AU1755300A - Cellular phone radiation shield - Google Patents

Description

S&F Ref: 440528D1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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444 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Princeton Advanced Technology Pty Limited 4 Callistermon Close Caves Beach NSW 2281 Australia David Princehor Spruson Ferguson St Martins Tower 31 Market Street Sydney NSW 2000 Cellular. PhoneRadiation Shield ASSOCIATED PROVISIONAL APPLICATION DETAILS [31] Application No(s) [33] Country [32] Application Date PO9979 AU 23 October 1997 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c [R:\LIBW]21633.doc:vsg CELLULAR PHONE RADIATION SHIELD Field of the Invention The present invention relates to apparatus for protecting the users of mobile telephones from electromagnetic radiation and, in particular, to a mobile telephone radiation shield that both absorbs and reflects electromagnetic radiation.

Background of the Invention Mobile telephone electromagnetic radiation shielding devices that are known, may be categorised into two broad groups. One category includes a electromagnetic radiation shield in which a shielding material is incorporated into a relatively soft mobile phone protective case, where the mobile phone case is constructed to fit individual types of mobile phones. This type of radiation shield usually also incorporates a sliding switch to shield the user from electromagnetic radiation emanating from the mobile telephone's antenna. This arrangement has the advantage that the radiation shield is attached to the phone. However, any particular electromagnetic radiation shield case will only fit one 5 is particular type of mobile telephone. In order to provide a shield for all the different models of mobile telephones, the manufacturer must produce many different types of cases. In addition, integration of the shield into the case increases the manufacturing costs of such items and reduces their commercial economic viability.

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Further, there is a certain amount of electromagnetic energy that is reflected back towards the mobile phone antenna in such arrangements. This is due to the construction .o* of the shield case in that it encloses the mobile phone and antenna. The reflected energy may also cause interference in the mobile telephone reception signal in the form of static noise, thus reducing the quality of the transmission signal from the mobile telephone.

The second category of mobile phone electromagnetic radiation shields includes a shield arrangement which is fixed to the top (antenna end) of the mobile phone. Such shields intend to protect the user by reducing the amount of electromagnetic radiation that is emitted towards the head of the user. In some cases these shields are integrally formed into the plastic casing of the mobile phone. Such an arrangement suffers from several disadvantages. First, since the electromagnetic radiation shield is fixed to the mobile [R:/libpp]440528.doc -2telephone and sometimes incorporated into the telephone casing, the arrangement is not versatile. If the user has purchased a mobile telephone that does not include one of these shields, the user must seek an alternative method of protection. Second, the arrangement causes a certain amount of electromagnetic energy to be reflected back towards the mobile phone antenna. In some cases, the amount of reflected energy can be substantial. As noted above, the reflected energy may cause interference in the mobile phone reception signal in the form of static noise, and also problems in the quality of the transmission signal from the mobile telephone.

In many instances, reflective shields are often small compared to the wavelengths of concern that some are doubted in achieving any advantageous result.

A further disadvantage in this arrangement, is that there is a certain amount of electromagnetic energy that is diffracted around the edges of the shield. In some prior art arrangements the amount of diffracted energy can be quite substantial. This diffracted energy reduces the effectiveness of the shield and therefore reduces the amount of ooooo protection that is given to the mobile telephone user.

It is an object of the present invention to substantially overcome, or ameliorate, 00..

0000 0one or more of the deficiencies of the above mentioned arrangements.

00". Summary of the Invention O. In accordance with one aspect of the present invention there is provided a radiation shield comprising an absorbent portion affixed to a metallic reflector plate, said absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said absorbent portion is integrally formed with a portable telephone handset having a radio frequency antenna, and wherein said absorbent portion is configured to allow positioning of said plate between said antenna and the head of a user of said telephone handset.

In accordance with another aspect of the present invention there is provided a radiation shield comprising an absorbent portion affixed to a metallic reflector plate, said absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said absorbent portion is integrally formed with a hand-held portable [R:/libpp]440528.doc -3radio frequency emitter device having a radio frequency antenna, and wherein said absorbent portion is configured to allow positioning of said plate between said antenna and the head of a user of said device.

In accordance with still another aspect of the present invention there is provided a radiation shield comprising an absorbent portion affixed to a metallic reflector plate, and an attachment means for attaching said shield to a hand-held portable radio frequency emitter device having a radio frequency antenna, the absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said attachment means comprises an adhesive permitting positioning of said plate and said absorbent portion between said antenna and the head of a user of said telephone handset.

Preferably, said bore is a blind or open bore.

S In accordance with still another aspect of the present invention there is provided a radiation shield comprising an absorbent portion affixed to a metallic reflector plate, said absorbent portion comprising materials at least substantially absorptive of 15 electromagnetic energy, wherein said absorbent portion is integrally formed within a •**-portable telephone handset having a radio frequency antenna, and wherein said absorbent oooo portion is configured to allow positioning of said plate between said absorbent portion and the head of a user of said telephone handset.

Brief Description of the Drawings Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a rear elevational view of a mobile telephone radiation shield of a first embodiment; Fig. 2 is a front elevational view of the mobile telephone radiation shield of Fig.

1; Fig. 3 is a side elevational view of the mobile telephone radiation shield of Figs.

1 and 2; Fig. 4 is a top plan view of a mobile telephone radiation shield of Figs. 1, 2 and 3.

[R:/libpp]440528.doc Fig. 5 is a top plan view of a mobile telephone radiation shield of a second embodiment; Fig. 6 is a front elevational view of the mobile telephone radiation shield of Fig.

Fig. 7 is a side elevational view of the mobile telephone radiation shield of Figs.

and 6; Fig. 8 is a perspective view showing the mobile telephone radiation shield, of Figs. 5 to 7, attached to a mobile telephone; Fig. 9 is a perspective view showing a mobile telephone radiation shield of a third embodiment; Fig. 10 is a perspective view showing a mobile telephone radiation shield of a fourth embodiment; Fig. 11 is a perspective view showing a mobile telephone radiation shield of a i" "fifth embodiment; Fig. 12 is a schematic cross sectional view of a mobile telephone showing a mobile telephone radiation shield ofa sixth embodiment; and Fig. 13 is a schematic cross sectional view of a mobile telephone showing a mobile telephone radiation shield of a seventh embodiment.

S .Detailed Description of the Drawings As best seen in Figs. 3 and 4, a mobile telephone radiation shield 20 of a first embodiment includes an absorbent portion 1 sandwiched between an attachment clip 2 and a metal plate 3.

As seen in Figs. 1 and 2, the absorbent portion 1 is of an oval configuration and arranged to extend further in the horizontal direction than the vertical direction as illustrated. In a specific embodiment the orthogonal dimensions and of the absorbent portion 1, are preferably 45mm, 3 8mmrn and 7mm, respectively. Another example of dimensions is about 40mm, 33mm and 6mm, respectively.

The absorbent portion 1 is preferably fabricated from specially modified electromagnetic energy absorbent material, such as the "C-RAM FLX" range of products [R:/libpp]440528.doc manufactured and available for purchase from Cuming Microwave Corporation at 230 Bodwell Street, Avon, MA 902322, U.S.A. The C-RAM FLX has been specifically designed to absorb microwave radiation in the frequency range of 800-2400 MHz. The C-RAM FLX is fabricated from a specially designed silicone rubber that has been impregnated with a magnetically lossy ferrite material in the form of filings. In this fashion the C-RAM FLX is able to be tuned for any particular range of frequencies from 800MHz to 5 GHz. Despite the small size of the absorbent portion 1 relative to the wavelength at 900/1800 or 2400 MHz, the loss mechanism of C-RAM FLX is through a hysteresis loss as RF magnetic fields act upon the magnetic domains within the material.

These domains are small, in the order of 10-100 microns, and loss occurs as the alternating magnetic field reverses the magnetic polarisation of each domain.

The metal plate 3 is preferably formed of a foil, such as copper or aluminium, which for example may have one or more surfaces sputtered with gold or other highly conductive (reflective) material. The plate 3 is affixed to a front face 10 of the absorbent S is portion 1 for example using an adhesive. As seen in Fig. 2, the metal plate 3 is of the same oval configuration as the absorbent portion 1 and is sized to be smaller than the absorbent portion 1 and preferably positioned about 3mm (dimension in from any point on the front edge of the absorbent portion 1 thereby only substantially covering a surface of the absorbent portion 1. The metal plate 3 is a reflector of electromagnetic radiation and the arrangement of the metal plate 3 in combination with the absorbent oo.e portion 1 is configured to reduce diffraction of electromagnetic waves around the edge of the absorbent portion 1.

The attachment clip 2 is securely affixed, to the back face 11 of the absorbent portion 1, preferably utilising double-sided tape 9, although another adhesive may be used. The base 4, of the attachment clip 2, is squarely fitted in the centre of the absorbent portion 1 with its longest side running parallel to the horizontal plane. The fixed attachment clip 2 is fitted so that integral bracing arms 7 and 8, of an attachment means 6 thereof obtrude from the back of the absorbent portion 1. The attachment clip 2 is a [R:ilibpp]440528.doc conventional unitary device which is commercially available and manufactured from resilient plastics material.

The clip 2 is configured to provide a releasable snap-fit connection to the antenna stub of a portable telephone handset sufficient to position the absorbent portion 1 between the antenna stub and the head of the user.

In an alternative to the clip 2, other attachment arrangements can be used such as an elasticised sleeve or a purpose constructed multi-size clip. Adhesives may be used between the attachment arrangement and the antenna to prevent rotation of the absorbent portion 1 from its intended position.

The mobile telephone radiation shield 20 of the first embodiment is readily attachable to the antenna of a mobile telephone, utilising the attachment means 6 of the fixed attachment clip 2. The front side 10 of the absorbent portion 1 can be aligned in any direction with respect to the front face of the mobile telephone. However, for maximum protection the front side 10 of the absorbent portion 1 is aligned parallel to the front face 15 of the mobile telephone, so that the metal plate 3 faces towards the mobile telephone user when the telephone is in use. In this position, any mobile telephone antenna transmissions which are directed towards the head of the mobile phone user are substantially absorbed or reflected by the absorbent portion 1, therefore increasing the level of protection afforded to the user. In addition, since the electromagnetic waves are absorbed by the absorbent portion 1, reflections back toward the antenna of the mobile telephone are avoided, thus avoiding interference.

As best seen in Figs. 5, 6 and 7, a mobile telephone radiation shield of a second embodiment includes an attachment section 51 affixed to an oblong absorbent portion 53.

A metal plate 59 is affixed to the front side 57 of the absorbent portion 53.

The attachment section 51 is of a half cylindrical configuration and arranged to include a tapered blind bore 55. In a specific embodiment the dimensions and of the shield 50 are preferably 20mm, 25.5 mm, 22.0 and 7mm, respectively.

The tapered blind bore 55 preferably has a largest diameter of 9 mm tapering to a smallest diameter of 6.5 mm.

[R:/libpp]440528.doc The absorbent portion 53 is preferably fabricated from specially modified electromagnetic energy absorbent material, such as "C-RAM FLX 800/900/1350/1800/2400". The metal plate 59 is preferably formed of a foil, such as copper or aluminium, with one or more surfaces preferably sputtered with gold or other highly conductive (reflective) material.

The mobile telephone radiation shield 50 of the second embodiment is readily attachable to an antenna of a mobile telephone, utilising the tapered blind bore 55 into which the antenna is inserted, as seen in Fig. 8. The mobile telephone radiation shield is secured to the antenna by an interference fit which is created between the antenna and the inside surface (not illustrated) of the tapered blind bore 55. The front side 57 of the absorbent portion 53 can be aligned in any direction with respect to the front face of the mobile telephone. However, for maximum protection the front side 57 of the absorbent portion 53 is aligned parallel to the front face of the mobile telephone, as seen in Fig. 8, i o so that the absorbent portion 53 faces towards the mobile telephone user when the oooo0 5 i telephone is in use. In this position, any mobile telephone antenna transmissions which are directed towards the head of the mobile phone user are substantially absorbed by the absorbent portion 53, therefore increasing the level of protection afforded to the user.

Figs. 9 and 10 show a third and fourth embodiment, respectively, of a mobile telephone radiation shield in accordance with the present invention. Both of the mobile telephone radiation shields 900, 1000 of the third and fourth embodiments comprise a tapered blind bore and are configured in a similar manner to the mobile telephone radiation shield 50 of the second embodiment. The mobile telephone radiation shields 900 and 1000 each have an absorbent portion 901 and 1001, respectively, integrally formed within the body of the radiation shields 900 and 1000, as seen in Figs 9 and As discussed above for the first and second embodiments, a metal plate (not illustrated) is also integrally formed within the body of the radiation shields 900 and 1000, respectively, such that the metal plate is arranged on one face of the absorbent portions 901,1001, similar to the above discussed embodiments. The metal plate is preferably arranged [R:/libpp]440528.doc -8between the absorbent portion 901, 1001 and the user of a mobile telephone when the telephone is in use.

Fig. 11 shows a fifth embodiment of a mobile telephone radiation shield 1100 in accordance with the present invention. The mobile telephone radiation shield 1100 of the fifth embodiment comprises a tapered open-bore 1101. The mobile telephone radiation shield 1100 is secured to the antenna by an interference fit which is created between the antenna and the inside surface 1102 of the tapered open-bore 1101. The mobile telephone radiation shield 1100 of the fifth embodiment is configured in a similar manner to the mobile telephone radiation shields of the above embodiments, and includes an absorbent portion 1103 and metal plate (not illustrated) integrally formed within the body of the mobile telephone radiation shield 1100.

00000 Some mobile telephones are now being manufactured with antennas that are mounted within the casing of the mobile telephone. Fig. 12 shows a cross section of a mobile telephone 1200 with a flat high frequency antenna 1201 mounted within the casing ooooo 15 1202 of the mobile telephone 1200. In accordance with a sixth embodiment of the present invention, a section of microwave radiation absorbent material 1205 is mounted within o oo the casing of the mobile telephone 1200 between the antenna 1201 and the front face 1207 of the mobile telephone 1200. As with the previously discussed embodiments, a metal plate 1211 is affixed to one face of the absorbent material 1205. The absorbent material 1205 is mounted substantially parallel to the front face 1207 of the mobile o telephone 1200. In this position, any mobile telephone antenna transmissions which are directed towards the head of a mobile phone user are substantially absorbed by the absorbent material 1205, therefore providing protection to the user. Again, the absorbent material 1205 is preferably manufactured from the "C-RAM FLX" range of products and the metal plate 1211 is preferably formed of a foil, such as copper or aluminium, with one or more surfaces preferably sputtered with gold or other highly conductive (reflective) material. In some implementations the material 1205 may be moulded on an inside of the front face 1207 and in such cases may be configured to cover substantially all of the front face 1207.

[R:/libpp]440528.doc In accordance with a further embodiment of the present invention the absorbent material 1205 and metal plate 1211 can be mounted as a perforated sticker 1209 (shown in phantom lines) which is mounted to the front face 1207 of the mobile telephone 1200, as seen in Fig. 12.

Fig. 13 shows a still further embodiment of the present invention, whereby absorbent material 1305 and a metal plate 1311 are incorporated within a mobile telephone protective outer cover 1307. The cover 1307 is typically formed as a sleeve that encloses the mobile telephone handset. The absorbent material 1305 and metal plate 1311 are arranged between the antenna 1301 and the user of the mobile telephone 1300, when the telephone is in use. Again, in this position, any mobile telephone antenna transmissions which are directed towards the head of the mobile phone user, when the telephone is in use, are substantially absorbed by the absorbent material 1305. The outer cover 1307 is preferably made of vinyl or leather as with a conventional mobile telephone cover.

.oooi S 15 The above described embodiments have a number of advantages over the prior art arrangements which are outlined below: o• •First, any electromagnetic energy that is directed towards the head of the user of S• the mobile telephone is greatly reduced due to the use of the highly electromagnetic wave absorbent portion 1 and absorbent portion 53 of the first and second embodiments, respectively. In addition, the configuration and mounting position of the metal plate 3 in the first embodiment, means that the amount of diffracted electromagnetic energy is greatly reduced compared to conventional mobile telephone electromagnetic wave radiation shields.

Second, the amount of electromagnetic energy that is reflected back towards the antenna of the mobile telephone is reduced due to the use of the highly electromagnetic wave radiation absorbent material. The electromagnetic radiation waves that are directed toward the shields 20 and 50 are cancelled out, as they come into contact with the resonating ferrite filings, instead of being reflected back towards the antenna which would [R:/libpp]440528.doc result in a distortion of the mobile telephone signals. As a result, the effect on the mobile telephone reception and/or transmission signal is minimised.

Third, due to the use of the attachment clip 6 and the tapered blind bore 55 of the first and second embodiments, respectively, the electromagnetic radiation shields 20 and 50 are able to be fitted to many different models of mobile telephones. This greatly increases the portability of the mobile telephone radiation shield and means that the user only has to purchase one radiation shield for any number of separate mobile telephones. In addition, this greatly reduces the overall manufacturing costs of the mobile telephone electromagnetic radiation shield and thereby greatly increases its commercial viability.

Fourth, the shields 20 and 50 are small enough so that they do not protrude from the outer edges of the mobile telephone casing. Therefore, the shields 20 and 50 do not greatly increase the overall size of the mobile telephone apparatus. Variations on the preferred dimensions mentioned above can be made where it is desired to adapt the shields 20 and 50 to particular mobile telephones.

The foregoing describes only several embodiments of the present invention, and modifications, can be made thereto without departing from the scope of the present invention.

For example, the shape and size of the absorbent portion 1 of the shield 20 may *be modified. The absorbent portion 1 may be sized to fit a particular type of mobile 20 telephone on for other radio frequency emitters, such as hand-held UHF and VHF twoway radios, cordless telephones, satellite telephones, and the like. In this regard C-RAM FLX has the ability to be tuned to provide optimal absorption within definable bandwidths.

Further, the attachment clip 2 may be aligned at any angle with respect to the absorbent portion 1 and in any position with respect to the centre of the absorbent portion 1. The attachment clip 2 may be positioned in order to fit any particular type of mobile telephone. Also, the attachment clip 2 may be replaced with any suitable type of attachment means, such as Velcro (Registered Trade Mark).

[R:/libpp]440528.doc -11- Furthermore, the shape and size of the metallic plate 3 may be modified. The metallic plate 3 may be sized to suit any particular absorbent portion.

It will be appreciated by someone skilled in the art that the embodiments described above are also suitable for use in conjunction with other communication devices, such as cordless and handheld radio communication devices.

In the context of this specification, the word "comprising" means "including principally but not necessarily solely". Variations of the word "comprising", such as "comprise" and "comprises" have correspondingly varied meanings.

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[R:/libpp]440528.doc

Claims (10)

1. A radiation shield comprising an absorbent portion affixed to a metallic reflector plate, said absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said absorbent portion is integrally formed with a portable telephone handset having a radio frequency antenna, and wherein said absorbent portion is configured to allow positioning of said plate between said antenna and the head of a user of said telephone handset.

2. A radiation shield according to claim 1, wherein said absorbent portion is manufactured from a resiliently flexible material impregnated with ferrite filings. 6

3. A radiation shield according to claims 1 and 2, wherein said absorbent portion •comprises C-RAM Flex 800, C-RAM Flex 900 or C-RAM Flex 2400.

4. A radiation shield according to any one of claims 1 to 3, wherein said absorbent portion and said plate are each similarly shaped, and said plate is sized to substantially cover a surface of said absorbent portion. o

5. A radiation shield according to any one of the preceding claims, wherein each of said absorbent portion and said plate are oval-shaped.

6. A radiation shield according to any one of the preceding claims, wherein said surface of said absorbent portion is about 40mm x 33 mm in orthogonal dimensions.

7. A radiation shield according to any one of the preceding claims, wherein said absorbent portion is about 6mm thick. [R:/libpp]440528.doc

13- 8. A radiation shield according to any one of the preceding claims, wherein said reflector plate comprises a metal foil and is affixed to said absorbent portion using an adhesive. 9. A radiation shield according to any one of the preceding claims, wherein said reflector plate includes at least one of copper, aluminium or gold. A radiation shield according to any one of the preceding claims, wherein said absorbent portion is oblong shaped. 11. A radiation shield according to any one of the preceding claims, wherein said .u o absorbent portion is configured to cover substantially all of an area defined by a front face oi of said telephone hand set. $fees: 15 12. A radiation shield according to any one of the preceding claims, wherein said absorbent portion is configured within an outer cover of said telephone handset, said outer S0.. 090 *fe o cover and said absorbent portion being removable. glo Oe SO S.. 13. A radiation shield according to claim 1, wherein said absorbent portion is about 20mm x 25 mm x 7mm in dimension. S

14. A radiation shield comprising an absorbent portion affixed to a metallic reflector plate, said absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said absorbent portion is integrally formed with a hand- held portable radio frequency emitter device having a radio frequency antenna, and wherein said absorbent portion is configured to allow positioning of said plate between said antenna and the head of a user of said device. [R:/libpp]440528.doc 14- A radiation shield comprising an absorbent portion affixed to a metallic reflector plate, and an attachment means for attaching said shield to a hand-held portable radio frequency emitter device having a radio frequency antenna, the absorbent portion comprising materials at least substantially absorptive of electromagnetic energy, wherein said attachment means comprises an adhesive permitting positioning of said plate and said absorbent portion between said antenna and the head of a user of said telephone handset.

16. A radiation shield substantially as herein described with reference to Figs. 12 and 13. DATED this sixteenth Day of February, 2000 Princeton Advanced Technology Pty Limited Patent Attorneys for the Applicant SPRUSON FERGUSON o. .°•ooi [R:/libpp]440528.doc