AU2014405615B2

AU2014405615B2 - RF shielding for mobile devices

Info

Publication number: AU2014405615B2
Application number: AU2014405615A
Authority: AU
Inventors: Richard P. Koeppel; Ronald H. Koeppel
Original assignee: Continental Accessory Corp
Current assignee: Continental Accessory Corp
Priority date: 2014-09-03
Filing date: 2014-09-03
Publication date: 2019-08-15
Anticipated expiration: 2034-09-03
Also published as: SG11201701727RA; KR102248202B1; JP2017531325A; IL250920A0; EP3189718A1; MX2017002874A; EP3189718A4; WO2016036353A1; CN112236027A; IL250920B; CN107006137A; MX382281B; KR20170093103A; AU2014405615A1

Abstract

An RF shielding device for mobile devices includes a conductive grid having horizontal and vertical wire traces in electrical contact with each other; a conductive trace disposed around the perimeter of the conductive grid, the conductive trace being in electrical contact with both ends of each of the horizontal and vertical wire traces; a first insulating film disposed on a top surface of the conductive grid; and a second insulating film disposed on a bottom surface of the conductive grid and the conductive trace. The first insulating film and the second insulating film are of a transparent material. The first and second insulating films are transparent, thus allowing viewing of the display of a mobile device on which the RF shielding device is disposed. The vertical and horizontal wire traces are spaced to form a grid that is opaque to signals in the frequency ranges utilized for mobile communication.

Description

RF SHIELDING FOR MOBILE DEVICES

I. FIELD OF THE INVENTION [0001] The present invention relates generally to radio frequency shielding for mobile cellular, or wireless devices including but not limited to mobile phones, tablets, such as Apple iPad®, and eReaders, such as Barnes & Noble Nook® and Amazon Kindle®.

II. BACKGROUND OF THE DISCLOSURE [0002] During normal operation, mobile devices transmit radio-frequency (RF) radiation intermittently during standby periods and continuously during active talk periods. Hereinafter, mobile devices include any device that is portable, and equipped with a cellular or wireless (e.g., Wi-Fi, Bluetooth, near field) communication capability and a display screen. Examples of mobile devices include mobile phones, personal digital assistants (PDA), tablet computers and eReaders. There is concern among public health professionals that the RF radiation emitted from mobile devices may cause a variety of health related issues.

[0003] In response to public concern over RF radiation from mobile devices, many devices and mobile device accessories have been marketed as blocking or reducing RF radiation. However, many of these products have drawbacks. For instance, some products are formed as cases to house the mobile device when not in use. However, when receiving or initiating a call, the mobile device will need to be removed from the protective case. Thus, exposing the user to the RF radiation. Other devices prevent the proper functioning of touch screen inputs on many current mobile devices.

[0004] Various attempts to reduce exposure to RF radiation from mobile devices are discussed in the following publications: U.S. Patent No. 5,367,309, U.S. Patent No. 5,335,366, U.S. Patent

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No. 5,336,896, U.S. Patent No. 5,657,386, U.S. Patent No. 5,726,383, U.S. Patent No. 6,001,282, U.S. Patent No. 6,075,977, U.S. Patent No. 6,095,820, U.S. Patent No. 6,184,835, U.S. Patent No. 6,341,217, U.S. Patent No. 6,356,773, U.S. Patent No. 6,359,213, U.S. Patent No. 6,377,824, U.S. Patent No. 6,404,403, U.S. Patent No. 6,505,036, U.S. Patent No. 6,515,223, U.S. Patent No. 6,615,028, U.S. Patent No. 6,624,432, U.S. Patent No. 6,628,784, U.S. Patent No. 6,603,981, U.S. Patent No. 6,708,047, U.S. Patent No. 6,738,650, U.S. Patent No. 6,897,826, US Publication No. 2001/0041545, U.S. Publication No. 2002/0072337, U.S. Publication No. 2002/0097188, U.S. Publication No. 2002/0009976, U.S. Publication No. 2003/0228843, U.S. Publication No. 2003/0176164, U.S. Publication No. 2004/0198264, U.S. Publication No. 2004/0026100, U.S. Publication No. 2008/0014872, and U.S. Publication No. 2010/0240421.

[0005] A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

[0006] Where any or all of the terms comprise, comprises, comprised or comprising are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

III. SUMMARY OF THE DISCLOSURE [0007] It would be desirable to provide an RF shielding that protects the mobile device user from potentially harmful RF radiation, while allowing touch screen equipped mobile devices to operate.

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2014405615 04 Jul 2019 [0008] According to a first aspect there is provided an RF shielding device for a mobile device, the device comprising: a conductive grid having first wire traces and second wire traces in electrical contact with each other at intersection points; and a conductive trace disposed around the perimeter of the conductive grid, the conductive trace being in electrical contact with both ends of each of the first wire traces and the second wire traces; wherein the conductive grid has a pitch ranging between 2 mm and 5 mm, such that potential harmful RF radiation caused by the mobile device is shielded by the RF shielding device while allowing a touch screen of the mobile device to operate.

IV. BRIEF DESCRIPTION OF THE DRAWINGS [0009] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:

FIG. 1 illustrates an exploded view of an embodiment of the present invention;

FIG. 2 illustrates an alternative embodiment of the present invention;

FIG. 3 illustrates an alternative embodiment of the present invention; and

FIG. 4 and 5 illustrate alternative patterns in accordance with the present invention.

V. DETAILED DESCRIPTION OF DISCLOSURE [0010] Referring to FIG. 1, an embodiment of the present invention is shown in an exploded view. The RF shielding device of the present invention is constructed of a frame member 102 configured and dimensioned to envelop at least a top surface of a mobile device 110. The frame member 102 is particularly sized for a corresponding model of mobile device, thus one frame c:\pof\word\29890.pct.spec.doc

2014405615 04 Jul 2019 member 102 may be specific to an iPhone® 4/4s or 5/5s or 6 while a second frame member 102, having different dimensions, may be specific to a Google Nexus 10.

[0011] The frame member 102 maybe formed of a plastic, silicone, thermoplastic polyurethane, rubber or metal frame 102a. The frame member 102 has a display void 102b centrally formed thereon. The display void 102b is aligned with an area corresponding to a display 110a of the corresponding mobile device 110. Thus, the frame 102a encircles a perimeter of the mobile device 110 such that the entirety of the display 110a is aligned with and visible though the display void 102b.

[0012] Since many mobile devices 110 are equipped with forward facing cameras 110b and hardware buttons 110c on a top surface of the mobile device 110, the corresponding frame member 102 is configured with camera void 102c and button void 102d corresponding to the forward facing camera 110b and hardware buffon(s) 110c, respectively. Alternatively, the button void 102d corresponding with the hardware button(s) 110c may be formed of a flexible material, such as rubber or an appropriate plastic that allows for user actuation of the underlying hardware buffon(s) 102c. Moreover, cutouts may be provided for any other components disposed on the front face of the mobile device, for example speaker openings, microphone openings, ambient light sensors, and the like.

[0013] A RF shielding screen 104 is fitted against an inside surface of the frame member 102 such that the RF shielding screen 104 is aligned with the display void 102b. Thus the RF shielding screen 104 is disposed between the frame member 102 and the mobile device 110. The RF shielding screen 104 is constructed of a first clear film layer 104a that is electrically insulating, an electrically conductive grid layer 104b, and a second clear film layer 104c that is c:\pof\word\29890.pct.spec.doc

2014405615 04 Jul 2019 electrically insulating as well. The first clear film layer 104a and the second clear film 104c may be formed of any transparent material, such as plastic or glass.

[0014] In an embodiment of the present invention, the second clear film layer 104c functions as a substrate on which the grid layer 104b is formed by way of electronic printing, chemical vapor deposition, physical vapor deposition, and the like. In the case of printing, inks containing carbon nano tubes, copper, or other conductive materials can be used. Alternatively, the grid layer 104b may be a separately fabricated layer sandwiched between and bonded to the first plastic film layer 104a and the second plastic film layer 104c.

[0015] In an embodiment, the grid layer 104b is formed independent of the first clear film layer 104a and second clear film layer 104c. The wires of the grid layer 104b may be formed of individual wires woven together. It should be noted that the present invention does not require the first clear film layer 104a and the second clear film layer 104c for proper operation of the present invention. Rather, the grid layer 104b can be placed directly on to the mobile device

110. However, the first clear film layer 104a and second clear film layer 104c are provided for protection of both the surface of the display screen 110a from scratching by the grid layer 104b and protection of the wire traces of the grid layer 104b from damage due to contact with a user’s fingers or other foreign objects.

[0016] In an embodiment of the present invention, the thickness of the RF shielding screen 104 is less than or equal to 0.005 inches (5 mils). However, the appropriate thickness of the RF shielding screen 104 may be greater than 5 mils as well, but is limited by the need to properly transmit user contact to the touch screen of the mobile device 110.

[0017] FIG. 2 shows a detailed representation of the structure of the grid layer 104b. The grid layer 104b has a conductive trace 202 formed around the perimeter of the grid layer 104b.

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Additionally, vertical wire traces 204 are provided between two parallel sides of the conductive trace 202. The two parallel sides are oriented perpendicular to the direction of the vertical wire traces 204. Also, horizontal wire traces 206 are provided between the two other parallel sides of the conductive trace 202. The two other parallel sides are oriented perpendicular to the direction of the horizontal wire traces 206.

[0018] Moreover, at intersection points 208, the vertical wire traces 204 and the horizontal wire traces 206 are in electrical contact with each other. Both ends of each of the vertical wire traces 204 and the horizontal wire traces 206 are also in electrical contact with the conductive trace 202. In this way, the grid layer 104b forms a plane of equipotential charge that negates the charge of the impinging RF field. The mesh spacing should be fine enough to block a significant portion of the RF signal, but coarse enough not to disable the touch screen functionality.

[0019] The RF shielding screen 104 is dimensioned to be larger than the display 110a. In an embodiment, the RF shielding screen 104 is dimensioned to cover the entirety of the front face of the mobile device 110. The conductive trace 202 is dimensioned with a width as large as possible without impinging the display 110a. In an embodiment of the present invention, the conductive trace 202 is arranged to correspond with an outside perimeter edge of the display 110a and extends to the outside perimeter edge of the RF shielding screen 104.

[0020] There are two electromagnetic affects working in the shield. All the conductive portions of the shield are electrically connected forming a plane of common potential. The configuration of the pattern of the RF shielding screen 104 exploits the aperture phenomenon where RF waves react to a conductive mesh in a similar manner as a conductive sheet. If the spacing between the mesh elements is significantly smaller than the wavelength of the RF signal and the mesh c:\pof\word\29890.pct.spec.doc

2014405615 04 Jul 2019 elements are electrically connected, the mesh will reduce the transmission of, or block, the signal from the backside of the shield.

[0021] The second affect is the presence of the conductive material in close proximity of the phone's antenna. The conductive material presents a path of lower impedance, compared to air, for the RF and attracts the signal and redirects it.

[0022] The mesh spacing (or pitch) should be fine enough to block a portion of the RF signal, but coarse enough not to disable the touch screen functionality. For example, to block at least 70% of RF, a mesh having a pitch of no greater than 5mm is desirable. However, in the iPhone® 4/4s, for example, the pitch cannot be less than 2mm, otherwise the touch screen functionality will be degraded. Therefore, for an iPhone® 4/4s an appropriate RF shielding screen 104 has a pitch ranging between 2mm and 5mm.

[0023] In another embodiment, shown in FIG. 3, the RF shielding screen 104 is shown in which the horizontal conductive trace 202a and vertical conductive trace 202b forming the conductive trace 202 have different widths. The variation in widths is dictated by the particular mobile device model. Additionally, the embodiment in FIG. 3 has a button cut-out 302 in the horizontal conductive trace 202a in order to allow access to a hardware button 110c. Also, camera cut-out 304 allows the front facing camera 110b of the mobile device to remain unobstructed by the horizontal conductive trace 202a.

[0024] The dimensions of the RF shielding screen 104 is dictated by the placement of the antennas within the mobile device. For example, in most mobile devices 110 that have antennas positioned generally inset from the edge of the mobile device casing, the RF shielding screen 104 can be dimensioned to extend to the edges of the mobile device 110 case. However, when the antenna is positioned along the edges of the mobile device 110 case, as is the case with the c:\pof\word\29890.pct.spec.doc

2014405615 04 Jul 2019 iPhone® 4/4s, for example, the RF shielding screen 104 should extend beyond the edge of the mobile device 110 case by, for example, 0.08 inches in order to effectively block RF signals from transmitting in a generally forward direction toward a user’s body.

[0025] The above-described embodiments indicate that the RF shielding screen 104 has a grid pattern formed by intersecting wire traces at 90° with one another. However, grid alternative patterns may be effectively used as well. For example, FIG. 4 shows a diamond grid pattern in which the wire traces intersect at angles less than 90°. Alternatively, the grid pattern shown in FIG. 2 and 3 can be rotated at any angle between 10° and 80°, thus forming a diamond-like pattern with intersections at 90° therebetween. FIG. 5 shows a further embodiment in which the grid is patterned as first wire traces formed as concentric circles with radially extending intersecting lines formed of second wire traces.

[0026] In addition to the embodiment shown in FIG. 1 through FIG. 3, the present invention can be configured as a case, or pouch. In the present embodiment, the case is constructed with a layer of the RF shielding screen, which lines a portion of the inside of the case. The case main body may be constructed of a plastic, a fabric or other similar material, such as leather, nylon, neoprene, and rubber. The main body is formed into a shape conforming to the silhouette of the mobile device.

[0027] The main body is formed, at a front surface, with an opening through which a portion of the RF shielding screen is exposed. Additionally, at a second side laying perpendicular to the front surface, the main body has a second opening dimensioned to slidingly accommodate insertion of the mobile device into an interior void formed by the main body. A flap, configured to removably hold the mobile device 110 in the case, may be provided on the main body as well.

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2014405615 04 Jul 2019 [0028] Additionally, the case may be equipped with a clip allowing a user to fasten the case to an article of clothing, belt, pocket and the like, or to objects such as a strap of a pocketbook, and the like.

[0029] In an alternative embodiment of the present invention, the RF shielding device is disposed inside a mobile device. In such an embodiment, the RF material can be layered within the mobile device. For example, the RF material may be disposed behind the touchscreen of the mobile device, such that the touchscreen is directly contactable by a user of the mobile device. Alternatively, the RF material may be disposed in front of the touchscreen and within the mobile device enclosure.

[0030] In the case where the RF material is placed in front of the touchscreen, the RF material must be constructed of a material that allows viewing of the touchscreen. On the other hand, if the RF material is placed behind the touchscreen, the materials are not required to be optically transparent.

[0031] In an embodiment of the present invention, the film materials 104a and 104c are acrylic coated polyethylene terephthalate, commonly referred to as PET, such as films produced by DuPont Teijin Films. The grid layer 104b is formed of copper traces deposited directly onto a top surface of the bottom film material 104c. The top surface of the bottom film material 104c is defined as the surface of the bottom film material 104c that is in contact with a bottom surface of the top film material 104a when the embodiment is fully assembled. The top film material 104a and the bottom film material 104c are bonded together using very minute micron thick optically clear adhesive, such as adhesives produced by 3M as well as other manufacturers which are about 1 to about 400 microns thick, e.g., about 100 microns thick. The bottom surface of the top film material 104a has a black ink screen printed on the perimeter corresponding with a bezel of c:\pof\word\29890.pct.spec.doc

2014405615 04 Jul 2019 the phone to which the shield is to be attached. However, the ink screen may be white or any other color as well.

[0032] The traces 202, 204 and 206 forming the grid layer 104b are copper metal with a mixed sulfide/oxide treatment to darken the trace surface in order to reduce reflectivity. The traces are deposited onto the bottom film material 104b using a series of photosensitive coatings applied to the top surface of the bottom film material 104b. The photosensitive coatings are exposed to UV light through a photomask in order to create the desired trace pattern. The photosensitive coatings are developed such that areas of the photosensitive coatings not exposed to UV light are washed off the top surface of the bottom film material 104b. The bottom film material 104b is immersed in an electroless copper plate solution, which grows copper chemically on top of the remaining photosensitive coatings. The copper traces are approximately 5 microns wide and have a 4mm pitch, i.e. the distance between adjacent, parallel traces. The grid pattern is formed with 90° intersections between orthogonal traces. However, the entire grid pattern is rotated 30°, with respect to the x-y axis of the mobile device, in order to avoid Moire interference patterns from developing between the grid pattern of the RF shield and the phone’s LCD display. Additionally, by rotating the grid pattern in this way, traces are prevented from blocking entire rows of red, green or blue pixels on the LCD display that could lead to color artifacts.

[0033] The described embodiments of the present invention are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present invention. Various modifications and variations can be made without departing from the spirit or scope of the invention as set forth in the following claims both literally and in equivalents recognized in law.

Claims

What is claimed is:

1. An RF shielding device for a mobile device, the device comprising:

a conductive grid having first wire traces and second wire traces in electrical contact with each other at intersection points; and a conductive trace disposed around the perimeter of the conductive grid, the conductive trace being in electrical contact with both ends of each of the first wire traces and the second wire traces;

wherein the conductive grid has a pitch ranging between 2 mm and 5 mm, such that potential harmful RF radiation caused by the mobile device is shielded by the RF shielding device while allowing a touch screen of the mobile device to operate.
2. The device as in claim 1, further comprising:

a first insulating film disposed on a top surface of the conductive grid; and a second insulating film disposed on a bottom surface of the conductive grid and the conductive trace, wherein the first insulating film and the second insulating film are of a transparent material.
3. The device as in claim 1 or claim 2, further comprising an adhesive layer disposed on a surface of the RF shielding device intended for contact to a front surface of the mobile device.
4. The device as in any one of the preceding claims, wherein the conductive grid and the conductive trace are formed of materials selected from: metals, metal alloys, plastics, inks, and paints.

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5. The device as in any one of the preceding claims, further comprising a frame adapted to hold the RF shielding device in place against a front surface of the mobile device, preferably wherein at least a portion of the frame is formed of a material substantially transparent to RF radiation emitted and received by the mobile device.
6. The device as in claim 5, wherein the frame is configured to hold the mobile device within the frame.
7. The device as in claim 5 or claim 6, wherein the frame is formed as a case having a second opening on a side dimensioned to accommodate sliding a mobile device into the void.
8. The device as in any one of the preceding claims 2 to 7, wherein the conductive grid and the conductive trace are formed of materials selected from: metals, metal alloys, plastics, inks, and paints.
9. The device as in claim 8, further comprising an adhesive layer disposed on a surface of the RF shielding device intended for contact to a front surface of the mobile device.
10. The device as in claim 8 or claim 9, further comprising a frame adapted to hold the RF shielding device in place against a front surface of the mobile device preferably wherein at least a portion of the frame is formed of a material substantially transparent to RF radiation emitted and received by the mobile device.
11. The device as in claim 10, wherein the frame is configured to hold the mobile device within the frame.
12. The device as in claim 10 or claim 11, wherein the frame is formed as a case having a second opening on a side dimensioned to accommodate sliding a mobile device into the void.
13. The device as in any one of the preceding claims 2 to 12, wherein:

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2014405615 04 Jul 2019 both the first wire traces and the second wire traces are formed of copper traces deposited onto the top surface of the second insulating film, such that the first wire traces are oriented orthogonally to the second wire traces and intersection between the first wire traces and the second wire traces is at 90°, the conductive grid being rotated by 30° with respect to an x-y axis of the mobile device; and the device further comprises an optically transparent adhesive disposed between the bottom surface of the first insulating film and the top surface of the second insulating film.