WO2008067570A2

WO2008067570A2 - Screened wireless telephone device and method

Info

Publication number: WO2008067570A2
Application number: PCT/ZA2006/000141
Authority: WO
Inventors: Ralph Bysäth
Original assignee: Nes No-Elektro-Smog Ag; Aqua Filter (Pty) Ltd
Priority date: 2006-12-01
Filing date: 2006-12-01
Publication date: 2008-06-05
Also published as: WO2008067570A3

Abstract

In the wireless telephone device according to the invention, screening means (42) for the protection of a user against electromagnetic waves emitted by a transmission antenna (31) of the wireless telephone device, are integrated in a casing (10) of the wireless telephone device, in particular in a front portion (12) of the housing which faces the user. The screen means (42) includes screening paints (32), screening fabrics (34) and screening foils (40). SAR reductions better than 80 % are attained.

Description

Screened wireless telephone device and method

The present invention relates to a wireless telephone device according to claim 1 , a method of screening a wireless telephone device according to claim 11 and a use as claimed in claim 20.

The present disclosure is based in part on an invention described in EP 05 012 109.4 which has not yet been published. To that extent protection for that disclosure is sought for PCT member states not covered by EP 05 012 109.4. Protection for new matter now disclosed is sought for all PCT member states and regions.

Telephone devices, in particular mobile wireless telephones, cordless telephones and Bluetooth®-speaker devices, (cordless head sets), permit communication from numerous localities with remote stations without spatial limitation due to supply cables. Generally, the communication is based on an exchange of data between the mobile wireless telephone device and a basis station. For the data exchange electromagnetic waves in the high frequency range, for example according to the GSM-standard at 900 MHz and at 1800 MHz or according to the Bluetooth®- standard (IEEE 802.15.1 ) at 2,4 GHz, are used.

The electromagnetic waves generated by such devices are not only carriers of information but also of energy. Depending on the frequency range and the transmission output as well as the distance of a user from the transmitting antenna, the electromagnetic waves penetrate more or less deeply into the body of the user and, as a result of absorption processes during their passage in the body, deposit their energy in biological tissue. This can be of particular importance, in particular with wireless telephone devices in which, during transmission, the transmission antenna is removed by only a few centimetres from the head of the user.

The absorption or "deposition" of high frequency electromagnetic waves in human tissue may lead to thermal and/or even non-thermal effects. In particular, long term effects of non-thermal action, for example an increased risk of cancerous diseases, have to date been inadequately researched and cannot be excluded. Investigations in Scandinavia have revealed that persons who frequently communicate through wireless telephone devices report more frequently headaches, tiredness and skin irritations than persons who, by comparison, telephone less.

The industry accordingly routinely tests such devices for the rate at which such radiation absorption takes place under conditions of use, by standardised methods known as Specific Absorption Rate Testing (SAR testing).

Besides the thermal and non-thermal effects of electromagnetic waves on biological tissue, electronic instruments can be interfered with. This may, for example, apply to heart pace makers, to intensive care stations in hospitals or in case of aircraft.

In known wireless telephone devices, the electromagnetic waves are, accordingly suppressed by screening means which may be provided outside the housing of the wireless telephone devices, for example in the form of covers for mobile wireless telephones, in order to thereby prevent or reduce the thermal and non-thermal effects in biological tissue or technical interference effects. Screening has also been applied inside wireless telephone devices in order to suppress internal interference within such devices.

GB 2390957 A discloses a wireless telephone device including a housing having a front portion and a back portion, the housing containing circuitry for generating electromagnetic waves, a transmission antenna for emitting the electromagnetic waves and screening means against electromagnetic waves generated by the circuitry, the front portion, in the present context, being considered to be that portion which, in use, faces the user. Although in GB 23 909 57A many steps are described for screening the device, inter alia, in order to reduce "energy deposition" in the body of the user, heavy emphasis is placed on enhancing radiation performance for improved transmission characteristics (increased connectivity between transmitter and receiver) as well as on the screening of components against internal interference.

Indeed, on closer inspection it is clear that the embodiments described, whether alone or in combination and in spite of the complicated and expensive measures proposed, cannot be expected to attain more than partial screening of the user against deposition of RF energy and to attain such very low SAR ratings as would be desired, inter alia in view of the continued use of external antennae without any screening and for other reasons which will become apparent from what follows. No data on reductions in SAR values are disclosed.

It is accordingly an object of the present invention to propose screened wireless telephone devices and methods of screening which have been proven to be capable of attaining excellent SAR reductions without impairing the desired transmission performance.

It is a further object to achieve the aforegoing in a particularly simple and inexpensive manner which can be applied inter alia to almost all types of mobile telephones and similar devices.

It is generally an object of the present invention to minimise the technical and biological effect of electromagnetic waves on the user during the operation of a wireless telephone device.

This object is attained by the wireless telephone device according to claim 1. The wireless telephone device according to the invention is of the type including a housing having a front portion and a back portion, the housing containing circuitry for generating electromagnetic waves, a transmission antenna for emitting the electromagnetic waves and screening means against electromagnetic waves generated by the circuitry, the front portion being that portion which, in use, faces the user.

According to the invention the front portion and transmission antenna are provided with screening means against electromagnetic waves generated by the circuitry, substantially uninterruptedly, over so much of the area of the front portion and transmission antenna facing the user, including all apertures through the front portion, that deposition of the energy of the generated electromagnetic waves in the body of the user which would occur in the absence of such screening is largely prevented or suppressed. More particularly, the deposition as measured by Specific Absorption Rate (SAR) testing is reduced by not less than about 70%, preferably not less than about 80%, more than 80% and even between 90 and 100% improvement being attainable by following the present teachings carefully.

Preferably, the entire area facing the user of the front portion is screened by the screening means substantially uninterruptedly.

It has been found to be particularly important that all apertures through the front portion, i.e. facing the user when using the device, are completely screened off. this applies in particular to loudspeaker apertures, microphone apertures and keypad apertures. It was found that even if the solid parts of the housing front portion are thoroughly rendered impervious to the generated electromagnetic radiation, the effect on SAR values is unsatisfactory unless these apertures are thoroughly covered by screening. For this purpose covering with a suitable flexible screening cover, e.g. foil or fabric is particularly effective.

According to preferred embodiments the screening includes a fine-meshed grid-like screening fabric which covers at least parts of the front portion of the housing, which include loudspeaker apertures and/or, if present, microphone apertures of the housing and/or the rear of a keypad or keypad assembly, preferably applied in such a manner that the fabric alone or in combination with the other screening materials forms a continuous substantially uninterrupted screen extending over substantially the entire area covered by the front portion. "Substantially uninterrupted" denotes the avoidance of gaps through which radiation can bypass the screen and escape through the front portion. In this context it is to be noted that the screening materials inside the housing act as reflector by which the radiation may be reflected repeatedly until it finds a gap through which to escape. Such gaps must, therefore, be avoided.

Also, where the front portion includes a display window, this must also be suitably screened to render it impervious or resistant to the passage of generated electromagnetic waves other than visible light, for example in that the display window is formed from or screened by a transparent material having screening properties against the generated electromagnetic waves other than visible light.

For the screening effect to be effective it is particularly important that the transmission antenna is also screened towards the user. This may be achieved in that the transmission antenna is accommodated in a position wherein the front portion, including the screening means associated with the front portion, screen the user against generated electromagnetic radiation emitted by the antenna, e.g. in that the transmission antenna is accommodated inside the housing.

Generally, the screening means are electrically conductive and are connected in an electrically conductive manner to one another and/or, where appropriate to an earthing contact. Such screening means may include a screening coating and/or screening fabric and/or a screening foil and/or the feature that the housing and in particular the front portion thereof js made of a material having screening properties, e.g. being moulded from a conductive plastics.

Conductive screening paints may be used for a screening coating and also for adhesively bonding various screening materials, e.g. fabrics or foils to one another and/or to the housing regions and parts to be screened. In these various manners and as described further below, the screening may be effectively integrated with and/or accommodated and/or applied in or to the housing, inside or outside of the housing, preferably inside, and in particular to the front portion of the housing.

The invention can be practised such that the screening means can be introduced into the housing in a standardised manner during the manufacture of the wireless telephone device, involving minimal additional space requirement, and cannot intentionally or by accident be removed, wrongly dimensioned or faultily applied. In addition to this, the screening means can be designed and fitted effectively, that is to say, with an optimal screening effect involving minimal material consumption. An additional external cover involving screening means is not necessary.

According to a further aspect of the invention there is provided a method of screening a wireless telephone device of the type as aforesaid. The invention is characterised by the features set out in claim 11. The method may be used to improve the Specific Absorption Rate (SAR) of a wireless telephone device by from about 80 to about 100% as compared with the same device without said screening.

The invention may also be applied by retrofitting existing devices.

A specific embodiment is illustrated purely diagrammatically in the accompanying drawing:

Fig. 1 shows the interior of a front portion of a housing of the wireless telephone device according to the invention and

Fig. 2 shows the rear portion associated with the front portion of the housing shown in Fig. 1 together with functional modules installed therein. The wireless telephone device to be described in detail in what follows represents a mobile wireless telephone also known as a cell phone. However, a person skilled in the art will have no difficulties as part of his normal skills to apply the features described in what follows also to other wireless telephone devices, for example, cordless telephones, wireless hand sets, Bluetooth®- speaker devices, (cordless head sets), etc..

The mobile wireless telephone comprises a bipartite housing 10, including a front portion 12 of the housing shown in Fig. 1 and a rear portion 14 of the housing illustrated in Fig. 2 and co-acting in mutually fitting relationship with the front portion 12 of the housing. In the front portion 12 of the housing loudspeaker apertures 16 for a loudspeaker 18 fitted inside the housing and microphone apertures 20 for a microphone 22, likewise placed inside the housing, for the entry and emission of sound waves, are formed. The loudspeaker apertures 16 and the microphone apertures 20 are indicated in Fig 1 by broken lines.

The front portion 12 of the housing furthermore includes integrated therewith a display window 24 as well as a keypad matrix 26 inserted on the inside of the housing. The keypad matrix 26 is fitted with keys 28 of rubber elastic material which project through the key apertures 30 in the front portion of the housing 12. In the open state of the housing 10, that is to say, when the front portion 12 of the housing has been removed, the keypad matrix 26 is provided inside the front portion 12 of the housing and, as shown in Fig. 2, the loudspeaker 18 as well as the microphone 22 are accommodated in the rear portion 14 of the housing.

In order to screen off electromagnetic waves which are generated by the circuitry and emitted by a transmission antenna 31 likewise accommodated inside the rear portion 14 of the housing, the inside of the front portion 12 of the housing is coated with a screening coating 32. In the embodiment shown in Fig. 1 the screening coating 32 there applied is represented by ESnord-HF- screening paint 362. The painted on screening coat 32, in its dried condition, has a coating thickness between 20 μm and 30 μm. The electrical resistance of the screening coat 32 on a screened surface, in accordance with the specification VDE0303 / Section 3 amounts to less than 1,5 Ohm. The screening coat 32 suppresses the emitted electromagnetic waves in the frequency range of 200 MHz up to 18O00 MHz and when positioning the coated surface normal to the emission direction of the electromagnetic waves by up to 50 dB. Alternatively, it is, of course, also possible to coat the front portion 12 of the housing on the outside of the housing with the screening coat 32. It will be understood that by multiple application of the paint the coating thickness and screening effect can be increased.

The rear portion 14 of the housing shown in Fig. 2 is not provided with a screening coat 32, in order not to inhibit the spreading of the electromagnetic waves, emitted by the transmission antenna 31 and moving away from the user, towards the base station for purposes of data transmission. Alternatively, parts of the rear portion other than the region accommodating the antenna 31 may be coated as well.

The loudspeaker apertures 16 and the microphone apertures 20 in the front portion 12 of the housing as well as their surroundings inside the housing are covered by an air- and, accordingly, sound-pervious finely meshed grid-like screening fabric 34. In the embodiment illustrated in Fig. 1 a high efficiency silver/polyamide mixture is used as the screening fabric 34, available under the trade mark Aaronia-shield® of the firm Aaronia AG, having a fabric thickness of 0,1 mm and a weight of 15 g/m². In the high frequency range of the electromagnetic waves the suppression achieved by the screening fabric 34 amounts to between 40 dB and 50 dB.

As can be seen from Fig. 1, the screening fabric 34 covers in the front portion of the housing likewise the keypad matrix 26 and the transmission antenna 31 , as well as a module for high frequency generation which is not shown in the drawing. In this manner, the emission of electromagnetic waves through the keypad matrix 26 and the housing region which, on the front side of the housing, surrounds the transmission antenna 31, is prevented or inhibited. In Fig. 1 the lower portion of screening fabric 34 is shown only in part in order not to obscure part of the key matrix 26 as keys 28. Normally, the fabric covers the entire width of the front portion 12.

Because the radiation intensity of the electromagnetic waves in the housing region of the transmission antenna 31 is particularly high, the screening in that region can be increased by increasing the effectiveness of the screening fabric 34, for example, by using a plurality of layers and/or a reduced mesh width of the screening fabric 34 and/or by a combination with other screening means.

The screening fabric is conductively and adhesively connected to other screening means, e.g. screening foil (see further below), regions coated with a screening paint and parts of the front portion made of conductive screening material using the screening paint as an adhesive, so that an uninterrupted screening of the front portion, free of gaps through which generated electromagnetic radiation can escape in the direction of the user, is produced.

The keypad matrix 26 co-acts with a keyboard module 36 shown in Fig. 2, fitted with a corresponding number of electrical switch contacts. In an alternative embodiment, the keypad matrix 26 and the keypad module 36 can be formed as a closed structural unit. In that case, a screening fabric 34 is applied directly onto this structural unit.

The display window 24 through which a display module 38 shown in Fig. 2 is visible to the user is covered in the housing interior by a screening foil 40. A transparent foil supplied by the firm ESnord under the trade name ESnord- HF-Abschirmklarsichtfolie 062 is used as the screening foil 40. The screening foil 40 is transparent to visible light and causes virtually no readability loss. It suppresses the electromagnetic waves in the frequency range of 200 MHz up to 18'0OO MHz by about 20 dB. Alternatively, the screening foil 40 can be integrated into the display window 24 or the display 24 itself can be manufactured from a screening foil 40. In addition to the aforegoing, it is possible to interconnect the screening means 42 comprising the screening coating 32, the screening fabric 34 and the screening foil 40 or any other screening means electrically conductively to one another. Moreover, one or more of the screening means 42 may be connected electrically conductively to an earthing contact.

Besides the aforesaid screening means 42, it is possible as an alternative, to apply electrically conductive grids, plates, fibres or coatings to the inside or outside of the front portion 12 of the housing, respectively to the housing 10 or casting these into or enclosing them in the front portion 12 of the housing or the housing 10 respectively or, for example, to mould the front portion 12 of the housing in part or completely of an electrically conductive plastics.

The application, inserting, installing and/or affixing of the screening means 42 in the front portion 12 of the housing proceeds preferably during the manufacture of the front portion 12 of the housing or of the housing 10, and thus, independently of and in parallel to the manufacture of other constructional units of the mobile wireless telephone.

The screening means 42 may, by their integrated installation, be adapted effectively to the constructional specifics of the wireless telephone device, for example the construction of the transmission antenna 31 or the high frequency module.

In the alternative, it is possible to fit the housing 10 or the front portion 12 of the housing with the screening means 42 during the final assembly, or to retrofit already existing wireless telephone devices with screening means 42.

Although the invention is practised particularly easily with devices when the transmission antenna is inside the housing, it can also be adapted to systems using the external, e.g. so-called stub antenna. Such sets, e.g. Nokia 6101, are frequently supplied with a protective cover for the antenna. According to the invention such a cover can be provided with screening on the side directed towards the user which screening is drastically conductively connected to the screening means of the front portion. Moreover where, as is the case with Nokia 6101, the set is of the flap type, where the flap, in its opened condition, provides the loudspeaker, held against the ear. The shielding of the flap in accordance with the invention will provide some additional screening for the stub antenna.

By definition the flap forms part of the front portion of the housing and is, therefore, also provided with screening means which are to be electrically connected to the screening means of the remainder of the front portion.

SAR tests were conducted by a well known testing laboratory in accordance with CENEL EC EN 50360 and 50361 to determine the effects of screening in accordance with the invention on a mobile telephone set of the type as described in the example. A handset model type NMH-5NX of Nokia Corporation, Model number 3310 (a recent, commercially successful model) was used in the test. The testing was performed at 1800 MHz GSM top channel on the unshielded set and on such set whereof the front cover had been shielded as described in the example.

The shielding resulted in a SAR reduction of 83% for the 1-gram SAR average (i.e. to 0.053)and 82% for the 10-gram SAR average (i.e. to 0,035). Partial screening of the back cover portion led to a further reduction to a total of up to 92% in both cases (i.e. 0,026 and 0,016 respectively, this is a substantial improvement over recently published SAR values for recent market leading modules of various manufacturers.

Because of these highly satisfactory reductions no measurements were made with heavier shielding, which would undoubtedly have resulted in even greater reductions.

Experts who witnessed the tests stated that they had never before witnessed comparable improvements of SAR values or achieved with such simple and cost effective means.

Claims

1. Wireless telephone device including a housing having a front portion (12) and a back portion (14), the housing containing circuitry for generating electromagnetic waves, a transmission antenna (31) for emitting the electromagnetic waves and screening means (42) against electromagnetic waves generated by the circuitry, the front portion (12) being that portion which, in use, faces the user, characterised in that the front portion (12) and transmission antenna are provided with screening means against electromagnetic waves generated by the circuitry substantially uninterruptedly over so much of the area of the front portion and transmission antenna facing the user, including all apertures through the front portion, that deposition of the energy of the generated electromagnetic waves in the body of the user which would occur in the absence of such screening, is largely prevented or suppressed.

2. Device as claimed in claim 1 , characterised in that the deposition as measured by Specific Absorption Rate (SAR) testing is reduced by not less than about 80%.

3. Device as claimed in claim 1 or 2, characterised in that the screening includes a fine-meshed grid-like screening fabric (34) which covers at least parts of the front portion (12) of the housing, which include loudspeaker apertures (16) and/or, if present, microphone apertures (20) of the housing and/or the rear of a key pad or key pad assembly.

4. Device ad claimed in claim 3, characterised in that the fabric alone or in combination with other screening materials forms a continuous, substantially uninterrupted screen extending over substantially the entire area covered by the front portion (12).

5. Device as claimed in any one of claims 1 to 4, characterised in that the front portion (12) includes a display window (24) formed from or screened by a transparent material having screening properties against the generated electromagnetic waves other than visible light.

6. Device as claimed in any one of claims 1 to 5, characterised in that its transmission antenna (31) is accommodated in a position wherein the front portion (12), including the screening means (42) associated with the front portion, screen the user against generated electromagnetic radiation emitted by the antenna.

7. Device as claimed in claim 6, characterised in that the transmission antenna (31) is accommodated inside the housing.

8. Device as claimed in any one of claims 1 to 7, characterised in that the screening means (42) are electrically conductive and are connected in an electrically conductive manner to one another and/or, where appropriate, to an earthing contact.

9. Device as claimed in any one of claims 1 to 8, characterised in that the screening means (42) includes a screening coating (32) and/or a screening fabric (34) and/or a screening foil (40).

10. Device as claimed in any one of claims 1 to 9, characterised in that it is a mobile wireless telephone or a cordless telephone or a cordless headset.

11. A method of screening a wireless telephone device of the type including a housing having a front portion (12) and a back portion (14), the housing containing circuitry for generating electromagnetic waves, a transmission antenna (31 ) for emitting the electromagnetic waves, in order to reduce the exposure of the user to generated electromagnetic waves, characterised in that at least the front portion (12) being that portion of the housing which, in use, faces the user and the transmission antenna (31) are provided with a screening against electromagnetic waves generated by the circuitry substantially uninterruptedly, over so much of the are of the front portion and transmission antenna facing the user, including all apertures through the front portion, that deposition of the energy of the generated electromagnetic waves in the body of the user which would occur in the absence of such screening, is largely prevented or suppressed.

12. The method as claimed in claim 11, characterised by improving the Specific Absorption Rate (SAR) of a wireless telephone device by from about 80 to about 100% as compared with the same device without said screening.

13. The method as claimed in claim 1, characterised by applying to the inside of the front portion (12) a fine-meshed grid-like screening fabric (34), so as to cover at least parts of the front portion (12), including loudspeaker apertures (16) and, if present, microphone apertures (20) of the housing and/or the rear of a key pad or key pad assembly.

14. The method as claimed in claim 13, characterised in that the fabric alone or in combination with other screening materials is applied as a continuous substantially uninterrupted screen extending over substantially the entire area covered by the front portion (12).

15. The method as claimed in any one of claims 11 to 14, characterised in that, where the front portion (12) includes a display window (24), the latter is formed from or screened by a transparent material (40) having screening properties against the generated electromagnetic waves.

16. The method as claimed in any one of claims 11 to 15, characterised in that it is applied to a wireless telephone device whereof the transmission antenna (31) is accommodated inside the housing.

17. The method as claimed in any one of claims 11 to 16, characterised in that the screening means (42) employed are electrically conductive and these are connected in an electrically conductive manner to one another and/or, where appropriate, to an earthing contact.

18. The method as claimed in any one of claims 11 to 17, characterised in that for said screening a screening coating (32) and/or or a screening fabric (34) and/or a screening foil (40) is applied and/or that the housing or part thereof is made of a material having screening properties.

19. The method as claimed in any one of claims 11 to 18, characterised in that it is used for screening a mobile wireless telephone or a cordless telephone or a cordless headset (bluetooth (A)).

20. A use of the wireless telephone device as claimed in claim 1 for reducing SAR values by not less than 80%.