AU8950398A - Cellular phone radiation shield - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Princeton Advanced Technology Pty Limited 4 Calllstermon Close Caves Beach New South Wales 2281

AUSTRALIA

David Princehorn Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Hales, 2000, Australia Cellular Phone Radiation Field ASSOCIATED PROVISIONAL APPLICATION DETAILS [31] Application No(s) [331 Country P09979 AU [32] Application Date 23 October 1997 The following statement is a full description of this invention, including the best method of performing it known to melus:- CELLULAR PHONE RADIATION SHIELD Field of the Invention The present invention reiates 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 S'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 m6bile 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 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 A Iand reduces their commercial economic viability.

Further, there is a certain amount of electromagnetic energy that is reflected 'i l back towards the mobile phone antenna in such arrangements. This is due to the construction 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 725 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 !i 77 phone. Such shields intend to protect the user by reducing the amount of (n:'libpp]C0728:LDP

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-2electromagnetic 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 telephone and sometimes incorporated into the plastic 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 S* 1i 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 form 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 protection that is given to the mobile telephone user... It is an object of the present invention to substantially overcome, or ameliorate, one or more of the deficiencies of the above mentioned arrangements.:.

Summary of the Invention In accordance with one aspect of the present invention there is disclosed a radiation shield: including a body portion affixed to a metallic reflector plate, and attachment means-for attaching said shield to a portable telephone handset having a radio frequency antenna,- the body portion comprising materials at least substantially absorptive of electromagnetic energy wherein ,said attachment means permits Sn:ibpplOO728:LDF P ~Ml -3positioning of said plate between said body portion and a head of a user of said telephone handset.

Preferably, the body portion is connected (sandwiched) between the plate and the attachment means.

Advantageously, both the body portion and plate are of similar oval shapes and preferably the plate being sized smaller than the body.

Preferably, the body portion is connected to the attachment means by an adhesive, and preferably the base of the attachment means is positioned in the centre of the body portion.

Sto Preferably, the metallic reflector plate is affixed to the front face of the body portion, and preferably the plate is positioned 3mm in from any point on the front edge of the body portion.

Brief Description of the Drawings A preferred enibodiment 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 the t preferred 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; and Fig. 4 is a top plan view of a mobile telephone radiation shield of Figs. 1, 2 and 3.

Detailed Description of the Drawings As best seen in Figs. 3 and 4, a mobile telephone radiation shield 20 includes a Sbody 1 sandwiched between an attachment clip 2 and a meial plate 3.

As seen in Figs. 1 and 2, the body 1 is of an oval configuration and arranged to extend further in the horizontal direction than the vertical direction as illustrated. In SIn:\libpp00728:LDP /.c -4a specific embodiment the orthogonal dimensions and of the body 1, are preferably 45mm, 38mm and 7mm, respectively. Another example of dimensions is about 40mm, 33mm and 6mm, respectively.

The body 1 is fabricated from specially modified electromagnetic energy absorbent material, such as "C-RAM Flex 800" or "C-RAM Flex 900". Both of these materials are manufactured and available for purchase from Cuming Microwave Corporation at 230 Bodwell Street, Avon, MA 902322, U.S.A. The "C-RAM Flex 900" has been specifically designed to absorb microwave radiation in the frequency range of 890-915 MHz. The C-RAM Flex is fabricated from a specially designed silicone rubber that has been impregnated with ferrite material in the form of filings. Despite the small size of the body 1 relative to the wavelength at 900 MHz, the S'loss mechanism of C-RAM Flex 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.

S'The metal plate 3 is preferably formed of a foil, such as copper or aluminium, A 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 body 1 S for example using an adhesive As seen from Fig. 2, the metal plate 3 is of the same oval configuration as the body 1 and is sized to be smaller than the body 1 and preferably positioned about 3mm (dimension in from any point on the front edge of the body 1 thereby only substantially covering a surface of the body 1. The metal plate 3 is a reflector of electromagnetic radiation and the arrangement of the metal 'plate 3 in combination with the body 1 is configured to reduce diffraction of ,J 25 electromagnetic waves around the edge of the body 1.

|The attachment clip 2 is securely affixed, to the back face 11 of the reflector 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 body 1 with its (n:\libpp)00728:LDP t, 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 body i. The attachment clip 2 is a 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 body 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 body 1 from its intended position.

The mobile telephone radiation shield 20 of the preferred embodiment is easily 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 body I 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 body 1 is aligned parallel to the front face of the -i 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 body 1, therefore increasing the level of protection afforded to the user. In addition, since the electromagnetic waves are absorbed by the body I, reflections back toward the antenna of the mobile telephone are avoided, thus avoiding interference.

The above described embodiment has a number of advantages over the prior art arrangements which are outlined below: First, any electromagnetic energy that is directed towards the head of the -user of the mobile telephone is greatly reduced due to the use of the highly electromagnetic wave absorbent body 1. In addition, the configuration and mounting position of the (n:\libppj00728:LDP I i p -6metal plate 3, 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 electroinagnetic radiation waves that are directed toward the shield are cancelled out, as they come into contact with the resonating ferrite filings, instead of being reflected back towards the antenna which would result in a distortion of the mobile telephone signals. As a result, the io effect on the mobile telephone reception and/or transmission signal is minimized.

S°Third. due to the use of the attachment clip 6, the electromagnetic radiation shield 20 of the preferred embodiment is 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 4 manufacturing costs of the mobile telephone electromagnetic radiation shield and A thereby greatly increases its commercial viability.

Fourth, the shield 20 is generally small enough so that it does not protrude from the outer edges of the mobile telephone casing. Therefore, it does 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 ;shield 20 to particular mobile telephones.

The foregoing describes only one embodiment of the present invention, and modifications, can be made thereto without departing from the scope of the present 25 invention. 1 For example, the shape and size of the body portion I of the shield 20 may be modified. The body portion I may be sized to fit a particular type of mobile telephone.

[n:Vibpp]00728:LDP 1<C~~P -7- Further, the attachment clip 2 may be aligned at any angle with respect to the body portion 1 and in any position with respect to the centre of the body 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).

Furthermore, the shape and size of the metallic plate 3 may be modified. The metallic plate 3 may be sized to suit any particular body portion.

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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Claims (10)

1. A radiation shield including a body portion affixed to a metallic reflector plate, and attachment means for attaching said shield to a portable telephone handset having a radio frequency antenna, the body portion comprising materials at least substantially absorptive of electromagnetic energy wherein said attachment means permits positioning of said plate between said body portion and a head of a user of said telephone handset.

2. A radiation shield according to claim 1, wherein said body portion is positioned between said attachment means and said plate.

3. A radiation shield according to claim 1 or 2, wherein said attachment means is configured to attach said shield to said antenna of said portable telephone handset.

4. A radiation shield according to claim 1, 2 or 3, wherein said body portion and said plate are each similarly shaped, and said plate is sized to substantially cover a -surface of said body portion. z0 5. A radiation shield according to claim 4, wherein each of said body portion and said plate are oval-shaped.

6. A radiation shield according to claim 5, wherein said surface of said body portion is about 40mm x 33 mm in orthogonal dimensions.

7. A radiation shield according to claim 6, wherein said body is about 6mm thick. -p [n:\libppI00728:LDP JA: _r I: :1 -Ar 4r~ -I I

8. A radiation shield according to any one of the preceding claims, wherein said body portion is manufactured from silicone rubber materials impregnated with ferrite filings. s 9. A radiation shield according to any one of claims 1 to 7, wherein said body portion comprises C-RAM Flex 800 or C-RAM Flex 900. A radiation shield according to any one of the preceding claims, wherein said reflector plate comprises a metal foil affixed to said body portion using an adhesive.

11. A radiation shield according to claim 10, wherein said reflector plate includes at least one of copper, aluminium or gold.

12. A radiation shield according to any one of the preceding claims, wherein said attachment means comprises a resilient snap-fit connector.

13. A radiation shield substantially as described herein with reference to the drawings. DATED this Twenty-third Day of October 1998 Princeton Advanced Technology Pty Limited Patent Attorneys for the Applicant SPRUSON FERGUSON i 5 t a: ~I Is ii3i n:\libpp00728:LDP