ELECTRONIC RECOGNITION AND IDENTIFICATION SYSTEM

• US 3,816,708 A
• Filed: 05/25/1973
• Issued: 06/11/1974
• Est. Priority Date: 05/25/1973
• Status: Expired due to Term

• Current Assignee: Charles A. Walton
• Original Assignee: Charles A. Walton
• Inventors: Walton, Charles A.
• Primary Examiner(s): Cook, Daryl W.
• Application Number:
  US05/363,851
• Time in Patent Office: 382 Days
• Field of Search: 235/61.11H,61.7B 340/149A,152T,258C 343/6.5SS,6.8R
• US Class Current: 340/5.8
• CPC Class Codes: G06K 7/086 sensing passive circuit, e.g. resonant circuit transponders

Abstract

An improved electronic recognition and identification system for recognizing and identifying the resonant frequency of a coded external passive network. The system comprises an active network including a radio frequency sweep oscillator driving a sensing coil to generate an external electromagnetic field for inductive coupling to the passive resonant network when said passive network is brought within the proximity of the sensing coil. The active network further includes a vector detector for detecting variations in the signal across said sensing coil due to said passive network and for generating detector signals representative of the resonant frequency of the passive network, an internal reference signal generating network for establishing select signals representative of a reference identification frequency, and a comparator network responsive to said detector and said select signals for generating control signals indicative of coincidence of non-coincidence of the detector and select signals, said logic comparator network having signal integrating capability to permit recognition of a sustained signal from the detector network and distinguish the sustained signal from random noise or other disturbances.

Claims

1. An improved electronic recognition and identification system for identifying electrically coded passive objects and generating control signals responsive to the code of the passive objects, the system comprising a coded external passive electrical identification object including a passive electrical circuit, said passive circuit having a coded resonant frequency and adapted to be brought within an external sensing zone;

an active electrical signal generation network including a first sensing coil, a radio frequency signal source means adapted to provide stimulating electrical signals repeatedly sweeping through a range of radio frequencies, said frequency range including said coded resonant frequency of the passive electrical object, said radio frequency signal source means being joined to said sensing coil to permit said first sensing coil to produce electromagnetic field signals within said external sensing zone for inductive coupling with the external passive object when said object is within said external sensing zone, a first detector means engaged to said sensing coil for detecting perturbations in the envelope of the signal across said first sensing coil as the frequency of said electromagnetic field in said external sensing zone approaches said coded resonant frequency of the external passive object, said first detector means being adapted to produce condition signals responsive to the timing of said perturbations of the envelope of frequency signals across said first sensing coil;

an internal reference signal generator means engaged to said radio frequency signal source means, said internal reference signal generator means including an internal passive circuit means having a select reference resonant frequency which reference resonant frequency is within the range of said radio frequency source means, second detector means for detecting coincidence of said resonant frequency of said internal passive object and the radio frequency signal source, said second detector means being adapted to produce internal reference signals responsive to the timing at which the frequency of said radio frequency signal source coincides with the resonant frequency of said internal passive circuit means; and

logic comparator means having input terminal means for receiving said condition signals and said internal reference signals, the logic comparator means being adapted to generate control signals responsive to time coincidence of the condition signals and internal reference signals.

2. The electronic recognition and identification system of claim 1 in which the internal reference signal generator includes a second sensing coil joined to said radio frequency generating source means to permit said Second coil to produce electromagnetic field signals within an internal sensing zone, a reference coded passive electrical object having a reference coded resonant frequency and adapted to be positioned within said internal sensing zone for inductive coupling to said second sensing coil, a second detector means engaged to said second sensing coil for detecting perturbations in the envelope of the signal across said second sensing coil as the frequency of said electromatic field in said internal sensing zone approaches said coded resonant frequency of the reference coded passive electrical object, said second detector means being adapted to produce reference signals responsive to the timing of said perturbations of the envelope of radio frequency signals across said second sensing coil.

3. The electronic recognition and identification system of claim 2 in which said first detector includes stripping means for stripping the radio frequency signals of the envelope of said signal across said first sensing coil and separating said perturbations from said envelope and providing condition digital pulse signals responsive to said perturbations;

said second detector includes stripping means for stripping the radio frequency signals of the envelope of said signal across said second sensing coil and separating said perturbations from said envelope and providing an internal reference digital pulse signal train responsive to said perturbations in the envelope of the signal across said second sensing coil; and

in which the comparator means includes a logic comparator network responsive to said condition digital pulse signals and said reference digital pulse signal train.

4. The electronic recognition and identification system of claim 3 in which the internal reference signal generator further includes a pulse separation logic means for receiving said primary reference digital pulse signal train and separating alternate pulses of said reference signal train to separate internal reference trains, the number of individual separate internal reference trains coinciding with the number of internal reference passive circuits within said internal reference signal generator means.

5. The electronic recognition and identification system of claim 4 in which the comparator means includes a logic comparator network responsive to the condition digital pulse signal train and each of said separate reference trains, said comparator network being adapted to generate a first output control signal only when timing coincidence exist between a first separate internal reference train and the condition digital pulse signal train and timing coincidence exist between a second separate internal reference train and the condition digital pulse signal.

6. The electronic recognition and identification system of claim 5 in which said logic comparator network includes a first AND gate responsive to said condition digital pulse signals and said first separate internal reference train, a first storage means engaged to the output of said first AND gate for developing a first charge potential responsive to repetitive coincidence of said condition digital pulse signal train and said first separate internal reference train, a second AND gate responsive to said first charge potential, said condition digital pulse signal and said second separate internal reference train, the output of said second AND gate being dependent on the magnitude of said charge potential and the coincidence of said second separate internal reference train and the condition digital pulse signal train.

7. The electronic recognition and identification system of claim 6 in which the first detector means includes a first unidirectional conductive element responsive to the positive portions of the envelope across said first sensing coil and generating a first signal train responsive to perturbations in the positive portion of said envelope, a second unidirectional conductive element responsive to the neGative portions of the envelope across said first sensing coil and generating a second signal train responsive to perturbations in the negative portion of said envelope, and a differential amplifier means for combining said first and second signal trains to a composite signal train.

8. The electronic recognition and identification system of claim 7 in which the first detector further includes a differentiator network for differentiating said composite signal train and producing said condition signals, and an amplifier stage having a preset threshold level, said amplifier stage receiving said differentiated composite signal train and amplifying those signals of a magnitude greater than the threshold level.

9. The electronic recognition and identification system of claim 8 wherein said logic comparator network further includes a second storage means engaged to the output of said second AND gate for developing a second charge potential responsive to repetitive output signals of said second AND gate.

10. The electronic recognition and identification system of claim 9 wherein said logic comparator network further includes an operational amplifier engaged to said second storage means, and an inverter engaged across the output and input of said operational amplifier to vary the threshold level of said operational amplifier responsive to the output of said amplifier.

11. The electronic recognition and identification system of claim 7 wherein said first detector means further includes an automatic sensitivity network to suppress harmonics of said composite signal train, said automatic sensitivity network including threshold level signal control means for controling the threshold level of said amplifier stage to a magnitude exceeding the peak magnitude of the unwanted harmonic signals of the composite differentiated signal train.

12. The electronic recognition and identification system of claim 11 wherein said automatic sensitivity network includes a storage charge capacitor tied in series with a unidirectional conductive device extending to the differentiator network whereby the charge on said capacitor is dependent on the magnitude of said differentiated signal, and a voltage divider network across said capacitor and joined to said amplifier stage at a threshold level terminal of said amplifier.

13. The electronic recognition and identification system of claim 3 in which the signal source means of the active electrical signal generation network includes a fixed frequency oscillator means, a sweep oscillator means, a first mixer network engaged to said fixed frequency oscillator and said sweep oscillator means, said first mixer being adapted to the stimulating electrical signal within a frequency range dependent on the difference between the sweep frequency and fixed frequency;

said first detector means including a second mixer network joined to said sensing coil and said sweep oscillator to generate an envelope of a frequency corresponding to the frequency of said fixed frequency oscillator and adapted to produce condition signals responsive to the timing of said perturbations of the envelope of the output signal of the second mixer network.