DE19652324A1 - Transponder with a microwave receiving antenna - Google Patents

Abstract

Disclosed is a transponder characterized by a reflection factor modulator (8,10) used to modulate the reflection factor of the microwave receiver (4b,5). This means that the usual transmit antenna can be dispensed with, thereby considerably simplifying the structure of the transponder and the systems contained therein.

Description

The present invention relates to a transponder according to the preamble of claim 1, d. H. a transponder with a microwave receiving antenna.

Transponders are electrical devices that are capable of this are independent with a transmitting / receiving station on their Reason to communicate.

Especially for relatively short distances (up to a few Meters) between the transponder and the transmitting / receiving station put transponders can do without their own power supply men; the energy required for proper operation can be obtained from the sending / receiving station.

Both the energy transmission from the transmitting / receiving station to the transponder as well as the communication, d. H. the info mation exchange between the sending / receiving station and the Transponders are usually wireless.

Depending on the application of the transponder, various technical effects can be used:
With short distances between the transmitting / receiving station and the transponder (distances up to several tens of centimeters), the energy transfer and the information exchange can take place via stationary fields, more precisely via an inductive / transformer near-field coupling in the shortwave range.

With larger distances between the sending / receiving station and the transponder (distances from about 70 cm) energy transmission and information exchange about  electromagnetic waves occur. A transponder of this Art is known for example from EP 0 070 047.

The transponder known from the cited publication is one integrated in a contactless chip card, for receiving gen and sending of microwaves designed transponders and consists essentially of a semiconductor chip, one Power generation unit, a receiving antenna and one Transmitting antenna. Since the transponder described does not have any has its own power supply, it is inactive if and as long as there is no transmitting / receiving station nearby. If the transponder comes close to a sending / receiving station or start one near the transpon to send the located transceiver station, the Energy generation unit from that of the send / receive station sent and via the receiving antenna of the Trans ponders received microwaves that are used to operate the Trans Extract energy required by the ponders, which makes the Trans ponder, more precisely the semiconductor chip of the same act fourth. When activated, the transponder is in the Able to in a predetermined manner with the transmitting / receiving station communicate. For this purpose (parallel to energy generation) the microwaves received by the transponder with regard to evaluated useful information contained therein. Surrendered thereby that a reply from the transponder in question is expected, he sends this via the transmitting antenna to the requesting send / receive station.

The one described above, known from EP 0 079 047 A2 Transponder is a transponder according to the generic term of Claim 1.

Chip cards containing such transponders or other Objects and systems can be used in a variety of ways and who which will probably be widespread in the near future gain.  

A disadvantage of such transponders, however, is their rela tivly complicated structure. In particular the practical reali sation of the transmit and receive antennas requires a he considerable technical effort.

The present invention is therefore based on the object the transponder according to the preamble of claim 1 to further develop such that this is a simplified, but nevertheless extremely reliable working structure.

According to the invention, this object is characterized by the solved the part of claim 1 claimed feature.

Accordingly, the transponder has one for modulating the Re provided the flexion factor of the microwave receiving antenna Reflection factor modulator.

If a low reflection factor is set, the Microwave receiving antenna normal than receiving antenna where on the other hand, the setting of a high reflection factor more or less complete reflection of the reception causes incoming microwaves, causing the As a result, the receiving antenna acts like a transmitting antenna.

The provision of the reflection factor modulator thus enables a waiver of a separate transmission antenna and the Generation of the signals required to be sent parts such as RF generators and the like.

The possible elimination of the components mentioned enables a simplified, but nonetheless excellent radio tioning transponder structure.

Advantageous developments of the invention are the subject of subclaims.

The invention is described below with reference to exemplary embodiments len explained with reference to the drawing. It demonstrate

Fig. 1 is a plan view chip card containing a one embodiment of the transponder according to the invention,

Fig. 2 is a cross-sectional view through an integrated in the smart card of FIG. 1 smart card module along a dashed line in Fig. 1 plotted line,

Fig. 3 is a cross-sectional view of the smart card module shown in Fig. 2 in in a chip card body, a set state,

Fig. 4 is a schematic view illustrating the interconnection and the reflection factor modulation of an antenna of the transponder,

Fig. 5 shows an alternative embodiment module of the chip card,

Fig. 6 shows an alternative embodiment of the antenna of the transponder, and

FIG. 7 shows a cross-sectional view of a chip card containing the antenna according to FIG. 6.

The transponder described in more detail below is an in a transponder provided for a contactless chip card.

At this point, however, it should be pointed out that the described transponder not only in chip cards, but - if necessary with appropriate adjustment  the respective relationships - in principle also in any other objects and systems can be installed.

The chip card in which the transponder described inte is not allowed to have its own power supply to operate the have circuits provided thereon or therein. The for Operation of said circuits may require energy the electromagnetic radiation are taken from a sending / receiving station is broadcast to nearby to address existing chip cards.

However, there is no restriction to this either. The be written transponder is basically also in objects and systems can be used that have their own power supply for the circuits contained there.

The electromagnetic radiation to which the transponder responds should speak or address, are in the example considered Microwaves, preferably millimeter waves, in particular especially in the frequency range between 2.45 GHz and 5.8 GHz. Of the named frequency range is in the considered embodiment game preferred because the antennas from the dimensions of which can be accommodated relatively well in chip cards are and because of the use of these frequencies for long distance active radio systems of low power, including those with contact systems that work without smart cards count, official Ge approvals are available.

Nevertheless, there is always the possibility with Fre outside the specified frequency range sequences to work. For those described in more detail below Chip cards can still be used in the MHz range, for example lying frequencies are used.

The transponder described and the transmitting / receiving stations, Which of these can be addressed for so-called Long-range systems with ranges of more than 70 cm  (hands-free systems); the necessary for this Chen conditions are due to the use of electro magnetic waves as energy and information carriers fills.

In principle, the transponder and the send / receive station, however, for any other range be designed.

As can be seen in particular from FIGS. 1 and 3, the chip card containing the transponder consists of a chip card body 4 and a chip card module 2 inserted into a corresponding recess of the same.

The chip card body 4 is constructed in several layers; it consists, as can be seen in particular from FIG. 3, of a plate-shaped lower part 4 a, also a plate-shaped upper part 4 c of an electrically conductive layer 4 b arranged between them.

The lower part 4 a and the upper part 4 c are made of plastic, preferably PVC or the like. The electrically conductive layer 4 b is a metal layer applied to the lower part 4 a essentially over the entire surface. The provided with the electrically conductive layer 4 b lower part 4 a and the upper part 4 c are connected to one another, for example, by lamination.

The electrically conductive layer 4 b forms the conductive base plane of a microstrip antenna integrated in the chip card.

The upper part 4 c has a punched-out or milled-out portion, which forms the aforementioned recess in the chip card body 4 for inserting the chip card module 2 .

The chip card module 2 , as can be seen in particular from FIG. 2, essentially consists of a film-like plastic module carrier partially provided with an electrically conductive layer, a semiconductor chip 1 applied to the coating side and a chip cover 6 covering the latter.

The electrically conductive layer is structured as shown in FIG. 1; they form two radiation surfaces 5 , a feed line 3 a connecting these and a strip line 3 b.

The radiation surfaces 5 are planar rectangular structures, which in cooperation with the the electrically conductive layer 4 b of the chip card body 4 each show a planar microstrip antenna bil.

Microstrip antennas are ideal for use in chip cards due to their design and size. The size or the geometrical dimensions can be kept particularly low in cards in chip integrated microstrip antennas, as the between the radiation surfaces 5 and the electrically conductive layer 4 b From located sections of the chip card body 4 and the smart card module 2 acting elektrikum than a wavelength shortening factor bedingendes Di .

The radiation surfaces 5 and this connecting feed line 3 a form in the illustration according to FIG. 1 an upside down U. The length of the U-leg corresponding length of the radiation surfaces 5 is λ / 2, as already indicated above was, λ is not about the wavelength λ _{0 of} the electromagnetic waves for which the antenna is laid out, but the material wavelength and is based on the equation

calculated. The lateral distance between the two radiation surfaces 5 , more precisely the distance between the centers thereof, is preferably λ for an in-phase excitation by the receivable elec tromagnetic radiation (microwaves with the wavelength λ ₀ ), but can also be chosen differently.

The radiation energy received via the radiation surfaces 5 is converted into electrical energy by this and is coupled out as such via the feed line 3 a and fed to the semiconductor chip 1 and / or other circuits. In the example under consideration, the decoupling takes place with high impedance at the empty longitudinal ends of the radiation surfaces 5 ; From the coupling, however, can also be done with a low resistance at the current belly in the middle of the radiation surfaces 5 .

Each individually functioning as antennas radiating surfaces 5 are connected in parallel to each other by the as described and shown in the figures angeord designated feeder line 3 a, whereby the removable electric power increased accordingly.

As can be seen in particular from FIG. 4, the decoupled from the radiation surfaces 5 , overlapping on the feed line 3 a antenna voltages are gripped approximately in the middle of the feed line 3 a at a connection point 7 and fed to a circuit in which they are visible the energy and information contained therein can be utilized or evaluated.

The processes taking place depend inter alia on the position of a switch 8 shown in FIG. 4. The position of the switch 8 is controlled by an evaluation circuit 10 which evaluates the signals received by the antenna in terms of content; When the evaluation circuit 10 is in a de-energized, ie non-operated state, the switch 8 is open.

If and as long as the switch 8 is open, the downstream of the feed line 3 a circuit, which incidentally is completely accommodated in the chip card module 2 and can at least partially be part of the semiconductor chip 1 , electrically to the radiation surfaces then acting as the receiving antenna 5 and the connecting feed line 3 a fitted to; this means that a maximum of energy can be taken from the antenna. The generated by a suitable radiation field in the radiation surfaces 5 and tapped by them via the feed line 3 a voltage is rectified by a rectifier ter 9 and used as a supply voltage for the circuit shown in FIG. 4. With the provision of the supply voltage, the circuit can start operating. This also activates the evaluation circuit 10 already mentioned above.

When the evaluation circuit 10 is activated, it starts monitoring and evaluating the signals received via the antenna. It is determined in particular whether the chip card in question is addressed by the received signals and whether feedback to the sending transceiver station is required.

If it is determined by the evaluation circuit 10 that a reaction to the signals sent by the transmitting / receiving station is required, this is caused by a closing of the switch 8 or a certain sequence of opening and closing operations.

By closing the switch 8 , a connection from the connection point 7 of the feed line 3 a to the strip line 3 b, more precisely a connection point 7 thereof, is provided. The length of the strip line 3 b is such that it acts in cooperation with the connection to the feed line 3 a as a λ / 4 line. The strip line 3 b and the connec tion to the feed line 3 a are idle. This means that no electrical consumers of any kind are supplied with energy when the switch 8 is closed; due to their dimensions, they do not act as emitters.

The open (open) termination of the λ / 4 line is transformed (as a result of the reflection taking place at the line end of the λ / 4 line) into a short circuit at the beginning of the line (at the connection point 7 of the feed line 3 a). The short circuit at the beginning of the λ / 4 line also acts as a short circuit formed by the radiation surfaces 5 and the elec trically conductive layer 4 b antenna, thereby resulting in He at the radiation surfaces 5 incoming electromagnetic waves essentially completely to the transmitting / receiving station be reflected back.

The from the transponder antenna to the transmitting / receiving station back-reflected waves can be received by this and be evaluated.

As a result, the switch 8 and the evaluation circuit 10 controlling it form a reflection factor modulator, by means of which the reflection factor of the transponder antenna can be changed and modulated.

By switching the switch 8 back and forth, the transponder can transmit any information coded to the transmitting / receiving station.

At times during which the switch 8 is closed (the transponder antenna is short-circuited), the rectifier cannot obtain the energy required for operating the semiconductor chip 1 and / or other circuits; the rectifier 9 even blocks in this state. To bridge these times, the transponder contains an energy store such as, for example, a capacitor or the like connected in parallel with the rectifier 9 , with the aid of which an intended operation of the semiconductor chip 1 or the other circuit can be maintained. The capacitance of the capacitor can be relatively small, because due to the high carrier frequency (MHz or GHz) only very short interruptions are required to send clearly identifiable information.

By providing a reflection factor modulation on a separate transmitting antenna for the active sending of informa tion from the transponder to the sending / receiving station will.

The described way of short-circuiting the trans ponder antenna makes it unnecessary to produce an electrical connection to the electrically conductive layer 4 b. This is advantageous in that an indirect or direct connection of the electrically conductive layer 4 b accommodated in the chip card body 4 to one or more of the radiation surfaces 5 accommodated in the chip card module 2 can be connected with a not inconsiderable effort.

In the chip card described, in particular due to the elegant solution to the antenna problem, almost all components of the transponder can be accommodated in the chip card module 2 ; only the electrically conductive layer 4 b is still in the chip card body 4 . Since no electrical contact has to be made to the electrically conductive layer 4 b, no electrical connections need be provided between the chip card module 2 and the chip card body 4 . The chip card module 2 must therefore only be used in the intended saving from the chip card body 4 and in the set position with this (for example by an adhesive 11 ). The manufacture of the chip card module 2 itself is relatively simple, because the circuit components mentioned above (switch 8 , rectifier 9 , evaluation circuit 10 ) can (but do not have to) be integrated into the semiconductor chip 1 ; The switch 8 and the rectifier 9 are realized in this case either by a CMOS-FET or Schottky diodes or as bipolar construction elements in BiCMOS technology. The entire chip card production is very easy and can be done largely or even completely by conventional chip card manufacturing processes.

Although the way of short-circuiting the transponder antenna described above proves to be very advantageous, there is no restriction to this. In principle it is also possible to effect or to connect the desired short circuit on belie bige other way one or more of the radiation surfaces 5 b via controllable switch with the electrically conductive layer. 4 The possible omission of the provision of a separate transmitting antenna in the transponder is independent of the manner in which the transponder antenna is short-circuited.

The reflection factor modulation described above he leaves it selectively one of two different reflections select factors. Although this is not the case here Is described in detail, it would also be conceivable To provide intermediate stages. This could result in an amplitude modulation of the transponder to the transmitting / receiving station realize reflected waves.

In the embodiment described above, the radiation surfaces 5 and the feed line 3 a are directly connected to each other; they are formed by a corresponding metallic coating of the side of the module carrier carrying the semiconductor chip 1 .

Instead, however, also possible to provide only the supply line 3 a and the strip line 3b on the semiconductor chip-carrying side provide the module carrier 2, whereas the radiation surfaces 5 on the opposite side of the module carrier are disposed. Are pelt "only" capacitively gekop Such a smart card module structure in which the radiation surface 5 and the feed line 3 a to each other, 5 is shown in Fig..

The capacitive coupling ratio is determined by the thickness of the module carrier and the overlap area between the respective radiation areas 5 and the feed line 3 a.

The smart card module according to Fig. 5, towards the chip card module of FIG. 2 has the advantage that the radia tion surfaces 5 have radiation characteristics due to their exposed position (at or near the chip card surface), a better reception and Ab.

The simple manufacturability of the chip card, which is based in particular on the fact that there must be no electrical connections between the chip card module 2 and the chip card body 4 , is not impaired by this.

The transponder antenna can also be modified with regard to the number of radiation areas 5 . Was already indicated above, each of the radiation surfaces acts to 5 in sammenwirken with the electrically conductive layer 4 as a b (also individually operable) antenna. In the examples considered so far, two such antennas are connected in parallel (interconnected to form an antenna pair that effectively adds up). However, several antennas can also be interconnected.

A possible arrangement and connection of six antennas is shown in FIG. 6. The arrangement shown consists of three identical pairs of antennas which, more precisely, whose feed lines 3 a are connected to one another via connecting lines 3 c.

To achieve an in-phase excitation of the respective antenna pairs, these, or more precisely their centers, are each spaced from one another by λ. The maximum antenna gain can be achieved if the connecting lines 3 c are each λ long.

Such or a differently constructed antenna group can be subjected to a reflection factor modulation by connecting to the still existing open strip line 3 b.

Such, consisting of a plurality of radiation fins 5 microwave antenna group is one of only one or two radiation surfaces 5 having antenna in several respects clearly superior. It has a higher antenna gain and a better directional characteristic, which makes it more sensitive and suitable for longer ranges.

Such an antenna group is preferably on one chip card insert forming its own chip card layer brought.

A cross section through a chip card containing 12- containing chip card is illustrated in FIG. 7.

In accordance with the chip card according to FIG. 3, the chip card according to FIG. 7 has a plate-like lower part 4 a with an electrically conductive layer 4 b applied thereon. Above this, however, a middle part 4 d, the chip card inlay 12 and a top part 4 c modified over the top part 4 e are arranged.

The chip card ticker 12 consists of a film-like ticking carrier, one of the radiation surfaces 5 , the feed lines 3 a, the strip line 3 b and the connec tion lines 3 c forming, electrically conductive coating, the semiconductor chip 1 and the chip cover 6 , the like shown in Fig. 7, are thus disposed substantially in the same relative position as in the chip card module 2.

In contrast to the module carrier, the ticking carrier shows an area corresponding to the chip card area.

The middle part 4 d has a punched out or milled out, which is dimensioned and positioned in such a way that the semiconductor chip 1 and the chip cover 6 can come to lie when the chip card insert 12 is placed thereon.

The upper part 4 e to be placed over the chip card insert 12 , unlike the upper part 4 c according to FIG. 3, has no savings and is used purely to cover the underlying chip card components.

The lower part 4 a with the electrically conductive base surface 4 b provided thereon, the central part 4 d, the chip card inlay 12 and the upper part 4 e can be connected to one another, for example, by lamination.

In the chip card shown in FIG. 7, almost all transponder components can be accommodated in the chip card insert 12 ; only the electrically conductive layer 4 b is still in the chip card body 4 . Since no electrical contact has to be made to the electrically conductive layer 4 b, kei nerlei electrical connections must be provided between the chip card insert 12 and the chip card body 4 . The chip card inlay 12 therefore only has to be connected mechanically (for example by gluing and / or laminating) to the remaining chip card components. The production of the chip card according to FIG. 7 is thus very simple and can be carried out as far as possible or even completely by conventional chip card production processes.

In summary, it can be said that the described NEN transponder have such a simple structure that not only their construction itself, but also their intent into a chip card or other objects and systems can be carried out with considerably less effort than before. The transponder acting as a transmitting and receiving antenna Despite its simple structure, antenna is of high quality outstanding (good efficiency, high antenna gain, effective full reflection), so that the transmission power of the Trans ponder responsive send / receive station very low can be used and even with larger ranges no ge drive for people in the radiation field poses.

Claims (15)

1. Transponder with a microwave receiving antenna ( 4 b, 5 ), characterized by a provided for modulating the reflection factor of the microwave receiving antenna reflection factor modulator ( 8 , 10 ). 2. Transponder according to claim 1, characterized in that the reflection factor modulator ( 8 , 10 ) contains a switch ( 8 ), via which a short-circuiting of the microwave receiving antenna ( 4 b, 5 ) taking place according to the modulation to be carried out can be accomplished. 3. Transponder according to claim 1 or 2, characterized in that the microwave receiving antenna ( 4 b, 5 ) is a planar microstrip antenna which by arrangement of at least one substantially rectangular radiation surface ( 5 ) on a projecting on all sides electrically conduct Base area ( 4 b) is formed. 4. Transponder according to claim 3, characterized in that the at least one radiation surface ( 5 ) has a length of λ / 2. 5. Transponder according to Claim 3 or 4, characterized in that the radiation energy absorbed by the radiation surface ( 5 ) and converted into electrical energy is coupled out with high resistance at an idling longitudinal end. 6. Transponder according to one of claims 3 to 5, characterized in that the radiation surfaces ( 5 ) are provided in pairs, each radiation surface pair consisting of two spaced apart radiation surfaces ( 5 ), the longitudinal ends of which are connected via a feed line ( 3 a) are. 7. Transponder according to claim 6, characterized in that a capacitive coupling of the radiation surface (s) ( 5 ) and the feed line ( 3 a) is provided. 8. Transponder according to claim 5 or 6, characterized in that the antenna voltage via the feed line ( 3 a) is tapped in the middle thereof. 9. A transponder according to claim 8, characterized in that the antenna voltage tapped from the feed line ( 3 a) is used to supply a downstream circuit ( 10 ) with the energy required for its operation and, at the same time, processing for detecting and evaluating the information contained therein is subjected. 10. Transponder according to one of claims 6 to 9, characterized in that a plurality of radiation surface pairs, each spaced by λ, are provided, the feed lines ( 3 a) of which are connected to one another via connecting lines ( 3 c). 11. Transponder according to one of claims 6 to 10, characterized in that the feed line ( 3 a) with an idle λ / 4-Lei device ( 3 b) can be connected. 12. Transponder according to claim 11, characterized in that the making and breaking of the connection between the feed line ( 3 a) and the idle λ / 4 line ( 3 b) can be accomplished by actuating the switch ( 8 ). 13. Transponder according to claim 11 or 12, characterized in that the idle λ / 4 line ( 3 b) is essentially formed by an open strip line. 14. Transponder according to one of the preceding claims, characterized in that the transponder on the electrically conductive base surface ( 4 b) of the microstrip antenna is completely integrated into a chip card module ( 2 ) of a chip card. 15. Transponder according to one of claims 1 to 13, characterized in that the transponder on the electrically conductive base surface ( 4 b) of the microstrip antenna is completely integrated into a chip card inlay ( 12 ) of a chip card.