An intrusion detection system having a zone of protection about a periphery, comprising:

means for generating a radio frequency signal which continuously sweeps from a first frequency to a second frequency, means for radiating said radio frequency signal connected to said radio frequency generating means, means for receiving said radio frequency signal from said radiating means and reflections of said radio frequency signals from an object entering the electro-magnetic field caused by said radiated radio frequency signal, means for mixing said received radio frequency signal received from said radiating means with said radio frequency signal reflected from said intruded object generating a beat signal connected to said receiving means, means for passing said generated beat signal of a predetermined frequency bandwidth connected to said mixing means, said means for passing said generated beat signal determining the periphery of the zone of protection, means for detecting amplitude changes of said band passed beat frequency connected to said band passing means, and means for generating an alarm responsive to said amplitude changes detected by said change detected means connected to said change detecting means whereby amplitude changes in said band passed signal is indicative of an intruding object entering said protected perimeter of said radio frequency radiation field, whereby an intruder in said zone of protection about said periphery causes said alarm to be sounded.

9. An intrusion detection system having a zone of protection about a periphery defined in claim 8, but further characterized by said means for generating continuously varying radio frequency signal, is provided with means for varying the rate of the frequency sweep whereby said periphery of said zone of protection is changed when said frequency sweep rate is changed.

10. An intrusion detecting system as defined in claim 2, but further characterized by said receiving means having an antenna, a tuned circuit means tuned to said frequency modulated signal having an input and an output, said means for detecting amplitude changes having an input and an output, said antenna connected to said tuned circuit input, said output of said tuned circuit connected to said input of said means for detecting amplitude changes, and an amplifier means having a tuned bandpass filter, said amplifier means having an input and an output, said amplifier input being connected to said output of said means for detecting amplitude changes and said amplifier output having a signal which is indicative of the amplitude of the received frequency modulated signal.

11. An intrusion detection system as defined in claim 1, but further characterized by said means for generating a frequency modulated signal comprising:

an electronic valve having means connected thereto to cause said valve to oscillate, means causing the frequency of said oscillating valve to change connected to said oscillating electronic valve, and means for changing the rate of frequency change of saId oscillating electronic valve connected to said frequency changing means.

12. An intrusion detection system as defined in claim 11, but further defined by said means for causing said oscillating frequency to change comprising a variable capacitance diode and said means for changing rate frequency changes comprising a sawtooth wave generator.