EP1936740B1 - System and method for measuring movement information according to the Doppler principle - Google Patents

Description

The invention relates to an antenna for measuring a movement information, in particular speed or distance, according to the Doppler principle, a transponder with such an antenna, a system with transponders and a reading antenna and a corresponding method.

A transponder has an antenna and a chip which can be coupled or coupled to the antenna and which are arranged on a carrier. An exemplary microwave transponder according to the prior art is in Fig. 1 shown. The chip stores data which are contactlessly accessible via the antenna using a suitable reading device.

Transponders are used for example in the so-called ticketing area as electronic tickets, for example in public transport. Each passenger liable to pay carries a transponder in the use of affected means of public transport, in which data is stored, which allow a calculation of the fare to be paid for the use. Optionally, a credit can be stored in the chip, which is used directly for the payment of the fare.

As a transponder for ticketing, for example, remote coupling systems are used with a range of up to 1 m, more precisely typically proximity-coupling contactless smart cards according to the ISO standard 14443, a range of about 7 to about 15 cm and operate at a resonant frequency of 13.56 MHz. For example, transponder detection readers are located at entrances to restricted access areas in the vicinity of the means of transport, such as platforms and / or at doors of transportation, and require that one or both of them passengers alighting, hold their transponder directly to the reader and thereby register their entry or exit. Such a system, which registers passengers entering and / or exiting, is also referred to as a check-in / check-out system.

Alternatively, long-range transponders are used for ticketing in so-called long-range systems, with a range of 1 m to typically 10 m, which operate at a resonant frequency in the microwave range of 2.45 GHz, 915 MHz or 868 MHz. Transponders in long-range systems also include transponders with a resonant frequency of 5.8 GHz or 24.125 GHz. In long-range systems, an incoming or outgoing passenger does not have to actively hold his transponder to a reader, but the transponder carried in the pocket, for example, is detected automatically as soon as the passenger gets into the transmission range of the reader. For example, a reading device is mounted on doors to a means of transport, which wakes up and registers the transponder from an idle state. Within the means of transport, a monitoring reader is mounted which continuously monitors the presence of registered transponders at short intervals. A fare is determined from the presence of the transponder within the means of transport or from the distance traveled during the journey. Such a system, in which the presence of passengers is registered, is also referred to as Be-in / Be-out system. An example of a Be-in / Be-out system is the Dresden pilot project ALLFA (see for example http://efa.vvo-online.de/allfa/index.html).

Transponders are still used, for example, in warehousing. Here, a transponder is mounted on each stored goods or containers for storage of goods, in which specific for the goods Data are stored. To read out the data from transponders, a reader must reach the range of the transponder.

Relatively long-range measurements using transponders are possible according to the Doppler principle.

The principle of measuring a movement information, in particular speed or distance, according to the Doppler principle by means of a microwave transponder, for example, in " Klaus Finkenzeller, RFID Handbook, 2nd edition 2000, Carl Hanser Verlag Munich Vienna, ("RFID Handbook") Chapter 10.4.2 An electromagnetic wave of a certain frequency emitted from a reading antenna to the transponder and reflected back from the transponder to the reading antenna is distorted depending on the relative movement of the reading antenna and the transponder, and if the reading antenna and the transponder move towards each other, the wave reflected on the transponder is compressed As the reading antenna and the transponder move away from each other, the reflected wave is stretched and thus the frequency detected at the reading antenna is reduced relative to the frequency of the transmitted wave The frequency emitted by the reading antenna and the reflected wave frequency detected at the reading antenna are referred to as the Doppler frequency. By measuring the Doppler frequency, the relative velocity between the transponder and the reading antenna can be determined In addition, a distinction can be made between a transponder moving towards the reading antenna and a transponder moving away from the reading antenna.

A Doppler radar speedometer for the microwave range is, for example, in DE 3219 819 C2 described. In the speedometer, a Doppler radar sensor is attached to a moving body and emits microwaves that are reflected from the (stationary) ground. Parts of the emitted and reflected microwaves are mixed, thereby generating Doppler signals from which the velocity of the moving body is derived.

US 5,680,459 describes an electronic identification system for an automatic fare collection with multiple transponders, in which the simultaneous identification of multiple transponders is made possible by the fact that the individual transponders are read in different time windows.

DE 100 56 148 A1 describes a contactless chip card with two antennas for two different frequencies, so that the contactless chip card can be operated with different readers.

mit der Lichtgeschwindigkeit c. Bei einer Resonanzfrequenz des Transponders von 868 MHz und einer relativen Bewegungsgeschwindigkeit zwischen Transponder und Lesegerät von 1 m/ s ergibt sich eine Dopplerfrequenz von 6 Hz, die zu messen fast unmöglich ist. Durch eine Erhöhung der ausgesendeten Frequenz kann in anderen Anwendungen die Dopplerfrequenz erhöht werden, beispielsweise bei der Fahrzeugerfassung. Zudem ist die Bewegungsgeschwindigkeit bei der Fahrzeugerfassung in der Regel hoch, so dass der Dopplereffekt problemlos messbar ist. In den Bereichen z.B. Ticketting und Lagerhaltung ist zu berücksichtigen, dass einerseits die Sendefrequenz der verwendeten Lesegeräte für die Transponder durch Normen wie z.B. ISO 18000-6 oder ISO 18000-4 festgelegt sind und im Mikrowellenbereich von ungefähr 800 MHz bis ungefähr 6 GHz liegen müssen. Die Bewegungsgeschwindigkeiten v bei z.B. Ticketting und Lagerhaltung sind andererseits in aller Regel gering, z.B. in der Größenordnung von 1 m/s oder sogar darunter. Eine direkte Übertragung eines für beispielsweise Fahrzeugerfassung bekannten Systems der Geschwindigkeitserfassung mittels Doppler-Effekt auf Bereiche wie Ticketting oder Lagerhaltung, mit niedrigen Frequenzen und Bewegungsgeschwindigkeiten, ist daher nicht möglich, da die Dopplerfrequenz bei einer zu niedrigen Frequenz liegen würde.In principle, a measurement of a movement information, in particular speed or distance, according to the Doppler principle would also be desirable, for example in ticketing or in storage. This would allow long-range measurements without the need to hold the transponder directly to a reader, thus making the capture of transponders comfortable. The Doppler frequency fD results from the difference of the emitted frequency f and the frequency f 'distorted by the relative movement with relative velocity v of the reading device and transponder $$\mathrm{fD}=\mathrm{f\; \text{'}}-\mathrm{f}=\mathrm{f}*\left(\mathrm{1}+\mathrm{v}/\mathrm{c}\right)-\mathrm{f}=\mathrm{f}*\mathrm{v}/\mathrm{c}$$

with the speed of light c. At a resonance frequency of the transponder of 868 MHz and a relative movement speed between transponder and reader of 1 m / s results in a Doppler frequency of 6 Hz, which is almost impossible to measure. By increasing the emitted frequency, the Doppler frequency can be increased in other applications, for example in vehicle detection. In addition, the speed of movement during vehicle detection is usually high, so that the Doppler effect is easily measurable. In the areas of eg ticketing and warehousing, it should be noted that, on the one hand, the transmission frequency of the transponder transponders used is defined by standards such as ISO 18000-6 or ISO 18000-4 and must be in the microwave range of approximately 800 MHz to approximately 6 GHz. On the other hand, the speeds of movement v in, for example, ticketing and storage are generally low, for example of the order of magnitude of 1 m / s or even less. Direct transmission of a known for example for vehicle detection system speed detection by Doppler effect on areas such as ticketing or storage, with low frequencies and movement speeds, is therefore not possible because the Doppler frequency would be too low a frequency.

Frequency-selective surfaces (FSS) are periodic conductive structures on surfaces which have filter properties relative to electromagnetic waves. Depending on the geometric dimensioning of the structures, low-pass, high-pass, band-pass or band-stop filter properties can thus be realized in relation to an incident electromagnetic wave.

Frequency-selective surfaces have been known for almost 100 years (first patents in 1919 by Marconi) and have been intensively studied since the 1960s. Known applications are z. B. building structures such as Radar domes, which should be uninterrupted for the radar frequency range, window covers for microwave ovens, which should achieve a particularly high attenuation in the microwave frequency range, or even wallpapers, which block specific frequency ranges (eg Bluetooth), but adjacent frequency ranges pass unhindered (z B. mobile communications). Frequency-selective layers are used in the micro and millimeter wave range for the effective use of reflector antennas, as filters and artificial dielectrics, as a mirror to increase the pumping efficiency of lasers and as polarizers, beam splitters or filters and in the optical field to increase the efficiency of solar panels.

If there are conductive areas on a nonconductive surface, we speak of patch geometries, if there are nonconductive areas on a conductive surface, this is referred to as aperture geometries.

When an electromagnetic wave hits an FSS, it generates electrical currents on the conductive areas of the FSS. As a result, a part of the wave can be reflected when hitting the layer. The complex amplitudes of the reflected or transmitted components, based on the amplitude of the incident wave, are referred to as reflection or transmission coefficients. The so-called backscatter cross section of the FSS for the incident wave indicates what proportion of the incident wave is reflected at the FSS. If the wavelength of a wave incident on an FSS is of the same order of magnitude as the dimensions of the elementary cell (individual regions) of the FSS, strong resonances occur as the frequency of the incident wave changes. When a patch geometry is excited by an incident electromagnetic wave, essentially the entire wave is reflected at the resonance frequency-and in real FSS in a surrounding frequency range. The backscatter cross section of FSS for the incident wave has a maximum at the FSS in patch geometry at the resonant frequency. In contrast, in the aperture geometry, the incident wave is substantially completely transmitted at the resonant frequency. The backscatter cross section of the FSS for the incident wave has a minimum at FSS in aperture geometry at the resonant frequency. By coupling a load resistor to the FSS, at a frequency of the incident electromagnetic wave near the resonance frequency of the FSS, the backscatter cross section of the FSS for the wave can be largely changed. As a result, by coupling or decoupling a suitable load resistance of the reflected at the RSS portion of the electromagnetic wave can be varied widely. The principle of the backscatter cross section of an antenna by coupling or uncoupling a suitable load resistance is also referred to as a modulated backscatter cross section and is described, for example, in the aforementioned RFID manual, Chapter 4.2.4.

WO 2006/027112 A1 describes the use of a frequency-selective surface as an authenticity feature for eg banknotes or chip cards.

US 4,917,458 A discloses an arrangement of a frequency-selective surface, which is superimposed with an antenna to accommodate the antenna to save space in the frequency-selective surface area.

WO 92/16031 A1 discloses a bandpass filter having an antenna structure with a frequency selective surface.

DE 196 52 324 A1 describes a transponder with a periodic antenna structure in patch geometry.

The invention is based on the object to enable measurements of motion information, in particular speed or distance, according to the Doppler principle also for systems with transponders whose Doppler frequency is hardly or not measurable without further precautions.

The object is achieved by a system according to claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

The system according to the invention for managing the use of at least one paid means of transport by passengers comprises: for each pay passenger at least one transponder, each paying passenger using the means of transport being obliged to carry the transponder during use of the means of transport; at least one reading antenna mounted on an access to the means of transport adapted for communication with the transponder at the second resonance frequency and capable of measuring movement information, in particular speed or distance, of a transponder relative to the reading antenna according to the Doppler principle at the second resonance frequency is such that between a transponder-equipped passenger who enters or leaves the means of transport or a restricted access area surrounding the means of transport is distinguishable.

The transponder is equipped with an antenna according to one of the embodiments and variants described below and with a chip electrically coupled or coupleable to the antenna. Optionally, the antenna and the chip are arranged on an arbitrarily designed carrier. Optionally, the transponder is designed as a label, (contactless) chip card, voluminous transponder or transponder of other design.

The antenna is provided for measuring movement information, in particular speed or distance, according to the Doppler principle and has an antenna surface made of a conductive material. The antenna has a predetermined antenna structure by which a first resonance frequency of the antenna is set. The antenna is characterized in that the antenna surface is provided with a frequency-selective surface (FSS), by which a second resonance frequency of the antenna is set, which is different from the first resonance frequency.

The second resonant frequency results in a second Doppler frequency which is also at a different frequency than the Doppler frequency due to the first resonant frequency, assuming the same relative velocity between the antenna and a reader antenna of a reader.

With the antenna according to claim 1, therefore, a possibility is provided to perform measurements of motion information, in particular speed or distance, according to the Doppler principle for systems with transponders whose Doppler frequency is barely or not measurable without further precautions, since the Doppler frequency too low or is too high to measure.

The inventive system according to claim 1 is thus a ticketing system. It is particularly applicable for public transport. The system according to the invention is particularly convenient compared to known ticketing systems. Since in the system according to the invention the detection the transponder is done according to the Doppler principle, a very long-range measurement is possible. Consequently, it is possible to detect the boarding and disembarking of passengers without having to hold their transponder used as a ticket to a reader, which is an advantage over conventional check-in / check-out systems. On the other hand, within the vehicle no surveillance antenna need be provided to monitor the presence of detected passengers throughout the ride, which is an advantage over conventional long-range loading / unloading systems.

In the system according to the invention for managing the use of at least one payable means of transport, the second resonant frequency is used to measure movement information according to the Doppler principle, in particular to detect the entry and exit of passengers. On the other hand, communication with the chip of the transponder preferably takes place at the first resonance frequency, which is determined, for example, by a standard such as e.g. ISO 18000-6 or ISO 18000-4, optionally according to any prior art communication method.

The reader antenna is optionally configured to communicate with the antenna, but not to communicate with the chip. Optionally, communication with the chip is possible at the first resonant frequency, optionally with a suitable reader other than the reader antenna.

For example, a door or a doorway or a doorway or the like of a means of transportation (eg, bus, subway train, railroad car, tramcar, etc.) may be provided as access to the means of transportation be. For example, access to a platform may be provided as access to an access restricted area.

In the system, a reader antenna is optionally arranged at each passenger access access to a means of transportation or to the restricted access area.

Optionally, between a transponder-equipped passenger entering or leaving the means of transport or a restricted access area surrounding the means of transport is distinguishable in that the reading antenna for the Doppler measurement has a spatial directional characteristic such that the transponder is oriented in an inward direction the means of transport or the restricted access area with the reading antenna is more or less detectable than in an outside direction out of the means of transport or the restricted access area. For example, a reading antenna on a doorway of a vehicle (bus, train, etc.) has a directional characteristic directed toward the exterior of the vehicle. An ascending passenger is thus detected as a transponder to be moved to the reading antenna until the passenger passes through the doorway. As soon as the passenger has passed through the doorway, his transponder inside the means of transport is no longer detected by the reading antenna. A descending passenger is first detected as soon as he passes through the doorway from inside to outside and is then detected as moving away from the reading antenna transponder.

The system further optionally has a reading device attached to an access to the means of transport, which is set up for communication with the transponder, in particular with the chip of the transponder, at the first resonance frequency. The reading device is for example in particular adapted to write fare information about a payable by the passenger fare in the chip of the transponder or read from the chip.

Optionally, the second resonant frequency is at a higher frequency than the first resonant frequency. This alternative of the invention is particularly preferred for applications such as ticketing, warehousing, animal monitoring, and the like, since relatively low first resonance frequencies are enshrined in standards and, on the other hand, the relative movements of the antenna and reader antenna of a reader are low.

As is known from the prior art, the frequency-selective surface consists of a periodically structured conductive structure.

Optionally, the frequency-selective surface is designed in aperture geometry, wherein the electrically conductive antenna surface is provided with a periodic arrangement of apertures. The apertures may be designed as openings in the electrically conductive antenna surface and may optionally be filled with a dielectric.

Optionally, the frequency-selective surface is designed in patch geometry, the antenna surface being provided with a periodic array of electrically conductive elements which are electrically isolated from the antenna surface, e.g. through a dielectric interlayer.

The first resonant frequency is optionally in the microwave range, in particular in the frequency range from about 800 MHz to about 6 GHz, in particular at a frequency of 868 MHz or 915 MHz or 2.45 GHz, optionally at a frequency fixed by a standard.

Optionally, the antenna with the frequency-selective surface further comprises an adjusting device with which a backscatter cross section of the frequency-selective surface in a frequency range encompassing at least the second resonant frequency can be changed. The adjusting device may have one or more load resistors, for example, in the case of a frequency-selective surface in patch geometry, which can be selectively coupled to or decoupled from the conductive elements. Depending on the load resistance coupled to the conductive elements, the backscatter cross section of the antenna is different due to the frequency-selective surface. In this variant, the frequency-selective surface can optionally be switched on and off in relation to a reading antenna of a reading device which emits electromagnetic waves at a fixed frequency, in particular the second resonance frequency.

• Die Transponder haben - wahlweise in Patchgeometrie gestaltete - frequenzselektive Oberflächen und eine Einstelleinrichtung, mittels derer ein Rückstreuquerschnitt der frequenzselektiven Oberfläche in einem zumindest die zweite Resonanzfrequenz umfassenden Frequenzbereich veränderbar ist.
• Die Transponder sind in einem Grundzustand des Systems nicht aktiviert, wobei die Transponder bei der zweiten Resonanzfrequenz einen Grundzustand-Rückstreuquerschnitt haben.
• Die Leseantenne für die zweite Resonanzfrequenz und die Leseeinrichtung für die erste Resonanzfrequenz sind derart zum Zusammenarbeiten eingerichtet, dass mindestens ein beliebiger einzelner Transponder durch die Leseeinrichtung für die erste Resonanzfrequenz (d.h. z.B. die Leseeinrichtung für insbesondere die Kommunikation mit dem Chip) mittels der Einstelleinrichtung aktivierbar ist, indem an dem Transponder ein vom Grundzustand-Rückstreuquerschnitt unterschiedlicher Aktiv-Rückstreuquerschnitt, insbesondere ein extremer - wahlweise maximaler oder minimaler - Rückstreuquerschnitt, einstellbar ist, und an dem aktivierten einzelnen Transponder bei der zweiten Resonanzfrequenz eine Messung einer Bewegungsinformation nach dem Doppler-Prinzip bei der zweiten Resonanzfrequenz durchführbar ist. Wahlweise wird der Transponder zudem durch die Leseeinrichtung bei der ersten Resonanzfrequenz mit Energie versorgt.

The system, which additionally has a reading device adapted to communicate with the transponder at the first resonant frequency, is optionally further configured as follows.

• The transponders have frequency-selective surfaces-optionally designed in patch geometry-and an adjusting device by means of which a backscatter cross section of the frequency-selective surface can be changed in a frequency range encompassing at least the second resonant frequency.
• The transponders are not activated in a ground state of the system, the transponders having a ground state backscatter cross section at the second resonant frequency.
• The second resonance frequency reading antenna and the first resonance frequency reading device are arranged to cooperate such that at least one of the individual transponders is read by the first resonance frequency reading device (ie, the reading device for in particular the communication with the chip) can be activated by means of the setting device, in that on the transponder a backscatter cross section differing from the ground state backscatter cross section, in particular an extreme - optionally maximum or minimum - backscatter cross section, and at the activated individual transponder at the second resonance frequency, a measurement of motion information according to the Doppler principle at the second resonant frequency is feasible. Optionally, the transponder is also powered by the reading device at the first resonant frequency with energy.

In the system designed in this way, therefore, a transponder is woken up at the "fundamental frequency" of the transponder (first resonance frequency) and then the Doppler measurement is carried out on the alert transponder at the "FSS frequency" (second resonance frequency). As a result, individual transponders for the measurement according to the Doppler principle can be isolated in a targeted manner in the case of a large number of transponders present at the same time in order to avoid collisions that could occur due to a simultaneous communication with the multiplicity of transponders.

Optionally, in the system described above, in a predetermined spatial area, e.g. at a single access, e.g. at a single doorway to a transport, only a single transponder activated at a time. In this way, collisions are avoided by a simultaneous communication with the plurality of transponders.

In a method for measuring movement information according to the Doppler principle with the system described above, at least one, optionally exactly one, any individual transponder through the Reading device for the first resonant frequency activated by the setting and carried out on the activated individual transponder, a measurement of motion information according to the Doppler principle at the second resonant frequency.

Fig. 1

einen Transponder mit einem Chip und einer Antenne, gemäß dem Stand der Technik;

Fig. 2

einen Transponder mit einem Chip und einer Antenne mit einer FSS in Aperturgeometrie, gemäß einer ersten Ausführungsform der Erfindung;

Fig. 3

einen Transponder mit einem Chip und einer Antenne mit einer FSS in Patchgeometrie, gemäß einer zweiten Ausführungsform der Erfindung.

In the following the invention will be explained in more detail with reference to exemplary embodiments and with reference to the drawing, in which:

Fig. 1

a transponder with a chip and an antenna, according to the prior art;

Fig. 2

a transponder with a chip and an antenna with an FSS in aperture geometry, according to a first embodiment of the invention;

Fig. 3

a transponder with a chip and an antenna with an FSS in patch geometry, according to a second embodiment of the invention.

Fig.1 shows a transponder 100 with a chip 110 and an antenna 120, which are arranged on a carrier 130, according to the prior art. The transponder 100 is designed here by way of example as a chip card in the format ID-1 according to ISO 7810. The antenna 120 has a first resonance frequency at 868 MHz due to its design and its geometric dimensions. For this frequency, the in Fig. 1 exemplified planar antenna design, in which the antenna 120 has a planar antenna surface.

Fig. 2 shows a transponder 200 with a chip 210 and an antenna 220 on a carrier 230, wherein the antenna 220 with an FSS 240 in aperture geometry is provided, according to a first embodiment of the invention. Compared to the transponder 100 off Fig.1 has the transponder 200 off Fig. 2 at the antenna surface of the antenna 220, a plurality of periodically arranged apertures (apertures) 250 which in their entirety constitute the frequency selective surface FSS 240. The antenna 220 has a first resonant frequency at 868 MHz due to its design and geometrical dimensions. Due to the FSS 240, the antenna 220 has a second resonant frequency at a frequency of over 10 GHz, typically about 70 ... 150 (200) ... GHz. The Doppler frequency corresponding to the second resonant frequency is for v = 1 m / s and a second resonant frequency of 200 GHz in the order of magnitude of approximately 1300 Hz, ie in a well-measurable frequency range.

Fig. 3 1 shows a transponder 300 with a chip 310 and an antenna 320 with a FSS 340 in patch geometry, arranged on a carrier 330, according to a second embodiment of the invention. Compared to the transponder 100 off Fig. 1 has the transponder 300 off Fig. 3 on the antenna surface of the antenna 320, a plurality of periodically arranged conductive elements 350, which in their entirety form the frequency-selective surface FSS 340. Arranged between the antenna surface of the antenna 320 and the conductive elements 350 of the FSS 340 is an electrically insulating intermediate layer 360, with which the antenna 320 and the conductive elements 350 of the FSS 340 are electrically isolated from each other. The intermediate layer 360 is formed from a dielectric, for example from a plastic, for example from a plastic film. The individual conductive elements 350 are electrically connected to each other. The interconnected conductive elements 350 are electrically coupled or coupled to the chip 310, eg via one or more supply lines and logic lines. To the conductive elements 350 is further on - preferably variable - load resistor (not shown separately) can be coupled. The layer structure of the transponder 300 with the carrier 330, the antenna 320 arranged on the carrier 330, the insulating intermediate layer 360 arranged on the antenna 320 and the electrically conductive elements 350 arranged on the intermediate layer 360 is in the lower part of FIG Fig. 3 in a sectional view along the line AB in the upper part of Fig. 3 illustrated. The antenna 320 has a first resonant frequency at 868 MHz due to its design and geometric dimensions. Due to the FSS 340, the antenna 320 has a second resonant frequency at a frequency of approximately well over 10 GHz, eg 70 ... 150 (200) ... GHz.

The conductive elements 350 of the transponder 300 Fig. 3 are designed as rectangular areas. Optionally, the elements 350 may have any other suitable shape. Similarly, the apertures 250 of the transponder 200 can be made Fig. 2 have any suitable shape.

In order to carry out a measurement according to the Doppler principle at the second resonant frequency on a transponder 300 with a reading antenna, a suitably dimensioned load resistor is coupled to the conductive elements 350. The signal for coupling the load resistor is transmitted to the chip 310 at the first resonant frequency with a suitable suitable reader. The chip 310 causes the coupling of the load resistor. By coupling the load resistor, the backscatter cross-section of the frequency-selective surface 340, which is low without the load resistor, is increased to a maximum value. As a result, the transponder 300 is activated and the Doppler measurement at the second resonance frequency can be performed.

Claims (12)

1. A system for administrating the use by passengers of at least one transport means requiring payment, with

   - at least one transponder (200, 300) utilized as an electronic ticket for means of transport requiring payment, with an antenna (220, 320) having an antenna area that is made of a conductive material and has a predetermined antenna structure, by which a first resonance frequency of the antenna is adjusted, and with a chip (210, 310) that is or can be electrically coupled with the antenna (220, 320), and

   - at least one reading antenna attached at an access to the transport means or to a restricted-access area surrounding the transport means,
   characterized in that

   - the antenna (220, 320) is adapted to measure movement information, in particular speed or distance, in accordance with the Doppler principle, wherein the antenna area is supplied with a frequency-selective surface (240, 340) by which a second resonance frequency of the antenna (220, 320) is adjusted that is different from the first resonance frequency,
   and in that

   - the reading antenna is adapted for communication with the transponder (200, 300) at the second resonance frequency, and with the antenna it is possible to measure, in accordance with the Doppler principle, movement information, in particular speed or distance, of a transponder (200, 300) relative to the reading antenna, in such a fashion that it is possible to distinguish between a passenger equipped with a transponder (200, 300) entering and leaving the transport means or the restricted-access area surrounding the transport means.
2. The system according to claim 1, wherein a reading antenna is arranged at each access to a transport means or to the restricted-access area provided for passengers.
3. The system according to claim 1 or 2, wherein it is possible to distinguish between a passenger equipped with a transponder (200, 300) entering and leaving the transport means or a restricted-access area surrounding the transport means by the reading antenna having a spatial directional characteristic, such that the transponder (200, 300) can be detected by the reading antenna more or less strongly in an inward direction into the transport means or the restricted-access area than in an outward direction out of the transport means or the restricted-access area.
4. The system according to any of the claims 1 to 3, further having a reading device that is attached at an access of the transport means and is adapted to communicate with the transponder (200, 300), in particular with the chip (210, 310) of the transponder (200, 300) at the first resonance frequency.
5. A system with an antenna (220, 320) according to any of the claims 1 to 4, wherein the second resonance frequency is at a higher frequency than the first resonance frequency.
6. A system with an antenna (220) according to any of the claims 1 to 5, wherein the frequency-selective surface (240) is configured in aperture geometry, wherein the antenna area is supplied with a periodical arrangement of apertures (250).
7. A system with an antenna (320) according to any of the claims 1 to 7, wherein the frequency-selective surface (340) is configured in patch geometry, wherein the antenna area is supplied with a periodical arrangement of electroconductive elements (350) which are electrically isolated from the antenna area.
8. The system with an antenna (220, 320) according to any of the claims 1 to 7, wherein the first resonance frequency is in the microwave range, in particular in the frequency range of around 800 MHz to around 6 GHz, in particular at a frequency of 868 MHz or 915 MHz or 2.45 GHz.
9. The system with an antenna (220, 320) according to any of the claims 1 to 8, which further has an adjusting device by which a back-scattering cross-section of the frequency-selective surface can be changed in a frequency range including at least the second resonance frequency.
10. The system according to claim 9, wherein

    - the transponders (200, 300) are not activated in a basic state of the system, wherein the transponders (200, 300) have a basic-state back-scattering cross section, and

    - the reading antenna for the second resonance frequency and the reading device for the first resonance frequency are so adapted to cooperate that by the reading device for the first resonance frequency, by means of the adjusting device, at least one arbitrary individual transponder (200, 300) is activatable by an active back-scattering cross section being adjustable in the transponder, the active back-scattering cross section being different from the basic-state back-scattering cross section, in particular being extreme - optionally maximal or minimal -, and that on the activated individual transponder (200, 300) a measurement of movement information in accordance with the Doppler principle can be carried out.
11. A method for measuring movement information in accordance with the Doppler principle with a system according to claim 10, wherein by the reading device for the first resonance frequency, by means of the adjusting device, at least one, preferably exactly one, arbitrary individual transponder (300) is activated and a measurement of movement information in accordance with the Doppler principle is carried out on the activated individual transponder (300).
12. The method according to claim 11, wherein in a predetermined spatial area respectively only one individual transponder (300) is activated at any one time.

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