CA2142498A1 - Short-range microwave identification system - Google Patents
Short-range microwave identification systemInfo
- Publication number
- CA2142498A1 CA2142498A1 CA 2142498 CA2142498A CA2142498A1 CA 2142498 A1 CA2142498 A1 CA 2142498A1 CA 2142498 CA2142498 CA 2142498 CA 2142498 A CA2142498 A CA 2142498A CA 2142498 A1 CA2142498 A1 CA 2142498A1
- Authority
- CA
- Canada
- Prior art keywords
- label
- reader
- circuitry
- transmission
- phase
- 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.)
- Abandoned
Links
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
- G06K19/0723—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 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
-
- 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
Abstract
In a system of short-range microwave identification by data exchange according to a determined protocol between at least one reader and at least one active label, the label comprises an activation circuitry comprising means enabling the activation of a writing circuitry and a transmission circuitry of the label when a determined sequence of the exchange protocol transmitted by a reader within radioelectrical range is detected, the transmission circuitry of the label comprising means that generate a phase-modulated transmission signal whose frequency is stabilized irrespectively of the mismatching presented to the transmission/reception antenna of the label.
Description
`:` 21 l2498 -SHORT-RANGE MICROWAVE IDENTIFICATION SYSTEM
BACKGROUND OF THE lNV~N'l'ION
l. Field of the Invention The present invention relates to a system for the short-range microwave identification of objects or persons. The field is that of short-range communications using microwaves.
BACKGROUND OF THE lNV~N'l'ION
l. Field of the Invention The present invention relates to a system for the short-range microwave identification of objects or persons. The field is that of short-range communications using microwaves.
2. Description of the Prior Art Existing short-range microwave communications d systems use reflective or amplifier passive badges with the reflection of the received wave through its modulation by data elements internal to the badge.
The labels or badges are of two types:
- Badges without internal power, namely without any battery. They are put into operation by the detection of the power sent out by a beacon. The range is limited to about l to 4 meters.
- Badges with batteries: In this case, the range is about l0 meters.
2~J In any case, the badges are of the reflection type, namely they reflect a microwave in modulating it by means of the data contained in the badge. This makes it necessary for the interrogator beacons to make permanent transmission. The beacons therefore consume power and are non-portable. Furthermore, such a principle prevents a beacon from managing a large number of badges in radioelectrical range, giving rise to problems of collision between received messages. The limited range of the readers makes it 31~ necessary to send out a non-modulated wave during the transmission stages of the badges. Consequently, the autonomy of these readers is limited and the RF space is cluttered by permanent transmission that creates self-jamming in the presence of several readers in one and the same communications zone. In an environment that is very noisy from the .
radioelectrical point of view, the ranges are limited since the signals received by the beacon undergo attenuation twice in open space. The readers using the passive badges are far more difficult to make as regards performance characteristics, and use two antennas. Furthermore, these badges have directional antennas and cannot be interrogated in every direction.
The different problems to be resolved by the 0 invention are:
- making a label that is insensitive to the radioelectrical environment created, for example, by motor vehicle ignition, radiotelephones, etc.
- making the downline communications from the reader to the label independent of the upline communications from the label to the reader, - preventing the self-jamming of the system owing to the large number of objects to be identified in radioelectrical range, 20- achieving control over the range even when there is no disturbance, - designing a label in such a way that the readers are truly portable while maintaining a high degree of autonomy.
25A system of data exchange by electromagnetic waves, forming the object of a French patent application No. 2 666 941 filed by the present Applicant, uses a fixed reader communicating with a badge comprising a microwave oscillator in its ,o modulator-demodulator or modem part.
This oscillator is formed by a single transistor, preferably a field-effect transistor that works either in demodulator mode or in oscillator mode generating the frequency of the signal sent out by ~5 the badge. The main drawback of this oscillator is that it works as a free oscillator, i.e. the frequency can vary as a function of the mismatching presented to the antenna of the badge. This drawback becomes a major one in applications requiring high stability of the frequency generated by the oscillator. This is the case, for example, for applications in very narrow standardized frequency bands that are themselves subdivided into sub-bands.
SUMMARY OF THE lNV~NlION
The aim of the invention is to overcome the 1~J above-mentioned drawbacks.
To this end, an object of the invention is a system of short-range microwave identification by data exchange according to a determined protocol between at least one reader and at least one active label, the reader and the label respectively comprising means for the modulation and demodulation of data elements, coupled with a transmission/reception antenna, and digital processing means managing the data transmitted or received, said label furthermore comprising an activation circuitry comprising means enabling the activation of a writing circuitry and a transmission circuitry of the label when a determined sequence of the protocol transmitted by a reader within ~s radioelectrical range is detected, the transmission circuitry of the label comprising means that generate a phase-modulated transmission signal whose frequency is stabilized irrespectively of the mismatching presented to the transmission/reception antenna of ,o the label, the transmission circuitry also comprising, at output, switching means controlled by digital processing means enabling the alternate switch-over of the transmission circuitry and the writing circuitry of the label respectively to send ,5 and receive data elements according to the protocol, and said reader comprising switching means controlled 2142~98 by digital processing means enabling the alternate switch-over of the transmitter and the receiver of the reader respectively to transmit and receive data elements according to the protocol.
s The microwave label according to the invention has the advantage of making it possible to overcome radioelectrical disturbances external to the label and mismatching presented to the label, of being light and of consuming little power with the greatest ll~ possible compactness, very low price and very great autonomy.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the invention shall appear more clearly from the following description, made with reference to the appended drawings, of which:
- Figure 1 shows a functional diagram of a microwave label according to the invention, - Figure 2 shows a functional diagram of a portable reader according to the invention, - Figure 3 shows a protocol of communications between a portable reader and a microwave label according to the invention, and - Figure 4 shows a functional diagram of a second 2s embodiment of a microwave label according to the invention.
DESCRIPTION OF THE INVENTION
The label shown in Figure 1 has a low-gain omnidirectional transmission-reception antenna .o coupled to an antenna filter 2 providing sufficient filtering so that a jammer does not desensitize the badge in activation or writing mode.
The output of the filter 2 is coupled respectively to an activation circuitry 3, a writing circuitry 4 and a transmission circuitry 5.
~, The activation circuitry 3 has amplitude-detection means 6 coupled at output to means 7 for the recognition and activation of the label. The writing circuitry 4 has amplification means 8 for the amplification of the data received by the antenna 1.
The amplification means 8 are activated by a signal delivered by the recognition means 7. The activation and writing means 3 and 4 are respectively coupled by their output to a first input and a second input of 1~ digital processing means 9 comprising a logic unit and a memory block that are known, for example a microprocessor. The transmission circuitry 5 has a variable oscillator-transmitter 10 demarcated by a dashed box. The variable oscillator-transmitter 10 has a reference oscillator 11, for example a quartz oscillator, delivering for example a frequency of 19.14 MHz. The reference oscillator 11 delivers a clock signal firstly to the digital processing means 9 and secondly to the phase-locked loop 12 or PLL.
2!~ This look 12 has known means (not shown) formed by a phase comparator, a frequency divider circuit, a filter and an amplifier. The variable oscillator-transmitter 10 also has a VCO (voltage controlled oscillator) 13. The VCO 13 delivers a frequency, ~5 equal in this example to 1225 MHz, on a second input of the PLL 12 and on a first input of the phase modulation means MdP 14. The VCO 13 receives a command, Cde CVO, at its input, delivered at output of the PLL 12. The phase-modulation means MdP 14 receive, at a second input, a PSK (phase-shift keying) type of modulation signal delivered by its digital processing means 9. The output of the phase modulation means MdP 14 is coupled to the input of frequency doubler means 15. The output of these .s means 15, corresponding also to the output of the oscillator-emitter 10, is coupled to a first input of ,-an antenna relay 16. This relay 16 is activated by a transmission-reception command, Cde E/R, delivered by the digital processing means 9. At transmission, the activation and writing means 3 and 4 are inhibited whereas in reception it is the tr~n~m;~sion circuitry that is inhibited.
The servo-control of the frequency of the oscillator-transmitter 10 is similar to that of a known type of phase loop.
ii) The frequency delivered by the VCO 13 which, in the example, is equal to 1225 MHz, is divided by 64 before being compared in phase with a frequency of 19.14 MHz coming from the reference quartz oscillator 11. The electrical signal delivered by the phase comparator represents the phase difference between the frequency of 1225 MHz divided by 64 and the frequency of 19.14 MHz of the quartz oscillator 11.
The signal is then amplified and filtered by the filtering circuit and then applied to the input 2ij called the frequency control input of the VCO 13.
The filtering circuit of the PLL 12 carries out a servo-control of the transmission frequency on a determined wideband so as to make the VCO 13 insensitive to the disturbances that are external and ~5 internal to the system according to the invention.
Indeed, the antenna 1 may be masked by metal objects that mismatch it. It may also pick up powerful radioelectrical rays which may or may not be deliberately sent. The VCO 13 must therefore be very swift in phase-locking.
The phase modulation means MdP 14 are formed, for example, by a linear phase shifter circuit inserted between the VCO 13 and the frequency doubler 15. The phase excursion at this level is therefore equal to half O and ~/2 for the frequency doubler 15 doubles the modulation index; the phase modulation means MdP
`` ` 21~2~98 -14 are formed, for example, by capacitors, varicap diodes and inductors. The PSK modulation data coming from the digital processing means 9, filtered in baseband mode, control the varicap diodes. The spectrum transmitted is thus limited in terms of spectral occupancy.
In transmission mode, all the circuits of the oscillator are supplied and the signal delivered by the oscillator-transmitter 10 is sent to the antenna Figure 2 shows a functional diagram of a portable reader according to the invention.
This reader has a logic unit 17, for example a microprocessor, enabling the management of the information elements sent and received by the reader.
This reader also has a frequency synthesizer 18 generating a first frequency, for example a frequency of 2450 MHz, and a second frequency, for example a frequency of 2380 MHz. The difference between these ?o two frequencies constitutes an intermediate frequency FI therefore equal to 70 MHz in this example. The synthesizer 18 receives, at its input, a command Cde E/R from the logic unit 17 enabling the selection of the frequency to be delivered by the synthesizer 18.
'5 The reader then has a transmitter 19 that is variable in amplitude, transmitting a signal at the frequency 2450 MHz generated by the synthesizer 18.
The transmitter 19 receives a command with reduced power, Cde PR, at a first input, the ~o transmission/reception command Cde E/R at a second input and the two-phase data to be transmitted at a third input. These three commands are generated by the logic unit 17.
The reader has a receiver/phase demodulator 20 ,5 demodulating the signal received at a first input at 21~2q98 the frequency of 2380 MHz, corresponding to the second frequency generated by the synthesizer 18.
The receiver 20 receives, at a second input, a reception command Cde R generated by the logic unit 17. At a first output, it delivers the demodulated two-phase data elements received and at a second output, it delivers the information on the amplitude of the detected field. These two information elements are injected respectively into a first input and a second input of the logic unit 17.
An antenna 21, used both for transmission and reception, is coupled to an antenna filter 22 centered on the 2450 MHz frequency in the example processed, itself coupled to a switching means 23, a relay for example, controlled by the command Cde E/R.
This command enables the selection of either the output of the transmitter 19 or the input of the receiver 20.
The working of the reader is as follows:
In the mode of interrogation or search for labels to be identified, the transmitter 19 briefly transmits, in amplitude modulation, activation messages comprising a particular activation sequence followed by the identity of the reader. Then the transmitter 19 is switched over into resting mode by the command Cde E/R and the receiver 20 is activated pending one or more responses coming from one or more activation labels, hence labels within radioelectrical range. The receiver 20 demodulates !O the phase-modulated data elements transmitted by the labels. These data elements are transmitted to the logic unit 17 which interprets them. This logic unit 17 then alternately activates the transmitter 19 and the receiver 20 to transmit and receive the data ,5 elements. The reception periods are far longer than the transmission periods. This enables the reader to ` ` 2142498 have great operating autonomy with rechargeable batteries having a capacity of 1 ampere/hour enabling it to be portable. The transmitted power is about 200 milliwatts and is compatible with health S standards (< 10 milliwatts/1 cm2 at a distance of 1 cm from the antenna 21 of the reader). The receiver is of the superheterodyne type with an intermediate frequency FI of 70 MHz. Consequently, when the receiver 20 is in operation, the frequency lii of the synthesizer 18 is equal to the tr~nsm;~sion frequency minus the value of the intermediate frequency, giving 2380 MHz. The received spectrum is wide, in the range of +/- 500 KHz, owing to the high bit rate of the data elements and of the two-phase 1' FMO encoding used and the precision of the frequency transmitted by the labels is in the range of +/- 250 KHz. The selectivity of the receiver 20 is done in intermediate frequency FI, for example by the use of a surface wave filter having a passband in the range 2v of +/- 2 MHz. The sensitivity of the receiver 20 is then - 90 dBm for a bit error rate (BER) of the order of 10-6.
To prevent jamming or interference between neighboring readers, it is possible to change the 2~ transmission frequency by programming the frequency of the synthesizer 18, the reception frequencies being always the same.
The low-gain omnidirectional antenna 21 (1 to 2 dBi) can be replaced by a directional antenna with ,l~ higher gain to increase the range of the reader.
A reduced power command, Cde PR, reduces the power transmitted so as to reduce the range of interrogation should the carrier of the reader seek to identify a particular label, for example a label ,~ borne by a vehicle.
-A protocol for the exchange of information between a label and at least one reader according to the invention is illustrated in Figure 23 and also enables an explanation of the working of the label and of the reader during such an exchange.
When there is no reader in radioelectrical range, only the activation means 6 and 7 of the label are supplied by a battery (not shown) whose consumption is below 5 microamperes, thus giving the label autonomy of over 5 years. None of the other circuits is supplied.
When a reader is within range, it sends out a brief amplitude-modulated microwave signal modulated by a OOK or ASK type "all or nothing" operation by an activation sequence followed by data elements identifying the reader. The activation means 6 of the label then detect this message and turn on the activation sequence recognition means 7. If this activation sequence is truly recognized, then all the 2ij other circuits of the label are supplied. The writing circuitry 4 amplifies the data elements sent by the reader which are then processed by the digital processing means 9.
It then carries out a series of information ~5 exchanges between the label and the reader in accordance with the protocol used. This protocol has a first stage for the identification of the label by the transmission of data elements to the reader in the time intervals randomly chosen from a determined ,~} number of possible time intervals, a reservation stage where the reader orders the different activated labels to transmit their data elements also within well-determined time intervals, a stage for the transmission of the data elements contained in the .5 label to the reader, a stage for the acknowledgment of the reader, a stage for the repetition of -exchanges in the event of failure, namely in the event of a collision of messages and a stage for repositioning the label in watching mode.
Among the stages of downline transmission, namely s transmission from the reader to the label, the reader transmits in amplitude modulation mode and the labels are in demodulation mode in using the writing circuitry 4 and the digital processing means 9 to process the signal received by the antenna 1.
r, During the upline transmission stages, namely transmission from the label to the reader, the reader no longer transmits. The label activates its oscillator-transmitter 10 by phase modulating it according to two states 0 or ~ at the rate of the data elements to be transmitted, in the range of 250 Kbits/s. Indeed, the phase modulation is chosen in the label-to-reader direction as it is more efficient than the amplitude modulation and can be easily achieved in a very small-sized object such as a 70 credit card for example that costs little.
The power sent out by the oscillator-emitter 10 is low but sufficient to be undisturbed by the radioelectrical noise sent out, for example by the label-bearing vehicle. The range thus depends only ~s on the activation threshold. The consumption of the oscillator-transmitter 10 is very low, lower than 10 milliamperes, and lasts only some milliseconds necessary to transmit the data elements to the reader.
Consequently, the reader awaiting a response from the label or labels does not need to continuously transmit a wave as necessary for reflective passive labels. This prevents cluttering the RF space and possibly jamming other neighboring readers.
Furthermore, the reader needs only one antenna 21 for the transmission/reception unlike certain existing ```- 21~2~98 .
systems that require two distinct antennas, one for transmission and one for reception.
The electrical characteristics of the reader are considerably simplified and very easy to achieve.
The range is thus well controlled and depends only on the downline reader-to-label path by the transmission of a short message to activate the object to be identified by the reader.
Figure 4 illustrates a second embodiment of a 1~ label in an identification system according to the invention. The elements similar to those of Figure 1 are designated by the same references. In this embodiment, the architecture of the oscillator-transmitter 10 is modified by the use of an ASIC
(applications specific integrated circuit) 24 demarcated by a box of dashes. The oscillator-transmitter 10, in this second embodiment, has a VCO
25 tuned directly to the frequency to be transmitted equal, in the example, to 2450 MHz, a PLL 26 2~ including a circuitry of dividers by N, a comparator/phase demodulator as well as a filtering circuit not shown.
The use of an ASIC enables the optimizing of the current consumption which thus goes below 5 ~5 milliamperes in active phase. The ASIC 24 also brings together the detection means 6 of the activation circuitry 3 and further comprises automatic testing means 27 that can be used to test the efficient working of the label. This test, which 3~ simulates the reception of the data sent by a reader in radioelectrical range, can be done regularly, it being known that the label is essentially in a permanent watching state, hence without disturbing the operation of the system in the event of exchanges ~5 between the label and a reader. The test consists in reinjecting a fraction of the microwave signal ``. 2142498 ~,_ delivered by the VCO 25, at the 2450 MHz frequency, amplitude-modulated by the testing means themselves, into the input of the activation means 6. These testing means 27 receive, at a first input, a test command generated by the digital processing means 9.
At a second input, they receive the signal delivered by the VCO 25. At a first input, the VCO 25 receives the control signal, Cde VCO, delivered by a PLL 26 and furthermore receives, at a second input, a power control, Cde P, generated by the digital processing means 9 enabling the adjustment of the level of the input power of the VCO 12. The PSK modulation command is delivered by the digital processing means 9 and is injected directly into a third input of the PLO 26, the first and the second input respectively receiving the signal delivered by the quartz oscillator 11 and the signal delivered by the VCO 25.
Since the other elements of the label are similar to those of Figure 1, they are not described again.
Other alternative embodiments are possible without in any way departing from the scope of the invention. The transmission frequency may be different from the reception frequency and the adjustment of the emitted power may be programmed on 2c the basis of the data el-ements transmitted by the reader which will have measured the field received in its receiver and will have decided that the power transmitted by the label is too high or too low.
This makes it possible to avoid cluttering the RF
0 space. Furthermore, the bit rate of the information elements transmitted may be increased to over 1 Mbit.
The labels or badges are of two types:
- Badges without internal power, namely without any battery. They are put into operation by the detection of the power sent out by a beacon. The range is limited to about l to 4 meters.
- Badges with batteries: In this case, the range is about l0 meters.
2~J In any case, the badges are of the reflection type, namely they reflect a microwave in modulating it by means of the data contained in the badge. This makes it necessary for the interrogator beacons to make permanent transmission. The beacons therefore consume power and are non-portable. Furthermore, such a principle prevents a beacon from managing a large number of badges in radioelectrical range, giving rise to problems of collision between received messages. The limited range of the readers makes it 31~ necessary to send out a non-modulated wave during the transmission stages of the badges. Consequently, the autonomy of these readers is limited and the RF space is cluttered by permanent transmission that creates self-jamming in the presence of several readers in one and the same communications zone. In an environment that is very noisy from the .
radioelectrical point of view, the ranges are limited since the signals received by the beacon undergo attenuation twice in open space. The readers using the passive badges are far more difficult to make as regards performance characteristics, and use two antennas. Furthermore, these badges have directional antennas and cannot be interrogated in every direction.
The different problems to be resolved by the 0 invention are:
- making a label that is insensitive to the radioelectrical environment created, for example, by motor vehicle ignition, radiotelephones, etc.
- making the downline communications from the reader to the label independent of the upline communications from the label to the reader, - preventing the self-jamming of the system owing to the large number of objects to be identified in radioelectrical range, 20- achieving control over the range even when there is no disturbance, - designing a label in such a way that the readers are truly portable while maintaining a high degree of autonomy.
25A system of data exchange by electromagnetic waves, forming the object of a French patent application No. 2 666 941 filed by the present Applicant, uses a fixed reader communicating with a badge comprising a microwave oscillator in its ,o modulator-demodulator or modem part.
This oscillator is formed by a single transistor, preferably a field-effect transistor that works either in demodulator mode or in oscillator mode generating the frequency of the signal sent out by ~5 the badge. The main drawback of this oscillator is that it works as a free oscillator, i.e. the frequency can vary as a function of the mismatching presented to the antenna of the badge. This drawback becomes a major one in applications requiring high stability of the frequency generated by the oscillator. This is the case, for example, for applications in very narrow standardized frequency bands that are themselves subdivided into sub-bands.
SUMMARY OF THE lNV~NlION
The aim of the invention is to overcome the 1~J above-mentioned drawbacks.
To this end, an object of the invention is a system of short-range microwave identification by data exchange according to a determined protocol between at least one reader and at least one active label, the reader and the label respectively comprising means for the modulation and demodulation of data elements, coupled with a transmission/reception antenna, and digital processing means managing the data transmitted or received, said label furthermore comprising an activation circuitry comprising means enabling the activation of a writing circuitry and a transmission circuitry of the label when a determined sequence of the protocol transmitted by a reader within ~s radioelectrical range is detected, the transmission circuitry of the label comprising means that generate a phase-modulated transmission signal whose frequency is stabilized irrespectively of the mismatching presented to the transmission/reception antenna of ,o the label, the transmission circuitry also comprising, at output, switching means controlled by digital processing means enabling the alternate switch-over of the transmission circuitry and the writing circuitry of the label respectively to send ,5 and receive data elements according to the protocol, and said reader comprising switching means controlled 2142~98 by digital processing means enabling the alternate switch-over of the transmitter and the receiver of the reader respectively to transmit and receive data elements according to the protocol.
s The microwave label according to the invention has the advantage of making it possible to overcome radioelectrical disturbances external to the label and mismatching presented to the label, of being light and of consuming little power with the greatest ll~ possible compactness, very low price and very great autonomy.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the invention shall appear more clearly from the following description, made with reference to the appended drawings, of which:
- Figure 1 shows a functional diagram of a microwave label according to the invention, - Figure 2 shows a functional diagram of a portable reader according to the invention, - Figure 3 shows a protocol of communications between a portable reader and a microwave label according to the invention, and - Figure 4 shows a functional diagram of a second 2s embodiment of a microwave label according to the invention.
DESCRIPTION OF THE INVENTION
The label shown in Figure 1 has a low-gain omnidirectional transmission-reception antenna .o coupled to an antenna filter 2 providing sufficient filtering so that a jammer does not desensitize the badge in activation or writing mode.
The output of the filter 2 is coupled respectively to an activation circuitry 3, a writing circuitry 4 and a transmission circuitry 5.
~, The activation circuitry 3 has amplitude-detection means 6 coupled at output to means 7 for the recognition and activation of the label. The writing circuitry 4 has amplification means 8 for the amplification of the data received by the antenna 1.
The amplification means 8 are activated by a signal delivered by the recognition means 7. The activation and writing means 3 and 4 are respectively coupled by their output to a first input and a second input of 1~ digital processing means 9 comprising a logic unit and a memory block that are known, for example a microprocessor. The transmission circuitry 5 has a variable oscillator-transmitter 10 demarcated by a dashed box. The variable oscillator-transmitter 10 has a reference oscillator 11, for example a quartz oscillator, delivering for example a frequency of 19.14 MHz. The reference oscillator 11 delivers a clock signal firstly to the digital processing means 9 and secondly to the phase-locked loop 12 or PLL.
2!~ This look 12 has known means (not shown) formed by a phase comparator, a frequency divider circuit, a filter and an amplifier. The variable oscillator-transmitter 10 also has a VCO (voltage controlled oscillator) 13. The VCO 13 delivers a frequency, ~5 equal in this example to 1225 MHz, on a second input of the PLL 12 and on a first input of the phase modulation means MdP 14. The VCO 13 receives a command, Cde CVO, at its input, delivered at output of the PLL 12. The phase-modulation means MdP 14 receive, at a second input, a PSK (phase-shift keying) type of modulation signal delivered by its digital processing means 9. The output of the phase modulation means MdP 14 is coupled to the input of frequency doubler means 15. The output of these .s means 15, corresponding also to the output of the oscillator-emitter 10, is coupled to a first input of ,-an antenna relay 16. This relay 16 is activated by a transmission-reception command, Cde E/R, delivered by the digital processing means 9. At transmission, the activation and writing means 3 and 4 are inhibited whereas in reception it is the tr~n~m;~sion circuitry that is inhibited.
The servo-control of the frequency of the oscillator-transmitter 10 is similar to that of a known type of phase loop.
ii) The frequency delivered by the VCO 13 which, in the example, is equal to 1225 MHz, is divided by 64 before being compared in phase with a frequency of 19.14 MHz coming from the reference quartz oscillator 11. The electrical signal delivered by the phase comparator represents the phase difference between the frequency of 1225 MHz divided by 64 and the frequency of 19.14 MHz of the quartz oscillator 11.
The signal is then amplified and filtered by the filtering circuit and then applied to the input 2ij called the frequency control input of the VCO 13.
The filtering circuit of the PLL 12 carries out a servo-control of the transmission frequency on a determined wideband so as to make the VCO 13 insensitive to the disturbances that are external and ~5 internal to the system according to the invention.
Indeed, the antenna 1 may be masked by metal objects that mismatch it. It may also pick up powerful radioelectrical rays which may or may not be deliberately sent. The VCO 13 must therefore be very swift in phase-locking.
The phase modulation means MdP 14 are formed, for example, by a linear phase shifter circuit inserted between the VCO 13 and the frequency doubler 15. The phase excursion at this level is therefore equal to half O and ~/2 for the frequency doubler 15 doubles the modulation index; the phase modulation means MdP
`` ` 21~2~98 -14 are formed, for example, by capacitors, varicap diodes and inductors. The PSK modulation data coming from the digital processing means 9, filtered in baseband mode, control the varicap diodes. The spectrum transmitted is thus limited in terms of spectral occupancy.
In transmission mode, all the circuits of the oscillator are supplied and the signal delivered by the oscillator-transmitter 10 is sent to the antenna Figure 2 shows a functional diagram of a portable reader according to the invention.
This reader has a logic unit 17, for example a microprocessor, enabling the management of the information elements sent and received by the reader.
This reader also has a frequency synthesizer 18 generating a first frequency, for example a frequency of 2450 MHz, and a second frequency, for example a frequency of 2380 MHz. The difference between these ?o two frequencies constitutes an intermediate frequency FI therefore equal to 70 MHz in this example. The synthesizer 18 receives, at its input, a command Cde E/R from the logic unit 17 enabling the selection of the frequency to be delivered by the synthesizer 18.
'5 The reader then has a transmitter 19 that is variable in amplitude, transmitting a signal at the frequency 2450 MHz generated by the synthesizer 18.
The transmitter 19 receives a command with reduced power, Cde PR, at a first input, the ~o transmission/reception command Cde E/R at a second input and the two-phase data to be transmitted at a third input. These three commands are generated by the logic unit 17.
The reader has a receiver/phase demodulator 20 ,5 demodulating the signal received at a first input at 21~2q98 the frequency of 2380 MHz, corresponding to the second frequency generated by the synthesizer 18.
The receiver 20 receives, at a second input, a reception command Cde R generated by the logic unit 17. At a first output, it delivers the demodulated two-phase data elements received and at a second output, it delivers the information on the amplitude of the detected field. These two information elements are injected respectively into a first input and a second input of the logic unit 17.
An antenna 21, used both for transmission and reception, is coupled to an antenna filter 22 centered on the 2450 MHz frequency in the example processed, itself coupled to a switching means 23, a relay for example, controlled by the command Cde E/R.
This command enables the selection of either the output of the transmitter 19 or the input of the receiver 20.
The working of the reader is as follows:
In the mode of interrogation or search for labels to be identified, the transmitter 19 briefly transmits, in amplitude modulation, activation messages comprising a particular activation sequence followed by the identity of the reader. Then the transmitter 19 is switched over into resting mode by the command Cde E/R and the receiver 20 is activated pending one or more responses coming from one or more activation labels, hence labels within radioelectrical range. The receiver 20 demodulates !O the phase-modulated data elements transmitted by the labels. These data elements are transmitted to the logic unit 17 which interprets them. This logic unit 17 then alternately activates the transmitter 19 and the receiver 20 to transmit and receive the data ,5 elements. The reception periods are far longer than the transmission periods. This enables the reader to ` ` 2142498 have great operating autonomy with rechargeable batteries having a capacity of 1 ampere/hour enabling it to be portable. The transmitted power is about 200 milliwatts and is compatible with health S standards (< 10 milliwatts/1 cm2 at a distance of 1 cm from the antenna 21 of the reader). The receiver is of the superheterodyne type with an intermediate frequency FI of 70 MHz. Consequently, when the receiver 20 is in operation, the frequency lii of the synthesizer 18 is equal to the tr~nsm;~sion frequency minus the value of the intermediate frequency, giving 2380 MHz. The received spectrum is wide, in the range of +/- 500 KHz, owing to the high bit rate of the data elements and of the two-phase 1' FMO encoding used and the precision of the frequency transmitted by the labels is in the range of +/- 250 KHz. The selectivity of the receiver 20 is done in intermediate frequency FI, for example by the use of a surface wave filter having a passband in the range 2v of +/- 2 MHz. The sensitivity of the receiver 20 is then - 90 dBm for a bit error rate (BER) of the order of 10-6.
To prevent jamming or interference between neighboring readers, it is possible to change the 2~ transmission frequency by programming the frequency of the synthesizer 18, the reception frequencies being always the same.
The low-gain omnidirectional antenna 21 (1 to 2 dBi) can be replaced by a directional antenna with ,l~ higher gain to increase the range of the reader.
A reduced power command, Cde PR, reduces the power transmitted so as to reduce the range of interrogation should the carrier of the reader seek to identify a particular label, for example a label ,~ borne by a vehicle.
-A protocol for the exchange of information between a label and at least one reader according to the invention is illustrated in Figure 23 and also enables an explanation of the working of the label and of the reader during such an exchange.
When there is no reader in radioelectrical range, only the activation means 6 and 7 of the label are supplied by a battery (not shown) whose consumption is below 5 microamperes, thus giving the label autonomy of over 5 years. None of the other circuits is supplied.
When a reader is within range, it sends out a brief amplitude-modulated microwave signal modulated by a OOK or ASK type "all or nothing" operation by an activation sequence followed by data elements identifying the reader. The activation means 6 of the label then detect this message and turn on the activation sequence recognition means 7. If this activation sequence is truly recognized, then all the 2ij other circuits of the label are supplied. The writing circuitry 4 amplifies the data elements sent by the reader which are then processed by the digital processing means 9.
It then carries out a series of information ~5 exchanges between the label and the reader in accordance with the protocol used. This protocol has a first stage for the identification of the label by the transmission of data elements to the reader in the time intervals randomly chosen from a determined ,~} number of possible time intervals, a reservation stage where the reader orders the different activated labels to transmit their data elements also within well-determined time intervals, a stage for the transmission of the data elements contained in the .5 label to the reader, a stage for the acknowledgment of the reader, a stage for the repetition of -exchanges in the event of failure, namely in the event of a collision of messages and a stage for repositioning the label in watching mode.
Among the stages of downline transmission, namely s transmission from the reader to the label, the reader transmits in amplitude modulation mode and the labels are in demodulation mode in using the writing circuitry 4 and the digital processing means 9 to process the signal received by the antenna 1.
r, During the upline transmission stages, namely transmission from the label to the reader, the reader no longer transmits. The label activates its oscillator-transmitter 10 by phase modulating it according to two states 0 or ~ at the rate of the data elements to be transmitted, in the range of 250 Kbits/s. Indeed, the phase modulation is chosen in the label-to-reader direction as it is more efficient than the amplitude modulation and can be easily achieved in a very small-sized object such as a 70 credit card for example that costs little.
The power sent out by the oscillator-emitter 10 is low but sufficient to be undisturbed by the radioelectrical noise sent out, for example by the label-bearing vehicle. The range thus depends only ~s on the activation threshold. The consumption of the oscillator-transmitter 10 is very low, lower than 10 milliamperes, and lasts only some milliseconds necessary to transmit the data elements to the reader.
Consequently, the reader awaiting a response from the label or labels does not need to continuously transmit a wave as necessary for reflective passive labels. This prevents cluttering the RF space and possibly jamming other neighboring readers.
Furthermore, the reader needs only one antenna 21 for the transmission/reception unlike certain existing ```- 21~2~98 .
systems that require two distinct antennas, one for transmission and one for reception.
The electrical characteristics of the reader are considerably simplified and very easy to achieve.
The range is thus well controlled and depends only on the downline reader-to-label path by the transmission of a short message to activate the object to be identified by the reader.
Figure 4 illustrates a second embodiment of a 1~ label in an identification system according to the invention. The elements similar to those of Figure 1 are designated by the same references. In this embodiment, the architecture of the oscillator-transmitter 10 is modified by the use of an ASIC
(applications specific integrated circuit) 24 demarcated by a box of dashes. The oscillator-transmitter 10, in this second embodiment, has a VCO
25 tuned directly to the frequency to be transmitted equal, in the example, to 2450 MHz, a PLL 26 2~ including a circuitry of dividers by N, a comparator/phase demodulator as well as a filtering circuit not shown.
The use of an ASIC enables the optimizing of the current consumption which thus goes below 5 ~5 milliamperes in active phase. The ASIC 24 also brings together the detection means 6 of the activation circuitry 3 and further comprises automatic testing means 27 that can be used to test the efficient working of the label. This test, which 3~ simulates the reception of the data sent by a reader in radioelectrical range, can be done regularly, it being known that the label is essentially in a permanent watching state, hence without disturbing the operation of the system in the event of exchanges ~5 between the label and a reader. The test consists in reinjecting a fraction of the microwave signal ``. 2142498 ~,_ delivered by the VCO 25, at the 2450 MHz frequency, amplitude-modulated by the testing means themselves, into the input of the activation means 6. These testing means 27 receive, at a first input, a test command generated by the digital processing means 9.
At a second input, they receive the signal delivered by the VCO 25. At a first input, the VCO 25 receives the control signal, Cde VCO, delivered by a PLL 26 and furthermore receives, at a second input, a power control, Cde P, generated by the digital processing means 9 enabling the adjustment of the level of the input power of the VCO 12. The PSK modulation command is delivered by the digital processing means 9 and is injected directly into a third input of the PLO 26, the first and the second input respectively receiving the signal delivered by the quartz oscillator 11 and the signal delivered by the VCO 25.
Since the other elements of the label are similar to those of Figure 1, they are not described again.
Other alternative embodiments are possible without in any way departing from the scope of the invention. The transmission frequency may be different from the reception frequency and the adjustment of the emitted power may be programmed on 2c the basis of the data el-ements transmitted by the reader which will have measured the field received in its receiver and will have decided that the power transmitted by the label is too high or too low.
This makes it possible to avoid cluttering the RF
0 space. Furthermore, the bit rate of the information elements transmitted may be increased to over 1 Mbit.
Claims (6)
1. A system of short-range microwave identification by data exchange according to a determined protocol between at least one reader and at least one active label, the reader and the label respectively comprising means for the modulation and demodulation of the data elements, coupled with a transmission/reception antenna, and digital processing means managing the data transmitted or received, said label furthermore comprising an activation circuitry comprising means enabling the activation of a writing circuitry and a transmission circuitry of the label when a determined sequence of the protocol transmitted by a reader within radioelectrical range is detected, the transmission circuitry of the label comprising means that generate a phase-modulated transmission signal whose frequency is stabilized irrespectively of the mismatching presented to the transmission/reception antenna of the label, the transmission circuitry also comprising, at output, switching means controlled by digital processing means enabling the alternate switch-over of the transmission circuitry and the writing circuitry of the label respectively to send and receive data elements according to the protocol, and said reader comprising switching means controlled by digital processing means enabling the alternate switch-over of the transmitter and the receiver of the reader respectively to transmit and receive data elements according to the protocol.
2. A system according to claim 1, wherein the means enabling the activation of the writing circuitry and transmission circuitry comprise means to detect the amplitude of the signal received by the antenna coupled with means for the recognition of activation sequences of the label, wherein the writing circuitry comprises means for the amplification of the data elements received by the antenna, these means being activated by the recognition means, wherein the means of the transmission circuitry comprise a voltage-controlled oscillator or VCO whose control voltage is delivered by a phase-locked loop or PLL comparing the phase of a reference signal whose frequency is determined by a quartz oscillator at the phase of the signal delivered by the VCO, and comprise means for the modulation of the phase of the signal delivered by the VCO, the frequency of the signal delivered at output of the modulation means being matched by frequency multiplier means with the frequency with which the antenna of the label is matched.
3. A system according to either of the claims 1 or 2, wherein the amplitude detection means, the switching means as well as the means generating the transmission signal are made out of an ASIC enabling the diminishing of the current consumption of the label in its active phase.
4. A system according to any of the claims 1 to 3, furthermore comprising test means coupled to the output of the transmission circuitry and controlled by the digital processing means, the output of the test means delivering an amplitude-modulated means to the input of the means for the detection of the activation circuitry to simulate the reception of a signal transmitted by a radio within radioelectrical range and thus test the efficient working of the label.
5. A system according to any of the claims 1 to 4, wherein the reader used during data exchanges with at least one label is a portable reader.
6. A system according to any of the claims 1 to 5, wherein the microwave label has a credit card format.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9401691 | 1994-02-15 | ||
| FR9401691A FR2716317B1 (en) | 1994-02-15 | 1994-02-15 | Short range microwave identification system. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2142498A1 true CA2142498A1 (en) | 1995-08-16 |
Family
ID=9460086
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2142498 Abandoned CA2142498A1 (en) | 1994-02-15 | 1995-02-14 | Short-range microwave identification system |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0671702A1 (en) |
| JP (1) | JPH07240699A (en) |
| CA (1) | CA2142498A1 (en) |
| FR (1) | FR2716317B1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000298711A (en) * | 1999-04-12 | 2000-10-24 | Development Bank Of Japan | Reflected wave analyzing system and reflected wave scanner |
| JP4602661B2 (en) * | 2002-11-28 | 2010-12-22 | パナソニック株式会社 | Optical repeater system |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2119141B (en) * | 1982-04-21 | 1985-11-20 | Mastiff Security Syst Ltd | Transmitter token |
| SE466930B (en) * | 1990-02-23 | 1992-04-27 | Roland Braennstroem | RECEIVER AND TRANSMISSION DEVICE FOR A PRICE INFORMATION SYSTEM |
| GB9013349D0 (en) * | 1990-06-14 | 1990-10-17 | Marconi Gec Ltd | Transponder system |
| FR2669481B1 (en) * | 1990-11-16 | 1994-04-15 | Thomson Composants Microondes | ELECTROMAGNETIC WAVE DATA EXCHANGE SYSTEM. |
| NL9200142A (en) * | 1992-01-24 | 1993-08-16 | Nederland Ptt | IDENTIFICATION SYSTEM INCLUDING AT LEAST ONE DETECTION STATION AND AT LEAST A LABEL, AND DETECTION STATION AND LABEL FOR APPLICATION IN THE IDENTIFICATION SYSTEM. |
-
1994
- 1994-02-15 FR FR9401691A patent/FR2716317B1/en not_active Expired - Fee Related
-
1995
- 1995-02-10 JP JP7045067A patent/JPH07240699A/en not_active Withdrawn
- 1995-02-10 EP EP95400281A patent/EP0671702A1/en not_active Withdrawn
- 1995-02-14 CA CA 2142498 patent/CA2142498A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| FR2716317A1 (en) | 1995-08-18 |
| EP0671702A1 (en) | 1995-09-13 |
| JPH07240699A (en) | 1995-09-12 |
| FR2716317B1 (en) | 1996-03-22 |
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