Patent Publication Number: US-2009219138-A1

Title: Reader interfacing device

Description:
The present invention relates to a reader interfacing device for providing a communication path between a conventional reader operable at a first radiation frequency, for example in the order of 13.56 MHz, and a smart label or tag operable at a second radiation frequency, for example in the order of 2.45 GHz. 
     Conventional smart labels and tags are becoming increasingly used in a number of applications, for example in vehicle key fobs including tags for use in remote locking and unlocking of associated vehicles, smart labels attached to merchandise in retailing premises for use in counteracting merchandise theft, and personal identity cards comprising smart labels or tags for gaining authorised access to restricted premises. In practice, smart labels are often designed to be permanently attachable to items to mark them whereas tags tend to be used in portable items which can be personnel wearable. 
     A standard ISO 15693 is currently being established by a consortium of major international companies for smart labels and tags, the standard having the purpose of increasing the market for mutually compatible smart label and tag systems. The standard may lead in future to a significant deployed infrastructure of smart label and tag readers. Moreover, the standard is establishing a universal frequency of 13.56 MHz for radiation to be used to communicate to and from such tags and smart labels. Readers operating at 13.56 MHz will be capable of providing power and communicating with associated tags and smart labels at ranges of up to 2 metres therefrom. The readers will interrogate the tags or smart labels using amplitude modulated interrogating radiation and the tags or smart labels will communicate back to the readers by utilising load modulation at sub-carrier frequencies specified in the standard, namely the readers will detect an amount of power being absorbed by the tags or labels around the frequency of the interrogating radiation. 
     The inventors have appreciated that, in some applications, it is desirable for tags and smart labels to operate at other radiation frequencies than 13.56 MHz specified in the aforementioned standard, for example at a higher frequency in the order of 2.45 GHz, namely at least an order of magnitude greater than 13.56 MHz. Benefits of operating at such a higher frequency include:
     (a) selective directional smart label or tag reading;   (b) radiation propagation from readers to smart labels or tags which is more electromagnetic in nature compared to the aforementioned conventional readers operating at 13.56 MD which rely principally on magnetic coupling; moreover, losses can be reduced in some circumstances when operating at higher frequencies, for example in the order of 2.45 GHz; and   (c) optional mounting of smart labels on metallic surfaces from which the labels are electrically isolated is feasible at higher frequencies, for example in the order of 2.45 GHz.   

     The inventors have appreciated that operation at a radiation frequency at least an order of magnitude lower than 13.56 MHz provides enhanced radiation propagation through objects, for example in articles whose smart labels or tags are concealed from view therein. 
     A number of conventional longer range tagging systems are commercially available. However, they do not conform to the aforementioned standard and so cannot be interoperated with readers conforming to the standard. For applications where infrastructure operating at a radiation frequency of 13.56 MHz and adhering to the standard has already been installed, the cost of installing a parallel reader and associated smart label system operating at other interrogating radiation frequencies will often be prohibitive and, if the infrastructure is modified (DEA-199 08 879) to operate at another interrogation frequency, then it will no longer comply with the original standard. 
     According to a first aspect of the present invention, there is provided a reader interfacing device for providing a communication path between:
     (a) a reader configured to emit and receive interrogating radiation at a first radiation frequency; and   (b) a remote tag or smart label configured to be interrogated using radiation of a second frequency,
 
the first and second frequencies being mutually different by at least an order of magnitude, and the reader being operable to communicate through the device to the remote tag or smart label.
   

     The invention provides the advantage that the interface device is capable of enabling the reader operating at the first frequency to communicate with the tag or smart label operating at the second frequency, such operation providing potential benefits including one or more of selective directional smart label or tag reading, reduced losses in some circumstances and optional mounting of smart labels on metallic surfaces. 
     In order to benefit noticeably from one or more of the advantages, the first and second frequencies need to be mutually different by at least an order of magnitude. 
     In order to make the reader convenient to use and install, the device advantageously includes power conversion means for converting interrogating radiation received at the device from the reader to generate power supply potentials for powering the device. 
     In many tag or smart label reading systems, the reader employs a loop antenna. Thus, to ensure ease of interfacing, the device is preferably mutually magnetically coupled to the reader for receiving the interrogating radiation therefrom and for providing a modulated load thereto for communicating back to the reader. Conveniently, the device includes a first loop antenna for magnetically coupling to a corresponding second loop antenna of the reader. 
     Conventional tag or smart label readers use load modulation to sense signals emitted back from tags or smart labels. Hence, the device advantageously incorporates a modulated field effect transistor connected to the first loop antenna for providing a variable load detectable at the reader, thereby communicating back from the device to the reader. 
     In order to achieve advantages described above, it is especially desirable that the second frequency is in a range of 300 MHz to 90 GHz. 
     Advantageously, in operation, the device is configured to emit radiation to the remote tag or smart label and receive radiation therefrom using patch antennae. Patch antennae are generally physically compact and potentially inexpensive to implement, especially in a frequency range of 300 MHz to 30 GHz. Conveniently, the second frequency is in a range of 2 GHz to 3 GHz. Preferably, the second frequency is 2.44 GHz, namely a harmonic of 13.56 MHz which is a standard frequency for the standard ISO 15693. 
     In order to interface to different, possibly non-standard, types of tag or smart label, the device preferably includes translating means for converting between a modulation format used by the reader for modulating information onto the interrogating radiation to be received by the device and a modulation format used by the remote tag or smart label for communicating therefrom to and from the device. Advantageously, the translating means includes an amplitude demodulator for demodulating a first received signal generated in the device in response to receiving thereat the interrogating radiation from the reader and thereby generating a first demodulated signal, the translating means further including a modulator supplied with a carrier signal at the second frequency and operable to modulate the carrier signal with the first demodulated signal to generate radiation for interrogating the remote tag or smart label. Moreover, in order to achieve a simpler design for the device, the translating means includes a demodulator for heterodyne mixing a second received signal generated in response to receiving radiation from the remote tag or smart label with the carrier signal to generate a second demodulated signal for use in providing load modulation detectable at the reader. Furthermore, to assist with achieving more stable frequency operation, the carrier signal is advantageously generated by a microwave oscillator frequency locked to the first frequency. 
     In a second aspect, the invention provides a remote tag or smart label for use with the device according to the first aspect of the invention, the remote tag or smart label incorporating amplifying means for reflectively amplifying a received signal generated therein in response to receiving interrogating radiation from the device, the amplified received signal useable for providing response radiation receivable at the device. 
    
    
     
       Embodiments of the invention will now be described, by way of example, with reference to the following drawings in which: 
         FIG. 1  is an illustration of a conventional prior art smart label reader conforming to the standard ISO 15693, the reader linked to a host computer and interfacing to a conventional low frequency smart label; 
         FIG. 2  is an illustration of a reader interfacing device according to the invention configured to interface between the convention card reader in  FIG. 1  and a high frequency smart label; 
         FIG. 3  is an illustration of coupling between the reader in  FIG. 1  and the device shown in  FIG. 2 ; and 
         FIG. 4  is a diagram of circuit components included in the device shown in  FIGS. 2 and 3 . 
     
    
    
     Referring now to  FIG. 1 , there are shown a conventional prior art smart label reader conforming to the standard ISO 15693 linked to a host computer system and interfacing to a smart label. The reader, the computer system and the label are indicated generally by  10 , and individually indicated by  20 ,  30 ,  40  respectively. The reader  20  further comprises a reader module  50  for interfacing between the computer system  30  and an antenna  60  of the reader  20 . The computer system  30  is linked also to other readers (not shown) similar to the reader  20 . 
     The conventional smart label  40  comprises an associated antenna  62  connected to an electronics module  64 . 
     Operation of the reader  20 , the label  40  and the computer system  30  will now be described with reference to  FIG. 1 . The computer system  30  commences by interrogating the reader module  50  to determine whether or not it is functional. If the module  50  is functional, the computer system  30  then instructs the module  50  to be receptive to sense smart labels placed within sensing range of the antenna  60 . The reader module  50  generates a 13.56 MHz magnetic field by driving the antenna  60  with a corresponding 13.56 MHz signal. The 13.56 MHz magnetic field comprises a number of magnetic field lines as illustrated, for example a field line  70 . 
     When the label  40  is brought within sensing range of the reader  20 , the antennae  60 ,  62  become mutually magnetically coupled, thereby coupling the 13.56 MHz field to the label  40  and generating a received signal in the antenna  62 . The module  64  receives the received signal which it rectifies to provide operating power for itself and then proceeds to load modulate the antenna  62  according to data, for example a signature code, generated or stored within the module  64 . Such load modulation is detected at the reader module  50  via its antenna  60  which thereby senses the data of the label  40 . The module  50  then processes the data to provide a response back to the computer system  30  concerning the label  40 . When the label  40  is moved to be outside the sensing range of the reader  20 , the module  64  receives insufficient power from its associated antenna  62  to operate and hence the reader  20  then ceases to receive data from the label  40 . 
     The sensing range from the reader  20  to the module  64  is in the order of 2 metres. 
     The label  40  optionally incorporates a microprocessor and associated memory in its module  64  although simpler hardware circuits are also possible. 
     The reader  20  and the label  40  conform to the aforementioned standard ISO 15693. 
     The inventors have appreciated that it is desirable to operate the reader  20  and its associated label  40  at radiation frequencies greater than 13.56 MHz. If the reader  20  is modified to operate at a frequency higher than 1356 MHz, it will no longer conform to the aforementioned standard. In order to address such a conflict, the inventors have devised a reader interfacing device compatible with the reader  20  and capable of communicating with smart labels operating at frequencies at least an order of magnitude higher than 13.56 MHz, for example in a range of 300 MHz to 90 GHz although 2.45 GHz is a preferred nominal frequency. 
     Referring now to  FIG. 2 , there is shown is a schematic illustration of an interface device according the invention configured to interface between the card reader  20  and a high frequency smart label  110 ; the device, the reader  20  and the smart label  110  are indicated generally by  100 . Moreover, the device is indicated by  120  and is included within a dashed line  125 . 
     The interfacing device  120  comprises a low frequency interface  130 , a power supply  140 , an external power supply  150 , a modulation translator  160 , a high frequency transmitter  170 , a high frequency receiver  180  and a modulation translator  190 . The interface  130  is coupled at its port Q to the reader  20 ; this coupling is achieved using mutually inductively coupled antennae. The interface  130  includes an output “Detected Signal Out” which is connected to an input of the power supply  140  and also to an input of the modulation translator  160 . The power supply  140  comprises a negative supply output V− and a positive supply output V+; these V−, V+ outputs are both connected to corresponding power inputs of the translators  160 ,  190 , the transmitter  170  and the receiver  180 . The external supply  150  also incorporates corresponding power outputs V−, V+ which are connected in parallel to those of the power supply  140 . The translator  160  includes an output which is connected to an input of the transmitter  170 . Likewise, the receiver  180  comprises an output which is connected to an input of the translator  190 . Moreover, the translator  190  includes an output which is connected to a “Load Modulation In” input of the interface  130 . 
     Operation of the device  120  in combination with the reader  20  and the smart label  110  will now be described with reference to  FIG. 2 . The reader  20  outputs an alternating magnetic field at 13.56 MHz from its associated antenna  60 . The magnetic field is received at an antenna associated with the interface  130  to generate a corresponding signal which is received at the port Q of the interface  130 . The interface  130  outputs the signal to its “Detected Signal Out” output wherefrom the signal propagates to the power supply  140 . The supply  140  rectifies the signal to generate a supply potential difference which is output at the V−, V+ outputs of the supply  140 . The supply  140  thereby provides power to operate the translators  160 ,  190 , the transmitter  170  and the receiver  180 . If necessary, the supply potential difference generated by the supply  140  is supplementable from the external power supply  150  which can, for example, be connected to a mains electrical supply. The signal also propagates to the translator  160  which translates the format of the signal into a suitable form for the label  110 . Thus, the translator  160  outputs a translated signal at its output, the signal propagating to the input of the transmitter  170 . The transmitter  170  amplifies the translated signal and then uses the amplified signal to modulate an output signal from a microwave source associated within the transmitter  170  to generate a modulated microwave signal. The modulated signal is then output from the transmitter  170  to a patch antenna (not shown in  FIG. 2 ) which radiates the modulated signal as microwave radiation  192  which is subsequently received at the label  110  to generate a received signal therein. The label  110  then processes the received signal and generates a corresponding output signal which the label  110  radiates as microwave radiation  194 . 
     The receiver  180  receives the radiation  194  at its associated patch antenna (not shown in  FIG. 2 ) to generate a received amplified signal which propagates from the receiver  180  to the input of the translator  190 . The translator  190  translates the amplified received signal into a format suitable for transmission via the low frequency interface  130 . The interface  130  receives the translated signal from the translator  190  and uses it to modulate a load applied to its antenna, thereby providing load modulation which is detected by the reader  20 , the reader  20  thereby receiving a version of the translated signal from the translator  190 . 
     Thus, the device  120  enables the reader  20  conforming to the aforementioned standard to communicate with the non-standard smart label  110 . The device  120  will now be described in further detail with reference to  FIGS. 3 and 4 . 
     In  FIG. 3 , there is shown the device  120 , the reader  20 , the smart label  110  and the host computer system  30  indicated generally by  300 . The device  120  includes an associated antenna  310  which is mutually coupled to the antenna  60  of the reader  20 . These two antennae  60 ,  310  are operable to magnetically couple at 13.56 MHz whereat the reader  20  is sensitive to load presented by the device  120  to its associated antenna  310 . 
     The antennae  60 ,  310  are loop antennae comprising one or more turns depending upon values of associated tuning capacitors used; the antennae  60 ,  310  provide inductive impedances at their respective terminals tuned by the tuning capacitors to nominally 13.56 MHz. The device  120  further comprises two patch antennae  320 ,  330  for emitting and receiving microwave radiation at 2.45 GHz respectively. The patch antennae  320 ,  330  are nominally of square form and are preferably fabricated as metal film electrodes in the order of 100:m thick on an insulating substrate such as alumina ceramic. 
     In operation, the computer system  30  communicates instructions to the reader module  50  which interprets the instructions and then modulates them onto a 13.56 MHz carrier which is coupled from the antenna  60  to the antenna  310  of the device  120  to generate a received signal therein. The received signal is rectified and translated in the device  120  and then modulated onto a 2.45 GHz carrier which is emitted as the microwave radiation  192  from the patch antenna  320 . The radiation  192  is received at the smart label  110  to generate a corresponding detected signal therein which is processed and then subsequently emitted from the label  110  as the radiation  194 . The patch antenna  330  receives the radiation  194  and generates a received signal which is used in the device  120  to load modulate the antenna  310 . Such load modulation is detected by the reader  20  and used by the reader module  50  to generate data for relaying back to the computer system  30 . Thus, the computer system  30  is capable of communicating through the standard reader  20  and the interface  120  to the non-standard smart label  110  operating at microwave frequencies, namely at 2.45 GHz. 
     In  FIG. 4 , there is shown the device  120  in more detail. The antenna  310  is connected to the supply  140  which includes a network of diodes for rectifying a signal generated by the antenna  310  on receipt of 13.56 MHz magnetically coupled radiation from the reader  20  (not shown in  FIG. 4 ). The antenna  310  is also connected to the translator  160  which also includes a network of diodes for detecting an amplitude modulated signal modulated by the reader onto the 13.56 MHz radiation; the translator  160  thereby generates a demodulated signal which the transmitter  170  receives. The transmitter  170  includes an amplitude modulator which amplitude modulates a 2.45 GHz carrier signal generated by a microwave source  400  with the demodulated signal to provide a modulated microwave signal which propagates from the modulator to the patch antenna  320  wherefrom it is radiated as the radiation  192  to the smart label  110 . 
     The patch antenna  330  is operable to receive the radiation  194  from the smart label  110  and to generate a corresponding received signal. The received signal passes from the antenna  330  to a mixer  410  whereat it is mixed with a 2.45 GHz microwave signal provided from the microwave source  400  to generate a demodulated received signal which the receiver  180  receives and amplifies to generate an amplified output signal. The device  120  also includes a field effect transistor (FET)  420  comprising a source electrode ‘s’ connected to the supply output V−, a drain electrode ‘d’ connected through a resistor R s  to the antenna  310 , and a gate electrode ‘g’ connected to the receiver  180  for receiving the amplified output signal therefrom. 
     The FET  420  is operable to provide a variable load to the antenna  310 , the load varying in response to the amplified output signal applied to the gate electrode ‘g’. The reader  20  is capable of detecting the variable load provided by the FET  420  by virtue of mutual magnetic coupling of the antennae  310 ,  60 . 
     In some situations, the device  120  is not capable of emitting sufficiently powerful microwave radiation to provide power to the label  110  when the label  110  is at relatively greater distances from the device  120 . For operation at greater distances from the device  120 , the smart label  110  must therefore incorporate its own power source, for example a small button cell or solar cell. The smart label  110  preferably includes amplifiers operating in reflection mode, namely incorporating field effect transistors operating at low drain-source currents of a few microamperes and providing amplification by reflecting amplified versions of received microwave signals; reflective amplification is described in our granted patent GB 2 284 323B whose specification is hereby incorporated by reference with regard to reflective amplification at low transistor currents. 
     It will be appreciated by those skilled in the art that modifications can be made to the device  120  without departing from the scope of the invention. For example the device  120  can be modified to interface with tags or smart labels operating at microwave frequencies other than 2.45 GHz. The device  120  can be adapted to operate at any microwave frequency, microwave frequencies being defined as being included in a range of 300 MHz to 90 GHz. The microwave source  400  can, if required, be frequency locked to radiation received at the device  120  from the reader module  50 ; such frequency locking is achievable by incorporating a phase-locked-loop (PILL) device and associated prescalers into the device  120 , the prescalers required for dividing down the signal generated by the source  400  to a suitable frequency acceptable for the PLL device. 
     Moreover, when the device  120 , is operated at lower microwave frequencies, for example around 1 GHz, loop antennae can be alternatively employed instead of the patch antennae  320 ,  330 . Furthermore, at higher microwave frequencies, the patch antennae can be substituted by waveguides coupled through tapered microwave horns. At very high microwave frequencies, quasi-optical microwave components can be employed for emitting radiation from and receiving radiation at the device  120 . 
     Although the device  120  is designed to operate with conventional readers conforming to the aforementioned standard, the device  120  can be adapted to other standards which may become established in the future. 
     The device  120  can be adapted to interface between the reader  20  and an optical reader unit operable using laser interrogation to read a range of 2-dimensional shapes, for example bar codes, affixed or printed onto merchandise; laser interrogation in the context of the invention is defined as using interrogating radiation having a wavelength in a range of 2:m to 150 nm. The reader unit can be designed to interpret and communicate information regarding the shapes through the device  120  to the reader  20 . Moreover, whilst interfacing through the device  120  to the optical reader unit, the reader  20  can be simultaneously operable to interrogate standard 13.56 MHz smart labels or tags offered thereto. Furthermore, the reader  20  can, if required, be substituted with a low frequency 125 kHz RFID reader system and the device  120  adapted to operate at 125 kHz. 
     Where the reader  20  itself is substituted with an optical reader unit, for example a laser bar code reader as employed at contemporary retailing payment counters, the device  120  can be equipped with a liquid crystal display in its interface  130  for interfacing to the optical reader unit. In such a situation, the device  120  can interface between the optical reader unit and smart labels or tags functioning at an interrogation frequency such as 13.56 MHz. 
     Although use of the device  120  for interfacing between 13.56 MHz tag or smart label readers and remote tags or smart labels is described in the foregoing, the device  120  can be adapted to function at other frequencies, for example for interfacing between 125 kHz tag or smart label readers and 13.56 MHz tags or smart labels.