Radio-identification system using transponder badges

Attorney or Agent

ALCATEL AUSTRALIA LIMITED , BOX 525 G.P.O., SYDNEY N.S.W. 2001 (57) Claim

I. A radio-identifier system for the identification of persons or objects fitted with transponder-type badges, said system including at least one interrogating unit fitted with a UHF transmitter controlled to transmit a UHF interrogation code, a plurality of identification badges being of the transponder-type and using the energy transmitted by a UHF interrogation code received from an interrogating unit to transmit an individual UHF response code transposed from the interrogation code received, at least one identification receiver, capable of decoding by correlation the individual UHF response codes sent by the badges.

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P/00/011 28/5/91

Regulation 3.2

AUSTRALIA

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Invention Title:

RADIO-IDENTIFICATION SYSTEM USING TRANSPONDER BADGES

The following statement is a full description of this invention, including the best method of performing it known to us:,.. i

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This invention relates to a radio-identification system for the identification of persons or objects, fitted for this purpose with identification badges of the transponder type. It also relates on the one hand to the units required to make up such a system, such as a badge interrogating unit and a receiver processing at least in part the responses supplied by the badges, in addition to the unit which each individual badge makes up, and on the other hand, to the operating facilities fitted with such a system.

Fitting badges to objects or people for identification purposes is a method conventionally applied directly for access or passage control as well as indirectly for presence control.

Each badge features a characteristic which can be acknowledged by a suitable identification system, these characteristics may for instance be individualistic or pertain to a category.

Acknowledgment of a badge characteristic by an identification system implies using an information receiver with which the badge must communicate.

In some applications, this communication may be initiated by the badge holder, for instance when the holder requires access, it may also be automatically initialised by the badge holder whereby the latter need not specifically intervene, for instance the initialisations triggered by the mere fact that the badge holder passed through an access fitted for this purpose.

In radio communications, and in particular in radio paging, it is standard practice to trigger the transmitter of a transceiver by sending a signal via an interrogating unit to its receiver.

This can be operated using a transceiver built as a badge, thus freeing the badge holder from having to establish the communication, hence such badges may be fitted to carriers incapable of taking responsibilities, such as objects or animals.

Then, the badge must cither have its own power supply needed to transmit to the radio-identification system rcccivcr(s), or receive an external power supply in order to be able to transmit and communicate.

For technical and financial reasons well known in the radio transmission field, whenever possible, transmissions from interrogating units and badges arc not continuous and arc triggered only when necessary.

One of the technical reasons requiring that badge transmission be limited to the minimum is that it consumes energy coming from a source which, when integrated to the badges, must be periodically checked to know if it is exhausted and/or worn.

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This constraint is a major drawback in radio-identification systems where badge holder responsibility with regard to radio-identification hardware must often be kept to a minimum, and sometimes is non-existent.

Another technical reason requiring that badge transmission duration be kept to 5 a minimum concerns the radio congestion and interferences likely to be generated by lengthy and/or simultaneous transmissions, which would be detrimental to the radioidentification system involved as well as to its environment.

Indeed, the duration and eventually the concurrent badge transmissions have a direct effect on the identification capabilities of the radio-identification system to • ’·· 10 which they belong, and on the complexity of the identification receivers) and of the

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β ft f ’ti The present invention thus ] roposes a radio-identification system for the identification of persons or objects, fitted for this purpose with identification badges of the ' '&lt;'/ transponder type. It also relates on the one hand to the units required to make up such a system, such as a badge interrogating unit and a receiver processing at least in part the responses supplied by the badges, in addition to the unit which each in, dividual badge makes up, and on the other hand, to the operating facilities fitted with ‘ ’ such a system.

&lt; r. f ‘¹ * Accordingly, there is provided at least one interrogating unit fitted with a UHF /, 20 transmitter controlled in such a way that it transmits at least one UHF interrogation ( « U code, several transponder-type identification badges using the energy transmitted by a UHF interrogation code received from an interrogating unit to transmit an indiJ vidual UHF response code transposed from the interrogation code received, at least ,’h j one UHF identification receiver capable of decoding the badges' individual UHF rc25 sponse codes.

Furthermore, the invention proposes operating facilities similar to an application server, one of their characteristics being that they include a radio-identification system as defined above which processes the identification information supplied by the latter, the radio-identification system control unit(s) being directly or indirectly 30 connected for this purpose to the server facilities control unit via at least one transmission link.

In a preferred embodiment, the operating facilities arc made up of a telephone installation such as intercom or ISDN switchboard which receives the information supplied by the radio-identification system in order to know in real time the location of at least some of the telephone installation subscribers in order to page them and/or r-

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In another preferred embodiment, the operating facilities made up of a telephone installation such as intercom or ISDN switchboard are designed such that specific facilities, associated with the category to which the telephone installation subscriber belongs and normally assigned to the subscriber's usual telephone set or terminal, can be transferred to a telephone set or terminal close to which the subscriber is temporarily located, when this subscriber receives or places a telephone call, this being achieved by combining the capabilities of the radio-identification system control unit and the telephone installation switching unit.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the drawings, in which:

Figure 1 is a diagrammatic example of the operating facilities using a radioidentification system in accordance with the invention.

Figure 2 is a radio-identification system in accordance with the invention.

Figure 3 is the schematic wiring diagram of a badge address.

Figure 4 is a scaled diagram giving the amplitude level in relation to the time of the identification receiver correlator output signal, following an interrogation and in the absence of a response from the badge.

Figure 5 is a scaled diagram giving the amplitude level in relation to the time of the identification receiver correlator output signal, further to an interrogation and when there is a response from the badge.

The facilities shown in Figure I correspond to one of the possible ways of implementing a radio-identification system in accordance with the invention. In the example selected this system is intended for localisation of persons or objects fitted with a badge (O), such as (0_Λ), (O_B), (O ), used to identify them when these badges are of the transponder type. The example given shows the floor of a closed building containing several rooms accessible from the outside via an access (1) being shown here as a single entry point to simplify the description. This access leads into a room communicating with a corridor via an access (2), the corridor communicates via individual accesses (3 to 7) and (9 to 12) with as many rooms, each room having a single access, except the room with access 7 which also communicates with another room via access 8. The room with access 8 leads to a second corridor via access 13. The second corridor communicates via individual accesses (14 to 22) to as many rooms having a single access.

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Each access mentioned above is for instance fitted with a radio-identifier bearing the same reference. The latter is made up of a badge interrogating unit (21) and an identification receiver (24) - reference Figure 2.

In this instance, interrogating unit (23) is fitted with a UHF transmitter controlled to transmit one UHF interrogation or several if necessary.

Interrogation code transmission is designed to allow identification of the transponder badges which, in this instance, use the energy transmitted by a UHF interrogation code received in order to transmit an individual UHF response code transposed from the interrogation code received.

The badges (O) arc conventionally designed for individual or category identification of persons or objects to whom/which they arc assigned and upon whom/which they are usually placed.

The receiver (24) of a radio-identifier which is also of the UHF type is suitably arranged to decode the individual UHF response codes transmitted by the badges (O) upon reception of an interrogation supplied by an interrogating unit (23) when the badges are located within its field of action.

To avoid complications resulting from processing of concurrent responses, at radio-localisation system level and in particular at identification receiver (24) level, it is possible to limit the eventual concurrent responses by precisely limiting the transmission/rcception field of a radio-identifier for instance.

With the facilities shown in Figure 1, this can be easily achieved by limiting the passage at radio-identifier level to a single badge (0) holder at a time, for instance by physical means or by choosing the appropriate interrogating unit transmitting beam and efficient receptivity sector of the identification receivers, using techniques well known to the skilled workman.

A control unit (25) built around at least one processor (39) and some auxiliaries, in particular memories, is used to process the badge (0) identification information supplied by one or several radio-identifiers, according to techniques, not described here, making it possible to know the identity of the badge holder when the latter enters the field of action of a radio-identifier and hence, to keep track of his location as he moves aiong, in particular if the badge holder successively enters the individual fields of action of at least two rad io-local isers in the application example mentioned in relation with Figure 1. To this end, the information required for localisation of a badge under surveillance is stored in a memory of the radio-identification system control unit or in the facilities incorporating such a system, once it has been obtained k

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Passage direction sensors associated with a radio-identifier can also be used to give the approximate location of a badge (O) holder with a single radio-identifier if need be. This can be achieved by various means, for instance by associating two light emitting barriers, infra-red in particular, cither side of the central part of the field of action of a radio-identifier, the order in which the barriers are crossed is communicated to the relevant control unit (25) which can thus obtain the required localisation information, using a common method, not discussed here, taking into account the ‘ 10 passages, the last of two barriers crossed by a badge holder indicating on which side •« « « &lt; ’ «' the badge holder is located.

«&lt; f ‘«J In another version of implementation, the radio-identification system is com’♦»*·* bined with application server facilities (26) capable of processing the identification information, relating to passage and/or localisation according to its own requirc15 ments, the system control unit (25) being directly or indirectly connected to the server facilities control unit (41), built around at least one processor, via at least one transmission link (40) of a standard appropriate type.

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The server facilities (26) may for instance be a telecommunications installation ’ · such as intercom or ISDN switchboard receiving the information supplied by the _s 20 radio-identification system in order to know in real time the location of at least some , t I ;

of the telephone subscribers and to perform the standard functions performed by paging systems and/or to transfer their incoming calls to a telephone set or terminal / . (42 or 43) close to their current location.

. \ : Furthermore, since, these subscribers may have access to specific facilities, asso25 ciated with the category to which they belong and normally assigned to their usual telephone set or terminal within the telecommunciation installation servicing them, the above mentioned combination of a radio-identification system with a telecommunication installation makes it possible to automatically transfer the facilities a subscriber is entitled to in accordance with his category, to a telephone set or terminal close to which he is temporarily located.

The processes allowing subscriber tracking and facility transfer imply the implementation of quite often elaborate software procedures being of common knowledge to the specialists in telecommunications, therefore they will not be described here since they are only indirectly connected to the present invention.

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Figure 2 also shows the make up of typical units in an example of a radioidentification system in accordance with the invention.

The interrogation unit (23) of a radio-identifier in the proposed system consists mainly of a UHF transmitter having, in this instance, a fixed frequency in the order 5 of 2 GHz supplied by an excitation generator (27).

The generator (27) drives a correlator (28) made up of a reed filter built as a surface wave circuit.

This correlator (28) is built according to a commonly known fashion to produce a coded signal which, preferably in accordance with the invention, is a BARKER 10 code with 13 elements having the value + 1 or -1, in fact this code corresponds to the sequence 11111-1-111-11-11.

It makes it possible to obtain a correlation peak having the value 1 for a 1/13 wave during its detection by a transverse filter, when the filter coefficients correspond to the above mentioned sequence.

The phase modulation implemented is a O or 180° modulation with overmodulation with raised cosine providing for a reduction of the spectrum in compliance with the appropriate standards.

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The badges (O) arc of identical make up. Each badge comprises a credit card type support containing a UHF antenna (30), made up for instance of a conducting area, in the usual appropriate shape Tor this field of application, which is printed on the support, for reception of interrogation codes as described above, and transmission 30 of an individual identification code via UHF channel.

Each of them also includes a surface wave circuit grouping two delay lines (31 and 32) in series, the first being solely used as a buffer to the second which acts as an individual address encoder for the badge.

The buffer line (31) is connected to the badge antenna (30). Its purpose is to delay the transmission, to the second delay line, of the UHF signals received by the

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0 « O9S badge, for a time at least equal to the time required by an interrogating unit (23) to transmit the excitation profile made up by a BARKER interrogation code.

The delay line (32) acts as transmission encoder, it is of the constant pitch comb filter type and includes output electrodes which may or may not be connected to the 5 badge antenna (30), via a common summer (33), in a specific way representative of the badge (O) address; in this instance, the structure of the assembly made up by this delay line (32) and its connections can be compared to the structure of the correlator (28), while having a different function, since there is summing rather than correlation at badge level.

The filter pitch is selected to be at least equal to the bit time used for the excitation profile generation by the identifier (23).

The theoretical example of Figure 3 shows that for easier reading of the address of each badge, the extreme positions of the electrodes of line (32) acting as encoder are used as start and stop bits, the intermediate electrodes arc used for the actual 15 addressing, as symbolised by the presence or absence of electrodes (33E) connection to the common summer (33), the address represented corresponding to a binary code 1010111 preceded by a start bit, followed by a stop bit, both having the value 1. After reception of a BARKER interrogation code, a badge transmits a UHF signal which, at each significant bit time, corresponds to the sum of the signals then avail20 able on all the electrodes of the delay line (32) which arc connected to the summer (33) of the relevant badge, and this during the time required for the correspond interrogation code to transit along this delay line (32).

The UHF identification signal retransmitted by a badge lit by an interrogating unit (23) is designed to be picked up by the identification receiver (24) associated with 25 this interrogating unit. To this end, this identification receiver (24) includes a receiving antenna (34) which is eventually merged with the transmitting antenna (29) and connected to an input of a correlator (35), identical to correlator (28) of interrogating unit (23).

Correlator (35) drives an envelope detecting circuit (36), via an amplifier (37) and the envelope detector is connected at the input of a delay line (38) making up a register for the control unit (25) of the relevant radio-identifier.

If an interrogation code is transmitted by the interrogating unit (23) and if no suitable badge is likely to respond, the signal received by the identification receiver (24) consists of an amplitude modulated signal at the output of correlator (35) which is shaped as shown in Figure 4.

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This signal has a central wave peak corresponding to the signal obtained, when the interrogation code has been entirely received and is entirely contained within the successive elements making up the delay line included in correlator (35), the weak waves preceding or following this peak being produced when the code bits are not or 5 no longer placed in the correlator (35).

The UHF identification signal picked up by an identification receiver (24), issued from a badge lit by the interrogating unit associated with this receiver, appears at the output of correlator (35) as a signal shaped as shown in Figure 5.

This signal initially consists of a scries of low amplitude waves corresponding to 10 the elements of the UHF signal generated by the badge prior to the first correlation detected which is translated as a first amplitude peak at the output of correlator (35) and corresponds to the action caused by the first of the address connections included in the delay line (32) acting as encoder for the transponder badge.

The following amplitude peaks of the correlator output signal arc indicative of 15 as many other correlations detected, they being caused by the individual and successive actions of the other address connections along the delay line (32) of the relevant badge.

The address of the badge which transmitted the signal received by the correlator (35) is given by the correlator (35) and is then temporarily stored in the delay line (38) 20 to be used by the processor (39) with a port (P) to which the outputs of this delay line (38) arc connected, the start bit received first being used to trigger for instance an acknowledge interrupt IT in processor (39), when the entire address is stored.

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