CA1272786A - System for identifying particular objects - Google Patents

System for identifying particular objects

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Publication number
CA1272786A
CA1272786A CA000538987A CA538987A CA1272786A CA 1272786 A CA1272786 A CA 1272786A CA 000538987 A CA000538987 A CA 000538987A CA 538987 A CA538987 A CA 538987A CA 1272786 A CA1272786 A CA 1272786A
Authority
CA
Canada
Prior art keywords
signals
signal cycles
frequency
reader
binary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
CA000538987A
Other languages
French (fr)
Inventor
Alfred R. Koelle
Jeremy A. Landt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Amtech Systems Inc
Original Assignee
Amtech Corp
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Publication date
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Publication of CA1272786A publication Critical patent/CA1272786A/en
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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/82Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B61RAILWAYS
    • B61LGUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L25/00Recording or indicating positions or identities of vehicles or vehicle trains or setting of track apparatus
    • B61L25/02Indicating or recording positions or identities of vehicles or vehicle trains
    • B61L25/04Indicating or recording train identities
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B61RAILWAYS
    • B61LGUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L25/00Recording or indicating positions or identities of vehicles or vehicle trains or setting of track apparatus
    • B61L25/02Indicating or recording positions or identities of vehicles or vehicle trains
    • B61L25/04Indicating or recording train identities
    • B61L25/045Indicating or recording train identities using reradiating tags
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/758Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using a signal generator powered by the interrogation signal
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06KGRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/0008General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06QINFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q10/00Administration; Management
    • G06Q10/08Logistics, e.g. warehousing, loading or distribution; Inventory or stock management
    • G06Q10/087Inventory or stock management, e.g. order filling, procurement or balancing against orders
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/20Individual registration on entry or exit involving the use of a pass
    • G07C9/28Individual registration on entry or exit involving the use of a pass the pass enabling tracking or indicating presence
    • GPHYSICS
    • G07CHECKING-DEVICES
    • G07CTIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00Individual registration on entry or exit
    • G07C9/00174Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C9/00896Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys specially adapted for particular uses
    • G07C2009/0092Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys specially adapted for particular uses for cargo, freight or shipping containers and applications therefore in general

Abstract

SYSTEM FOR IDENTIFYING PARTICULAR OBJECTS
Abstract of the Disclosure A reader interrogates an object. The object has a tag with a data source such as a read-only memory (ROM) which produces an identifying sequence of binary 1's and 0's in an individual pattern and transmits these signals to the reader.
Each "1" or "0" is converted to a plurality of signal cycles at first and second harmonic frequencies. For example, a "1" may be identified by two signal cycles at the second frequency (e.g.
40 kHz) and then one signal cycle at the first frequency (e.g.
20 kHz) and a "0" may be identified by a signal cycle at the first frequency and then two signal cycles at the second frequency. The transponder also produces a plurality of signal cycles in an individual code (different from any combination of "1's" and "0's") to indicate the end of the transmission of the signal cycles identifying the object and the start of another transmission. The reader receives the signal cycles identifying the object and delays these signal cycles by (a) a first time such as 1/4 period of a cycle at the second frequency, (b) a second time such as 1/2 of such period and (c) a third time corresponding to such period. The reader compares the received signals and the first delayed signals to produce first phase-locked signals. The reader compares the received signals and the second delayed signals to produce additional phase-locked signals at the times that the first phase-locked signals are not produced. The reader then produces clock signals from the first and additional phase locked signals. The reader produces information signals from a comparison of the received signals and the third delayed signals. The reader synchronizes the information signals with the clock signals to identify the object.

* * * * * * * *

Description

~2~2~6 1 This invention relates to systems Eor identi~ying
2 objects on a remote basis. More particularly, the invention
3 relates to a system including a reader for providing a simple
4 and reliable identification of an object, when the object is displaced by a considerable distance from the reader, by 6 detecting an individual sequence of signal cycles identifying 7 the object.

g As commerce becomes increasingly complex, the volume of products requiring individual identifications increases. For 11 example/ containers holding goods are stacked on merchant ships.
12 When the merchant ships reach a destination port, only 13 individual ones of such containers have to be unloaded and the 14 remaining containers may be retained on the merchant ship until subsequent destination p~rts are reached. It would be desirable 16 to identify, on a remote ~asis such as in the order of 30 to 40 17 feet, the containers whi~h have to be unloaded at the 18 destination port. By identifying such containers on a remote 19 basis, any need for merchant seamen or longshoremen at the destination port to have to inspect such containers individually 21 may be eliminated.

23 Systems have been developed for identifying an object 24 on a remote basis. Such systems include a reader displaced from the object for interrogating a tag at the object. The tag has 26 an identifying code whicb is individual to the object being 27 interrogated. This code is represented by a sequence of binary 28 l's and binary O's in a pattern individual to the object. Each 29 of the binary 1's and binary O's in this sequence i5 converted to a plurality of signal cycles which are transmitted to the ~2 a~

1 reader. The signal cycles In each plurality may have first and 2 second frequencies in a particular pattern to identify a binary 3 "1" and may have first and second frequencies in another pattern 4 to identify a binary "0~.

6 The systems in use have certain difficulties. One 7 dificulty is that the patterns o~ signal cycles identifying 8 binary l's and binary O's are in a form which creates problems 9 at the reader. Another problem is that the reader cannot identify easily when a transmission of the signal cycles 11 identifying the individual sequence of binary l's and binary 12 signal cycles for an object has been completed. A third problem 13 is that detection of the information represented by the patterns 14 of signals in the binary l's and the binary O's has been inhibited. This inhibition has resulted partly from the 16 inability of the reader ~ generate clock signal cycles on a 17 self-synchronous basis ~rom the signals received from the 18 transponder. This inability of the reader to generate clock 19 signals on a self-synchronous basis has impeded the operation of the reader in identifying the individual pattern of binary l's 21 a~d binary O's in the sequence.

23 A considerable effort has been made to overcome the 24 disadvantages discussed in the previous paragraph. In spite of such efforts, such disadvantages still exist in systems for 26 identifying objects on a remote basis. These disadvantages have 27 tended to limit the willingness of individuals and organizations 28 to employ systems for identifying objects on a remote basis. It 29 has also impeded the systems from fulfilling their theoeetical ranges of operability~

b78~;

1 This invention provides a systern which overcolnes the 2 disadvantages discussed above. The system produces pluralities 3 of cycles of signals at first and second harmonic frequencies.
4 The cycles of the signals identifying a binary "l" are s~mmetrical to the signals identi~yiny a binary "0". In other 6 words, the cycles at the second frequency occur before a cycle 7 at the first freguency to represent a binary "1" and the cycle 8 at the first frequency occurs before the cycles at the second 9 fre~uency to identify a binary l'On.
11 The system of this invention is also advantageous in 12 that it provides a code identifying the end o~ the transmission 13 of signal cycles identifying an object and the start of another 14 such transmission. This code is in a form which is distinctive from the pluralities of signal cycles identifying binary l's and -16 binary O's regardless o ~he combinations of binary l's and 17 binary O ' s which follow the code identifying the start of the 18 information transmission. The code identifying the end of one 19 transmission and the start of the next transmission i~ also advantageous because it occurs in a minimal time~

22 The system also provides a generation of clock signals 23 on a self-synchronizing basis regardless of the patterns of 24 binary l's and binary O's transmitted to the reader. This facilitates the detection by the reader on a straightforward 26 and reliable basis of the sequence o binary l's and binary O's 27 identi~ying the object.

29 The reader receives the signal cycles identifying the object and delays these signal cycles by (a) a first time such 1 as one fourth (1/4) of the period of a cycle at the second 2 frequency, (b) a second time such as one half (1/2) of such 3 period and (c) a third time such as such one (1~ such period, 4 The reader compares the received signal cycles and the first delayed signal cycles to produce first phase-locked signals for 6 generating the clock signals. The reader compares the received 7 signal cycles and the second delayed signal cycles to produce 8 additional phase-locked signals at the times that the first 9 phase-locked signals for generating the clock signals are not produced. The reader then produces clock signals from the first 11 and additional phase-loc~ed signals.

13 The reader produces information signals from a 14 comparison of the received signal cycles and the third delayed signal cycles. The reader synchronizes the in~ormation signals 16 with the clock signals ~o~identify the object. By identifying 17 the object, the object ma~ be segregated from adjacent objects 18 and individual operatîons may then be performed on such 19 segregated object. For example, containers disposed on a merchan~ ship and destined for a particular port may be 21 identified and segregated at such particular port by the system 22 consit;tuting this invention.

24 In the drawings:
26 Figure 1 is a simplified block diagram of a reader and 27 a transponder included in one embodiment of the inventio~ for 28 iden~ifying at the reader an object associated with the 29 transponder;

l Figures 2, ~b, 2c and 2d constitute complementary 2 block diagrams illustrating on a somewhat detailed basis the 3 construction of the reader shown in Figure 1;

Figure 3 illustrates waveforms produced in the 6 transponder and detected at the reader to identify a binary "1~, 7 a binary n 0~ and a code indicatin~ the end of the generation at 8 the transponder of sequences of signal cycles in the pattern of 9 binary 1's and binary O's identifying tne object;

ll Figure 4 illustrates waveforms of signal cycles 12 generated at the reader to detect the sequence of binary 1's and 13 binary O's identifying the object;

Figure 5 illustrates waveforms of signal cycles 16 generated at the reader ~p produce phase-locked signals used at 17 the reader to provide clo~k .signals for synchronizing the 18 operation of the reader shown in Figures 2a, 2b, 2c and 2d, and Figure 6 illustrates waveforms of additional signals 21 senerated at the reader to produce additional phase-locked 22 signals for providing the clock signals.

24 In one embodiment of the invention, a source lO o~
interrogating rf signals is connected to an antenna 12 at a 26 reader generally indicated at 14. The interrogating rf signals 27 from the source 10 may have a suitable frequency such as nine 28 hundred and fi~teen megahertx (915 MHz). When the sour~e lO of 29 interrogating rf signals is energized, the antenna l2 transmits activating signals to a suitable antenna 16 (such as a dipole ~2~;278G

1 antenna) at a transponder genercllly indicated at 18~ The 2 transponder 18 is loc~ted at an object (not shown) to identiy 3 the object. The transponder includes A data source such as a 4 read-only memory 22 which provides a sequence of binary l's and binary O's in an individual pattern to identify the object.
7 A binary ~1~ in the read-only memory 22 causes a 8 modulator X0 to produce a first plurality of signal cycles and a 9 binary "on in the read~only memory 22 causes the modulator 20 to produce a second plurality of signal cycles different from the 11 first plurality of signals~ The pluralities of signal cycles 12 5equentially produced by the modulator ~0 to represent the 13 pattern of binary l's and binary O's identifying the object are 14 introduced to the dipvle 16 for transmission to the antenna 12 at the reader.

17 The antenna 12 introduces the received signals to a 18 mixer 26 for comparison in the mixer with the interrogating rf 19 si~nals from the source 10. The mixed signals are introduced to an amplifier 28 and are demodulated in a demodulator 30. The 21 demodulator produce~ signals in a sequence having a pattern 22 iden~ifying the pattern of l's and O's in the read-only memory 23 22 at the transponder. This sequence may be compared in the 24 reader with a desired sequence to determine whether the object 25 being identified is one being sought by the reader.

27 The system described above represents the prior art on 28 a simplif ied basis . Such a system is disc~osed in United States 29 Patent No. 4, 075, 632 issued on February 21, 1978, to Howard A.
Baldwin, Stephe~ W. ~epp, Alfred R. Koelle and Robert W.

2'7~6 1 Freyman and assigned of record to the United States of America 2 as represented by the United States Department of Energy.
3 Applicant's assignee of record in this application has ob-tained 4 rights from the United States Government under patent 47075,632 to make, have made, use and sell the invention disclosed in such 6 patent and covered by the claims o such patent.

8 This invention provides an improvement on the system 9 disclosed and claimed in United States Patent No. 4,075,632.

The assignee of record of this patent application has advanced 11 the system of United States Patent No. 4,075,632 in accordance 12 with the improvements disclosed and claimed in this patent 13 application.

The system of this invention employs a reader, 16 generally indicated at 24~; which is shown in detail in Figures 17 2a, 2b, 2c and 2d and whi~h may be considered to be similar in 18 so~e details to that shown in Figure 1 and described above. The 19 signals are transmitted by the dipole 16 in Figure 1 to an Z0 antenna 26 (Figure 2a) and are introduced to mixers 32 and 34.
21 The interrogating rf signals from a source 30 (corresponding to 22 the source 10 in Figure 1~ are also introduced to the mixer 32 23 and are shifted in phase by 90 as at 36 and are then introduced 24 to the mixer 34. The signals from the mixers 32 and 34 are respectively amplified linearly at 40 and 42 and are then 26 introduced to a mixer or third channel combiner 44~ The signals 27 from the amplifiers 40 and 42 and from the mixer 44 are 28 respectively introduced to amplifiers 46, 48 and 50, each of 29 which provides a high gain and then a limitation in amplitude after providing such high gain.

7~

1 The signals from the limiting amplifiers 46~ 48 and 50 2 respective.ly pass to shiEt registers (Figures 2b) 54 and S6 in 3 series, 58 and 60 in series and 62 and 64 in series. The 4 signals at mid points in the shift registers 54, 58 and 62 respectively pass to exclusive OR gates 66, 68 and 70. Signals 6 are also respectively introduced to the input terminals of the 7 exclusive OR gates 66, 68 and 70 from the output terminals of 8 the limiting ampl.ifiers 46, 48 and 50.
9 ..
Connections are made from the output terminal of the 11 exclusive OR gate 66 to input terminals of AND gates 72 and 74, 12 from the output terminal of the OR gate 68 to input terminals of 13 the AND gate 72 and an AND gate 76 and from the output terminal 14 of the OR gate 70 to input terminals of the AND gates 74 and 76.
The output terminals of the AN~ gates 72, 74 and 76 are 16 connected to input termi~ls of cm OR gate 80. (Figure 2c).
17 The AND gates 72, 74 and ~6 are shown in Figures 2b and 2c.

19 In like manner, the signals from the limiting amplifiers 46, 48 and 50 (Figure 2b) are respectively introduced 21 to exclusive OR gates 82, 84 and 86. Second input terminals o~
22 ~he exclusive OR gates 82 r 84 and 86 respectively receive 23 signals rom the output terminals of the shift registers 54, 58 24 and 62. Signals are introduced from the output terminal of the exclusive OR gate 82 to input terminals o AND gates 90 and 92, 26 from the ou~.put terminal of the exclusive OR gate 84 to input 27 terminals of the AND gate 90 and an AND gate 94 and from the 28 output terminal of the exclusive OR gate 86 to input terminals 29 of the AND gates 92 and 94. The output terminals of the AND
gates 90; g2 and 94 are connected to input terminals of an OR

... ..... " , " .. , .. .. ~ .. ........

J~136 gate 9G. ~Figure 2c). The AND gates 90, 92 and 94 are shown in 2 Figures 2b and 2c.

4 Correspondingly, the output terminals of the shift registers 56, 60 and 64 ( Figure 2b) respectively pass to input 6 terminals of exclusive OR gates 100, 102 and 104. The exclusive 7 OR gates 100, 102 and 104 also have input terminals respectively 8 connected to the output terminals of th.e limiting amplifiers 46, 9 48 and 50. Connections are respectively made from the output terminals of the exclusive OR gates 100, 102 and 104 to input 11 terminals of AND gates 110 and 112, input terminals o the AND
12 g~te 110 and an AND gate 114 and input terminals of the AND
13 gates 112 and 114~ The signals passing through the AND gates 14 110, 112 and 114 are introduced to input terminals of an OR gate 116. (Figure 2c)~ The. A~D gates 110/ 112 and 114 are shown in ~6 Figures 2b and 2c.

18 The signals from the OR gate 80 pass to a phase-locked 19 loop 120 which may be constructed in a conventional manner. The phase-locked loop may include a phase detector and a 21 voltage-controlled oscillator. ~n output terminal o~ the phase 22 detector of the phase-locked loop 120 is connected to a movable 23 arm o~ a switch 122, the positioning of which may be controlled 24 by the signal from the OR gate 96. This is indicated by broken 25 lines in Figure 2c. The switch 1~2 is ~hown as a mechanically 26 operated switch but it preferably constitutes a semi conductor 27 deviceO
~8 29 The stationary contact of the switch 122 is connected to a resistance 124 in series with a parallel combination of a ~2 _ g _ .
.. . . ........ . . . . . . ... .

1 capacitance 126 and a resistance 128. The parallel combination 2 of the capacitance 126 and the resistance 128 is connected 3 through a capac.itance 130 to a reerence potential such as 4 ground. The terminal common to the resistances 124 and 126 and the capacitance 128 is connected to an input terminal of the 6 voltage-controlled oscillator in the phase-locked loop l20~ The 7 resistances 124 and 128 and the capacitances 126 and 130 may be 8 considered to be included in a low pass loop filter indicated in 9 broken lines at 134 in Figure 2c~ The signals from the voltage-controlled oscillator of the phase-locked loop 120 are ll introduced to the clock terminal of a low-pass digital filter 12 132.

14 When the dipole 16 at the transponder 18 in Figure 1 receives the interrogating rf signals from the reader 24; it ~6 generates pluralities of signal cycles in a code dependent upon 17 the pattern of l's and O's provided in the data source such as 18 the read-only memory 22 ~o identify the object associated with l9 the transponder. For example, a binary n o" may be represented by a first signal cycle at a suitable requency such as twenty 21 kilohertz (20 k~z) and then by additional signal cycles at a 22 suitable frequency which is a harmonic of the first requency.
23 Preferably, the second frequency i~ forty kilohertz (40 k~z) 24 when the first frequency is twenty kilohertz (20 XHz). ~his is illustrated at 140 in Figure 3. Similarly, a binary n 1 n may be 26 represented by two (2) cycles ak the second f requency such as 27 forty lcilohertz ~ 40 kHz) and then by an additional cycle at the 28 first frequency such as twenty kilohertz (~0 k~z). This is 29 illustrated at 142 in Figure 3.

.....

1 The read-only mernory 22 cause5 -the modulator 20 to 2 produce the pluralities of signal cycles respectively coding 3 Eor the sequences of binary l's and binary O's in the individual 4 pattern. Tlle modulator 20 introduces these signals to the dipole 16 (Figure 1) for transmission to the reader 24. These 6 signals are received by the antenna 26 (Figure 2a) and are 7 introduced to the mixers 32 and 34 (Figure 2a). The mixer 32 8 al50 receives the interrogating rf signals from the source 10 9 and the mixer 34 receives the interrogating rf signals from the source 10 after the signals have been shifted in phase by 90 by 11 the stage 36. The mixed signals from the mixers 32 and 34 12 respectively pass through the amplifiers 40 and 42 to the 13 limiting amplifiers 4~ and 50. The signals from the amplifiers 14 40 and 42 are also mixed in the stage 44 and these mixed signals 1~ are introduced to the limuting amplifier 48.
16 ~
.17 If anly one mixer such as the mixer 3~ were used, the 1~ output from the mixer could disappear or become null if the 19 received signal happened to be in quadrature phase (90- or 270-) 20 with respPct to the interrogating rf signal. By providing the 21 mixers 32 and 34 and by providing a 90 shift in phase in the 22 interrogating signal introduced to the mixer 34, a null cannot 23 simultaneously occur at both of the mixers. As a result, an 24 ou~put signal will pass ~rom at least one of the mixers under all of the different phase relationships possible between the 26 received signal and the interrogating rf signal.

28 There is still one possibility of a null in the 29 output. This may occur when the outputs of the mixers 32 and 34 have opposite polarities. That is, the output of one of the 1 mixers 3~ and 34 may be the inverse of the output of the other 2 mixer. To preven-t a null from occurring uncler SUC}I
3 circumstances, the combiner 44 is included to combine the 4 outputs of the signals from the linear amplifiers 40 and 42.
The signals from the combiner 44 are introduced to the limiting 6 amplifier 48. Since outputs ara obtained from the three 7 limiting amplifiers and since the outputs of these amplifiers 8 are paired (e.g., in the AND gates 72, 74 and 76), an output is g obtained from at least two (2~ of these three (3) AND networks under all pocsible circumstances.
11 ' , 12 The shift registers 54 and 56 (Figure 2b) delay the 13 signals from the amplifier 46. The delay provided by the shift 14 register 54 corresponds to one-half of the period of a signal cycle at the second fre~uency such as forty kilohertz ( 40 k~z) .
16 This signal cycle is intr;~duced to the exclusive OR network 82.

..
17 (Figure 2b). Similarly, ~he exclusive OR network 66 receives 18 from the shi~t register 58 the signal cycles delayed by a 19 quarter of the period of a signal at the second ~requency such a~ forty kilohertz (40 k~z). ~he shift regist2r 56 provides the 21 same delay as the shift register 54 so that the signal cyc].e Z2 introduced to the exclusive OR network 100 has a phase shift 23 corresponding to a complete period of a signal cycle at the 24 second frequency such as forty kilohertz ~40 kHz~. The exclusive OR networks 68g 84 and 102 receive signal cycles 26 respectively delayed by the same time period as the signal 27 cycles received by the exclusive OR networks 66, 82 and 100.

28 This same phase relationship is also present in the signal 29 cycles introduced to the exclusive O~ networks 70, 86 and 104.

31 . .

~2~

1 The exclu~ive 0~ gate 84 compares the amplitude of the 2 signal c~cles from the amplifier 48 with the amplitude oE the 3 delayed signal cycles from the shift register 5B. When the 4 amplitudes of the signal cycles are both simultaneously high or are both simultaneously low, the exclusive OR gate 82 produces a 6 signal with a high amplitude. ~t all other times, the signals 7 Prom the exclusive OR gate 82 have a low amplitude. The 8 exclusive OR gates 84 and 86 respectively provide a similar 9 comparison of the signal cycles from the amplifier 48 and the delayed signals from the shift register 5B and with the signal 11 cycles ~rom the amplifier 50 and the delayed signals from the lZ shift register 62. The signals passing through the exclusive OR
13 gates 82, 84 and 86 are introduced in individually paired 14 relationships to the AND gates 72, 74 and 76 (Figures 2b and 2c). The AND gates 72, 7~ and 76 in turn pass signals to the OR
16 gate 80 which operates ~o~provide an output signal when it 17 simultaneously receives slgnals of high amplitudes from two of 18 the AN~ gates 72, 74 and 76.
~9 In effect, the exclusive OR gate~ 66, 68 and 70 and 21 the AND gates 72~ 74, 76 and 80 operate to provide a comparison 22 of the amplitudes of the received signal cycles and the received 23 signal cycles delayed by one guarter of a time period of a 24 signal cycle at the second frequency such a~ forty kilohertz l40 k~z). This comparison is indicated in Figure 5. In Figure 5, 26 the ~eceived ~ignal cy~les are indicated at 146 and the delayed Z7 signal cycles are indicated at 1480 The output from the OR gate 28 80 is indicated at 150 in Figure 5. This output has a frequency 29 which constitutes the fourth harmonic (e.g. 80 k~z) of the first frequency such as twenty kilohertz (20 kHz). The signals 150 ~72~8~;

l occur in most cycles at the third frequency (e.g. 80 ~Hz) but, 2 as will be seen at 152, do not occur itl al.l cycle~. The .signals 3 150 have a high amplitude when the amplitudes of the signal 4 cycles 146 and 148 are simultaneously high or simultaneously low.
6 The exclusive OR gates 82~ 84 and 86 re~pectively 7 compare the amplitudes of the signals ~rom the limiting 8 amplifiers 46, 48 and 50 with the amplitudes of the output g signals from the shift registers 54, 58 and 62. This comparison is indicated in Figure 6. As will be seen in Figure 6, the ll signal cycles from the amplifiers 46, 58 and 50 are indicated at 12 146 and the signal cycles from the phase shifters 54, 58 and 62 13 are indicated at 154~ As a result of the comp~rison, signals 14 are produced as indicated at 156 in Figure 6. The signals 15 have a high amplitude when both the signals 144 and 154 16 simultaneously have a lo~amplitude or simultaneously have a 17 high amplitude. The sign~ls 156 are produced at the third l8 frequency te.g. 80 kHz) at the times that the signals 152 in l9 Figure 6 are not produced at ~his frequency. As a result, when the signals 150 and 156 are combined, the combination occurs at 21 a periodic rate corresponding to the third freyuency such as 22 eighty kilohertz (80 kHz)~

24 The signals lSO passing through the OR gate 80 ~Figure 2c) are introdu~ed to the pha~e detector of the phase-locked Z6 loop 120 in Figure 2c to obtain the production by the oscillator 27 of signals at a partlcular frequency~ For exampler this ~8 ~re~uency may be l.28 megahertz. As will be appreciated, a 29 frequency of 1.28 megahertz is a harmonic of the first frequency of twenty kilohertz (20 kHz) and the second frequency of forty ~2 1 kilohertz (40 kHz) and is also a harmonic of the phase-locked 2 signals at the third ~requency Oe eighty kilohertz (80 kH~) from 3 the OR gate 80 and 96. As a result, the signals from the OR
4 gate 80 and 96 constitute phase-locked signals to obtain the generation by the voltage~controlled oscillator in the 6 pha~e-locked loop 120 of the clock signals at the frequency of 7 1.28 megahertz.

g During the time that the phase-locked signals pass through the OR gate 80, the switch 122 ~Figure 2c) remains 11 closed. This causes current to flow through the circuit 12 including a voltage source 160, a resistance 162, the voltage-13 controlled oscillator in the phase-locked loop 120, the switch 14 122~ the resistance 124, the resistance 128 and the capacitance 126 in parallel and the capacitance 130. This current charges 36 the capacitance 126. This current is also instrumental in 17 obtaining the generation ~y the voltage-controlled oscillator 18 in the phase-locked loop 120 of the signals at the clock 19 frequency of 1.28 megahertz.
2~ .
21 When a signal passes thro~gh the OR yate 96 ~Figure 22 2c), it causes the swi~ch 122 to open. The capacitances 12~ and 23 130 then hold the input into ~he voltage-controlled oscillator 24 in the phase-locked loop 120 and cause the voltage-controlled oscillator to continue maintaining the generation of the clock 26 signals by the voltage-controlled oscillator at the frequency of Z7 1.28 megahertz. In this way, the signals from the OR ga~es 80 2~ and g6 are instrumental in obtaining the generation by the 2g voltage-controlled oscillator in the phase-locked loop 120 of 3~

.... ~ ... .. .... . . . . . .. .. . .... .. . . .

1 t.he clock signals at the Erequency of 1.28 meyahertz on 2 consi~stent basis.

4 The clock signals at the frequency o~ 1.28 megahertz from the voltage-controlled oscillator in the phase-locked loop 6 1.20 are introduced to the low pass digital filter 132. The 7 filter 132 also receives the signals passing through the OR gate 8 116. The operation of the OR gate 116 may be seem from Figure 9 4. In Figure 4, the received signal cycles are indicated at 146 and the delayed signal cycles from the shift re~isters 56, 60 11 and 64 are indicated at 168. The results of the comparison 12 between the signal cycles ~re indicated at 170~ The signal 13 cycles 170 represent the demodulated signals identifying the 14 object associated with the transponder 18. ~he filter 13 filters the demodulated signals 170 to pass only the low 16 frequencies represented ~ the demodulated signals and to 17 prevent the passage of short pulses signals representing noise.

19 Figure 2d illustrates on a somewhat simplified schematic basis a sys~em for utilizing a sequence of signals 178 21 (Figure 3) coding for the end of the sequence of binary l's and 22 binary O's identifying the object associated with the 23 transponder 18 and also coding for the beginning of the next 24 such sequence! The system shown in Figure 2d in~ludes the voltage-controlled oscillator in the phase~locked loop 120 and a 26 frequency divider 180. The frequency divider 180 receives the 27 signals from the voltage-controlled oscillator 120 and divide~
28 these ~ignals to produce clock signal~ at the second frequency 29 such as ~orty kilohertz (40 k~z). These signals are introduced .. . .. ,., .. , . ,.. ,. . . . . . .. . . ~ .

78~

1 to a terminal of a shift register 186, another input terminal of 2 which is connected to receive the dernodulated signals 170.
3 (Pigure 4).

The shift register 186 has six output terminals each 6 of which is connected to the shift register to produce an output 7 upon a successive occurrence of one of the signals from the 8 frequency divider 180. When the six output terminals from the 9 shift register 186 simultaneously have signals of high amplitude, a signal passes through an AND gate 188. This signal 11 indicates that the transmission of the pluralities of signal lZ cycles from the transponder 18 to identify the associated object 13 has been completed and that a new sequence of such transmission 14 is being initiated. The signal from the AND gate 188 is introduced to an AND gate-l90, another terminal of the AND gate 16 being connected to receiv~ the demodulated signals 170. The 17 output from the AND gate 190 accordingly synchronizes the start 18 of a new transmission of the pluralities of signal cycles 19 iden~ifying the object.

21 The signals 178 have certain important advantages when 22 used to indicate the end o~ a sequence of inormation signals 23 identifying the objec~ associated with the transponder 18 and Z4 the start of the next such sequence. One advan~age is that the sequence 178 is different from any combination of signals 26 identifying successive values of binary 1's and binary O's.
27 Another advantage is that the sequence 178 occurs in only a ~8 minimal amount of time. For example, the sequence 178 occurs in 29 a period of time corresponding to the transmission of two binary 3~

~L2 7~ 3 6 l lls or two binary 019. The sequence 178 is further advantageous 2 in that it requires the same period o~ time as the generation o~
3 two binary l's or two binary O's.

Although this invention has been disclosed and 6 illustrated with reference to particular embodiments, the 7 principles involved are susceptible for use in nurnerous other 8 embodiments which will be apparent to persons skilled in the 9 art. The invention is, there~ore, to be limited only as indicated by the scope of the appended claims.

1~

~3

Claims (30)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGEIS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination in a system including a reader and a transponder displaced from the reader for identifying an object associated with the transponder, means at the reader for transmitting interrogating signals at a particular frequency to the transponder, means disposed at the transponder and responsive to the interrogating signals for generating successive pluralities of signal cycles in a pattern individual to the object, the signal cycles in each plurality including signal cycles at both first and second frequencies in a pattern representative of a binary "1" or a binary "0", means disposed at the transponder for transmitting the successive pluralities of signal cycles at the first and second frequencies to the reader, and means at the reader for decoding the pattern of the frequencies of the signal cycles in each of the successive pluralities to identify the object.
2. In a combination as set forth in claim 1, the generating means including means providing initially at least one signal cycle at the first frequency and subsequently a signal cycle at the second frequency in individual ones of the pluralities to represent a binary "1" and providing initially at least one signal cycle at the second frequency and subsequently at least one signal cycle at the first frequency in other ones of the pluralities to represent a binary "0".
3. In a combination as set forth in claim 1, the first frequency being a harmonic of the second frequency, the generating means including means providing initially a particular number of signal cycles at the second frequency and subsequently a signal cycle at the second frequency in individual ones of the pluralities to represent a binary "1" and providing initially at least one signal cycle at the first frequency and subsequently the particular number of signal cycles at the second frequency in other ones of the pluralities to represent a binary "1", the particular number of signal cycles at the first frequencies in each plurality being dependent upon the harmonic relationship between the first and second frequencies.
4. In a combination as set forth in claim 3, the generating means generating signals of the same time duration to represent a binary "0" as to represent a binary "1".
5. In combination in a system including a reader and a transponder displaced from the reader for identifying an object associated with the transponder, means at the reader for transmitting interrogating signals at a particular frequency to the transponder, means disposed at the transponder and responsive to the interrogating signals for generating successive pluralities of signal cycles in a pattern individual to the object, the signal cycles in each plurality including one signal cycle at a first frequency and two signal cycles at a second frequency constituting the second harmonic of the first frequency, the signal cycles at the second frequency preceding the signal cycle at the first frequency in each plurality representative of a binary "1" and the signal cycles at the first frequency preceding the signal cycle at the second frequency for each plurality representing a binary "0", means at the transponder for transmitting the successive pluralities of signal cycles at the first and second frequencies to the reader, and means at the reader for decoding the pattern of the frequencies of the signal cycles in each of the successive pluralities to identify the object.
6. In a combination as set forth in claim 5, means at the transponder for generating an individual pattern of signal cycles at the first and second frequencies to identify the end of the successive pluralities of signal cycles generated at the first and second frequencies and identifying the object, and means at the reader for decoding the individual pattern of the signal cycles at the cycles at the first and second frequencies to identify the end of the successive pluralities of signal cycles generated at the first and second frequencies and identifying the object.
7. In a combination as set forth in claim 5, means at the transponder for generating, at the end of the successive pluralities of signals at the first and second frequencies, a sequence of signal cycles having a greater number of successive signal cycles at the second frequency than that represented by any combination of signal cycles coding for sequential 1's and 0's in the successive pluralities, and means at the reader for decoding the sequence of signal cycles to identify the end of the successive pluralities of signal cycles at the first and second frequencies.
8. In a combination as set forth in claim 6, the generating means including means for generating the sequence comprising six signal cycles at the second frequency and one signal cycle at the first frequency to identify the end of the successive pluralities of signal cycles at the first and second frequencies and the start of another such generation of such successive pluralities.
9. In a combination as recited in claim 6, the means for generating the pattern of the signals to identify the end of the successive pluralities of signal cycles including means for generating the signals at the first and second frequencies in an individual pattern different from a binary "1" or a binary "0" or any combination of a binary "1" or a binary "0" and occurring in a time period constituting an integral multiple of the time period for generating the signals representing a binary "1" or representing a binary "0".
10. In a combination as set forth in claim 9, the generating means including means for generating six (6) successive signals at the second frequency and the one (1) signal at the first frequency to identify the end of the successive pluralities of signal cycles generated at the first and second frequencies and identifying the object.
11. In a combination as recited in claim 6, means disposed at the reader and responsive to the decoding of the end of the successive pluralities of signal cycles generated at the first and second frequencies and identifying the object for generating the successive pluralities of signal cycles at the first and second frequencies to identify the object.
12. In combination in a system including a reader and a transponder displaced from the reader for identifying an object associated with the transponder, means at the reader for interrogating the transponder, means disposed at the transponder and responsive to the interrogation from the reader for generating successive pluralities of signal cycles in an individual pattern identifying the object, the signal cycles in each plurality having patterns of signal cycles at both first and second frequencies to identify a binary "1" or a binary "0", means for transmitting the successive pluralities of signal cycles to the reader, means at the reader for receiving the transmitted signal cycles, means at the reader for delaying the successive pluralities of the received signal cycles by a first delay time, first means at the reader for comparing the received signal cycles and the signal cycles delayed by the first delay time to obtain a demodulation of the information represented by the signal cycles in the successive pluralities, means at the reader for delaying the successive pluralities of the received signal cycles by a second delay time different from the first delay time, second means at the reader for comparing the received signal cycles and the signal cycles delayed by the second delay time to generate phase-locked signals, means responsive at the reader to the phase-locked signals for generating clock signal cycles at the reader to facilitate the decoding of the information represented by the signal cycles in the successive pluralities, means at the reader for delaying the successive pluralities of the received signal cycles by a third delay time different from the first and second delay times, third means at the reader for comparing the received signal cycles and the signal cycles delayed by the third delay time to generate control signals, and means responsive to the control signals for generating additional phase-locked signals at times synchronous with the phase-locked signals generated by the second comparing means to facilitate the generation of the clock signal cycles on a periodic basis.
13. In a combination as set forth in claim 12, wherein the first delay means includes means for delaying the received signal cycles by a period of time corresponding to the time for the production of a signal cycle at the second frequency, the second delay means includes means for delaying the received signal cycles by a period corresponding to one fourth (?) of the fist delay time, and the third delay means includes means for delaying the received signal cycles by a period corresponding to one half (?) of the first delay time.
14. In a combination as set forth in claim 13, switching means having first and second states of operation, means responsive to the control signal cycles from the third comparing means for obtaining a controlled operation of the switching means in the first and second states in accordance with the pattern of such control signal cycles, and the means for generating the additional phase locked signal cycles includes means responsive to each operation of the switching means in the second state for generating the additional phase-locked signal cycles.
15. In a combination in a reader for identifying an object associated with a transponder displaced from the reader wherein the transponder generates, in a particular pattern identifying the object, pluralities of signal cycles at first and second frequencies in a first sequence to identify a binary "0" and in a second sequence, different from the first sequence, to identify a binary "1" and transmits the pluralities of signal cycles in the particular pattern of the first and second sequences to the reader, first means for receiving the pluralities of signal cycles in the particular pattern of the first and second sequences, second means for comparing the received pluralities of signal cycles and the received pluralities of signal cycles delayed by a first time period to detect the information coded by the received pluralities of signal cycles, third means for comparing the received pluralities of signal cycles and the received pluralities of signal cycles delayed by a second time period different from the first time period to generate phase-locked signals, fourth means for comparing the received pluralities of signal cycles and the received pluralities of signal cycles delayed by a third time period different from the first and second time periods to generate additional phase-locked signal cycles at times different from the phase-locked signals generated by the third means, and fifth means responsive to the phase-locked signals generated by third and fourth means for synchronizing the detection of the information generated by the received pluralities of signals with the generation of the phase-locked signals and the additional phase-locked signals.
16. In a combination as set forth in claim 15, switching means having first and second states of operation, the fourth means including means for maintaining the switching means in the second state of operation, and means responsive to the operation of the switching means in the second state for generating the additional phase-locked signals, the third means being operative to generate the phase-locked signals when the switching means is in the first state.
17. In a combination as set forth in claim 16, the means for generating the additional phase-locked signals including a capacitance responsive to the operation of the switching means in the first state for becoming charged and responsive to the operation of the switching means in the second state for discharging to generate the additional phase-locked signals.
18. In a combination as set forth in claim 15, low pass digital filter means responsive to the demodulated signals for eliminating noise signals.
19. In combination in a reader for identifying an object associated with a transponder displaced from the reader wherein the transponder generates, in a particular pattern identifying the object, pluralities of signal cycles at first and second frequencies in a first sequence to identify a binary "0" and in a second sequence, different from the first sequence, to identify a binary "1" and transmits the signal cycles in the particular pattern of the first and second sequences to the reader, means for receiving signals in the particular pattern of the first and second sequences, means for delaying the signal cycles for a first particular time period related to the first and second frequencies, means for delaying the signal cycles for a second particular time period related to the first and second frequencies but different from the first particular time period, means for delaying the signal cycles for a third particular time period related to the first and second frequencies but different from the first and second particular time periods, means for comparing the received signal cycles and the signal cycles delayed by the first time period for generating phase-locked signals, means for comparing the received signals and the signals delayed by the second time period for generating additional phase-locked signals at the times not generated by the first comparing means, means for comparing the received signal cycles and the signal cycles delayed by the third time period for generating demodulated signals, and means responsive to the demodulated signals and the phase-locked signal cycles and the additional phase-locked signal cycles for recovering the code identifying the object.
20. In a combination as set forth in claim 19, the first delaying means including means for providing a delay of one fourth (?) of the period represented by one of the signal cycles at the second frequency, the second delaying means including means for providing a delay of one half (?) of such period, and the third delaying means including means for providing a delay of such period.
21. In a combination as set forth in claim 19, means for responding to the signal cycles at the first and second frequencies to indicate when the particular pattern of the first and second sequences has been completed.
22. In a combination as set forth in claim 20, the transponder generating a plurality of signal cycles in a third sequence of signal cycles at the first and second frequencies where the third sequence is different from any combination of the first and second sequences to identify an object, and means at the reader for responding to the third sequence of signal cycles to indicate when the particular pattern of the first and second sequences has been completed.
23. In combination in a system for identifying an object, means displaced from the object for transmitting interrogating signals to the object, means responsive at the object to the interrogating signals for generating signals in a first pattern of signals at first and second frequencies representative of a binary "1" and in a second pattern of signals at the first and second frequencies representative of a binary "0", the first frequency being a harmonic of the second frequency and the duration of the signals representing binary "0" being the same as the duration of the signals representing a binary "1", means disposed at the object for transmitting the successive pluralities of signals at the first and second frequencies in representation of the binary "0's" and the binary "1's", means at the displaced position for receiving the transmitted signals, and means at the displaced position for decoding the received signals to identify the pattern of binary "0's" and binary "1's" represented by such signals.
24. In a combination as set forth in claim 23, the generating means including means for generating a greater number of signals at the first frequency than at the second frequency for each binary "1" and binary "0" by a ratio corresponding to the ratio of the first and second frequencies.
25. In a combination as set forth in claim 24, the first frequency being the second harmonic of the second frequency and the number of signals at the first frequency being twice as great as the number of signals at the second frequency.
26. In a combination as set forth in claim 25, the generating means generating two (2) signals at the first frequency and then one (1) signal at the second frequency to represent a binary "1" and generating one (1) signal at the second frequency and then two (2) signals at the first frequency to represent a binary "0".
27. In combination in a reader for identifying an object associated with a transponder displaced from the reader wherein the transponder generates, in a particular pattern identifying the object, pluralities of signal cycles at first and second frequencies in a first sequence to identify a binary "1" and in a second sequence, different from the first sequence, to identify a binary "0", switching means having first and second states of operation and normally being operative in the first state, charge storage means, means responsive to the operation of the switching means in the first state for charging the charge storage means, means responsive to first particular patterns of the signals in the first and second states for generating phase-locked signals at a particular frequency, means responsive to second particular patterns of the signals in the first and second states for obtaining an operation of the switching means in the second state, means responsive to the operation of the switching means in the second state for obtaining a discharge of the charge storage means, and means responsive to the discharge of the charge storage means for obtaining the generation of additional phase-locked signals at the particular frequency.
28. In a combination as set forth in claim 27, means responsive to the phase-locked signals and the additional phase-locked signals and the pluralities of signals generated by the transponder for identifying the object associated with the transponder.
29. In a combination as set forth in claim 27, the means for generating the phase-locked signals including means responsive to the signals at the first and second frequencies in the particular pattern and responsive to such signals delayed by a first particular time for passing the phase-locked signals at each instant in accordance with the relative amplitudes at such instant of such signals and such delayed signals, the means for generating the additional phase-locked signals including means responsive to the signals at the first and second frequencies in the particular pattern and responsive to such signals delayed by a second particular time different from the first particular time for passing the additional phase-locked signals at each instant in accordance with the relative amplitudes at such instant of such signals and such delayed signals.
30. In a combination as set forth in claim 29, including, the first frequency being the second harmonic of the second frequency, means for delaying the signals at the first and second frequencies in the particular pattern by one fourth of the time period of signals at the first frequency to provide the signals delayed by the first particular time, and means for delaying the signals at the first and second frequencies in the particular pattern by one half of the time period of the signals at the second frequency to provide the signals delayed by the second particular time.
CA000538987A 1986-07-14 1987-06-05 System for identifying particular objects Expired - Lifetime CA1272786A (en)

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US4739328A (en) 1988-04-19
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ES2027264T3 (en) 1992-06-01
JP2613890B2 (en) 1997-05-28
IL82576A0 (en) 1987-11-30
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HK87193A (en) 1993-09-03
AU7557587A (en) 1988-01-21
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JPS6329281A (en) 1988-02-06
EP0253368B1 (en) 1991-10-23

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