SE544048C2 - Case for mobile device - Google Patents

Abstract

There is provided a case for a mobile device with an antenna, where said mobile device has a back side, where said case can easily be attached and detached to the mobile device, said case being made of a metal, where said case has a back wall for being in contact with and covering a substantial part of the back wall of the mobile device where said case is characterized in that the inner surface of the back wall has a plurality of grooves for dampening radio waves emitted from the antenna of the mobile device. In addition, the aluminium material, or a mixture of different metals such as copper and aluminium, also will absorb extremely low frequency electromagnetic fields.

Description

Case for mobile device Field ofthe invention This invention relates to a case for a mobile device, such as a mobile phone, that protects against electromagnetic radiation.

Background The antennas of mobile devices emit electromagnetic radiation. ln addition, so-called ex-tremely low frequency electromagnetic fields (ELF-EMFs) are emitted by the electronicsand power supply ofthe mobile device. Many users are concerned about possible healtheffects of this radiation. There is therefore a need for ways to shield the radiation from the antenna and the ELF-EMF:s from the mobile device.

Summary of invention ln a first aspect of the invention there is provided a case for a mobile device with an an-tenna, where said mobile device has a back wall, where said case can be easily be at-tached and detached to the mobile device, said case being made of alumini, where saidcase has a back wall for being in contact with and covering a substantial part ofthe backwall of the mobile device, said case characterized in that the inner surface ofthe back wallhas a plurality of grooves for dampening radio waves emitted from the antenna ofthe mo- bile device where said grooves have a depth of from 0.1 to 3 mm. .

The grooves have the advantage of dampening the radio waves. The case also protects thephone, is recyclable and environmentally friendly (due to its long life). Furthermore, it makes the telephone firesafe.

The case may be arranged for insertion ofthe mobile device by sliding the device into thecase in a defined direction and at least one of the grooves is parallel to the direction ofsliding, and the groove is arranged to receive a protruding part, for example a cameralens, ofthe mobile device. The advantage of this arrangement is that the at least onegroove can serve both the purpose of receiving the protruding part and dampening radio WaVeS.

The use of aluminium results in a low-weight case that also looks stylish. Aluminium is also rather easy to machine. ln a second aspect of the invention there is provided an assembly of a mobile device and a case as described above, in particular a mobile device with a camera lens.

Brief description of drawings The accompanying drawings form a part of the specification and schematically illustratepreferred embodiments of the invention and serve to illustrate the principles of the invention.

Figs. 1-3 show a case for a mobile device.

Fig. 4 schematically shows the inner surface of the back wall of a case for a mobile device.Figs. 5-7 schematically show different kind of grooves.

Fig. 8 schematically shows a criss-cross pattern of grooves on the inner surface of the backwall of a case for a mobile device.

Fig. 9 shows a test setup.

Detailed description With reference to Figs. 1-3 the case 1 is intended to be attached to a mobile device suchas a mobile phone (such as an iPhone, Samsung Galaxy or a Huawei phone) or a tablet computer (for example an iPad) which has an interior antenna for communication with a base station for transmitting data or voice traffic. The mobile device can also be a laptopcomputer. The mobile device typically has a screen, typically a touch screen. The case 1 isarranged so that it can be attached and detached to the mobile device, preferably by slid-ing the mobile device into the case 1. Once attached, the case 1 is typically not detachedfrom the mobile device, but typically it is easy to remove the mobile device from the case 1 if the user so wishes.

The case 1 is designed to fit to a particular model of mobile device. The case shown in Figs. 1-3 is adapted to iPhone X.

The case 1 has a back wall 10 that covers a substantial part of the back wall ofthe mobiledevice. The back wall of the mobile device is typically a substantially flat surface that pref-erably does not have a screen. The screen is typically on the side opposite the back wall ofthe mobile device. Typically, the back wall ofthe mobile device has an opening for the lensof a camera. The lens, or its casing, may protrude somewhat from the surface of the backwall ofthe mobile device. Preferably, the back wall 10 ofthe case 1 covers at least 70%,more preferably at least 80%, more preferably at least 90 %, more preferably at least 95% and most preferably 100 % ofthe surface of the back wall of the mobile device.

The case 1 preferably has a slot 2 for insertion ofthe mobile device. The mobile device isinserted into the slot 2 and brought (for example by pushing the device) in the directionindicated with an arrow 3. The device is preferably held in the case 1 with a press fit. Theslot 2 may also be used for accessing the charging interface and/or headphone jack ofthe device.

The case 1 has a first aperture 4 for the screen of the mobile device. The back wall 10 ofthe case 1 typically has a second aperture 5 for the lens of the camera ofthe device. The case 1 may also have apertures 6a, 6b for accessing buttons on the device.

Aperture 4 for the screen may be covered with a transparent material, for example glassor a polymer material. The transparent material may be chosen so that it blocks radio magnetic waves.

The case 1 is made of a metal. The metal is preferably chosen so that it absorbs electro-magnetic radiation. Preferred metals are copper and aluminium, or mixtures thereof,where aluminium is preferred because of the low weight and low cost. A person skilled inthe art can identify other metals that are useful. For example, the case 1 may be cast in one piece of metal or machined using a CNC milling machine.

The inner surface ofthe back wall 10 of the case 1 has a pattern that reflects and/ordampens the electromagnetic radiation from the antenna ofthe device. The pattern mayhave any suitable shape, for example comprise dimples or small pyramids protruding fromthe back wall 10. ln a preferred embodiment the pattern comprises grooves 7a, 7b, 7c, 8.Where the pattern comprises grooves 7a, 7b, 7c, 8 they may be parallel or arranged in acriss-cross pattern. The width ofthe grooves may be from 1 mm to 5 mm, where 1.5-2.5mm is preferred. The grooves may be spaced from 1 mm to 20 mm apart. The depth of the grooves may be from 0.1 mm to 3 mm.

The pattern and the thickness of the metal of the case 1 should be arranged to dampen asubstantial portion of the radiation but should not completely block the radiation as this would block the communication between the device and the base station.

At least one groove 8 may be parallel to the direction of insertion 3 of the mobile device.Groove 8 may have a width to accommodate a protruding part of the device, for examplethe camera lens ofthe device, to enable sliding ofthe camera lens to reach aperture 5when the mobile device is inserted into the case 1. Slot 2 may have a recess 9 where slot 2meets groove 8 for accommodating the lens of the camera during insertion of the device into case 1.

Fig. 4 shows the inner surface ofthe back wall 10 of a shell1 with grooves parallel to the direction 3 of insertion of the mobile device.

The grooves 7,8 can have a variety of shapes. Some useful examples are shown in Figs. 5- 7. The pattern shown in Fig. 5 is preferred.

Fig. 8 shows example of a criss-cross pattern of grooves. Many different types of patternsare possible. The angle between the two set ofgrooves in Fig 8 is approx. 30° but the in- vention is not limited to this angle. The angle may be for example 45° or 90°.

Example 1 I\/leasurements of radiation from a P20 Huawei mobile phone inserted into an aluminiumcase adapted for a P20 Huawei with grooves as shown in Figs 1-3 according to the inven-tion was carried out according to the CTIA standard for measurement of antenna perfor-mance (I\/|ethod of I\/|easurement for Radiated RF Power and Receiver Performance, Ver-sion 3.7.1, February 2018) by Ektos Testing & Reliability Services A/S, Copenhagen, Den-mark.

The test setup is shown in Fig 9. I\/leasurements where done for the indicated angles at a calibrated distance of about 4 m. The results are shown in table 1.

Angle 0 15 30Without shell (mW) 11.91 12.68 24.42With shell (mW) 0.36 0.36 0.35 Table 1 The results show that the case blocks a substantial amount of the radiation from the mobile phone.

While the invention has been described with reference to specific exemplary embodiments, the description is in general only intended to illustrate the inventive concept and should not be taken as limiting the scope ofthe invention. The invention is generally defined by the claims.

Examgle 2 Power density as root mean square was measured on a Huawei P20 using a Gigahertz Solutions HF 35C HF-Analyzer instrument.

The measurements were carried out by VerkotanOy, Oulu, Finland. The results are shown in Table 2.

Claims (6)

1. A case(1) for a mobile device with an antenna, where said mobile device has a back wall, where said case can be easily be attached and detached to the mobile device, said case being made of a metal, where said case has a back wall for being in contact with and covering a substantial part of the back wall of the mobile device, said case characterized in that the inner surface of the back wall has a plurality of grooves for dampening radio waves emitted from the antenna of the mobile device.

2. The case according to claim 1 where the case is arranged for insertion of the mobile device by sliding the device into the case in a defined direction and at least one of the grooves is parallel to the direction of sliding, and the groove is arranged to receive a protruding part of the device.

3. The case according to claim 1 where the protruding part is a camera lens.

4. The case according to any one of claims 1 to 3 where the metal is aluminium.

5. An assembly of a mobile device and a case according to any one of claims 1 to 4.

6. An assembly of a mobile device with a camera lens and a case according to claim 3 or 4.