COMBINED ULTRASONIC AND ELECTROMAGNETIC INTRUSION ALARM SYSTEM

• US 3,846,778 A
• Filed: 06/21/1973
• Issued: 11/05/1974
• Est. Priority Date: 06/21/1973
• Status: Expired due to Term

• Current Assignee: ADT Security Services Incorporated (Apollo Global Management, Inc.)
• Original Assignee: Aaron A. Galvin, Shapiro L. Dennis
• Inventors: Galvin, Aaron A., Shapiro, L. Dennis
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/372,193
• Time in Patent Office: 502 Days
• Field of Search: 340/258A,16R 343/5PD,7.7,6R
• US Class Current: 340/522
• CPC Class Codes: G08B 13/1645 using ultrasonic detection means and other detection means, e.g. microwave or infrared radiation
• CPC Class Codes: G08B 13/2494 by interference with electro-magnetic field distribution combined with other electrical sensor means, e.g. microwave detectors combined with other sensor means

Abstract

An intrusion alarm system for detecting the presence of moving targets in one or more surveillance zones and in which electromagnetic and ultrasonic signals are simultaneously or alternatively employed with common signal processing circuitry. The electromagnetic and ultrasonic signal frequencies differ from each other in a predetermined ratio such that the wavelengths of the signals being propagated are substantially identical to permit the processing of both received electromagnetic and ultrasonic signals by the common circuitry.

Claims

1. An intrusion alarm system comprising:

means for transmitting an electromagnetic signal of first frequency into a zone under surveillance;

means for transmitting an ultrasonic signal of second frequency into a zone under surveillance, said electromagnetic and ultrasonic signals being related in frequency to have substantially the same wavelengths in air;

means operative to receive electromagnetic signals returned from a surveillance zone and to provide a first electrical signal in response thereto;

means operative to receive ultrasonic signals returned from a surveillance zone and to provide a second electrical signal in response thereto;

frequency shifting means operative in response to at least one of said first and second electrical signals to provide electrical signals of a common frequency;

common signal processing means operative in response to said common frequency electrical signals to provide an output signal in the presence of a valid moving target and including means for establishing a threshold representative of the steadystate condition of the surveillance zones in the absence of a valid moving target; and

means operative to provide an alarm indication in response to exceedance of said threshold by said output signal.

2. An intrusion alarm system according to claiM 1 wherein said frequency-shifting means comprises:

first signal source means operative to provide a first signal having said first frequency;

second signal source means operative to provide a second signal having said second frequency, one of said first and second signals having a frequency identical to said common frequency, the other of said first and second signals having a frequency different than said common frequency;

source-frequency offsetting means operative in response to said common frequency signal and to said other signal to provide an offset signal representative of said other signal and offset by said common frequency; and

mixing means operative in response to said offset signal and to at least one of said first and second electrical signals to provide said common frequency electrical signals representative of said first and second electrical signals.

3. An intrusion alarm system according to claim 1 wherein said first frequency is within the microwave range.

4. An intrusion alarm system according to claim 1 wherein said common frequency is equal to said second frequency.

5. An intrusion detection system comprising:

means for transmitting an electromagnetic signal of first frequency into a zone under surveillance;

means for transmitting an ultrasonic signal of second frequency into a zone under surveillance, said electromagnetic and ultrasonic signals being related in frequency to have substantially the same wavelengths in air;

means operative to receive electromagnetic signals returned from a surveillance zone and to provide a first electrical signal in response thereto and containing Doppler information in the presence of a moving target in a surveillance zone;

means operative to receive ultrasonic signals returned from a surveillance zone and to provide a second electrical signal in response thereto and containing Doppler information in the presence of a moving target in a surveillance zone; and

frequency shifting means operative in response to at least one of said first and second electrical signals to provide electrical signals of a common frequency and containing said Doppler information, said common frequency signal being suitable for processing by common signal processing circuitry capable of providing an output indication of a moving target.

6. An intrusion alarm system comprising:

means for transmitting an electromagnetic signal of first frequency into a first zone under surveillance;

means for transmitting an ultrasonic signal of second frequency into a second zone under surveillance, said electromagnetic and ultrasonic signals being related in frequency to have substantially the same wavelengths in air;

means operative to receive electromagnetic signals returned from said first surveillance zone and to provide a first electrical signal in response thereto;

means operative to receive ultrasonic signals returned from said second surveillance zone and to provide a second electrical signal in response thereto;

frequency shifting means operative in response to at least one of said first and second electrical signals to provide electrical signals of a common frequency;

common signal processing means operative in response to said common frequency electrical signals to provide an output signal in the presence of a valid moving target and including means for establishing a threshold representative of the steady state condition of said first and second surveillance zones in the absence of a valid moving target; and

means operative to provide an alarm indication in response to exceedence of said threshold by said output signal.

7. An intrusion alarm system according to claim 6 wherein said first and second surveillance zones are conterminous.

8. An intrusion alarm system according to claim 7 wherein the first surveillance zone extends beyond said second surveillance zone.

9. An intrusion alarm system according to claim 7 wherein said first surveillance Zone is separate from said second surveillance zone.

10. An intrusion alarm according to claim 2 wherein said source-frequency offsetting means includes a lead and lag network receiving said common frequency signal and providing output signals, mixers receiving the output signals from said lead and lag network and said other signal, and a summing circuit receiving the output from the mixers and providing said offset signal.

11. An intrusion alarm system according to claim 2 wherein said source-frequency offsetting means includes a ramp generator receiving said common frequency signal and a microwave phase modulator receiving the output of said ramp generator and said other signal and providing said offset signal.