OBJECT IDENTIFICATION SYSTEM

• US 3,737,911 A
• Filed: 08/17/1970
• Issued: 06/05/1973
• Est. Priority Date: 02/03/1968
• Status: Expired due to Term

• Current Assignee: Johji Sakuragi, Kazuhiko Kameda
• Original Assignee: Johji Sakuragi, Kazuhiko Kameda
• Inventors: Sakuragi, Johji, Kameda, Kazuhiko
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/064,585
• Time in Patent Office: 1,023 Days
• Field of Search: 343/6.5SS
• US Class Current: 340/10.4
• CPC Class Codes: B61L 25/043 using inductive tags

Abstract

An object identification system comprising a frequency sweep generator which generates an interrogation signal to be transmitted by the transmitter; a response device, consisting of passive resonance elements, mounted on the object to be identified; a receiver for receiving the reply signals; a phase shifter connected to the output of the frequency sweep generator; phase detector which compares the output of the receiver with the phase shifter output; and the series connection of a low pass filter, amplifier, and Schmitt circuit connected to the output of the phase detector in order to detect the steep phase variation of the signal received from the object.

Claims

1. An object identification system comprising frequency-sweep means to generate an interrogation signal to sweep a predetermined frequency range, a transmitting and receiving means to transmit the interrogation signal toward a response device mounted on an object to be identified and to receive a response signal from said response device, said response device consisting of a plurality of passive resonance elements and means to detect steep phase variation of said response signal with the phase of the interrogation signal as a reference, said steep phase variation being produced due to the frequency-phase characteristics of said resonance elements when the interrogation signal sweeps successively each resonance point of a plurality of said resonance elements.

2. An object identification system comprising a frequency sweep generator which generates an interrogation signal to be transmitted by a transmitter;

a response device, consisting of passive resonance elements, mounted on an object to be identified;

a receiver for receiving a response signal from said response device;

a phase shifter connected to the output of the frequency sweep generator;

phase detector which compares the output of the receiver with the output of said phase shifter; and

the series connection of a low pass filter, an amplifier, and a wave shaping circuit connected to the output of the phase detector in order to detect the steep phase variation of the signal received from the object.

3. In an object identification system having frequency-sweep means to generate an interrogation signal to sweep a predetermined frequency range, a transmitting and receiving means to transmit the interrogation signal toward a response device mounted on an object to be identified and to receive a response signal from said response device, said response device including a plurality of resonance elements respectively having predetermined resonance frequencies, and means to detect steep phase variation of the received signal occurring at respective resonance frequency points of said resonance device, the improvement wherein said frequency sweep means comprises a sweep generator, said transmitting and receiving means comprises a high output impedance amplifier adapted to amplify the oUtput of said sweep generator, a transmitting and receiving coil to transmit the output of said amplifier toward said response device mounted on the object, said response device includes a loop coil, a condenser connected to said loop coil and a plurality of resonance elements connected in parallel to the series connection of said loop coil and condenser, each of said resonance elements having a different resonance frequency, said loop coil being arranged to transmit to said transmitting and receiving coil a signal including steep phase variation occurring at frequencies corresponding to resonance frequencies of said resonance elements, and wherein said means to detect phase variation comprises a phase shifter to which the output from said sweep generator is supplied, a phase detector to which the output from said phase shifter as a reference signal is supplied and a signal received by said transmitting and receiving coil and containing said variation are supplied, a low pass filter to which the output signal from said phase detector is supplied, a low pass filter to which the output signal from said phase detector is supplied, and a wave shaping circuit to amplify and shape the output signal from said low pass filter thereby to identify said object.

4. An object identification system according to claim 3, wherein said response device comprises a circuit including a loop coil and a condenser, a circuit including resonance elements and lines having distributed constants and adapted to interconnect said circuits so that said loop coil and said resonance elements may be located at different positions of said object.

5. In an object identification system having frequency-sweep means to generate an interrogation signal to sweep a predetermined frequency range, a transmitting and receiving means to transmit the interrogation signal toward a response device mounted on an object to be identified and to receive a response signal from said response device, said response device including a plurality of resonance elements respectively having predetermined resonance frequencies, and means to detect respective resonance frequency points of said resonance elements of said response device, the improvement wherein said frequency sweep means comprises a plurality of sweep oscillators;

and transmitting and receiving means comprises an adder to combine the outputs from said sweep oscillators, a high output impedance amplifier to amplify the output from said adder, and a transmitting and receiving coil to transmit the output to said response device, said response device including a loop coil, a condenser connected in series with said loop coil, and a plurality of resonance elements having different resonance frequencies and respectively connected in parallel to the series connection of said loop coil and condenser, said resonance elements being divided into a plurality of groups of the number equal to that of sweep oscillators with respect to their resonance frequency ranges, and the resonance frequencies of said resonance elements belonging to respective groups being included in the range of sweep frequency of corresponding sweep oscillators, said transmitting and receiving coil being arranged to receive a signal containing steep phase variation occurring at frequencies corresponding to resonance frequency points of said resonance elements; and

said steep phase variation detecting means comprises a plurality of phase shifters connected to receive output signals from said sweep oscillators, a plurality of phase detectors connected to receive outputs from said phase shifters as the reference signals and to receive said signal received by said transmitting and receiving coil and containing said variation as the input signal, a plurality of low pass filters connected to receive output signals from said phase detectors, and a plurality of wave shaping circuits to shape the output signals from said low pass filters, thereby to identify said object.

6. An object identification system according to clAim 5, wherein said response device comprises a circuit including a loop coil and a condenser, a circuit including a plurality of resonance elements and line having distributed constants and adapted to interconnect said circuits so that said loop coil and said resonance elements may be located at different positions of said object.