GB2416924A - Radio communication method and device with antennae arranged close to a body - Google Patents

Abstract

A radio communication method or device comprises signal generating means 4 located close to a human body which is connectable to at least two antennae 10- 15 where each of the said antennae is located at different positions close to the body. The signal generating means 4 may include antenna selection means used to select at least one of the antennae as the communication antenna. An individual antenna or a particular combination of phase adjusted antennae may be used. The antennae may be tested cyclically to identify, by standing wave ratio or received signal strength, the antenna arrangement which is likely to be the most efficient signal transmitter. The power supplied to the selected antenna may be reduced to minimise the irradiation level being applied to the body. The antennae 10 - 15 and signal generating means 4 and possibly vital parameter sensors (e.g. temperature and /or pulse) may be built into a multi-layered textile used to form clothing. This clothing may be used by firefighters. Connection between the signal generator and the antennae may be provided via overlapping regions of their support means where inductive coupling could be employed. During an emergency situation frill transmission power may be applied to all the antennae.

Description

Method and device for the radio transmission of signals nenerated close to

the body The invention relates to a method and a device for the radio transmission of signals generated close to the body.

An application is conceivable wherever personal transmission units have to be carried by users under changing environmental conditions. Examples are to be found above all with the use of transmission units arranged close to the body, when the carrier of these transmission units is in motion and a reliable radio transmission is required.

Decisive advantages of wireless systems for data transmission compared with wire-bound systems are rapid applicability and low fitting cost, availability for area coverage and, frequently, advantages with handling. Especially in the case of a fitting close to the body, there are scarcely any restrictions on freedom of movement.

In the wake of technical improvements, a further increase in the widespread use of wireless radio transmission systems is to be expected. Possible or associated potential hazards or adverse effects linked to such a development need to be reliably identified and reduced.

One factor that is at any rate associated with the possibility of sporadic adverse effects is the increased penetration of the human living space with electromagnetic alternating fields.

Unfavourable effects on health or well-being are at least imputed in part to harmonic-rich digital signals and high frequency fields in particular. These adverse effects that have been considered can be explained in part physically, especially in connection with polar fluids, usually not demonstrably at relevant field strengths, but also not to be ruled out with certainty. The responsible handling of technical infrastructure, however, also requires the elimination of hypothetical adverse effects on health as far as possible.

In justified cases, where such a hypothetical adverse effect has to be accepted, the potential risk needs to be kept as low as possible. In addition, minimization of radiation exposure due to electromagnetic alternating fields is also appropriate in order further to improve acceptance of wireless systems, which could pave the way to utilising the undoubted advantages of such systems in further areas of application.

Such an area of application is the use of physical sensors directly on the human body. A wire connection has decisive handling drawbacks here compared with a wireless connection.

Especially with the application of various sensors, however, their handling should be as simple as possible and the carrier's freedom of movement limited as little as possible.

A particularly sensitive subject is the generation of high-frequency electromagnetic fields in the immediate vicinity of the body, which is certainly caused at least in part by the widespread popularization of high-frequency mobile telephony. Vicinity of the body is to be regarded in this connection as the region characterized by distances from the surface of the body that are similar to or smaller than the dimensions of the human body.

On the one hand, the use of transmitters for radio transmission requires certain minimum levels in order to guarantee reception; on the other hand, it is precisely the acceptance of arrangements close to the body that offers decisive advantages as regards comfort, availability and possible applications of wireless transmission systems. The signals to be transmitted are often generated directly in the vicinity of the body. If they are sent from close to the place of generation, this means a reduction in expenditure, since the fitting of means for routing the signals from the place of generation to a separately arranged transmitter can largely be dispensed with.

Transmitters arranged directly in the vicinity of the body, however, give rise to other technical problems. Part of the transmission power may be absorbed by the tissue of the human body.

This is the case especially with high frequencies that come into consideration. This gives rise to an unfavourable radiation characteristic. If the human body is located between the transmitter and the receiving antenna, the former as an absorbing obstacle has to be overcome by an increased transmission power. Particularly at frequencies above 1.3 Gigahertz, attenuation by water molecules is particularly effective. This is associated with an unwanted marked signal attenuation. Depending on the transmission power, moreover, undesired heating of the body fluid can also occur, since the water molecules are excited into oscillations on account of their polar character. A high radiation exposure of this kind in the head region is particularly problematic, which is potentially associated with the possibility of the occurrence of eye damage.

A concentration of the transmission power on the head region is therefore relatively unfavourable. It is precisely in this area, however, according to the prior art, that a particularly marked transmission power output takes place, especially in mobile phone technology.

In principle, it is possible in the case of poor transmission quality or reception reliability to overcome any obstacles standing in the way by increasing the transmission power. 4 -

Furthermore, it is known to optimise the reception geometry by using several receiving antennas and a possible switch-over between these antennae. The use of several receiving antennae in cars can be mentioned here as an example.

The present invention is as claimed in the claims.

The present invention provides a method and a device which make it possible to achieve multidirectional radiation with low transmission power and high reception reliability.

The invention proceeds from the fact that the transmission power required for the transmission from a transmitter to a receiver is essentially influenced, apart from by the distance between transmitter and receiver, by whether obstacles attenuating the transmission are located in the direct transmission path. In the case of transmitters carried close to the body, the carrier's body, when the carrier himself is in motion, can move as an attenuating obstacle into the transmission path. In such cases, constant fluctuations of the received power occur during reception when the carrier is in motion. In order to avoid a partial interruption of reception in such cases, it is in principle possible to work with an overall increased transmission power.

The invention, however, proceeds on the basis that it is possible, with the use of several antennae, to arrange at least one in such a way that no particularly marked attenuating obstacle is arranged between it and the receiver. If one antenna meets this requirement, then at least it is used as a transmitting antenna. This enables the reliable transmission of signals generated close to the body with a small transmission power. If the radiation properties change, a switch from one antenna to another can also be made during the transmission. The method according to the invention consists in a radio transmission of signals generated close to the body by means - 5 - of an arrangement of at least two antennae arranged at different positions close to the body, wherein a selection of at least one antenna is made before or during the transmission, said antenna acting as the transmitting antenna.

The method Is implemented with a device for a radio transmission of signals generated close to the body, said device comprising at least one electronic module which generates the signals to be sent, at least two antennae arranged at different positions close to the body and affixed to at least one means of support, and means for selecting the antenna or the antennas by means of which the transmission of the signals is to take place. Articles of clothing, items of equipment carried on the body or various means of fixing can be used as the means of support.

The selection of the transmitting antenna can take place in various ways. The effect of this is that at least one antenna can communicate with a receiving station as directly as possible, without having to overcome markedly attenuating obstacles. In this way, it is possible always to work with minimum transmission power by selecting in good time the antenna that is optimum at the time, without there being a risk of reception being interrupted.

The selection of the antenna can take place through a simple prediction and manual selection. It may be expedient for the selection of the antenna to take place in dependence on at least one technical parameter characterizing the radio transmission. Such a technical parameter is the standing wave ratio. The standing wave ratio characterizes the radiated transmission power in relation to the supplied transmission power. If only a small part of the supplied power is actually radiated, the antenna is operating inefficiently. In order to guarantee a reliable radio transmission, the supplied power would have to be increased markedly. In the method - 6 - according to the invention, however, a change to another antenna takes place, which is characterized by a better standing wave ratio.

As an alternative to determining the antenna with the best standing wave ratio at the given time, a process arrangement can be present in which a check is merely made to see whether a selected transmitting antenna has a standing wave ratio that lies above the preset threshold value. If several antennas lie above this threshold value, an antenna is selected from this plurality as the transmitting antenna according to a further criterion.

The integration of a shielding layer into the protective clothing is particularly advantageous. This effectively prevents irradiation of the supplied transmission power into the region of the body interior.

One possibility of concentrating transmission power in directions pointing away from the human body is to use the antennas as shortened l/4 radiators with an earthing base, which project at right angles to the earthing area consisting of a textile structure. This has the advantage that the earthing area required for the antenna shortening can also be integrated into the textiles, for example by the weaving-in of electrically conductive fibres. This antenna principle almost completely eliminates radiation in the direction of the body. The length of the radiators can be shortened by the use of extension coils and by the use of helix antennas in the case where high radio frequencies are used, to such an extent that the radiators together with the sensors can be integrated in small sensor modules into the textiles.

An increase in the radiation power is possible with an arrangement of radiators in groups, so- called phase-coupled antenna arrays with directional characteristic. If the receiver is located in - 7 the direction of the maximum radiation power, transmission powers that are again reduced can thus be worked with.

Examples of the length dimensioning of such antennas are known from CB radio. Frequencies of 27 megahertz, for example, are used there, corresponding to a wavelength of 11 m and a \/4 radiator of just under 3 m. In actual fact, however, short-rod antennae with lengths around 12 cm are used, which can be achieved by the use of extension coils. If this design principle is transferred to frequencies commonly used in the mobile radiotelephone service, a scaling factor of approx. 60 emerges. A 12 cm long short-rod antenna becomes a 2 mm long antenna. The 1.6 Gigahertz range can be made accessible with such miniaturized antennae. The 2.4 Gigahertz range, the 5 GHz range or the range of the ISM bands, i.e. 868 megahertz or 910 megahertz, can similarly be made accessible.

Other antenna structures, i.e. flat structures such as helix antennae or dipole structures arranged essentially parallel to the surface of the body, can also be designed to produce directivity pointing away from the body and be integrated into textile layers. Good radiation results can also be achieved if the trunk of the body is used as a shielding or reference area of antenna radiators fitted at the extremities.

If such antenna structures are integrated into multi-part items of clothing, care must be taken on account of the high frequencies to ensure that reliable screening takes place in overlapping areas. This is achieved for example by clear-cut overlapping of the individual parts of the clothing. Much larger dipole geometries can also be produced by arranging antenna structures parallel to the surface of the body, which means that it is possible to work at low frequencies.

The transmission power, which is supplied from the transmission end stage into the individual 8 - antennae, must be adapted to the circumstances, e.g. different items of clothing with alternating equipment. Cyclical switching between the individual antennae can then improve the effective radiation when the person is in motion. A situation-adapted direct selection of individual antennae can also improve the effective radiation and thus minimise transmission errors. An integrated measurement of the reflection factor or a determination of the standing wave ratio integrated into the transmission sequence, for example, can assist in selecting the antenna with the best or at least an adequate transmission effect.

An alternative to this is offered by the possibility of evaluating the received power on the receiving side by cyclical changing of the antennas and selecting the antenna which enables optimum reception. This, however, requires a bi-directional data exchange, since the selection must be initiated from the receiver.

A rapid reaction to changing radiation conditions is possible through the use of the method according to the invention. These can change for example if the radiation of the intended transmission power is temporarily hindered by the motion-related position changes of various items of equipment in a rucksack or metallic compressed-air bottles. The same applies to antennas positioned on the abdomen side if a person is moving along flat over ground beneath him that may even be metallic. In both cases, a reduction in range may be the consequence. In both cases, a concentration of the transmission power according to the invention, for example to antennae arranged close to the shoulders, is advisable. If, in particularly unfavourable cases, excessively strong attenuation of all the antennae occurs on the upper body, it is possible for a short period to switch over to an antenna integrated for example into the helmet or otherwise fitted in the vicinity of the head, until the transmission conditions for using the other antennae are more favourable again. This can take place automatically, for example as a result of - 9 corresponding movements of the transmitting person or the removal of attenuating obstacles, or can be brought about in a targeted manner.

In emergency situations, it is in addition advantageous to provide for the possibility of triggering cyclically, with full transmission power, all the antennas available on the body, i.e. including a helmet antenna close to the head that is not prioritised in the normal situation, in order to ensure that an emergency call that may need to be transmitted is reliably received.

It may also be of advantage to integrate a multi-part antenna structure according to the invention into an additional article of clothing that can be used as an accessory to the existing items of equipment. Such an antenna structure, for example in the form of a jacket, can be designed as an accessory for mobile phones. Particularly for frequent usem of mobile phones, the use of such a jacket can be an alternative to the transmission power constantly delivered in the vicinity of the head.

The connection of individual antennae among one another can take place in a wire-bound manner. A system of electrical conduction paths woven into textile structures can be provided for this purpose. Textile structures modified in this way can be incorporated without problem into articles of clothing to be produced.

If individual items of clothing are overlapping, the individual items of clothing can be connected to one another in the overlapping area by means of an inductive coupling with the aid of inductive transmission means.

- 10 - A frequency range of less than 1 megahertz, for example 125 kHz or 134 kHz, can be used with the inductive coupling, which means that the electromagnetic load does not need to be taken into consideration with respect to energy absorption by human tissue. In the case where use is made of higher frequencies (for example 13.56 MHz) for the coupling, shielding layers on the body side can be used in the overlapping areas of the individual items of clothing, said shielding layers suitably attenuating the radiation directed towards the body.

As an alternative to integrating the antenna structure into the clothing, the fixing of antennas according to the invention can take place in a tack-on fashion by means of pieces of textile fixable for example with Velcro. In addition, consideration can be given to the integration of antennae according to the invention into so-called pads, for example as sticking or electrode plasters for direct application on the skin.

Without being limited thereto, further explanations concerning advantageous developments of the invention are provided using the example of protective clothing for firefighters.

Appertaining thereto, the figures show the following: Fig. 1 is a schematic diagram of an exemplary layer structure contained in an article of clothing designed according to the invention, Fig. 2 is a schematic drawing of preferred areas for the fitting of antennas according to the invention to protective clothing, Fig. 3 is a schematic detail from protective equipment for firefighters equipped according to the invention.

A particularly advantageous use of the method according to the invention can be achieved by items of equipment that contain a multilayer structure of textile layers. Fig. 1 shows one such layer structure diagrammatically. Various sensors 1 for measuring vital parameters are contained in a lower layer 2. They can, for example, be embedded temperature and pulse sensors. Above the latter is a layer 3, into which operating and evaluating electronics 4 and possibly batteries are integrated. The battery arrangement can also be designed as a separate layer 5. Above the latter is a suitably modified textile layer 6, which acts as a high- frequency shield. For this purpose, layer 6 acting as a shield can be interlaced or coated with metallic components.

In an advantageous form of embodiment, a number of shielding layers can be present and integrated between the individual functional layers. Above the latter is a textile layer 7, into which various high-frequency antennae 8 including a power end stage 9 are integrated.

Shielding layer 6 on the one hand prevents the irradiated transmission power getting into the interior of the body and, on the other hand, protects the integrated operating and evaluating electronics 4 against interference effects caused by irradiated transmission power during operation. Operating and evaluating electronics 4 include means that make it possible, by means of standing wave measurements, to determine the antennae which are irradiating a proportion of the energy fed into them that lies above a preset threshold value, or to determine the antenna which is irradiating as high a proportion as possible of the energy fed into it.

Operating and evaluating electronics 4 further include means for selecting individual antennae as the transmitting antenna. - 12

Fig. 2 shows preferred regions for the fitting of antennae according to the invention to protective clothing of firefighters.

When processed into wearable items of equipment, for example items of clothing, the multi-layer textile structure fomms a means of support for accommodating an antenna arrangement according to the invention. In this way, a number of antennae with sensors for monitoring vital parameters, batteries, operating electronics and other components can be integrated into a textile layer structure and thus into protective clothing. The layer structure is at least a component part of the protective clothing of firefighters.

Antennae are included in head region 10, shoulder region 11, abdomen region 12 and back region 13. Furthermore, antennae can be integrated on arms 14 and legs 15. All the antennae can be connected individually or in various combinations to power end stage 9, which in turn is connected to the outputs of the sensors for monitoring vital parameters or of operating and evaluating electronics 4.

During the movement sequences typical of operational personnel, very marked attenuation of the radiation of individual antennae occasionally occurs. When crawling on the stomach for example, only a small radiation of transmission power can take place from antennas in the abdomen region. In this case, it is possible according to the method according to the invention to switch over without problem to an antenna in the shoulder or back region.

It is particularly advantageous if variable different items of equipment are included as antenna carriers. These can be, for example, safety helmets, gloves, compressed-air bottles, rucksacks or suchlike. If the incorporation of individual items of equipment leads to the covering of 13 individual antennae, it is particularly advantageous if these items of equipment themselves include in turn an antenna and can act, as it were, as a replacement for the covered antenna.

It is advantageous if, at the location of the integrated antennae, there are arranged in each case inductive transmission means which, when the item of the equipment is being used, pemmit the signals originally intended for transmission through the covered antenna to be routed to the antenna of the item of equipment being used. This routing can take place according to the transformer principle.

Fig. 3 shows a detail from protective equipment for firefighters equipped according to the invention. Power end stage 9 is integrated into a jacket 15 with an antenna 11 close to the shoulder. A further antenna 10 is integrated into a fire protection mask 16. Power end stage 9 can be connected via connection lines 17 to antenna 1 1 close to the shoulder and/or to inductive transmission means 18 in the collar region. If fire protection mask 16 is duly put on, there is an overlap in the collar region between fire protection mask 16 and jacket 15. In this case, inductive transmission means 18 in the collar region correspond to inductive transmission means 19 in the lower region of fire protection mask 16, which are connected to antenna 10 via a connection line 20 integrated into the mask. By using interactive transmission means 18, 19, it is thus possible to connect power end stage 9 in jacket 15 to antenna 10 close to the head. In this way, antennae located on other items of equipment can be included in antenna configurations according to the invention and be used, according to the claimed method of selection, for the transmission of signals generated close to the body. In principle, other connection means can also be used so that the signals to be sent are routed over the boundaries of individual means of support.

Claims (26)

1. A method for the radio transmission of signals generated close to the body via an arrangement of at least two antennae arranged at different positions close to the body, wherein a selection of at least one antenna is made before or during the transmission, said antenna acting as the transmitting antenna.

2. The method according to claim 1, in which the selection of the antenna takes place in dependence on at least one technical parameter characterizing the radio transmission.

3. The method according to claim 1 or 2, in which, by means of standing wave measurements, the antenna is determined which is Irradiating the highest proportion of the energy fed into it and this antenna is selected as the transmitting antenna.

4. The method according to claim 1 or 2, in which, by means of standing wave measurements, the antennae are determined which are irradiating a proportion of the energy fed into them that lies above a threshold value and there is selected from these antennae at least one antenna which acts as the transmitting antenna.

5. The method according to claim 1 or 2, in which individual antennae or antenna combinations are used successively as the transmitting antennae, whereby the antenna or antenna combination is determined with which the maximum input signal strength will result at a receiver and the antenna or antenna combination thus determined Is selected as the transmitting configuration.

6. The method according to claim 1 or 2, in which individual antennae or antenna combinations are used successively as the transmitting antennae, whereby the antennae or antenna combinations are determined with which an input signal strength that lies above a threshold value will result at a receiver, in order to select a transmitting configuration from these antennas or antenna combinations.

7. The method according to claim 1 or 2, in which the antenna selected as the transmitting antenna holds out the prospect of the least irradiation into the body region.

8. The method according to claim 4 or 6, in which, in the case where the threshold value of the irradiated share of the power or of the input signal strength on the receiver side is exceeded with the use of various antennae or antenna combinations as the transmitting configuration, the transmitting configuration is selected that holds out the prospect of the lowest irradiation into the body region.

9. The method according to at least one of claims 1 to 8, in which the selection of the at least one antenna which is acting as the transmitting antenna is repeated cyclically.

10. The method according to at least one of claims 2 to 8, in which the technical parameter characterizing the radio transmission is checked cyclically and, when it lies outside a predetermined range, a new selection of the at least one antenna acting as the transmitting antenna is carried out.

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11. The method according to at least one of claims 1 to 10, in which a reduction of the transmission power is carried out after selection of the at least one antenna which is acting as the transmitting antenna.

12. The method according to claim 11, in which the transmission power is reduced until a predetermined maximum value of the input signal strength is fallen below.

13. The method according to at least one of claims 1 to 12, in which maximum transmission power is applied to all the available antennae after the occurrence of an emergency status characterized by at least one established parameter to be monitored.

14. A device for a radio transmission of signals generated close to the body according to claim 1, comprising at least one electronic module which generates signals to be sent, at least two antennae arranged at different positions close to the body and affixed to a means of support and means for selecting the antenna or the antennae by means of which the transmission of the signals is to take place.

15. The device according to claim 14, in which each of the antennae is capable of transmitting by itself alone.

16. The device according to claim 14 or 15, in which the means of support can be affixed to the body.

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17 - 17. The device according to any one of claims 14 to 16, in which at least parts of items of clothing serve as the means of support.

18. The device according to claim 17, in which the items of clothing comprise a multi-layer textile structure, which includes at least one layer with embedded sensors for the measurement of vital parameters, a layer with integrated operating and evaluating electronics, a layer for the shielding of high-frequency electromagnetic radiation and a layer with integrated antennae.

19. The device according to any one of claims 14 to 18, in which shortened quarter-wave radiators are comprised as antennae.

20. The device according to any one of claims 14 to 18, in which dipole structures arranged essentially parallel to the surface of the body are comprised as antennae.

21. The device according to any one of claims 14 to 18, in which phasecoupled antenna arrays are comprised as antennae.

22. The device according to any one of claims 14 to 21, in which at least one electronic module, which generates signals to be sent, is fixed to a means of support and at least one antenna is fixed to a further means of support, whereby the means of support have an overlapping region in which connection means are contained so that signals to be sent are routed from the electronic module to the antenna.

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23. The device according to claim 22, in which inductive transmission means for the routing of the signals to be sent are contained in the overlapping region of the means of support.

24. The device according to any one of claims 14 to 23, in which the means for the selection of the antenna or the antennae by means of which the transmission of the signals is to take place comprise means for a standing wave measurement.

25. A method of radio transmission of signals generated close to the body substantially as hereinbefore described, with reference to, and/or as shown in, the accompanying drawings.

26. A device for the radio transmission of signals generated close to the body substantially as hereinbefore described, with reference to, and/or as shown in, the accompanying drawings.