WO2009018790A1

WO2009018790A1 - Equipment for contactless integrated circuit reading

Info

Publication number: WO2009018790A1
Application number: PCT/CZ2008/000090
Authority: WO
Inventors: Jiri Bartos
Original assignee: Comimfo, A.S.
Priority date: 2007-08-08
Filing date: 2008-08-07
Publication date: 2009-02-12
Also published as: WO2009018790A8; CZ2007527A3

Abstract

For reading of contactless integrated circuits there is designed an equipment comprising a loop antenna (5) for transmission of oscillating magnetic field and means for detecting a contactless integrated circuit having an antenna coil and further provided with means for emitting short magnetic field pulses, means for detection a signal of an envelope of pulses detected from the loop antenna (5) which correspond to the magnetic field pulses and means for monitoring changes of the amplitude of the envelope of detected pulses and further provided with two independent sources (6,8) of high-frequency magnetic field, the first one of which being a source (6) of nominal output power pulses for communication with a contactless integrated circuit (7) and the second one of which being a source (8) of power output pulses of at least one order of magnitude lower than the nominal output power pulses, for mode of detection of presence of a contactless integrated circuit, while each of the two sources (6,8) of high-frequency magnetic field have a control circuit coupled to a common control unit.

Description

EQUIPMENT FOR CONTACTLESS INTEGRATED CIRCUIT READING

Technical Field The invention relates to equipment for contactless integrated circuit reading provided with a loop antenna for transmission of oscillating magnetic field and means for detecting a contactless integrated circuit having an antenna coil and further provided with means for emitting short magnetic field pulses, means for detection a signal of an envelope of pulses detected from the loop antenna which correspond to the magnetic field pulses and means for monitoring changes of the amplitude of the envelope of detected pulses

Background of the Invention

Significant development of contactless integrated. circuits and their application in movable items like contactless chip cards, contactless electronic identification cards and tags etc has taken place in recent years Reading equipments utilize data transfer by means of induction coupling in a given frequency band Generally there is used the frequency band of 13,56 MHz The data transfer systems utilizing induction coupling are incorporated in various protocols, some of which have become standards, like protocols comprised in standards ISO/IEC 15693, ISO/IEC 14443 a ISO/IEC 18000 These protocols include principles thereby the reading equipment can detect presence of a contactless integrated circuit within its communication range to enable desired communication The principles often comprise an identification request, which has to be repeatedly transmitted by the reading equipment Receiving such request an integrated circuit placed within detection range of the reading equipment answers with an identification signal The identification signal can be an individual one including circuit identification number, such as its serial number or any other identification The identification signal can be also provided for by a simple signal, e g one period of modulation of amplitude of magnetic field created by load modulation In applications with strong probability of simultaneous presence of several integrated circuits within the communication range of one reading equipment, the identification request is accompanied by an anti-collision protocol, enabling selection of a single integrated circuit Such a system of detection and/or identification of an integrated circuit requires the reading equipment permanently emits alternating magnetic field or at least a group of enabling to emit the identification request and receive the identification message or at least a group of magnetic field pulses having sufficient length to enable the integrated circuit to produce power voltage and absorb energy and thereby weaken the magnetic field An equipment of this kind as described in the patent paper EP 391 559 is equipped with antenna coil generating magnetic field which oscillates with a frequency of 13,56 MHz The contactless integrated circuit has its own antenna coil The reader transmits magnetic field pulse groups, each of which having length of 5 to 10 milliseconds The magnetic field envelope for identification request is amplitude modulated for a certain time interval, during which the request is transmitted A contactless integrated circuit being within a communication range answers the received request This system of detection and identification of a contactless integrated circuit features high power consumption for transmission of the magnetic field, which is disadvantageous especially in cases where readers are supplied from a battery or an electric cell According to other communication protocols the integrated circuit automatically transmits the identification signal when detecting presence of a magnetic field transmitted by the reading equipment This method of detection with automatic identification also features considerable consumption of electric power, as the reading equipment has to continuously emit a magnetic field or a group of magnetic field pulses having sufficient length to activate the integrated circuit to transmit the identification signal This disadvantage is removed by equipment utilizing infrared transmitter/receiver When out of communication period the reader is in active standby mode, when no magnetic field is transmitted and there is only monitored a signal coming from a sensor of infrared radiation As soon as a contactless integrated circuit enters the infrared radiation field, a reader detects modulation of received infrared radiation level and switches into active mode when magnetic field is transmitted, the field having a form of a continuous field or pulse groups and comprising or missing the identification request If there is no identification signal after a certain number of requests or pulse groups, the reading equipment returns back to standby mode At present time there exists also reading equipment featuring function of active standby mode with low power consumption Mutual induction between transmitter antenna coil and a coil of the contactless integrated circuit is utilized for the detection of the circuit At the moment the contactless integrated circuit enters communication range of the reading equipment its transmitter antenna becomes mistuned and high-frequency signal at the antenna live node changes The changes are detect e g by an envelope detector While in the active standby mode the reading equipment transmits only short pulses of the carrier frequency 13,56 MHz, the pulses having length of about 100 μs and intervals longer than 200 ms Such method provides for a considerable saving on energy An example of the reading equipment of this type is described in the patent paper EP 1459240 Utilization of a controlled oscillator which operates only during a time-period necessary for transmission of a high-frequency field provides saving of energy Nevertheless by equipment supplied from a battery or an electric cell the total energy consumption remains high It is an object of the invention to provide for a considerable decrease of energy consumption by known reading equipment

Disclosure and Obiect of the Invention

The forgoing object of the invention is achieved by equipment for contactless integrated circuit readout provided with a loop antenna for transmission of oscillating magnetic field and means for detecting a contactless integrated circuit having an antenna coil and further provided with means for emitting short magnetic field pulses, means for detection a signal of an envelope of pulses detected from the loop antenna which correspond to the magnetic field pulses and means for monitoring changes of the amplitude of the envelope of detected pulses as designed according to the present invention the subject matter of which presents an equipment provided with two independent sources of high-frequency magnetic field the first one of which being a source of nominal output power pulses for communication with a contactless integrated circuit and the second one of which being a source of output power pulses of at least one order of magnitude lower than the nominal output, for mode of detection of presence of a contactless integrated circuit, while each of the two sources of high-frequency magnetic field have a control circuit coupled to a common control unit In a preferred configuration the second source of high-frequency magnetic field is provided with an oscillator having start-up time below 1 μs, the oscillator being of a type of a phase-locked loop controlled oscillator or a digitally controlled oscillator The advantage of the invention consists in a considerable decrease of energy consumption in comparison with known solutions where the equipment is supplied from its own source, the decrease value being of at least one order of magnitude

Brief Description of the Drawings

The invention is further illustrated by way of examples of its practical implementation presented in the accompanying drawings, where

Fig 1 illustrates an elementary block diagram,

Fig 2 shows a block diagram with two independent transmitters and Fig 3 represents a block diagram with two independent transmitters, where the second transmitter oscillator is a part of a controller

Figs 4 a, b and c show waveforms of magnetic field by present equipment and by the equipment according to the invention

Description of Preferred Embodiment

Referring to Fig 1 , which shows a block diagram of elementary configuration, the said reading equipment comprise a control unit, namely a controller 1_, communication block 2 fitted with a transmitter 2J_. with means for reception of high-frequency pulses, detection block 3, monitoring block 4 with means for scanning amplitude envelope of the high-frequency pulses and a loop antenna 5 The controller 1 comprises a programmable microprocessor with low power consumption and sufficient computing performance Recent integrated microprocessors have multiple sources of system clocking pulses It is therefore possible to utilise low-input mode operating at 32768 Hz clocking pulse frequency To achieve full controller computing performance there is used higher clocking pulse frequency, either by switching to another oscillator or by means of a controlled oscillator Operation of the complete reading equipment and its blocks is software controlled

The loop antenna 5 comprising antenna coil L1 and the first capacitor C_l is tuned to the carrier frequency of 13,56 MHz One node of the loop antenna 5 is connected to ground, the other one is a live node 5_1 The live node 5J_ is on the one hand connected through a coupling capacitor C3 to a signal port 23 of the communication block 2, on the other hand through the monitoring block 4 to the detection block 3

The signal port 23 of the communication block 2 comprises a common node of a transmitter 2J_. and a receiver 22 The receiver 22 has its output 24 connected to a data input IJ_. of the controller 1 The transmitter 2_1 has its first input 25 connected to a data output 12 of the controller 1 and its second input 26 to means for transmission of short magnetic field pulses Operation of the communication block 2 is activated by a signal coming on his triggering signal input 27 from an output 15 of the first triggering signal of the controller 1 The said means for transmission of short magnetic field pulses are according to the invention provided for at one hand by a source 6 of nominal output power pulses which is determined for communication with a contactless integrated circuit 7 and on the other hand by a source 8 of decreased output power pulses, which is determined for mode of detection of presence of a contactless integrated circuit 7 during a standby operation The power output of the source

8 of decreased output power pulses is at least one order of magnitude lower than the power output of the source 6 of nominal output power pulses

Switching between the two sources 6, 8 is controlled by a signal from a first control output 13 of the controller 1 Output power of the transmitter 2J_. is controlled by a signal from a second control output 14 of the controller 1 The contactless integrated circuit antenna is provided with a second antenna coil L2 The generator of the 13,56 MHz frequency of the source 6 of a nominal output power is provided for by a crystal oscillator OSC having start-up time, incl stabilisation of its amplitude and frequency, within the range of milliseconds As mistuning of the transmitter antenna caused by a presence of a contactless integrated circuit 7 is used for the detection of such a situation, during the detection mode it is not necessary to apply the carrier frequency 13,56 MHz and also there is not demanded such a high stability of the carrier frequency as it is during communication with the contactless integrated circuit 7 Therefore the source 8 of decreased output power pulses advantageously applies a PLL type oscillator, i e an oscillator controlled by a phase-locked loop or a DCO type oscillator, i e a digitally controlled oscillator with a very fast start-up time below 1 μs, The oscillator having frequency in the range of twelve to fourteen MHz and being stabilized by a low-frequency oscillator by which the controller is clocked during no active mode of operation Typical frequency produced by the low- frequency oscillator of such a type is 32768 Hz Thus it is possible to apply an oscillator of the PLL or the DCO type operating at the frequency of 12 MHz to 14 MHz with a start-up time in the microseconds range This arrangement results in a significant decrease of current consumption while in the detection mode Application of the oscillator of the PLL or the DCO type may further result in increased detection sensitivity as during a calibration phase, by setting the frequency of the PLL or the DCO oscillator there can be established the maximum value of the detector analogue variable By this way there one can compensate for possible mistuning of the antenna caused by objects in the antenna surroundings or by the ambient temperature Fig 2 shows other solution provided with two independent units of the transmitter 21 The first one of the said units comprise the source 6 of nominal output power pulses, excited by the crystal oscillator frequency of 13,56 MHz and the other source contains the source 8 of decreased output power pulses excited by a controlled oscillator, which is stabilised by the controller 1 oscillator Switching the two sources 6, 8 of high-frequency magnetic field is provided for by an antenna switch 9, which is controlled by a signal from the second control output 14 of the controller 1 The source 6 of nominal output power pulses is connected at the antenna switch 9 through its own coupling capacitor C3.

Fig. 3 shows still another solution according the invention, where the controlled oscillator and the detection block 3 are integrated into the controller 1. This arrangement makes the solution substantially simpler. The controller 1 provides also for a transmitter of magnetic field of decreased output power in the mode of detection of a contactless integrated circuit 7. The first coupling capacitor C3 is arranged between the antenna switch 9 and the controller 1 output port. A signal from the live node 51 of the loop antenna 5 is connected to the input of the monitoring block 4 which scans an amplitude envelope of high-frequency pulses. The monitoring circuit 4 comprises a lowpass filter consisting of a resistor Rl and a second capacitor C2. On the output of the monitoring block 4 there appears an envelope signal corresponding to the amplitude envelope of high-frequency pulses received from the loop antenna 5. The envelope signal enters evaluation circuit of the detection block 3. An output signal of the evaluation circuit is connected to the detection signal input 16 of the controller 1. The output signal of the evaluation circuit indicates presence or absence of a contactless integrated circuit 7 within the communication range of the reading equipment. Operation of the detection block 3 is activated by a signal coming from an output 17 of the second triggering signal of the controller 1.

All circuits of the reader equipment are controlled by the controller 1. Its signals control power consumption of individual blocks. The controller 1 further provides data communication with a contactless integrated circuit 7 by means of signals coming from the controller data input H and the controller data output 12. The signal from the controller data output 12 is by means of the communication block 2 transferred to a high-frequency signal of nominal power and similarly the signal coming at the controller data input H is created from a high-frequency signal of nominal power by the communication block 2. All the communication with the contactless integrated circuit 7 is performed by nominal output power, by the decreased output power there is performed only detection of presence of any contactless integrated circuit 7 within the loop antenna 5 field. During the standby mode, i e in the mode of detection of presence of any contactless integrated circuit 7, short high-frequency signal sequences from the source 8 of decreased output power pulses are fed to the loop antenna through the antenna switch 9 The time peπod between the two consecutive sequences of high-frequency signals is 125 ms, the length of the sequence is 0,1 ms Thus a time interval without any high-frequency signal is 124,9 ms long Within this time interval all blocks, except the controller 1_, are switched-off, the controller 1 running in a low power mode Dunng the time penod when the sequence of high-frequency signals is transmitted, the evaluation circuit of the detection block 3, monitoring block 4 and the source 8 of decreased output power pulses are switched on The communication block 2 is completely switched off At the moment the detection block 3 locates a presence of a contactless integrated circuit 7, the reading equipment changes to active mode In the active mode, i e in the mode of communication with the contactless integrated circuit 7, the source 8 of decreased output power pulses and the detection block 3 with the monitoring block 4 are switched off On the other hand the communication block 2 is switched on and signals from the source 6 of the nominal output power pulses are fed through the antenna switch 9 on the loop antenna 5 The equipment verifies presence of a contactless integrated circuit 7 by transmission of a request signal RQST In a case of successful verification of presence of the circuit, the equipment starts communication with the contactless integrated circuit 7

Fig 4c presents a waveform of a magnetic field transmitted by the reading equipment according to the invention It is apparent that there exists a difference between the magnetic field transmitted during the standby mode and the field transmitted during the mode of communication with the contactless integrated circuit 7 Just for comparison Fig 4a shows a waveform of a magnetic field of an ordinary reading equipment, where the identification request is repeatedly transmitted in time intervals and Fig 4b shows a waveform of a magnetic field when the reading equipment in a standby mode transmits only a short carrier frequency pulse in intervals longer than 200 ms, the pulse of nominal output power having length of about 100 μs For design of the detection block 3 there may be utilized properties of oscillators with fast start-up time, like the digitally controlled oscillator DCO with fast start-up time or phase-locked loop controlled oscillator PLL. In the standby mode where no generation of the high-frequency signal is required this oscillator operates in low-power mode or is completely switched off. The oscillator of the DCO or PLL type is controlled by a signal from the controller 1 first control output 13. For transmission of a sequence of high-frequency signals the appropriate output frequency is set and the oscillator DCO, PLL output is activated. Both oscillator types allow fine tuning of the output frequency. This feature can be utilized for adjustment to antenna resonant frequency when no contactless integrated circuit 7 is present within the antenna field. Such a step increases sensitivity of the loop antenna 5 towards presence of the circuit 7 within the antenna communication range. There exist microprocessors comprising the said oscillators of the DCO or PLL type directly in the chip. The antenna switch 9 can be provided for by electromechanical or electronic means. It has to warrant good separation high-frequency signal of nominal output power and the signal of decreased output power.

The monitoring block 4 in its simplest embodiment comprises a detection diode the anode of which is connected to the live node 5_1 of the loop antenna 5. A cathode of the diode D_l is connected to a lowpass filter comprising a resistor Rl and capacitor D2. The lowpass filter limit frequency is much lower than the carrier frequency, e.g. 1 MHz against 13,56 MHz frequency of the nominal output power. The lowpass filter output presents signal corresponding to the amplitude envelope of the carrier frequency pulses. The detection block 3 scans changes of envelope amplitude and determines the limit value which is significantly lower than the value of envelope amplitude of antenna signal when no contactless integrated circuit 7 is present within the antenna field. The detection block 3 can be provided for e.g. by a differential amplifier or a system comprising a comparator and a D/A converter or by an A/D converter. Also this detection block 3 may be an integral part of the controller 1.

Claims

C L A I M S

1 Equipment for contactless integrated circuit reading provided with a loop antenna for transmission of oscillating magnetic field and means for detecting a contactless integrated circuit having an antenna coil and further provided with means for emitting short magnetic field pulses, means for detection a signal of an envelope of pulses detected from the loop antenna which correspond to the magnetic field pulses and means for monitoring changes of the amplitude of the envelope of detected pulses, characterized in, that it is provided with two independent sources (6,8) of high-frequency magnetic field, the first one of which being a source (6) of nominal output power pulses, for communication with a contactless integrated circuit (7) and the second one of which being a source (8) of output power pulses of at least one order of magnitude lower than the nominal output power pulses, for mode of detection of presence of a contactless integrated circuit, while each of the two sources (6,8) of high-frequency magnetic field have a control circuit coupled to a common control unit

2 Equipment for contactless integrated circuit readout according to claim 1 , characterized in, that the second source (8) of high-frequency magnetic field is provided with a phase-locked loop oscillator having start-up time below 10 μs

3 Equipment for contactless integrated circuit readout according to claim 1 , characterized in, that the second source (8) of high-frequency magnetic field is provided with a digitally controlled oscillator having start-up time below 10 μs

4 Equipment for contactless integrated circuit readout according to claim 1 or claim 2 or claim 3, characterized in, that the control unit is provided for by a controller (1)

5. Equipment for contactless integrated circuit reading according to any of the preceding claims, characterized in, that the second source (8) of high-frequency magnetic field forms an integral part of the control unit.