ELECTRONIC IDENTIFICATION & RECOGNITION SYSTEM

• US 3,752,960 A
• Filed: 12/27/1971
• Issued: 08/14/1973
• Est. Priority Date: 12/27/1971
• Status: Expired due to Term

• Current Assignee: Charles A. Walton
• Original Assignee: Charles A. Walton
• Inventors: Walton, Charles A.
• Primary Examiner(s): Sloyan, Thomas J.
• Application Number:
  US05/212,281
• Time in Patent Office: 596 Days
• Field of Search: 340/149A,152T,258C 343/6.5SS,6.8R 235/61.11H
• US Class Current: 340/5.8
• CPC Class Codes: B07C 3/12 using electric or electronic detecting means B07C3/14 takes precedence
• CPC Class Codes: B61L 25/043 using inductive tags
• CPC Class Codes: G06K 7/086 sensing passive circuit, e.g. resonant circuit transponders

Abstract

An electronic identification and recognition system for identifying or recognizing an object carrying an electrically passive circuit. The system comprises an active electrical signal generation network with a sensing coil for generating an electromagnetic field within the proximate area of said sensing coil; and an object having a passive electrical circuit with a coded resonant frequency, said object being adapted to move relative to and from said proximate area and adapted for inductive coupling with said active system. The active generation network being further adapted to generate digital control signals responsive to the resonant frequency of the passive object when said passive object is inductively coupled with said active system.

Claims

1. An electronic identification system for identifying electrically passive objects, the system comprising a passive electrical object including a passive electrical circuit having a coded resonant frequency;

an active electrical signal generation network including a sensing coil, said sensing coil being movable relative to the passive electrical object and adapted for inductive coupling with said passive electrical circuit when said object is within the proximity of said sensing coil, a variable frequency signal generating source for generating electrical signals within a select range of frequencies, said source being connected to said coil to generate an electromagnetic field within the proximity of said sensing coil which field is disturbed as the frequency of the generated field approaches the coded resonant frequency of said passive circuit, a detector means connected to said sensing coil for detecting changes in the electrical potential of said sensing coil as the frequency of the generated field approaches the coded resonant frequency of said passive circuit, the detector means being adapted to generate detector output signals responsive to the detected resonant frequency of the passive object, and a preset recognition code network having a tuned circuit means of a preset tuned frequency engaged to said signal generating source and adapted to present an output signal when the frequency of said signal generating source matches the preset tuned frequency of said tuned circuit means, and a coincidence detector means engaged to said detector means and to said tuned circuit means for detecting time coincidence of the output signals of said detector means and the output signals of said tuned circuit means, said coincidence detector means being adapted to generate a first command signal if time coincidence of said output signals is detected and a second command signal if there is not time coincidence of said output signals.

2. The electronic identification system of claim 1 wherein said variable frequency signal generating source includes a sawtooth waveshape generator engaged to a voltage controlled oscillator, the instantaneous frequency of said voltage controlled oscillator being responsive to the instantaneous value of the output of said generator.

3. The electronic identification system of claim 1 wherein said detector means includes a phase detector engaged to said oscillator and to said sensing coil, the phase detector being adapted to generate a signal of varying amplitude representative of the phase relationship of the oscillator signals and the signals of said sensing coil.

4. The electronic identification system of claim 3 wherein said detector means further includes a second detector joined to said phase detector to receive the output of said phase detector, said second detector being in the form of a differentiator network adapted to respond to the output of said phase detector and to generate a pulse signal as the time derivative of the amplitude of the output signal of said phase detector passes through a reference voltage level.

5. The electronic identification system of claim 4 wherein the active electrical signal generator network further includes a bridge isolation network to isolate the variable frequency generating source from the electrical load of the sensing coil.

6. The system of claim 1 wherein the preset recognition code network includes a plurality of tuned circuits each of a preset tuned frequency and each engaged to the variable frequency signal generating source, and each adapted to present an output signal when the frequency of said signal generating source matches the preset tuned frequency of the tuned circuit, and the coincidence detector means is engaged to said detector means and to each of said tuned circuits, said coincidence detector means being adapted to detect a matching time coincidence of a plurality of output signals of said detector and the response of said plurality of tuned circuits, and to generate a first command signal if a matching time coincidence is detected between said detector output signals and all of the output signals of said tuned circuits and a second command signal if there is not coincidence.