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WO2008118019A2 - Système de transpondeur - Google Patents

Système de transpondeur Download PDF

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Publication number
WO2008118019A2
WO2008118019A2 PCT/NL2008/050173 NL2008050173W WO2008118019A2 WO 2008118019 A2 WO2008118019 A2 WO 2008118019A2 NL 2008050173 W NL2008050173 W NL 2008050173W WO 2008118019 A2 WO2008118019 A2 WO 2008118019A2
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
transponder
transceiver
switch
signal
Prior art date
Application number
PCT/NL2008/050173
Other languages
English (en)
Other versions
WO2008118019A3 (fr
Inventor
Franciscus Hedrikus Elferink
Erik Bert Busking
Original Assignee
Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from EP07105058A external-priority patent/EP1976327A1/fr
Application filed by Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno filed Critical Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
Publication of WO2008118019A2 publication Critical patent/WO2008118019A2/fr
Publication of WO2008118019A3 publication Critical patent/WO2008118019A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q9/00—Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Definitions

  • the invention concerns a transponder system comprising an RF transceiver which is arranged to transmit an RF signal and to receive backscattered reflections of the transmitted signal from a passive transponder which comprises means which are arranged to modulate the backscattered signal.
  • Modulated backscattering is known e.g. from US2006/0132301, disclosing a base unit which transmits a wireless signal to a passive transponder, which passive transponder modulates the impedance of its antenna, thereby altering reflections of the wireless signal off its antenna.
  • the base unit detects the changes in the reflected signal which is used to distinguish data bits.
  • US6147605 discloses a radio frequency identification tag including a first and second antenna element and a radio frequency identification circuit which includes a load modulation circuit, optimized for radio frequency identification applications.
  • US6084503 discloses a radio-interrogated surface- wave technology sensor, in which the sensitive element is an impedance which is electrically connected as termination to a surface-wave structure of the sensor.
  • the known transponder systems thus comprise an RF transceiver which is arranged to transmit an RF signal and to receive backscattered reflections of the transmitted RF signal.
  • a (local) transponder comprises an antenna which is connected to a switch or modulator which is arranged to switch (modulate) the antenna's (terminating) impedance between at least two values, the switch being controlled by digital control means, e.g. keying/modulating the transponder's identification (ID) code or system status information upon reception of the RF signal from the RF transceiver, and thus (modulated) backscattering the transponder's ID code ("ID interrogation”) .
  • ID interrogation e.g. keying/modulating the transponder's identification (ID) code or system status information upon reception of the RF signal from the RF transceiver
  • One aim of the present invention is to "transmit” (rather “to reflect") not (only) fixed data, like a transponder bound ID code or status information but (besides) "variable” signals like voice, produced by a human being and entered into the transponder via a microphone, thus using such modulated backscattering type transponder as a (one-way) communication device, viz. for the transmission of digital voice or data from the side of the transponder to the side of the RF transceiver, wherein, however, the source/location of those voice or data cannot be located by external means, due to the passive nature of the (modulating) transponder.
  • This aim makes the transponder very suitable for e.g. military or similar "secret" operations.
  • a second aim of the present invention is to enable a reliable and precise location of a (e.g. voice/data backscattering) transponder, viz. by using radar, which is, due to its nature (viz. based on reflection time measurement and processing rather than field strength measurement and processing) , excellently suitable for locating objects like e.g. transponders. This aim still strengthens the system's suitability for military etc. operations.
  • Another aim is to use "Frequency Modulated Continuous Wave" (FMCW) radar for the RF transceiver, as FMCW is - rather than e.g. Continuous Wave (CW) or Doppler (based) radar, which is solely able to detect displacement speeds (and thus often used for speed measurements of e.g.
  • FMCW Frequency Modulated Continuous Wave
  • the RF transceiver' s transmitter emits a RF FM chirp signal and receives the backscattered echo from the transponder.
  • the signal propagation delay given by the distance from the transmitter to the transponder (and back) causes a beat signal in the transceiver's receiver.
  • advanced signal processing e.g. Fourier Transform
  • the beat frequency is converted to an accurate distance.
  • the FMCW principle has been illustrated in Fig. 10.
  • the invention aims to provide a system which is able to communicate voice and/or data from the side of the transponder towards a base station (mobile or fixed) , wherein the (passive) source of the data/voice cannot be located by any external means except the system's (FMCW) radar based base station/transceiver, but wherein the position of that source can be determined very accurately by that FMCW radar based base station.
  • FMCW system's
  • the system according to the invention very attractive for military etc. operations, undercover operations etc.
  • the (voice/data modulated) transponder could be part of the communication equipment of a front soldier, commando or a secret agent.
  • the communication towards the side of the transponder i.e.
  • commando, secret agent could be performed in a conventional way, viz. by providing the soldier etc. with a normal small radio receiver as, after all, the position of such (well shielded) military radio receiver cannot be detected by external means (of the enemy) .
  • two-way communication can be achieved without the chance to betray the communicator' s position by any external detection/monitoring system.
  • a transponder system comprising an RF transceiver which is arranged to transmit at least one RF signal and to receive backscattered reflections of said at least one transmitted RF signal;
  • the transponder system moreover, comprising at least one transponder comprising at least one antenna or antenna array connected to a switch or switch array respectively, arranged to switch (or modulate) the terminating impedance of each relevant antenna between at least two values, thus modulating the backscattered signal, and which modulating switch or switch array is controlled by digital control means
  • - the control means are arranged to be controlled by voice or data produced by a human user, thus using the transponder as a communication device for the transmission of digital voice or data from the side of the user to the side of the RF transceiver;
  • the RF transceiver is a FMCW radar based transceiver, arranged to measure the distance and the direction of said at least one transponder to the location of the transceiver
  • the transponder' s antenna has the form of a micro strip or printed antenna, e.g. a micro strip patch antenna or patch antenna, which is very advantageous in view of their efficiency, small (esp. flat) dimensions and their insensitivity for effects of parasitic capacitance, such as the so-called hand (or body) effect.
  • the (impedance modulating) switch or modulator may have any form of an (electronic) switch) , phase shifter, quadrature modulator, (e.g. PLL based) frequency modulator etc., all of them being able to modulate the reflected/backscattered signal.
  • corner reflector or retro reflector antenna may be used.
  • Such reflector can be defined as any instrument used to cause reflected radiation to return along paths parallel to those of their corresponding incident rays; one type, the corner reflector, is an efficient radar target (source: www.answers.com/topic/retroreflector).
  • the transponder system according to the invention comprises at least one antenna array including an array of mainly coplanar antenna surfaces, each single antenna of it including at least two of such coplanar antenna surfaces located around a symmetry axis which is common for all single antennas of the array.
  • the RF transceiver may be arranged to transmit at least two RF signals and to receive reflections of said at least two transmitted RF signals, where the transponder system, moreover, comprises at least two separate transponders, their antenna (s) or antenna array (s) being tuned to different frequencies selected from said at least two RF signals. In this way the relative position of the at least two transponders can be detected.
  • This option may be used to detect the mutual position of at least two transponders within one body, thus enabling to detect that body's altitude and/or inclination, or within separate bodies, enabling the mutual position (altitude and/or inclination) of the bodies w.r.t. each other.
  • the at least two transponders are arranged for keying the relevant switch (or switch array respectively) with a carrier which is modulated by the voice and/or data.
  • the carrier frequencies of different transponders preferably have mutually different values.
  • the transceiver moreover, comprises means which are arranged to discriminate between reflections from the different transponders based on their different carrier frequencies.
  • Fig. 1 shows schematically an exemplary embodiment of a transponder system according to the invention
  • Fig. 2 shows the structure of an antenna which preferably may be used, in plan view, Fig. 3 in bottom view
  • Fig. 4 shows the circuitry of the embodiment of the transponder part of Fig. 1 more in detail, Fig. 5 including means for setting and/or programming the transponder part
  • Fig. 6 shows the radiation pattern of the exemplary antenna structure
  • Fig. 7 shows a planar corner reflector configuration
  • Fig. 8 shows a system using two RF frequencies for e.g. altitude and/or inclination detection.
  • Fig. 9 shows an alternative system for e.g. altitude and/or inclination detection, using discriminating frequencies of carrier waves modulated by voice and/or data;
  • Fig. 10 gives a general illustration of FMCW radar;
  • Fig. 11 shows a transponder including a reflection booster module .
  • the system shown in Fig. 1 comprises an FMCW transceiver 1 which is arranged to transmit an FMCW signal 2 and to receive reflections 3 of the transmitted FMCW signal 2.
  • the transponder system further comprises an FMWC transponder 4 which comprises an antenna 5 which is tuned to the FMWC signal's frequency.
  • the antenna 5 is connected to a switch 6 which is arranged to switch the antenna's impedance between at least two values; the switch is controlled by digital control means 7, which may be a microcontroller, which is fed by a battery 8.
  • the control module 7 is controlled by digital data from a voice module, comprising a microphone 9 and an A/D converter 10.
  • the circuitry of Fig. 1 is thus arranged to control the reflectivity of the dipole 5 by means of the switch 6, which is controlled - via de A/D converter 10 and the microcontroller 7 - by any signal picked up by the microphone 9, the (analogue) microphone signal being converted, by the A/D converter 10, to a digital signal, which the microcontroller 7 uses to key the switch 6 with a carrier wave which is modulated by voice (or data) and thus to key the impedance of the dipole 5 with said carrier.
  • the dipole 5 receives a signal 2 from transceiver 1, the extent in which the signal 2 will be reflected to the transceiver 1 is thus modulated by the digitized microphone signal, causing that de transceiver 1 is able, by measuring the reflected (backscattered) signal strength to "read out" the digital reflections modulated by the microphone input. Subsequently the voice (or data) signal can be obtained by demodulating the reflected signal, e.g. using the carrier wave frequency.
  • the transponder 4 can act as a remote (secret) microphone, which can only be detected by means of a (directional) radar signal. Discovery of such a (passive modulated) transponder is substantially more difficult than a secret microphone system including a transmitter which broadcasts a modulated RF carrier.
  • the signals from different transponders may be discriminated.
  • different RF (radar) frequencies may be used which, however, will require transceivers using multiple RF frequencies. Both alternatives will additionally be discussed hereinafter.
  • the current consumption of the microcontroller, the AD- converter and the switch is that low that e.g. a lithium button battery cell may be sufficient for uninterrupted use during several years.
  • the transponder may - under control of the microcontroller - be activated only for restricted periods. For the main part of the time the transponder may be then in a so-called sleep mode .
  • the antenna is a micro strip or printed antenna, more preferably a micro strip patch antenna or patch antenna, the structure of which is shown separately in Figs. 2 and 3.
  • micro strip antennas also known as printed antennas
  • a patch antenna is a narrowband, wide-beam antenna fabricated e.g. by etching the antenna element pattern in metal trace bonded to an insulating substrate. Because such antennas have a very low profile, are mechanically rugged and can be conformable, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices.
  • Micro strip antennas are also relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry. They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency.
  • An advantage inherent to patch antennas is the ability to have polarization diversity.
  • Patch antennas can easily be designed to have Vertical, Horizontal, Right Hand Circular (RHCP) or Left Hand Circular (LHCP) Polarizations with a single antenna feed point. This unique property allows patch antennas to be used in many types of communications links that may have varied requirements.
  • Fig. 2 shows a plan view of configuration of the patch antenna as used in the present embodiment.
  • the surfaces 11 and 12 of the patch antenna are conductive layers supported by an intermediate carrier 13 of an electrically insulating material.
  • the patch antenna has a square shape, one side having a length of ⁇ /4.
  • the location of the feed point 14 is determinative for the impedance and the polarization of the antenna.
  • Fig. 3 shows the bottom view of the antenna, showing its ground surface 12 up.
  • Fig. 4 shows the configuration of the transponder more in detail, viz. a ⁇ /4 line 14 connected with the switch.
  • the combination of a make-and-break type switch 6 and the ⁇ /4 line performs better than using an on-off type switch as shown in Fig. 1.
  • Fig. 5 shows that the processor 7 may be set up and/or programmed by using an inductive coupling comprising two coils 15 and 16 to be able to control the processor 7 from an external programmer 17.
  • Fig. 6 shows a sensitivity curve of the patch antenna.
  • the antenna's sensitivity is high and has an opening angle of about 60°. From the rear side the sensitivity is about zero, thus enabling the transponder e.g. to be used in the vicinity of a (human) body without being hindered by any "hand effect", which would give signal attenuation.
  • the transponder system shown in Fig. 7 comprises an antenna array including an array of mainly co- planar antenna surfaces 5, e.g. provided on a carrier 13, each single antenna of it including at least two of such coplanar antenna surfaces 5 located around a symmetry axis 18 which is common for all single antennas of the array.
  • Each single antenna (formed by two antenna surfaces 5) of the antenna array is connected to a switch (6) which is part of a switch array, arranged to switch the terminating impedance of each antenna between at least two values; the switches 6 of the switch array are controlled by the digital control means 7.
  • Fig. 8 illustrates that the FMCW transceiver 1 may be arranged to transmit e.g. two FMCW signals 2a, 2b and to receive reflections 3a, 3b of those two transmitted FMCW signals.
  • the transponder system moreover, comprises (e.g.) at least two separate transponders 4a, 4b.
  • Their antenna (s) or antenna array (s) are tuned to different frequencies selected from said at least two FMCW signals, e.g. transponder 4a to the frequency of the signals 2a and 3a, transponder 4b to the frequency of signals 2b and 3b.
  • Fig. 9 shows an alternative and preferred system for e.g. altitude and/or inclination detection, using different frequencies of carrier waves which are modulated by voice and/or data.
  • two transponders 4a, 4b comprise digital modules 7a, 7b arranged for keying the relevant switches or switch array (not shown here) with carriers modulated by voice and/or data.
  • the carrier frequencies of both transponders have different values, indicated by fl and f2.
  • the transceiver 1 comprises means (not shown) which are arranged to discriminate between reflections from the different transponders (4a, 4b) based on their different carrier frequencies f1 and f2.
  • Fig. 10 gives a general illustration of FMCW radar.
  • the radar response is sampled which results in a time series of n samples.
  • FFT fast Fourier transform
  • a window should be used to eliminate the effect of start and end discontinuities.
  • Each bin from this range FFT represents the amplitude of the reflectivity of the environment on a certain distance.
  • Each sweep will produce one range FFT.
  • the sweep number as the new discrete time it is possible to define a new n dimensional time series (the nth range bin amplitude as function of the sweep number) .
  • the transponder information can be recovered (data recovery) from this new time series. This results in an ID code for a given range bin.
  • Fig. 11 shows an optional addition to the circuitry of the transponder, enabling it to boost its reflection power.
  • the circuitry of Fig. 11 is similar to Fig. 4, except the addition of a booster module which is formed by an RF amplifier 20 and a frequency shifter 21.
  • the amplifier is able to amplify ("boost") the signal received by the antenna and to supply the amplified signal back to the same antenna.
  • boost amplify
  • the transmitted signal from the received signal, e.g. by shifting its (basic) carrier frequency from f to (f+fojffset) ) •
  • the frequency offset is thus that the frequencies f and
  • the (f+ fo(ffset) ) belong to different frequency bands.
  • the (basic, i.e. not FM modulated) transmission frequency of the transceiver 1 is f and its (basic) reception frequency is (f+fo(ffset) ) • ⁇ n
  • booster module 20,21 improves the transponder's gain and thus its usability.
  • the booster module can be enabled - via processor 7 - solely when voice is coming in from the user's microphone, thus providing that the transponder is quite silent when not actively in use.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

L'invention concerne un système de transpondeur qui comprend un émetteur-récepteur radar FMCW (1) conçu pour transmettre un signal FMCW (2) et pour recevoir les réflexions rétrodiffusées (3). Le transpondeur (4) selon l'invention comporte une antenne (5) reliée à un commutateur (6). Ce modulateur sert à moduler l'impédance de sortie de l'antenne et de ce fait à moduler le signal rétrodiffusé. Il est commandé grâce à des moyens de commande numériques (7, 10) destinés à être contrôlés par la voix (9) ou par des données fournies par un utilisateur humain. Le transpondeur joue par conséquent le rôle d'un dispositif de communication transmettant une voix ou des données numériques entre l'utilisateur et l'émetteur-récepteur. Cette communication ne peut pas être interceptée par un système externe. L'émetteur-récepteur FMCW est capable de mesurer la distance et la direction du transpondeur. Ce système s'avère très intéressant dans le cadre d'opérations militaires, etc. Le signal réfléchi peut subir une déviation de fréquence et être amplifié par un module suramplificateur (20, 21).
PCT/NL2008/050173 2007-03-27 2008-03-26 Système de transpondeur WO2008118019A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP07105058A EP1976327A1 (fr) 2007-03-27 2007-03-27 Système de détection
EP07105058.7 2007-03-27
EP07112606.4 2007-07-17
EP07112606 2007-07-17

Publications (2)

Publication Number Publication Date
WO2008118019A2 true WO2008118019A2 (fr) 2008-10-02
WO2008118019A3 WO2008118019A3 (fr) 2008-11-20

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PCT/NL2008/050173 WO2008118019A2 (fr) 2007-03-27 2008-03-26 Système de transpondeur

Country Status (1)

Country Link
WO (1) WO2008118019A2 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102073834A (zh) * 2009-11-20 2011-05-25 数伦计算机技术（上海）有限公司 射频标识系统
US8362961B2 (en) 2009-11-03 2013-01-29 Honeywell International Inc. Modulated antenna for wireless communications
EP2597484A1 (fr) * 2011-11-24 2013-05-29 Nederlandse Organisatie voor toegepast -natuurwetenschappelijk onderzoek TNO Système de radar FMCW actif et procédé pour le transfert de données l'utilisant
DE102012003861A1 (de) * 2012-02-27 2013-08-29 Giesecke & Devrient Gmbh Kontaktlos-Transaktion mit einem Kontaktlos-Kommunikationselement

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6657580B1 (en) * 1999-03-26 2003-12-02 Isis Innovation Limited Transponders
DE10239303B4 (de) * 2002-08-27 2006-08-03 Siemens Ag Energieautark modulierter Backscatter-Transponder

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8362961B2 (en) 2009-11-03 2013-01-29 Honeywell International Inc. Modulated antenna for wireless communications
CN102073834A (zh) * 2009-11-20 2011-05-25 数伦计算机技术（上海）有限公司 射频标识系统
EP2597484A1 (fr) * 2011-11-24 2013-05-29 Nederlandse Organisatie voor toegepast -natuurwetenschappelijk onderzoek TNO Système de radar FMCW actif et procédé pour le transfert de données l'utilisant
WO2013077737A1 (fr) * 2011-11-24 2013-05-30 Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno Système de radar fmcw et procédé pour un transfert de données l'utilisant
DE102012003861A1 (de) * 2012-02-27 2013-08-29 Giesecke & Devrient Gmbh Kontaktlos-Transaktion mit einem Kontaktlos-Kommunikationselement

Also Published As

Publication number Publication date
WO2008118019A3 (fr) 2008-11-20

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