IDENTIFICATION SYSTEM

Abstract: The proposed device comprises an interrogator/receiver and a passive transponder. The interrogator/receiver comprises a clock signal generator (1), a group of bandpass filters (5), a section to decode the data received, means (4) for inductively coupling the interrogator/receiver to the transponder. The transponder comprises a section (E) for picking up the power signal transmitted by the interrogator/receiver, a section (B) to codify the signal obtained according to a predetermined code, stored in a memory (15), a section (G) for phase modulating the codified data so as to allow air transmission. Particularly, the bandpass filters (5) are capable to detect a frequency band width lower than one thousandth of the signal's frequency.

Description: - - "IDEWriFICATION SYSTEM" This invention relates to identification remote control and, in particular, it consists of an interrogator/receiver and a passive transponder. This group allows the univocal identification of a still or moving object, animal or person by producing a coded 5- identification signal in answer to a signal sent by the interrogator/receiver that is inductively coupled with the transponder. Some remote control identification systems have already been proposed and used in which an interrogator acts to generate an 10. A.C- clock signal that also acts as a power signal. By means of an inductive coupling, a transponder receives said signal and - 2 - uses it as its power supply, thus generating a coded reply signal that is picked up by the interrogator/receiver. The coded signal is characteristic to that transponder, thus the object, animal or person, to which the transponder is associated can easily be 5. recognized by the interrogator. Particularly, in the device described in the patent application WO 85/03831, the clock signal sent by the interrogator and received by the transponder by means of the inductive coupling is at first reduced in frequency, then its frequency is further 10. divided (for instance by eight or ten) . An alternate current signal is thus produced having a frequency varying between two values; any variation from a frequency to another represents a value of "zero" or "one". The encoding of this signal is obtained by means of a Manchester 15. encoder, while its modulation is carried out by means of FSK system (frequency shift keying) . The modulated signal returns to the interrogator by means of an inductive coupling, it is filtered through bandpass filters which partially eliminate the background noise, then it is sent to a FSK demodulator capable of 20. recognizing the frequency variations of the signal. Then a micro¬ computer extracts the identification code and is able to transfer it to a monitor, a printer, a disk or other storage systems or to another computer. The main disadvantage of this device is the need to use, for 25. isolating the signal sent by the transponder, bandpass filters having a frequency band width at least equal to the difference between the two frequency values of the signal. In this way the - 3 - background noise having a frequency comprised between the modulated signal frequency values, is allowed to pass through the filters and the recognition of the identification signal is sometimes difficult, particularly in a highly electromagnetically 5. disturbed environment. Thus only the reduction of the maximum allowable distance between the interrogator and the transponder allows a sure identification. Moreover, the device employs unalterable memories therefore its use is limited to simple identification systems. 10. Object of this invention is, therefore, that to increase the maximum distance between interrogator and transponder with no power increase and to allow transmissions to occur also in bad conditions. A further object is that to extend the utilization field of the 15. device. The main object has been achieved by providing a device of the kind mentioned above, that is made of an interrogator/receiver and passive transponder inductively coupled, in which the former generates a power signal of a predetermined frequency that is 5. received by the latter that utilizes it as a clock signal for generating a codified reply signal, said signal being phase modulated between two predetermined values such that each phase shift from a value to the other corresponds to a "zero" or a "one" of the binary identification code. Then the modulated 10. signal is sent again to the interrogator by means of an inductive coupling, filtered through bandpass filters, demodulated and decoded; the identification code is thus identified. From the aforeasaid it will be noted that in the proposed device bandpass filters can be used having a very narrow frequency band width (less than one thausandth of the modulated signal 5. frequency) , thus allowing a more efficacious discrimination of the signal from the background noise. This allows the use of the identification device also in environments highly disturbed electromagnetically, and also the increase of the maximum distance between the interrogator and transponder, distance, in 10. which it is still possible to have a sure identification. An improvement of the invention foresees the use of non-volatile memories of the EEROM and EEPROM kind that allow to modify, when necessary, the information contained in the transponder: it must be stressed that the use of the EEPROM memory allows the use of 15. the device not only as a recognition system but also as a register for data, which can be read and written at a distance. The above described invention will be schematized in the enclosed drawings in which: Fig. 1 is a block diagram of the interrogator/receiver; 20. Fig. 2 is a block diagram of the transponder; Fig. 3 is a diagram of the demodulator PSK; Fig. 4 is a diagram of the transponder; Fig. 5 is a block diagram for the reading and/or the writing of the EEPROM memory. 25. Referring to figure 1 it will be noticed that the proposed - 5 - interrogator/receiver comprises the following sections: A) An excitation section A, comprising a signal generator 1 , followed by an amplifier 2 and a capacitor 3. The capacitor 3 and the interrogator coil 4 are selected so as to resonate at 5> the frequency of the generated signal, so that the voltage across the coil is much greater than the voltage output from the signal generator. B) A. signal conditioning section B, connected to the interrogator coil 4, able to recognize the presence of a predetermined 1L. frequency signal and to discriminate it from the background noise. Said section comprises multistage bandpass filters 5, followed by an amplifier 6. C) A demodulating and decodifying section C connected to the amplifier 6 and comprising a PLL (phase locked loop) 7, a 15* demodulator PSK and a microcomputer 9. D) A section D for the inductive coupling between the interro¬ gator/receiver and the transponder, namely coil 4. Referring to figure 2 it will be noticed that the proposed transponder is made of the following sections: 20. E) A section Ξ for picking up the power signal transmitted by the interrogator/receiver comprising a coil 10 followed by a power supply 11, a squarer 12, capable of using said signal to supply all the device and, furthermore, using this signal as a clock signal for the generation and the codification of the - 6 - data. F) A section F for dividing the clock signal frequency by a preάaterminate value by means of a divider 13 and able to codify the resulting signal according to a predeterminate code 5. contained in a memory 15 accessible by means of an address counter 14, by means of a Manchester encoder 16. G) A section G for modulating the encoded data so as to allow air transmission by means of a modulator 17. Figure 2 shows the diagram of the demodulator PSK that comprises, 10. for instance, the following integrated circuits: - a TL082 - operational amplifier - two LM311 - voltage comparators - a 4001 - two entry NAND gate quadruple and other components such as resistors (R1, R2, ... R8) , 15. capacitors (C1 , C2, ... C6) and diodes (D1, D2, ... D6) . The respective values of the resistors and the capacitors are shown in the diagram. Figure 4 shows a diagram of the transponder realized in this embodizsnt with the following integrated circuits: 20. 4001 - rwo entry NOR gate - quadruple 4007 - four entry NOR gate - double 4017 - decade counter with ten decoded exists 4025 - three entry NOR gate - triple 4028 - decimal decoder 4081 - two entry AND gate - quadruple 4512 - eight channels data selector 4518 - double decimal synchronous counter 5. 4520 - double binary synchronous counter 40106 - sextuple "Schmitt-Trigger" inverter and other components such as resistors, capacitors and diodes (the resistors and the capacitors are characterized by their respective values) , as well as a EPR0M or ΞEPR0M memory. 10. Figure 5 is the transponder equipped with a non-volatile memory of the EEPROM kind that can be modified at a distance. Three sections Ξ, F and G are foreseen cσaprising the components described in Figure 2 with a voltage booster 18 added in section E for the generation of the particular programming voltage, and a 15. memory management block added in section F, comprising a writing/reading discriminator 19.

Claims: - 8 - C A I M S 1. An identification system comprising: - an interrogator/receiver made up of the following sections: A) a section (A) comprising a clock signal generator (1) having a predetermined frequency; 5. B) a section (13) comprising bandpass multistage filters (5) for recognizing the presence of a signal having predetermined frequency and able to discriminate the two characteristic components of said signali - the data 10. - the ground noise C) a section (C) able to decode the data received from the preceding section in order to make said data intellegible to a digital processor by means of an appropriate device (7,8) ; D) a section (D) comprising means for inductively coupling (4) 15. the interrogator/receiver with the transponder; - a passive transponder comprising the following sections: E) A section (E) for picking up the power signal transmitted by the interrogator/receiver comprising a coil (10) followed by a rectifier and a filter condenser able of using said signal 20. to supply all the device and furthermore to use said signal as clock for the generation and encoding of the data by means of a squarer (12) ; F) a section to encode the signal thus obtained according to a predetermined code, contained in memory (15), by means of an encoder (16) ; 5. G) a section to modulate the encoded data thus allowing their air transmission by means of a modulator (17); characterized in that the data are modulated and demodulated on the phase of the signal. 2. A system according to claim 1, characterized in that for 10. the phase modulation a PSK (phase shift keying) is used and that, similarly, the demodulating method uses the same system. 3. A system according to claim 1 or 2, characterized in that the bandpass filters (5) are very selective, that is capable of discriminating a frequency band width being not higher than one 15. thousandth of the frequency of the signal transmitted by the transponder. 4. A system according to claims 1, 2 or 3, characterized in that the bandpass filters (5) are of the "active" kind, that is able to amplify the signal at every filtering stage. 20. 5. A system according to any of the previous claims, characterized in that the memory (15) is of the EPROM non¬ volatile kind and can thus be modified when necessary. 6. A system according to claims 1 to 4, characterized in that the memory (15) is of the EEPROM kind, that is it can be 25. modified at a distance. - 10 - 7. A system according to claim 6, characterized in that also an additional memory management section is utilized comprising a reading/writing discriminator (19) and a positive voltage booster (18) for the generation of the particular programming voltage. 5. 8. A system according to any of the previous claims, characterized in that the squarer (12) is of the Schmitt-Trigger kind. 9. . A system according to any of the previous claims, characterzied in that the encoder (16) is of the Manchester kind. 1 °. 10. A system according to any of the previous claims, characterized in that the power signal frequency is comprised in the range of hundreds of kHz, and that the modulated signal frequency is in the range of tens of kHz, this last signal being obtained by using a frequency divider (13) located in the 15. transponder.

Inventors: HEFTI ALDO, HEFTI, ALDO
Applicants: AUDEMARS S A R, R. AUDEMARS S.A.
Application year: 1987
Main classification: G07C9
IPC codes: B61L25, G06K7, G07C9, G08G1