US20100231353A1

US20100231353A1 - System and portable device for transmitting identification signals

Info

Publication number: US20100231353A1
Application number: US12/526,873
Authority: US
Inventors: Andreas Haberli
Original assignee: Kaba AG
Current assignee: Kaba AG
Priority date: 2007-02-14
Filing date: 2008-02-14
Publication date: 2010-09-16
Also published as: JP5273871B2; WO2008098398A2; US20100048127A1; WO2008098398A3; JP5224546B2; EP2127161A2; JP2010518789A; WO2008098399A1; JP2010518790A; US20100144268A1; JP2010521079A; WO2008098397A1; US8798531B2; EP2127160A1; EP2127159B1; EP2127159A1

Abstract

A system is provided with a portable device for the transmission of a signal to a second device, wherein the portable device is wearable on the body of a user. The portable device includes at least two electrodes and transmitter electronics for the generation of an electrical signal between the electrodes, such that the signal is able to be coupled by the electrodes into the body of the user and detected by at least one electrode of the second device. A portable device is distinguished in that between the electrodes are arranged component parts of the transmitter electronics and/or of an application distinct from the transmitter electronics, and/or an air gap is present.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to the communication between a sender (transmitter) and a receiver over a capacitive coupling (sometimes also referred to as capacitive resistive coupling, “intrabody” coupling, RCID-coupling or PAN-coupling) in which small electrical currents which are used for the transmission of information between the transmitter and the receiver are generated in the human body, and/or in which the transmitter and the receiver interact with one another over very short distances via electric fields.
2. Description of Related Art
This method of coupling is disclosed in the US patent specifications U.S. Pat. Nos. 4,591,854, 5,914,701 and 5,796,827. Implementations thereof are described in the international patent application PCT/CH 2006/000518 as well as in further published specifications of various bearers.
A particular advantage of the capacitive coupling through the human body or, as the case may be, over short distances is the selectivity of the data transmission. Depending on the configuration, one can determine with a high degree of certainty that the signal received by the receiver can only have been transmitted by the person who is situated in direct proximity to or in physical contact with a receiver electrode that is designated for it.
A disadvantage is, among other things, that as a result of the poor signal to noise ratio (literally: signal-interference ratio), only a small amount of data can be transmitted. A good signal to noise ratio is only possible with a large amplitude of the transmission signal. However, a large amplitude (i.e. high voltage) would not be tolerated by the user. In the Swiss patent application No. 548/06, approaches are described, with which these problems can be addressed. Despite these the bandwidth of the signal transmission remains limited.
The layout of the electrodes in the transmitter is important for as effective a signal transmission as possible. According to the state of the art, these are designed as electrode pairs, which lie parallel and opposite one another in the manner of a plate capacitor. The electrodes should be as large as possible so as to maximize the coupling to the body and also to optimize the signal to noise ratio, in the situation in which no electrically conductive contact exists between the one electrode and the human body. However, these large electrodes have a problematic effect on the design and the dimensions of the transmitter. Furthermore, they cause the power consumption of the transmitter to be quite high, so that more frequent battery changing is necessary.
It has been further seen that depending on the geometric configuration, the signal can practically cancel itself, because the electricity that is coupled into the body by the first capacitor plate corresponds to, but has the opposite sign of, the electricity that is coupled into the body by the second capacitor plate.
With this background in mind, it is an object of the present invention to provide solutions for the layout of transmitter electrodes which ameliorate the above-mentioned disadvantages at least partly and which mean a further step toward the commercial application of the technology and its acceptance by consumers. The solutions mentioned should in particular be usable for access control.
These objects will be fulfilled by the invention, as it is described in the patent claims.

BRIEF SUMMARY OF THE INVENTION

A portable device according to the approach according to the invention is, for example, wearable on the body of a user; it can be designed as a card-like identification medium, as “smart card cover”, mobile telephone, watch, portable computer (for example of the “handheld computer” type) etc. It comprises at least two electrodes and means for the creation of an electrical signal between the electrodes, such that the signal is able to be coupled through the electrodes to the body of the user and is detectable from the body by at least one electrode of a second device. A device like this also makes possible a direct, short-range communication (not through the body), for example through holding of the portable device in direct proximity of a receiver electrode, i.e. applications of the invention are not limited to coupling through the human body, but rather also extend to cases in which the user carries the portable device on his or her person, holds it in the vicinity of a receiver electrode or otherwise makes it possible that the communication between transmitter and receiver takes place directly and not exclusively over the body.
According to an aspect of the invention, now two electrodes of a portable device (transmitter) are arranged such that between the electrodes there are arranged either component parts of the transmitter electronics and/or of another application distinct from the transmitter electronics, or an air gap is present, in which such a component part—for example with a “smart card” as the carrier of the part—can be inserted. Combinations of “air gap” with “transmitter electronics”, “other applications” and/or “battery” are possible. A component part of the transmitter electronics and/or of another application distinct from the transmitter electronics can also indicate a hard-wired or replaceable battery.
As component parts here are indicated active or passive, preferably electronic component parts, which are more than a mere separating layer between the electrodes, for example in particular active electronic component parts such as ASICs, processors, integrated circuits, memory modules, sender and/or receiver for contact-free information transmission, including active or passive RFID transponders, passive component parts such as antennas, resistors, capacitors, coils, etc. or also batteries, optical elements etc.
In particular the embodiments with a component part of another application arranged between the electrodes and the embodiments with a battery arranged between the electrodes, but also the embodiments with component parts of another application arranged between the electrodes, make possible new dimensions of integration. This is also true for the embodiments with air gaps, inasmuch as a corresponding component part is inserted into the air gap.
Of course the transmitter electronics and electronic component parts for the application which is distinct from the transmitter electronics may be integrated together with one another in at least one unified component—for example in an integrated circuit. The feature according to the invention of the “component part of an application which is distinct from the transmitter electronics” is simply that between the electrodes are arranged electronic elements which can administrate functions that are entirely distinct from the capacitive resistive information transmission and preferably from other contact-free information transmission methods, for example as they control or constitute the display of a mobile telephone, or as they store information and/or have stored information which is not communicated with the intrabody information transmission, etc.
This approach makes use of the new finding that for the transmission of data, the area of the electrodes is important, however not the capacitive coupling there-between. On the contrary, it has been found that for a given electrode size, a large capacitance is unfavorable, because a large capacitance creates a negative effect on the life of a battery of the portable device, since larger currents flow in the generation of signals. Furthermore, as a result of the larger flowing current of larger capacitance, the requirements on the electrode conductivity are higher. A further finding is that the two electrodes can lie in parallel planes, but that, however, this is by no means necessary. So for example the electrodes can be customized to fit the housing shape of the portable device, wherein in the design of the portable device substantially no consideration must be paid to the electrodes.
In the case of a plate capacitor, the capacitance is proportional to the area of the electrodes and to the dielectric constant of the material between the electrodes but inversely proportional to the distance between the electrodes. As a result of the approach according to the invention the two electrodes are in general farther apart from one another than according to the state of the art, without this precluding a compact design of the portable device. Through the larger electrode separation, the capacitance is limited. Particularly preferential is also the combination with the first aspect of the invention, because transparent electrodes, with their comparatively limited electrical conductivity, are extremely good to use together with the approach according to the invention because of the small flowing currents that result.
In embodiments in which between the electrodes there is an air gap in which the components of a distinct application—for example an identity card and/or smart card—are able to be inserted, the compatibility with existing systems as well as backwards compatibility are also a given.
According to a special embodiment of the invention, the portable device with the air gap can comprise a communications interface, over which data can be exchanged with the application that is inserted into the air gap. Such an interface can, for example, be formed like a conventional smart card reader.
According to a further special embodiment, a communication link can exist between the transmitter electronics and an input unit, wherein then the signals transmitted by the transmitter electronics can be dependent on data that are input. For example, the transmitted signal can include a PIN, which the user previously has input in the input unit. In this embodiment the portable device can, for example, be designed as a mobile telephone, wherein the input unit can correspond to the input unit of the mobile telephone (keypad, touchscreen, voice recognition device etc.).
According to a preferred embodiment of the invention, a portable device or also a receiver is distinguished in that at least one of the electrodes is at least partially transparent.
Transparent electrical conductors, for example of very thin layers of metal that are vacuum-metalized or applied via a sputter deposition technique on a transparent substrate, or certain doped semiconductors on an oxide base (TCOs as for example ITO-layers), are currently available. For a considerable time already, these have been well-known for certain applications, for example as components for flat-screen displays or thin-film solar cells. They have not yet been considered for information transmission, as they are known to have poor electrical conductivity and would result in unacceptably large losses when used with the high frequencies usually used in information transmission.
However, it has now been recognized that the capacitive resistive information transmission is configurable such that the conductive capacity of transparent electrodes is adequate. In particular, the combination of comparatively low voltages (for example less than 5V or even less than 3V) and currents and low frequencies (for example less than 2 MHz center frequency) allows the use of the electrodes with limited conductive capacity.
Through this technique, many new degrees of freedom arise with respect to the design of the transmitter, until now with respect to the portable device the design seemed to be of little relevance, because a portable device of the type according to the invention is generally carried in a bag or otherwise covered while worn. A further realization of the invention is that with the introduction of transparent electrodes, the design possibilities of portable devices multiply considerably:
Arrangement of the electrodes as layers on a card, comprising a label or labels—in the manner of an identification card or a “badge”, possibly with a photo—as well as possibly comprising further functionalities. The electrodes can form the outermost layers—with the exception of, if necessary, thin protective layers—of the card. If the badge comprises an antenna for wireless communication with another communication channel, the antenna is not covered locally by at least one of the electrodes.
Arrangement of the electrodes in a holder (“shell”, “cover”) for a smart card. Smart cards are often used as so-called “badges” for the control of access. In the process, they are introduced into transparent holders, which for example are attachable to a piece of clothing by means of a clip and are visible from the outside. According to the first aspect of the invention, it is now possible to form this holder out of rigid or flexible material as part of the transmitter. This arrangement has the additional advantage that the capacitance of the capacitor arrangement formed by the two electrodes is reduced, as will be described below in more detail with reference to the second aspect of the invention.
Combination with a different electronic device, for example a mobile telephone. Modern electronic devices often have large displays. According to the invention a first of the two sender electrodes can be arranged in or over the display, i.e. the display is furnished with or covered by the transparent electrode. This also has the advantage of a reduced capacitance, if the second—transparent or not transparent—electrode is, for example, arranged in the area of a back side of the device. Furthermore this results in multifaceted possible combinations of the functionality, as will also be described below in more detail with reference to the second aspect of the invention.
Furthermore the approach according to the preferred embodiment has appealing advantages in particular for use in “access control”, in that one does not notice that the electrodes are electrodes and thus a part of an electronic device. Rather, depending on the design, it seems to be simply a shell, a design element or another functional element.
As the portable device is a mobile telephone, the electrical supply for the transmitter electronics can be obtained by simple means: namely as the transmitter electronics are energized by the very powerful battery of the mobile telephone, for example over a 3V DC supply. The communication between the transmitter electronics and the remaining electronic component parts of the mobile telephone can be accomplished—in case these are not integrated with one another—over any known or yet to be developed interface, for example over a I²C data bus.
According to a further aspect of the invention, the transmitter includes an arrangement of electrodes, which contain electrode faces that are not parallel to one another.
For example, at least three electrodes can be present, wherein at least one of the electrodes is not parallel to another of the electrodes, and wherein each of two different pairs of electrodes is acted upon by an electrical signal.
Through this approach, according to the further aspect of the invention, the information transmission is improved. In particular, it can be practically eliminated that with two different electrode pairs the signal cancels itself.
In a possible embodiment of the further aspect of the invention, at least two electrode pairs can be present, wherein the electrodes of each electrode pair are parallel with one another, and wherein the electrode pairs are not parallel with one another, but rather stand at right angles or at another angle relative to one another.
As a further embodiment, three electrode faces can be present, of which at least two are not parallel. At any one time, the signal is generated between two of the three electrode faces, for example between the first and the third electrode faces as well as between the second and third electrode faces. The first and the second electrode faces can then optionally be wired in parallel electrically and for example even be formed in the same manner as a unified, non-planar electrode. As an alternative—if the electrodes are not wired in parallel, the electrode pairs can also be alternately acted upon by the signal. Although the data transmission speed is somewhat reduced thereby, the power consumption per electrode face is limited in comparison to the solution that is wired in parallel.
Subsequently, the power consumption of a portable device for the transmission of signals to a second device, wherein the portable device is wearable on the body of a user, comprising at least two electrodes and transmitter electronics for the generation of an electrical signal between the electrodes, so that the signal is able to be coupled through the electrodes into the body of the user and is detectable from the body by at least one electrode of the second device, will be discussed with reference to further aspects. In each case it will be assumed that the transmitter electronics are powered by a battery (rechargeable or not rechargeable).
The following aspects of the invention can contribute further to reduced power consumption. Each of the aspects can be employed singly, in combination with any of the other aspects, or in combination with any of the previously described aspects one to four:
Use of an activity detector (movement sensor) which turns off the emission of the signal as soon as the portable device is not moved for a long period of time and reactivates the signal if the device is moved. Such activity detectors are well-known and available—at low price—in the market.
At least partial supply of the transmitter electronics and/or charging of the battery by a solar cell and/or a generator, through which mechanical kinetic energy is converted into electrical energy.
Larger electrode spacing of at least 1 mm, preferably at least 1.5 or at least 2 mm.
A feature for the activation of the transmitter electronics by an external signal, e.g. a RFID- or UFH wake-up pulse. This wake-up pulse can also be coded, in order to only activate an authorized transmitter.
Design of the transmitter electronics or a part thereof as an ASIC, by which the power requirement is optimized by only activating the absolutely necessary electronic circuit elements and which for example in contrast to a non-application-specific microprocessor does not query any unused inputs.
Further there can be envisioned, also in any combinations with the above aspects, devices for the communication of the battery state to the user:
Transmission of a signal concerning the battery state—for example a specific bit, if the battery is almost empty—to the receiver. By means of this, it can then be effected that the information is conveyed to the user and/or another entity (control center, etc.), for example through an output device such as a display or an acoustic signal.
View of the battery state via an appropriate display feature of the portable device, for example at least an LED. Such an LED can blink, if the battery is nearly dead.
Provision for a “Low Comfort Mode” in which the transmitter electronics are inactive by default and must be actively activated, for example by pressing a button. After the activation it can be imagined that after a specific time the transmitter electronics automatically return to an inactive state. It can be imagined that the “Low Comfort Mode” is first engaged after a second, lower voltage threshold is crossed, while crossing a first, higher voltage threshold would only result in the activation of appropriate notifications (for example according to at least one of the above aspects).
The receiver comprises at least one receiver electrode and evaluation electronics, through which a signal that is generated by the capacitive-resistive signal transmission between the receiver electrode and a further electrode or between the receiver electrode and an electric ground can be detected and evaluated.
Particularly preferable in combination with the different aspects of the invention is the use of an information transmission method which relies on the spread spectrum method wherein the signal is transmitted as an ultra-broadband signal, preferably according to the example of WO 2007/112609. Ultra-broadband is defined as the use of a frequency range of a bandwidth of at least 20% of the center frequency or, as the case may be, carrier frequency. According to the teaching of this document, in particular a direct sequence spread spectrum is used. The data are preferably first modulated with a method of digital data modulation and subsequently spectrum-spread. In WO 2007/112609, methods are also described for the analysis of a capacitive resistive signal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention are illustrated by means of schematic figures. Shown are:

FIG. 1 is a depiction of a portable device according to the invention;

FIG. 2 is a depiction of a further embodiment of a portable device according to the invention with an inserted smart card of a further application;

FIG. 3 is a sectional view of a portable device with smart card;

FIG. 4 is a depiction of a portable device with an RFID module;

FIG. 5 is a mobile telephone in a form according to the invention;

FIG. 6 is a schematic of the mobile telephone from FIG. 5;

FIG. 7-9 are very schematic depictions of electrode arrangements according to the further aspect of the invention;

FIG. 10 is a schematic of a transmitter with possible in- and output units.

DETAILED DESCRIPTION OF THE INVENTION

The portable device according to FIG. 1 is substantially flat with a rigid support structure 2 of, for example, plastic. The device further comprises a first electrode 3 and a second electrode 4. The first and second electrodes 3, 4 are, for example, situated on or integrated into the outer surface of the larger faces of the support structure. They are manufactured of electrically conductive material, for example of a copper foil, aluminum foil or possibly another electrically conductive material. The support structure can be a single color and/or comprise inscriptions or similar (not depicted) on its outer surfaces, such that the electrodes are not recognizable as such by the user. As an alternative to this, the electrodes can also be manufactured from a transparent conductive material, which subsequently is further processed.
Also depicted schematically in the figure are a battery 6 and a set of control electronics 7, which comprise the means of generating a capacitive resistive signal through generation of an electrical voltage with a pre-determined time dependence between the two electrodes 3, 4. The integrated and/or applied electronic component parts of the control electronics can—this is true for all embodiments of the invention—for example include an ASIC for the control of the electrodes, EEPROM or EPROM memory, conductive pathways and/or further elements. Rather than plastic, the support structure can be of ceramic, of fabric or of a different material, the important factor is simply that the two electrodes are electrically isolated from one another.
The support structure 2 is now designed in such a way that between the electrodes an air gap 5 is present. Air has a very small dielectric constant of approximately 1 (i.e. nearly the vacuum value), therefore the capacitance of the capacitor that is created by the two electrodes is correspondingly small. Furthermore, the air gap can be used for other purposes, for example for the insertion of other elements.
The embodiment according to FIG. 1 comprises the portable device in addition to a schematically-depicted interface 8, which makes possible an exchange of data with a device that is inserted into the air gap, for example a “smart card”. The emitted capacitive resistive signal can thereby be made dependent on data that are input to this device. It is also possible that a data transmission object (plug connector or similar) of a device which otherwise remains outside the air gap can be inserted into the air gap, for example for the programming of the control electronics 7.
FIG. 2 depicts an illustrative example in which one of the electrodes is transparent. The transmitter 1 is designed as a so-called “smart card cover”. Smart card covers are known to those skilled in the art. They are designed as, for example, rigid, transparent shells, which for example can be attached to a piece of clothing and in which a smart card (i.e. a card-shaped medium with memory and communication functionalities) is able to be inserted.
The transmitter comprises a compartment for a battery 6 as well as control electronics for the at least partially transparent electrodes 3, 4, represented schematically by a chip 7. The smart card 11 is able to be inserted into an air gap. A possible inscription area 12 of the smart card remains visible behind the transparent first electrode 3.
FIG. 3 depicts a variant of the embodiment from FIG. 2, in which the smart card (or as the case may be other component part of an application which is distinct from the transmitter electronics) simultaneously serves as RFID identification medium. In addition to the elements already described, one sees schematically the RFID antenna 15, which here is not completely covered by one of the electrodes—in the depicted example by the transparent electrode 3. It has however been found that in cases of transparent electrodes—for example electrodes of ITO—the RFID communication also functions if, differently than is shown in the figure, both transparent electrodes completely cover the RFID antenna 15, i.e. if the transparent electrode 3 covers the entire upper surface shown in the figure.
FIG. 4 depicts a further embodiment that makes possible the combination with RFID technology. In this embodiment an—for example passive—RFID transponder 21 and an RFID antenna 22 are present in the portable device and at least partially situated between the electrodes 3, 4. A device according to FIG. 4 can, for example, serve as a key fob, which simultaneously serves as an identification medium for the access control (or another use) through utilization of the capacitive resistive coupling and as an RFID identification medium (“tag”). Since the need often exists—this is for example the case for a key fob—to keep the outer dimensions of the portable device relatively small, the electrodes 3, 4 should, if possible, cover a large portion of the device surface. Because the radio frequency signal that is generated by the electrically conductive electrodes is shielded, the problem can arise that the RFID signals inside the portable device are only weak. According to FIG. 4 it is thus imagined that the fields may be aligned by use of a magnetically soft ferromagnetic material 23 (for example a ferrite), such that they are coupled to the front face of the portable device, as is depicted schematically by the dotted lines in FIG. 4. The RFID antenna 22 is arranged corresponding to this field alignment, for example directly wound on the ferrite 23.
The RFID transponder 21 (or as the case may be the electronics that control the RFID functionality) can optionally have a communications link to the control electronics 7 which operate the capacitive resistive coupling. To this end there can be an electronic component that controls the RFID electronics 21 and the control electronics 7, or an integration of the RFID electronics and control electronics into a unified component—for example an ASIC—can be imagined.
FIGS. 5 and 6 relate to a portable device according to the invention that is designed as a mobile telephone 31. The first electrode 3 here is integrated into the display and is at least in the area of the display transparent, while the second electrode 4 as in the previous examples of transmitter electrodes is not necessarily transparent. The second electrode is situated on a reverse side of the mobile telephone (or rather as in the depicted example on the clamshell lid or on a different part of the mobile telephone) and can as the case may be also be formed by a conductive section of the housing. It is arranged at as large a fixed distance away from the first electrode as possible. In FIG. 6, it is very schematically depicted how the transmitter electronics 7 can be in connection with the remaining mobile telephone electronics: the mobile telephone supplies the transmitter electronics (3V), and a communication link exists over a I²C interface.
As an alternative to the depicted arrangement of the electrodes, both electrodes—of which then none must necessarily be transparent—can be present in an area of the mobile telephone distinct from the display, the placement of the electrodes at least partially next to one another is also possible.
Through the integration of the transmitter electronics 7 in a mobile telephone, several functionalities can be integrated together with one another in one portable device. The following are, for example, possible:
Dynamic alteration of the capacitive resistive transmitted data signals. The active data signal can be used as for example a PIN code, which can be altered arbitrarily often.
Increased security can be made possible, for example through so-called “rolling codes” or other known means of secure data transmission.
An even further increased security can be achieved as the UHF transmission means of mobile telephones (Bluetooth, 3G et.) is included in the information transmission procedure, for example as a downlink. This makes possible for example the use of known “challenge-response” systems. A central unit can also be included into communication and, for example, issue certificates (Cerberus etc.).
The mobile telephone with the transmitter electronics can be used as a programming device. A continuous data stream can be sent to the receiver with the help of the transmitter electronics.
Future mobile telephones will perhaps be furnished with NFC, active or passive RFID or low-power-wireless (for example as distributed under the brand name Wibree™ (www.wibree.com)) or Ultra Low Power Bluetooth or other standards of identification. Through the use of the capacitive resistive information transmission such an identification technology can be integrated into a single device, and the user must not necessarily know which technology is in actuality used. Particularly interesting is the combination of the approach according to the invention with other things, because for example the selective capacitive resistive information transmission follows a short-range (<10 m) contactless nonselective information transmission, and can work together with this.
Transmitter electronics for a mobile telephone can be designed according to standard dimensions and may be integrated in existing mobile telephone architecture without further ado.
Furthermore, the remarks made with respect to FIG. 4 concerning radio frequency signals and/or concerning interaction of RFID electronics with the control electronics for the capacitive resistive coupling, can also be valid for the integration into a mobile telephone.
Electronic devices are often furnished with a shield for electromagnetic fields, which protects the inner components of the device. These can, for example, be manufactured by sputter deposition technique on sections of the housing. According to an embodiment of the invention, now such a shield (“EMC shielding”) is arranged and contacted such that it can be used for the capacitive resistive coupling in the same manner as the first and second electrode. For example, the EMC shielding layer of the second housing part of a mobile telephone can be used as the first, or as the case may be the second electrode. This combination of the functionalities of “electrode for the capacitive resistive coupling” and “EMC shielding” is in particular unrestrictedly possible here, because the capacitive resistive signal frequencies proposed here are of less than 2 MHz, and are very small in comparison to the frequencies of the signals, for example UHF-signals, from which the mobile telephone electronics are shielded. The capacitive resistive signal functions quasi statically. For high frequencies the capacitance between the two electrodes functions like a short circuit of the electrodes against one another. Additionally, a parasitic capacitance and/or a capacitance specifically envisioned for it can operate between the electrodes (or as the case may be one of the electrodes) and a reference voltage (GND) as a virtual short circuit in relation to this reference voltage, while the electrodes are decoupled from one another, and if relevant from the reference voltage, for the lower frequencies of the capacitive resistive coupling.
FIGS. 7 to 9 relate to the further aspect of the invention and depict very schematically electrode arrangements with non-parallel electrode faces.
According to FIG. 7 two electrode pairs 71, 72 which stand at an angle to one another (at a right angle in the example shown) are present. The electrode pairs can be activated simultaneously or alternately or in an arbitrary sequence.
Other arrangements than those depicted are possible for such electrode pairs, for example in which the electrode pairs form four sides of a cube, which also features the electronic component parts.
A disadvantage of a configuration with two orthogonal or nearly orthogonal electrode pairs, is that large electrode faces must be accommodated by a relatively large volume of the whole transmitter.
FIG. 8 depicts an arrangement with three electrodes 51, 52, 53, which in cross-section form a triangle. The activated electrode pairs, between which the signal is generated, are for example, formed by the first and the third electrodes 51, 53 and by the second and the third electrodes, 52, 53.
FIG. 9 depicts an arrangement with three electrode faces, of which a first and a second electrode face 61.1, 62.2 are formed by a common bent first electrode 61. The third electrode face 62 is formed by a second electrode 62 that is separate from the first electrode.
As described above, the electrodes are preferably held at as great a distance from one another as possible, and the dielectric constant of the medium(s) between the electrodes is as small as possible. Still further aspects that are associated with as small an electrical consumption as possible and/or the monitoring of the battery charge are described with reference to FIG. 10. The components in the figure are optional and can be present singly or in combination.
The transmitter electronics 7 according to FIG. 10 have a connection to an output device 41, which makes possible a status message of the battery charge. Such a one can comprise a light emitting diode (LED) or many light emitting diodes. Furthermore an activity detector 44 can be present, which turns off the electrode controls if the portable device is not moved. As an alternative or possibly as a replacement thereof, it can also be imagined that the transmitter electronics are only active if a wake up signal, for example an LF-wake up signal, is detected. A corresponding detection unit is indicated by the reference numeral 45. Configurations with LF detectors for the starting-up of a circuit are already known to those skilled in the art.
In the figure, an “on” switch 42 is depicted. Such a one can for example be employed if the electronics have been shut off in a “low comfort mode” because of a nearly-empty battery. Through actuation of the switch the electronics are again activated for a limited time. Also depicted is an on-off switch, through which the whole portable device can be turned off if it is not needed. In the case of a connection to a “host system” (for example a mobile telephone) 31 the management of electrical requirement is possibly somewhat less important.
The “turning-off of the electronics” does not preclude that individual components from remaining active, for example the internal clock. By “turning-off” is expressly also meant the transition into such a partially active “sleep” mode.

Claims

1.-13. (canceled)

14. A portable device for the transmission of signals to a second device, wherein the portable device is wearable by a user, the portable device comprising:

at least two electrodes and transmitter electronics for the generation of an electrical signal between the electrodes, such that the signal is able to be coupled into the body of the user by the electrodes of the first device and detected by at least one electrode of the second device,

the portable device further comprising at least one of the group comprising:

component parts of the transmitter electronics arranged between the electrodes,

components of another application distinct from the transmitter electronics arranged between the electrodes, and

and an air gap between the electrodes.

15. The portable device according to claim 14, comprising an air gap between the electrodes, wherein the air gap has dimensions that are matched to those of an element distinct from the portable device, such distinct element being able to be inserted into the air gap with an accurate fit.

16. A portable device for the transmission of signals to a second device, wherein the portable device is wearable by a user, the portable device comprising:

wherein the distance between the electrodes amounts to at least 1 mm.

17. The portable device according to claim 16, wherein the distance between the electrodes amounts to at least 1.5 mm.

18. The portable device according to claim 17, wherein the distance between the electrodes amounts to at least 2 mm.

19. The portable device according to claim 18, further comprising at least one of the group comprising:

component parts of the transmitter electronics arranged between the electrodes,

and an air gap between the electrodes.

20. The portable device according to claim 14, comprising an air gap between the electrodes, the portable device further comprising, in the air gap, a communications interface for the exchange of data between the portable device and a device that is distinct from the portable device and can be inserted into the air gap.

21. The portable device according to claim 14, wherein a communications link exists or can be formed between the transmitter electronics and an input unit and the transmitter electronics are designed and/or programmed such that the electric signal is a function dependent upon the data that is input into the input unit.

22. The portable device according to claim 21, wherein component parts of an application distinct from the transmitter electronics are arranged between the electrodes, and wherein the portable device is designed as a mobile telephone and the input unit is the input unit of the mobile telephone.

23. The portable device according to claim 14, wherein at least one of the electrodes of the portable device is at least partially transparent.

24. The portable device according to claim 14, further comprising an antenna for communication by means of induction or over electromagnetic waves.

25. The portable device according claim 14, further comprising an active or passive RFID transponder.

26. The portable device according to claim 25, further comprising a ferromagnetic element through which electromagnetic fields are able to be directed such that they are strengthened in a region of an RFID antenna.

27. The portable device according to claim 14, wherein the electrodes further function to shield against electromagnetically interfering signals.

28. The portable device according to claim 14, wherein the electrodes are in an arrangement of electrodes with electrode faces that are not parallel with one another.

29. A method of controlling access to an object, the method comprising the step of:

providing a portable device for the transmission of signals to a second device, wherein the portable device is wearable by a user, the portable device comprising at least two electrodes and transmitter electronics for the generation of an electrical signal between the electrodes, such that the signal is able to be coupled into the body of the user by the electrodes of the first device and detected by at least one electrode of the second device, the portable device further comprising at least one of the group comprising:

component parts of the transmitter electronics arranged between the electrodes,

and an air gap between the electrodes,

the method comprising the further steps of using the portable device for transmitting authentication information between the first and the second device, and of using the authentication information to control the access.