RECOGNITION SYSTEM

• US 3,798,642 A
• Filed: 09/27/1972
• Issued: 03/19/1974
• Est. Priority Date: 09/27/1972
• Status: Expired due to Term

• Current Assignee: Harry A. Augenblick, William J. Engle
• Original Assignee: Harry A. Augenblick, William J. Engle
• Inventors: Augenblick, Harry A., Engle, William J.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/292,751
• Time in Patent Office: 538 Days
• Field of Search: 340/280,258R,258C 343/225,6.5R,6.5SS,7ED 325/8
• US Class Current: 342/42
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: G08B 13/2422 using acoustic or microwave tags
• CPC Class Codes: G08B 13/2431 Tag circuit details
• CPC Class Codes: G08B 13/2454 Checking of authorisation of a person accessing tagged items in an EAS system
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit

Abstract

A recognition system comprising a transmitter for radiating an amplitude modulated signal to a target that generates a harmonic of the received signal, detects the amplitude modulating signal and modulates the harmonic signal with the detected signal. The target contains a frequency selective network that produces a coded arrangement of signal components which comprise the signal returned by the target. A receiver detects the coded arrangement of signal components.

Claims

1. An electronic recognition system comprising transmitting means for transmitting an amplitude modulated signal;

target means adapted to receive said modulated signal for generating a harmonic signal having a plurality of signal components, having respective amplitudes, said target means further comprising amplitude varying means for varying the amplitude of at least one of said plurality of signal components to obtain an output signal having a preselected coded arrangement of the amplitudes of said plurality of signal components; and

receiving means responsive to said output signal, said receiving means comprising sensing means for producing a recognition signal when said preselected coded arrangement of amplitudes of said plurality of signal components is received.

2. An electronic recognition system as in claim 1, in which said transmitting means comprises signal-producing means for producing a signal of preselected frequency, and modulator means for amplitude modulating said signal of preselected frequency.

3. An electronic recognition system as in cliam 1, in which said transmitting means includes signal-producing means for generating at least two signals for different preselected frequencies.

4. An electronic recognition system as in claim 1, in which said target means comprises a harmonic generator for generating at least a harmonic signal from said modulated signal, detecting means for detecting the amplitude modulating signal, means for applying the detected signal to said amplitude varying means, and modulating means for modulating said harmonic signal with the signal from said amplitude varying means.

5. An electronic recognition system as in claim 1, in which said target means further comprises a diode connected across said amplitude varying means.

6. An electronic recognition system as in claim 1, in which said amplitude varying means comprises a frequency selective network for altering at least one of said plurality of signal components.

7. An electronic recognition system as in claim 1, in which said amplitude varying means comprises a plurality of frequency selective networks for altering different ones of said plurality of signal components.

8. An electronic recognition system as in claim 7, and disabling means for selectively disabling predetermined ones of said plurality of frequency selective networks.

9. An electronic recognition system as in claim 1, in which said amplitude varying means comprises a tuned circuit which is tuned to the frequency of one of said signal components.

10. An electronic recognition system as in claim 1, in which said transmitting means comprises at least one signal generator for generating a signal of pre-selected frequency, and said receiving means includes multiplying means connected to said transmitting means for multiplying said signal of preselected frequency to produce a component signal of said harmonic signal, mixing means for mixing said received harmonic signal with said multiplied signal, said sensing means comprising comparing means for comparing the amplitudes of said received signals and for producing said recognition signal when the amplitudes of said signal components are in said preselected arrangement.

11. An electronic recognition system as in claim 10, and an alarm device responsive to said recognition signal for producing an indication that said recognition signal has been generated.

12. An electronic recognition system as in claim 2, in which said modulating means comprises at least two signal generators for modulating said signal of preselected frequency with modulating signals of different frequencies.

13. An electronic recognition system as in claim 2, in which said modulator means comprises a variable frequency signal generator for modulAting said signal of preselected frequency with a signal the frequency of which varies with time.

14. An electronic recognition system as in claim 13, in which said sensing means further comprises amplitude responsive means for generating a signal proportional to the amplitude of said received signal.

15. An electronic recognition system as in claim 14, and alarm means connected to said amplitude responsive means for producing said recognition signal when the amplitude of the signal from said amplitude responsive means reaches a preselected value.

16. A recognition system comprising transmitting means for transmitting an amplitude modulated signal comprising a plurality of signal components, a target comprising harmonic generator means operable to receive said amplitude modulated signal for generating a harmonic output signal, detecting means for producing a detected signal comprising at least some of the components of the amplitude modulated signal, modulating means for modulating said harmonic output signal with said detected signal, and a frequency selective network for altering the amplitude of at least one of the components comprising said detected signal to produce a coded arrangement of signal components which comprise said harmonic output signal;

and receiving means for producing a recognition signal when said coded arrangement of signal components is sensed.

17. A recognition system as in claim 16, in which said transmitting means comprises oscillator means for generating at least two signals of different preselected fundamental frequencies, and an antenna for radiating said two signals to produce a composite amplitude modulated signal which is modulated by a signal having a frequency equal to the difference in frequency between said two signals.

18. A recognition system as in claim 16, in which said harmonic generator means, detecting means and modulating means comprise a diode connected across said frequency selective network.

19. A recognition system as in claim 16, in which said frequency selective network is a parallel resonant circuit.

20. A recognition system as in claim 16, in which said frequency selective network is a series resonant circuit.

21. A recognition system as in claim 16, in which said frequency selective network comprises a resistor connected to a reactive element.

22. A recognition system as in claim 16, in which said frequency selective network comprises a filter having a plurality of stop bands.

23. A recognition system as in claim 22, and switch means connected to said filter for selectively varying the stop bands of said filter.

24. A target for use with a recognition system adapted to produce an amplitude modulated signal at said target, said target comprising harmonic means for generating a harmonic of said amplitude modulated signal, detecting means for detecting the amplitude modulated signal, amplitude varying means for varying the amplitude of preselected components in said detected signal, and modulating means for modulating the harmonic signal with the signal from said amplitude varying means to produce an otuput signal having a predetermined coded arrangement of signal components.

25. A target as in claim 24, in which said amplitude varying a frequency comprises afrequency selective network.

26. A target as in claim 25, in which said amplitude varying means comprises a plurality of frequency selective networks.

27. A target as in claim 26, and selectively operable disabling means for disabling desired ones of said plurality of frequency selective networks.

28. A target as in claim 24, in which said harmonic means, detecting means and modulating means comprise a diode.