WO2000003352A1 - Appareil et procede de recuperation de signaux de donnees transmis sur etiquettes radiofrequences - Google Patents

Appareil et procede de recuperation de signaux de donnees transmis sur etiquettes radiofrequences Download PDF

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Publication number
WO2000003352A1
WO2000003352A1 PCT/US1999/015456 US9915456W WO0003352A1 WO 2000003352 A1 WO2000003352 A1 WO 2000003352A1 US 9915456 W US9915456 W US 9915456W WO 0003352 A1 WO0003352 A1 WO 0003352A1
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WIPO (PCT)
Prior art keywords
tag
signal
transition
data
transitions
Prior art date
Application number
PCT/US1999/015456
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English (en)
Inventor
Daniel J. Friedman
Original Assignee
Intermec Ip Corp.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Intermec Ip Corp. filed Critical Intermec Ip Corp.
Publication of WO2000003352A1 publication Critical patent/WO2000003352A1/fr

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0701—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips at least one of the integrated circuit chips comprising an arrangement for power management
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/0008—General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Definitions

  • the field of the invention is the field of Radio Frequency (RF) Transponders (RF Tags), wherein a Base Station sends power and information to one or more RF Tags which contain logic and memory circuits for sto ⁇ ng information about objects, people, items, or animals associated with the RF Tags
  • RF Tags can be used for identification and location (RFID Tags) of objects and to send information to the base station by modulating the load on an RF Tag antenna
  • RF Tags can be used in a multiplicity of ways for locating and identifying accompanying objects, items, animals, and people, whether these objects, items, animals, and people are stationary or mobile, and transmitting information about the state of the of the objects, items, animals, and people
  • RF radio frequency
  • the signal picked up by the tag antenna induces an alternating current m the antenna which can be rectified by an RF diode and the rectified current can be used for a power supply for the electronic components
  • the tag antenna loading is changed by something that was to be measured, for example a microphone resistance m the cited patent
  • the oscillating current induced in the tag antenna from the incoming RF energy would thus be changed, and the change in the oscillating current led to a change in the RF power
  • the antenna current also oscillates at a harmonic of the earner frequency because the diode current contains a doubled frequency component, and this frequency can be picked up and sorted out from the earner frequency much more easily than if it were merely reflected. Since this type of tag carries no power supply of its own, it is called a "passive" tag to distinguish it from an active tag containing a battery. The battery supplies energy to run the active tag electronics, but not to broadcast the information from the tag antenna. An active tag may also change the loading on the tag antenna for the purpose of transmitting information to the base station.
  • the "rebroadcast" of the incoming RF energy at the earner frequency is conventionally called “back scattenng", even though the tag broadcasts the energy m a pattern determined solely by the tag antenna and most of the energy may not be directed "back” to the transmitting antenna.
  • Pnor art tags have used electronic logic and memory circuits and receiver circuits and modulator circuits for receiving information from the base station and for sending information from the tag to the base station
  • Pnor art tags typically use a number of discrete components connected together with an antenna
  • a single chip connected to an antenna must be used In order to increase the range of passive tags, and to conserve battery life of active tags, the minimum current necessary for the tag functions must be used
  • Pnor art tags use receivers with automatic gain control to boost received signal or limit received signal when the tags are far from or near to the base station.
  • the automatic gam control mechanisms take up a lot of space on the chip, and use too much current.
  • the digital signals received by the tag with no automatic gain control are sampled at different points in the signal waveform depending on the prior history of the signal. In this way, automatic gain control is not needed to provide a series of pulses which have "perfect" shape and duration.
  • the data are sampled at different times t n after each type of transition.
  • the data are sampled at a first time after a midbit rise in the signal, and at a second time after a midbit fall in signal. The transitions at the bit boundaries are ignored.
  • Fig. 1 shows a system of a base station sending RF energy to an RF tag
  • Fig. 2 shows a block diagram of the tag antenna and part of the RF tag.
  • Fig. 3 is a block diagram of the tag clock section.
  • Fig. 4 shows the RF power for a steadily modulated signal sent from the base station with the rise and fall times of the signal exaggerated.
  • Fig. 5 shows the digital data output to the tag data recovery signal from this signal if the tag is far from the base station.
  • Fig. 6 shows the digital data output to the tag data recovery signal from this signal if the tag is near to the base station.
  • Fig. 7a shows a square wave data signal sent out from a base station to a tag.
  • Fig. 1 shows a system of a base station sending RF energy to an RF tag
  • Fig. 2 shows a block diagram of the tag antenna and part of the RF tag.
  • Fig. 3 is a block diagram of the tag clock section.
  • FIG. 7b shows the signal produced from the digital output of the tag receiver when the tag is close to the base station.
  • Fig. 7c shows the clock signal output of the tag oscillator.
  • Fie. 8 is a flow chart of a method of the invention. DETAILED DESCRIPTION OF THE INVENTION
  • Fig. 1 shows a system of a base station 10 having an associated computer 5 sending RF energy 20 from base station antenna 12 to a tag antenna 32 associated with an RF tag 30.
  • the RF frequency f 0 is preferably above 100 MHZ, more preferably above 900 MHZ, and most preferably above 2,300 MHZ.
  • the RF signal is preferably amplitude modulated at a frequency f, greater than 1 Khz, more preferably between 5 and 150 Khz, and most preferably between 20 and 60 Khz.
  • the RF signal may also be modulated by frequency modulation or by phase modulation methods, as is well known in the art of RF signal propagation.
  • the RF tag 30 may be a passive tag which receives all the energy needed to carry out the tag functions from the RF field broadcast by the base station, or it may be an active tag which carries a battery to store the required energy. Both types of tags can change the loading on the tag antenna 32 to change the antenna reflectivity and thus communicate with the base station 10. Active tags may also generate and transmit RF signals back to the base station.
  • Fig. 2 shows a block diagram of the tag antenna 32 and part of the RF tag 30. (Neither a possible RF tag transmitter section nor other sections such as measurement sections nor alarm section nor enable/disable sections are shown.)
  • the RF antenna 32 feeds RF power to the tag rectification power supply 34.
  • a battery tag would replace block 34 with a battery (not shown)
  • a tag rectification signal receiving section 36 comprising an RF diode, a signal capacitor, and a signal capacitor current drain is separate from the tag rectification power supply, but the oscillator section of the invention is also contemplated in the case that section 36 is part of the tag rectification power supply 34.
  • the tag power supply 34 supplies current at voltages VDD, and optionally voltages VPMR, and
  • VNMR on lines 52, 54, and 56 respectively These lines are used to power and control the vanous devices on the tag
  • the RF antenna 32 has two connections to the tag 30, denoted here by lines 50 and 58 Line 58 is the conventional ground
  • the tag rectification signal receiving section 36 receives an RF signal, which is preferably amplitude modulated at a frequency f,, from the antenna 32 over line 50, and rectifies and demodulates the RF signal and delivers a digital signal to the rest of the tag electronics over line 62 If the RF is modulated with a steady modulation frequency f, the output of the signal receiving section 36 is preferably a senes of square pulses of unit voltage at a frequency f, However, any pattern or subpattern in the signal sent out from the base station could be used to generate an output of the signal receiving section 36 in order to adjust the frequency and optionally the phase of the tag oscillator
  • the tag clock section 40 receives the digital demodulated digital signal from line 62 and sets the tag oscillator frequency using the modulation frequency f of the modulated RF signal
  • the tag clock section 40 delivers a clock signal on line 102 to the tag logic section 42, to the tag memory section 44, and to other tag electronic sections as needed
  • the tag logic section 42 communicates with the tag memory section 44 over communication channel 64
  • Fig 3 is a block diagram of the tag clock section 40
  • the tag oscillator 100 frequency is set by the voltages supplied by a connection denoted 302 from a calibrate module 300
  • the clock ticks are passed from the oscillator 100 over line 306 and 308
  • a local clock counter 200 counts the clock ticks since the clock counter has been reset and passes the count to the calibrate module 300 via a connection 304
  • the calibrate module 300 resets the local clock counter 200 via the connection 304, (and optionally resets the phase of the oscillator 100 over connection 116,) on a nsing edge of the digital input signal on line 62, and sets the voltages controlling the frequency of oscillator 100 to give a set number of counts between two nsing edges of the digital input signal 62 when the base station 10 is sending a steadily modulated RF signal
  • the oscillator 100 frequency is thus determined by the modulation frequency of the RF energy 20 transmitted by the base station 10 While the calibrate module may carry out its functions using a n
  • the calibrate module 300 supplies a local clock signal to the tag electronics over line 102.
  • Digital signals passed from the tag analog receiving section 36 to the tag data recovery system can have different widths (if no automatic gain control circuit is used) depending on the range of the tag to the base station and the relative orientation of the tag antenna and the base station antenna.
  • Fig. 4 shows the RF power for a steadily amplitude modulated signal sent from the base station with the rise and fall times of the signal exaggerated.
  • This signal is clipped by the tag to give a "unit" voltage if the signal is above a threshold voltage, and a zero voltage if the signal is below the threshold voltage.
  • the threshold may be high up the shoulder of the pulse if the tag is a long way from the base station, or if the tag antenna is not correctly oriented, so that the signal received by the tag is weak.
  • the threshold may be very near the baseline if the tag is close to the base station, and a lot of power is received at the tag.
  • Fig. 5 shows the digital data output to the tag data recovery section from the signal in fig. 4 if the tag is far from the base station. This signal is somewhat exaggerated in that it shows a threshold very near the maximum of the analog signal, which in practice would not be used because of fluctuations in the data signal.
  • Fig. 6 shows the digital data output to the tag data recovery section from this signal if the tag is near to the base station.
  • the broadened pulses and distorted pulses are particularly injurious to the data recovery process when the tag is close to the base station and the tag electronics clips the signals very close to the baseline.
  • Signals sent to the tag comprise a series of bits.
  • Manchester encoded signal bits are sent as a pair of one "on” period of the RF field and an equally long "off period. In the middle of each bit sent, the RF power changes from “off to "on” or vice versa. There must always be a change in the middle of a bit (midbit transition). There could be, or could not be a transition between two bits. There should be no more than one transition between midbit transitions. (An error signal is optionally generated when there is more than one such transition detected by the tag.)
  • the method of the invention is a method of sampling the signal data at different points in the signal depending on the prior history of the signal.
  • the signal data is sampled at a plurality of times t n after a plurality of transitions T n in the signal data, where n is an integer.
  • n is an integer.
  • Manchester encoded signals there are rising and falling midbit transitions in the data signal and rising and falling bit boundary transitions in the data signal.
  • the data are sampled at two different times after a midbit transition, depending on whether the midbit transition is a rising or falling transition. The bit boundary transitions are ignored.
  • the apparatus for carrying out the method of the invention is the apparatus of an RF tag carrying an oscillator 100 with a frequency set by the modulation frequency of the base station carrier frequency, as detailed in application number 08/780,765, but the invention would also work in a prior art tag having an oscillator with fixed frequency on the tag.
  • the tag oscillator is set so that the tag oscillator has an oscillation frequency between 8 and 9 times the modulation frequency of the base station.
  • the tag local clock counter 200 starts counting the pulses from the tag oscillator at a midbit transition.
  • the tag counter must be within a certain range for a transition to be counted as the next midbit transition. If the count is greater than a certain number, a tag counter reset circuit is enabled. Then, the next transition is counted as the midbit transition.
  • the tag counter is reset when a midbit transition is detected.
  • the phase of the tag oscillator is also optionally reset on the midbit transitions. The bit boundary transitions are ignored.
  • An error signal is optionally generated if there are too many counts of the tag counter between midbit transitions. (Long Pulse Error) . Long pulses are optionally sent out on purpose by the base station in a first step in the protocol to so that the tag can check that the communication protocol is proceeding correctly.
  • the method of the invention samples the signal at count 7 after a midbit rise in signal, and samples after a count of 5 after a midbit fall in signal.
  • the tag oscillator frequency is set at a time when the base station is sending out a steadily modulated carrier frequency, and in general, there will be between 8 and 9 counts of the tag counter between midbit transitions. It is clear to one skilled in the art that the particular counts used may be changed for different systems. For example, the tag oscillator would be more accurately set with respect to the base station modulation frequency if the number of counts between midbit transitions were an integer much greater than 8. However, the circuitry for setting the number higher requires more area on the chip and is thus more costly.
  • a typical Manchester encoded digital data signal which might be used in a communication system is shown in fig. 7a.
  • the signal is shown as a perfect square wave with no rise time or fall time.
  • a 0 bit is given by the field off, then on.
  • a 1 bit has the field on, then off.
  • the bits are denoted by the horizontal arrows and are 0 0 0 1 1 0 0.
  • This series of bits is chosen as an example to show that the RF power may be on for the full length of a bit, and off for the full length of a bit.
  • the average duty cycle is always .5 for Manchester encoding if the pulses are not distorted.
  • a typical data recovery system would sample this signal at a fixed time after the midbit transitions and would return data signals as denoted by the up arrows (for ones) and down arrows (for zeros) of fig. 7a.
  • Fig. 7b shows the signal that might be produced from the digital output of the tag receiver when the tag is close to the base station and when the base station is not sending out a perfect square wave. Note that the duty cycle is much greater than .5, and the "gaps" in the data signal are very much narrower than the gaps of fig. 7a.
  • the midbit transitions are noted, where T, denotes a rising midbit transition and T 2 denotes a falling midbit transition.
  • the clock counter is reset and the oscillator phase is reset at the midbit transitions.
  • Fig. 7c shows the clock signal output of the tag oscillator.
  • the tag oscillator frequency has been set in a prior step so that there are more than 8 and fewer than 9 pulses in one bit time. At every midbit transition, the phase of the tag oscillator and the clock counter are reset.
  • the method of the invention is that the data signal of fig. 7b is sampled on the seventh count or a time t, after a midbit rise in the signal, and on the fifth count or a time t, after a midbit fall.
  • the up and down arrows in fig. 7c denote that the sampling would return the same pattern of up and down arrows shown in fig. 7a.
  • Fig. 8 shows a flow chart of the method of the invention 500.
  • the tag resets the tag counter and the tag oscillator phase on a midbit transition of the Manchester encoded signal in step 505.
  • the tag also records whether or not the midbit transition was a signal rise.
  • the tag counter counts the pulses of the tag oscillator and in decision step 510 the tag decides the next step on the basis of whether the last midbit transition was a rise in the data signal or a fall in the data signal.
  • the tag checks the tag counter and the decision step 520 decides on a tag counter pulse of 7 to sample the data signal in step 540.
  • the tag passes the sampled data (a zero or a one) to the tag data processing section in step 550.
  • the tag checks the tag counter and the decision step 530 decides on a tag counter pulse of 5 to sample the data signal in step 540. Meanwhile, the tag midbit transition detector is enabled in step 535 as soon as the data has been sampled (either on the count of 5 or 7 depending on whether the previous midbit transition fell or rose). At the next data transition, the tag regards the data transition as a midbit transition and the system returns to step 505. There may or may not be a data transition prior to the data sample being taken, but the tag ignores the transition, if one is present, and relies on the midbit transition history to decide where to sample the data. In this way, the data is sampled at a point well clear of any possible transition.
  • the method of this invention could be used as well with other well known encoding systems, particularly other biphase encoding techniques such as FM0.
  • Such encoding systems are described in detail in "Digital Communications Fundamentals and Applications", by Bernard Sklar, Prentice Hall, NJ (1988). The above identified publications, books and patents are hereby included by reference. This invention increases the range over which the RF tags may be used.

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

La présente invention concerne un procédé selon lequel des données sont récupérées à partir d'un signal de données transmis par une station de base à un transpondeur radiofréquence (RF) (sur étiquette), ce signal de données étant échantillonné plusieurs fois (tn) en réaction à une pluralité de transitions (Tn) correspondantes dans le signal de données.
PCT/US1999/015456 1998-07-10 1999-07-09 Appareil et procede de recuperation de signaux de donnees transmis sur etiquettes radiofrequences WO2000003352A1 (fr)

Applications Claiming Priority (2)

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US11403798A 1998-07-10 1998-07-10
US09/114,037 1998-07-10

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WO2000003352A1 true WO2000003352A1 (fr) 2000-01-20

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6739507B2 (en) 2001-10-04 2004-05-25 Ford Motor Company Method of automated rail loading of automotive vehicles
FR2859842A1 (fr) * 2003-09-17 2005-03-18 Commissariat Energie Atomique Objet portatif a demodulation multiniveaux, couple inductivement a une station fixe
USRE46326E1 (en) 2000-10-20 2017-02-28 Promega Corporation RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags
USRE47599E1 (en) 2000-10-20 2019-09-10 Promega Corporation RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4807260A (en) * 1987-10-05 1989-02-21 Northrop Corporation Non high frequency clock dependent Manchester biphasic decoder and comparator
US5365547A (en) * 1991-08-28 1994-11-15 Frank Marinaro 1X asynchronous data sampling clock for plus minus topology applications
US5726650A (en) * 1995-06-07 1998-03-10 Silicon Systems, Inc. Adaptive manchester decoding with adjustable delay and power saving mode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4807260A (en) * 1987-10-05 1989-02-21 Northrop Corporation Non high frequency clock dependent Manchester biphasic decoder and comparator
US5365547A (en) * 1991-08-28 1994-11-15 Frank Marinaro 1X asynchronous data sampling clock for plus minus topology applications
US5726650A (en) * 1995-06-07 1998-03-10 Silicon Systems, Inc. Adaptive manchester decoding with adjustable delay and power saving mode

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE46326E1 (en) 2000-10-20 2017-02-28 Promega Corporation RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags
USRE47599E1 (en) 2000-10-20 2019-09-10 Promega Corporation RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags
US6739507B2 (en) 2001-10-04 2004-05-25 Ford Motor Company Method of automated rail loading of automotive vehicles
FR2859842A1 (fr) * 2003-09-17 2005-03-18 Commissariat Energie Atomique Objet portatif a demodulation multiniveaux, couple inductivement a une station fixe
WO2005029726A1 (fr) * 2003-09-17 2005-03-31 Commissariat A L'energie Atomique Objet portatif à démodulation multiniveaux, couplé inductivement à une station fixe
US7575165B2 (en) 2003-09-17 2009-08-18 Commissariat A L'energie Atomique Portable object having multi-level demodulation and being inductively coupled to a fixed station

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