WO1993015417A1

WO1993015417A1 - Device for information transfer

Info

Publication number: WO1993015417A1
Application number: PCT/SE1993/000030
Authority: WO
Inventors: Staffan Gunnarsson
Original assignee: Saab-Scania Combitech Aktiebolag
Priority date: 1992-01-23
Filing date: 1993-01-21
Publication date: 1993-08-05
Also published as: AU3465293A

Abstract

A device for information transmission, a so-called transponder, for receiving a first microwave signal, modulating and coding, and retransmission of a second microwave signal comprising at least one antenna means designed in micro strip technique and a ground plane. The device is primarily characterized in that the antenna layer (6) of the antenna means is provided with a recess (8), in which at least some of the electronic components (9, 16) of the transponder and/or micro strip conduits (12, 18) are located. Through this embodiment of the device, the device will be compact, light, inexpensive in manufacturing, and gives a well-defined and directed antenna lobe. The device will thereby have a good range and is especially adapted for use in material handling of for example parcels and containers.

Description

DEVICE FOR INFORMATION TRANSFER

The present invention relates to a device for information transmission, a so-called transponder, for receiving a first microwave signal, modulating and coding, -and retransmitting a second microwave signal, comprising at least one antenna means designed in micro strip technique and a ground plane.

Background of the invention

In applications for material flow automation, for example for distribution and customs clearance of airfreight goods and containers, problems often arise how to attach freight and customs documents to the goods safely. It would therefore be desirable if the documents were stored electronically in a data carrier that would accompany the goods.

A solution to the problem is to use optically coded tags, for example bar or dot codes, which are read with the aid of code readers after which freight data is fetched from a central data base which has been cαπrπtunicated over the tele or satellite network.

A problem with that solution, however, is how to update the data bases reliably across large geographic distances. Another problem is that the method is expensive, as principally all conceivable places of desti¬ nation must be provided with the intended information beforehand to admit access to the documents if the goods unintentionally would have arrived at an incorrect destination. A third inconvenience is that optic codes are sensitive to the mechanical damages that are likely to occur when the goods are handled.

A solution with electronic data carriers which accompany the goods and can be programmed in the field would admit a considerably less expensive and safer handling. However, it has not been possible hitherto to find a technique that is sufficiently cost efficient to admit location on every individual parcel, nor any technique which is sufficiently compact and at the same time admits reading at a distance up to several metres which in certain cases is desirable. A microwave transponder of the kind mentioned in the introduction is described in Swedish patent 9002493-6.

That is however not intended as a data carrier but for position determi¬ nation on automatic refuelling. The technique of the transponder referred to further describes a special substrate with double dielectric material and components located on either side of it, which solution is difficult to make cαπpact and inexpensive because the shown substrate is expensive. It also requires expensive electric vias in the substrate.

The transponder has also the disadvantage of becoming relatively thick, since space must be made inside the case for the cαπponents that are located on either side of the substrate.

In the application related to here, the transponder will sometimes be located on surfaces which are not of metal, for example cardboard boxes and wooden pallets, whereby the advantage described in 9002493-6 in making the ground plane as small as the antenna element cannot always be made use of.

The object and most iiriportant charachteristics of the invention

The object of the invention is to achieve a device of the kind mentioned in the introduction, which is suitable for programming in the field, can be read frαn a great distance and at the same time is sufficient¬ ly inexpensive in manufacturing, and cαπpact for being located on specific parcels and the like.

According to the invention this is achieved with a device of the kind mentioned in the introduction in that the antenna layer of the antenna means is provided with a recess, in which at least some of the electronic components and/or micro strip conduits of the transponder are located.

In an advantageous embodiment of the device according to the invention the antenna layer and the micro strip conduits are arranged to cooperate, through a substrate of a dielectric material, with the ground plane, because of which electric vias through the substrate are unnecessary. Hereby the size of the substrate can be minimized.

It is advantageous to let the substrate, that is the dielectric material, constitute a case for the transponder.

In a suitable embodiment, the substrate, that is the dielectric material, consists of a circuit card, located inside a case for the transponder.

The embodiment of the electronic components of the transponder can be varied within the scope of the invention. In an advantageous embodiment, a component, preferably a diode, is arranged to effect modulation as well as detection of the first microwave signal. This cαnponent, or the required cαnponents can suitably be integrated in the same electronic circuit, which comprises the oscillator and data memory circuits of the transponder.

The device can naturally be geometrically designed in many ways. One advantageous embodiment is that it consists of a compact box, intended to be attached on objects such as parcels or containers, included in material flow.

In one embodiment the device is arranged to admit information transmission at which the first and/or second microwave signal is/are entirely or partly cryptated, for example according to DES or RSA.

Description of the examples of embodiment

The invention will now be described more in detail with reference to the accompanying drawing, in which

Figure 1 shows a block diagram of a known transponder for information transmission;

Figure 2 shows a view of a section through a device according to the invention, and Figure 3 shows a view frαn above of the device in Figure 2 , with a removed upper cover.

The transponder in Figure 1 shows an antenna 1, a modulator-demodulator unit 2, an oscillator-memory circuit 3 and a power source in the form of a battery 5.

The antenna 1 receives a microwave frequency, for example at 2.45 GHz, from a transmitter/receiver unit and leads this signal further to modu¬ lation circuits in the modulator-demodulator unit 2. Depending on the memory contents in the oscillator-memory circuit 3 the modulator supplies information to the signal received by the transponder, and returns this modulated signal to the antenna 1, so that the information is radiated out in space in front of the transponder to the transmitter/receiver unit so that the latter can read information from the transponder.

In case data is to be written in the transponder, a modulated microwave signal is transmitted to the antenna 1, is demodulated in the circuit 2 and stored in a memory in the oscillator-memory circuit 3.

The modulator circuits are guided frcm the oscillator with a signal with low frequency compared with the microwave frequency, for example 32.8 kHz. A power source in the unit 5 provides the oscillator-memory circuit 3 with voltage.

The device according to the invention, as shown in Figures 2 and 3, comprises a patch antenna 6 acting towards a ground plane 7 through a substrate 11 of a dielectric material. A recess 8 is made in the patch antenna, that is the antenna layer 6. The dielectric material constitutes in this case at the same time a case for the transponder. The shown antenna, in which the antenna layer 6 has approximately as large a surface as the ground plane 7, will if located in free space radiate approximately as much in both directions of the perpendiculars, whereas if the ground plane 7 is considerably larger than the antenna layer 6, the radiation will be directed out from the antenna layer. The latter embodiment may be of special interest when the invention is placed on a surface of non-reflecting material and where simultaneously reflecting objects can be expected to occur on equal multiples of half a wavelength behind the transponder.

It is to be noted that the radiation originates from the edges of the antenna layer, and that no real radiation is formed directly from the central parts of the antenna layer surface. This surface can therefore be used for other purposes, for example, to mount in the recess 8, inside the antenna layer 6, the circuits that are required for achieving, with a modulator/demodulator diode 9, an electric modulation with information in the feeding point 10, and for receiving, from the feeding point of the antenna layer, and detecting, in the diode 9, incαning signals.

A signal caught by the antenna layer 6 will give an electric alternating field over the dielectric substrate 11 towards the ground plane 7 in the feeding point 10 of the antenna.

The received signal is guided by the micro strip conduit 12 to the diode 9, which is connected with one end in the point 14 and its other end in the point 13 (the point 15 is not connected inside the diode enclosure). The resistance of the diode can be varied between different values depend¬ ing on what voltage is put over these terminals. In the example of embodiment there is an integrated circuit 16, which on its output port 19 emits a control voltage to the connection point 14 of the diode 9, whereby the resistance of the diode will be affected.

One end of the diode is from a microwave viewpoint short-circuited to the ground plane 7 by the open quarter wave guide 18, and will therefore, depending on the output voltage from the circuit 16, microwavewise more or less connect the point 13 to the ground plane 7.

The above described resistance variation in the diode 9 will bring about that a wave front incident on the antenna layer 6 will give rise to a reflex modulated with information, where instantaneous phase position and amplitude are affected by the resistance in the diode 9. Because the circuit 16 is brought to contain data information that is made to act upon the resistance of the diode 9, for example by varying the fre¬ quency or phase of an alternating voltage on output 19 in a way repre¬ sentative for data information, a transponder has been achieved whose data on radiation can be read with the aid of an external communication unit. The communication unit is made to receive and decode the signal reflected frcm the transponder and modulated with data.

It is also possible, without disturbing the antenna function, to locate larger components as for example-a power source 21, for instance in the form of a battery or an accumulator, inside the radiating edge surfaces of the antenna layer.

The connections 20 and 17 feed voltage to the transponder circuit 16 frcm the power source 21.

The connection 17 has for space reasons been located in a break in the outer edge 7 of the antenna layer, but this is of no consequence for the functioning of the antenna since the antenna has a π nimum of current in this point. It could just as well be unbroken as shown in the dashed surface 22.

The diode 15 is also used to a plitudinally detect a signal incident on the transponder, which, if it represents a data flow to the transponder, makes writing of data into the circuit 16 possible. The data signal then reaches the memory in the circuit 16 via a connection condensor for data integrated in the circuit. The circuit comprises an autαnatic switch circuit between the modulation mode and demodulation mode, in that at even intervals it is connected for detection and analysis of whether microwave pulses incide on the diode 9.

One further use of the diode 9 is as a rectifyer of microwave pulses to be used for power supply of the transponder instead of, or as a com¬ plement to its inbuilt power source 21. The diode 15 can also be integrated in the circuit 16, so that a trans^¬ ponder with only one component in addition to the substrate is made possible.

The antenna layer can further be provided with one additional feeding point so that the transponder in a known manner at the same time can function in two orthogonal polarisations. The antenna layer recess can also be formed asymmetrically in different ways for example to make the polarisation of the transponder circular.

The antenna layer can also be given another embodiment, for example rectangular, without its principle of function being changed.

The modulation circuits can also be formed in other ways, for example by ccmpleting the diode 15 with, or replacing it by other components, for example transistors, preferably of field effect type.

In order to avoid demands that the transponder shall be oriented in any specific manner relative to the axis of rotation from the. trans¬ mitter/receiver, it can be designed for transmitting and receiving circu¬ larly polarised waves. The transponder will in this case, if it is linearly polarised, still be capable of being turned about said axis without loss of signal, since a circularly polarised wave contains E-fields in all directions perpendicular from the propagation direction.

In case a very high degree of safety is required, for example if the device is to store value related information such as electronic punches or money, it can be provided with means that give sufficient safety against unauthorized access. This can be done in a similar way as for money cards of magnetic strip type, for electronic memory cards or for microprocessor cards. In the latter case a microprocessor with cryptating functions, for example the standardized DES and RSA algorithms, can be implemented.

The invention is not limited to the examples of embodiment that have been given here, but can be varied within the scope of the claims set out.

Claims

1. A device for information transmission, a so-called transponder, for receiving a first microwave signal, modulating and coding, and retransmitting a second microwave signal, comprising at least one antenna means designed in micro strip technique and a ground plane, c h a r a c t e r i z e d in that the antenna layer (6) of the antenna means is provided with a recess (8), in which at least some of the electronic components (9, 16) of the transponder and/or microstrip conduits (12, 18) are located.

2. A device according to claim 1, c h a r a c ter i z e d in that the antenna layer (6) and micro strip conduit (12, 18) cooperate, through a substrate (11) of a dielectric material, with the ground plane (7) whereby electric vias through the substrate are not required.

3. A device according to claim 2, c h a r a c t e r i z e d in that said dielectric material (11) also comprises a case for the transponder.

4. A device according to any one of claims 2 to 3, c h ar a c t er¬ i z e d in that the dielectric material (11) consists of a circuit card, located in a case for the transponder.

5. A device according to any one of claims 1 to 4, c har a c t er¬ i z e d in that a component (9) , preferably a diode, is arranged to effect modulation as well as detection of the first microwave signal.

6. A device according to any one of claims 1 to 5, c h a r a c t e r¬ i z ed in that the component (9) or components for modulation and detection is/are integrated in the same electronic circuit (16) as comprises the oscillator and data memory circuits of the transponder.

7. A device according to any one of claims 1 to 6, c h ar a c t e r¬ i z e d in that the device is designed as a cαπpact box, intended to be attached to the object such as parcels or containers, which are parts in material flow.

8. A device according to any one of claims 1 to 7, c h a r a c t e r¬ i z e d in that the device is arranged to admit information trans¬ mission at which the first and/or second microwave signal is/are entirely or partly cryptated, for example according to DES or RSA.