TECHNICAL FIELD

The present invention relates to the field of antenna arrangements and housing elements for mobile devices, such as mobile phones. The invention also covers the field of methods to manufacture a housing element for a mobile device as well as mobile devices comprising such an antenna arrangement. BACKGROUND ART

There are today solutions available where antennas are integrated in an external cover to a mobile phone. As there is a trend today towards using metal as an external surface for external covers there is also a need to integrate antennas in such an external cover of a mobile phone. One such solution is the Nokia patent application WO 2008/122831 A1 . This document discloses an antenna arrangement and antenna housing. The antenna arrangement comprises an antenna occupying at least a first plane, a conductive structure that is isolated from the antenna but is arranged to be parasitically fed by the antenna. The conductive structure has a slot and occupies at least a second plane different but adjacent the first plane.

A drawback with this solution is that there is only one radiating element, in this case a slot element, limiting the possibilities to achieve multiple band operations with the same antenna arrangement.

There is thus a need for a solution for providing an antenna arrangement with improved possibilities for achieving multiple band operation where the antenna is integrated in a cover of a mobile phone and where the cover has metal as an external surface.

SUMMARY The object of the invention is to reduce at least some of the mentioned deficiencies with the prior art solutions and to provide:

• an antenna arrangement for a mobile device

· a housing element

• a method to manufacture the housing element

• a mobile device comprising the antenna arrangement to solve the problem to achieve an antenna arrangement with improved possibilities for achieving multiple band operation where the antenna is integrated in a cover for a mobile phone and where the cover has metal as an external surface.

The object is achieved by providing an antenna arrangement for a mobile device. The mobile device comprises radio frequency circuits and a ground plane. The antenna arrangement comprises a conductive element and at least one feeding element, said feeding element comprising a conductive pattern is arranged to be connected to the radio frequency circuits wherein the conductive element is a sheet having an outer first surface and an inner second surface. The conductive element comprises at least two radiating elements. The radiating elements are arranged to be fed through said feeding element. Said radiating elements are physically separated from each other by isolation means and said feeding element has an extension plane with one side of the feeding element facing the inner second surface of the conductive element with a gap between the conductive element and the conductive pattern of said feeding element.

The object is further achieved by providing a housing element for a mobile device wherein the housing element comprises the antenna arrangement according to any one of claims 1 -17 and an internal non-conductive structure wherein the outer first surface of the conductive element is an outer surface of at least a part of an external cover to the mobile device and the inner second surface of the conductive element is facing one side of said feeding element. The conductive element and the internal non-conductive structure are integrated into one unit.

The object is further achieved by providing a method to manufacture a housing element for a mobile device, according to any one of claims 18-21 wherein the radiating elements are applied to the internal non-conductive structure.

The object is still further achieved by providing a mobile device comprising the antenna arrangement according to any one of claims 1 -17.

The object is also achieved by providing a further antenna arrangement for a mobile device. The mobile device comprises radio frequency circuits and a ground plane. The antenna arrangement comprises a conductive element and at least one feeding element, said feeding element comprising a conductive pattern being arranged to be connected to the radio frequency circuits wherein the conductive element is a sheet having an outer first surface and an inner second surface. The conductive element comprises one radiating element. The radiating element is arranged to be fed through said feeding element and said feeding element having an extension plane with one side of the feeding element facing the inner second surface of the conductive element with a gap between the conductive element and the conductive pattern of said feeding element.

Further advantages are achieved if the invention is also given one or several characteristics according to the dependent claims not mentioned above. This will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically illustrates an example of a mobile device.

Figure 2 schematically illustrates one example of the feeding of the antenna arrangement in a side view.

Figure 3a schematically shows one example of a conductive element with locations of ground connection points at the radiating element and location of the feeding element.

Figure 3b schematically illustrates relative positions between different parts of the conductive element and the ground plane.

Figure 3c schematically shows one example of a radiating element with three ground connections.

Figure 4 schematically shows some examples of feeding elements.

Figure 5 is a perspective view from the outside, of an external cover for a mobile device.

Figure 6 is a perspective view seen from the inside of the mobile device showing an example of part of a housing element.

Figure 7 is an exploded perspective view showing an example of a conductive element and an internal non-conductive structure of a mobile device.

Figure 8 is a perspective view of an example of a housing element of the mobile device with two feeding elements. Figure 9 schematically shows an example of an RF matching network. Figure 10 schematically shows an example of a ground matching network.

Figure 1 1 is a block diagram of one example of the manufacturing method for the housing element.

Figure 12 is an exploded perspective view showing an example of an internal non-conductive structure with radiating elements and a feeding element.

Figure 13 shows a perspective view from the outside of an internal non- conductive structure. DETAILED DESCRIPTION

The invention will now be described with reference to the enclosed drawings. The dimensions in the drawings are not to scale and relations in dimensions between parts in the drawings have been chosen to improve clarity.

A mobile device is defined as a portable communication and/or computer device. The mobile device can e.g. be a mobile phone, a handheld computer, a lap top, a Personal Digital Assistant (PDA) or any other type of mobile device.

Figure 1 shows the mobile device 101 , exemplified with a mobile phone, comprising a control unit 107 configured to control communication with a mobile communication system 103. A keyboard 1 13, a display 1 15 and radio frequency (RF) circuits 109 are connected to the control unit 107 which together with an antenna arrangement 1 1 1 are arranged to establish a radio- interface 105 for communication with the mobile communication system 103. The mobile device also comprises at least one ground plane or at least one reference plane providing a ground or reference voltage for AC and DC. Henceforth the expression ground plane or ground is used for a ground or reference plane respective a ground or reference voltage. The antenna arrangement of the mobile device is connected to the RF circuits which in turn are connected to further electronic components. The antenna arrangement is normally also connected to the ground plane of the mobile device.

The invention covers an antenna arrangement for a mobile device. The mobile device comprises RF circuits and a ground plane. The antenna arrangement comprises a conductive element and at least one feeding element. The feeding element comprising a conductive pattern is arranged to be connected to the RF circuits.

The antenna arrangement of the invention thus comprises two main parts, a conductive element and at least one feeding element cooperating with the ground plane of the mobile device. The two main parts are located adjacent to each other. The feeding element is connected to RF circuits of the mobile device through a galvanic or non-galvanic connection and receives RF energy from the RF circuits in transmit mode (Tx-mode). The non-galvanic connection can be arranged e.g. via a capacitor. The feeding element is feeding the radiating elements of the conductive element non-galvanically. This does however not exclude a common ground connection between the feeding and radiating elements. The feeding element will excite current in the conductive element and the conductive element will radiate RF energy into space. In the non-galvanic coupling, electromagnetic energy is thus transferred through a dielectric medium such as air or a dielectric material. Due to the reciprocity principle of antennas the inventive solution is applicable both for transmission and reception if not otherwise stated. Henceforth in the description the invention will be described for the transmit mode (Tx-mode) if not otherwise stated. The conductive element is made of a conductive material such as metal and can e.g. be at least a part of an external cover of a mobile device such as a mobile phone. This means that the antenna arrangement can be implemented e.g. in mobile phones having the external cover, also called the external housing, made of metal. This is an important advantage as there is a trend today towards mobile phones having metal covers or covers with an external metallization as will be explained. By dividing the conductive element in at least two parts, the metal cover or metalized cover of a mobile phone can be used to integrate several antenna functions. Said parts are physically separated by isolation means. The isolation means can be a slit or a slit filled with a non-conductive material. Said parts are henceforth called radiating elements.

The invention also provides a housing element comprising the antenna arrangement, a method to manufacture the housing element and a mobile device comprising the antenna arrangement according to any one of claims 1 -17.

Figure 2 schematically shows a side view of one example of the feeding of the antenna arrangement comprising a first radiating element 201 and a feeding element 203. Only a part of the first radiating element is shown in figure 2. In this example the first radiating element 201 is a part of a back cover of a mobile phone. The feeding element 203 is connected to the RF- circuits through at least one first RF-connection 204 and may also be connected to the ground plane through a first ground connection 205, i.e. at least one feeding element may be arranged to be connected to the ground plane of the mobile device. There is a gap 207 between the feeding element and the first radiating element, defining a gap distance. The RF circuits and the ground plane are located on a Printed Circuit Board (PCB) 202 of the mobile phone. The first radiating element is connected to ground via a second ground connection 206. The first radiating element can have more than one ground connection, as schematically illustrated with a third ground connection 208. In certain applications, as will be explained, there is no ground connection between the radiating element and the ground. The feeding element 203 may have more than one ground connection as schematically illustrated with a fourth ground connection 209. The location of the possible ground connection/s of the radiating element and possible ground connection/s of the feeding element will affect the impedance matching of the antenna arrangement to the RF-circuits. Figure 2 also shows a second RF connection 210. A second RF connection can be used e.g. in applications when the feeding element should cover several frequency bands and when it is desirable to have a separate RF feed for certain frequency bands. The gap distance does not have to be constant along the feeding element but can vary due to the shapes and relative positioning of the feeding element and the radiating element. The feeding element in figure 2 may be manufactured as a stamped metal part shaped to a desired conductive pattern of the feeding element. The feeding element can be applied to the interior of the mobile device by conventional means such as non-conductive spacers. The gap 207 is the distance between the conductive pattern of the feeding element and the conductive element.

In a further example of the invention it is possible to have more than one feeding element to each radiating element. This can be an advantageous alternative when a separate feed is desirable for certain frequency bands.

An advantage with the present invention is that there are several possibilities for improved matching, i.e. to adjust the impedance of the antenna arrangement to the impedance of the RF-circuits of the mobile device. Good matching means that transmission losses between the RF-circuits and the antenna arrangement are minimized. The invention allows the matching to be performed by adjusting different parameters as will be described below. An improved impedance matching will improve both antenna efficiency and bandwidth. The adjustment of the impedance matching, some times referred to as the matching, is also described as tuning of the antenna arrangement or the radiating elements to a certain frequency band or bands.

Figure 3a schematically shows in a perspective view one example of a conductive element 300 with locations of ground connections to the first radiating element 301 and location of the feeding element 306. The conductive element 300, having an outer first surface 315 and an inner second surface 316, is made of a sheet such as a metal sheet or a sheet of other alternative material and comprises at least two radiating elements, in this case the first radiating element 301 and a second radiating element 302. The radiating elements thus also have an outer first surface (315) and an inner second surface (316). Examples of metals and other alternative material are described in association with figure 5. The radiating elements are separated by a slit 303 filled with a non-conductive material. A first ground connection point 304 and a second ground connection point 305 at the first radiating element 301 are also shown as well as the feeding element 306 facing the inner second surface of the conductive element. The feeding element, in this example a double loop antenna, is coupled non-galvanically to the first radiating element. In this case the first radiating element will be inductively loaded through the loops of the feeding element. The radiating elements comprise in this example a substantially planar part 309 with side parts 310 extending substantially perpendicular to the planar part at each side of the planar part except a side towards the slit 303. A coordinate symbol 307 defines the directions of the x-, y- and z-axis. The y-axis is extending along a length direction of the conductive element and the x-axis extends along a width direction of the conductive element. The z-axis is extending along a height direction of the conductive element coinciding with the extension direction of the side parts. There is normally one feeding element to each radiating element, i.e. one feeding element is arranged to feed one radiating element. The feeding element is facing the inner second surface 316 of the conductive element and the vertical projection of the feeding element towards the conductive element falls within the area of the corresponding radiating element. The exact location of the feeding element in relation to the radiating element can be used for fine tuning the matching between the antenna arrangement and the RF-circuits of the mobile device. It is also possible to have one feeding element arranged to feed more than one radiating element, i.e. at least two radiating elements. This also means that each feeding element will always be arranged to feed at least one radiating element. In this example of the invention the vertical projection of the feeding element towards the inner second surface of the conductive element can fall within the combined area of the radiating elements being fed by the feeding element. The gap distance and dielectric material between the feeding element and the radiating element affects the matching of the antenna arrangement. Choice of dielectric material and gap distance can therefore be used for matching the antenna arrangement to the RF-circuits. This is further explained in association with figure 6.

In summary the radiating elements are arranged to be fed through a feeding element. Normally there is one feeding element to each radiating element but one feeding element can also feed two or more radiating elements and there can be more than one feeding element feeding one radiating element. The radiating elements are physically separated from each other by isolation means and said feeding element has an extension plane. The feeding element has a first side and a second side with one side facing the inner second surface of the conductive element with a gap between the conductive element and the conductive pattern of said feeding element. The extension plane can be flat and extend in two dimensions or be curved and extend in three dimensions. The inventive antenna arrangement normally use two or more radiating elements, each radiating element covering a certain frequency band or bands or combination of frequency bands used e.g. for GSM (Global System for Mobile communication), UMTS (Universal Mobile Telecommunications System), Near Field Communication (NFC)/RFID (Radio Frequency Identification), FM-radio, DVB-H (Digital Video Broadcasting-Handheld) used for TV, Bluetooth, WLAN (Wireless Local Area Network), HLAN (Hiper LAN), Wimax, UWB (Ultra Wideband), GPS (Global Positioning System) and LTE (Long Term Evolution). The GSM system is divided in GSM-850, GSM-900, GSM-1800 and GSM-1900 working around 850 MHz, 900 MHz, 1800 MHz and 1900 MHz respectively.

In one example of the invention, adapted for operation at the frequency bands GSM-900, GSM-1800 and GSM-1900, the conductive element, ground connection points and feeding element can be configured as follows. The size of the planar area is approximately 100 mm in length and 50 mm in width. The side parts extend approximately 6 mm in z-direction. The coordinates mentioned below are calculated with the origin of the x/y/z coordinate system located at point 308. The first ground connection point 304 will then be located approximately at x/y/z coordinate 45/98/0 mm and the second ground connection point approximately at x/y/z coordinate 10/95/0 mm. An RF connection pad 31 1 and a ground connection pad 312 of the feeding element 306 are located in the area with x-coordinates approximately 20-30 and y-coordinates approximately 70-80 mm. The RF connection pad and the ground connection pad are normally positioned close to each other, in this example within a few millimetres. The location of these pads relative each other has influence on the matching of the feeding loops which is a well known fact to the skilled person. The feeding element can have the extension plane in the x/y plane at a Z-coordinate for the conductive pattern of the feeding element of 0,5-2 mm, i.e. there is a gap of 0,5-2 mm between the conductive pattern of the feeding element and the radiating element. Other gap distances are also possible, as will be explained. The gap can be filled with a non-conductive material, as an internal non-conductive structure, as will be described in association with figure 7 or the feeding element can be extended from the radiating element with other conventional means such as spacers and the gap will then comprise of air or a combination of air and non- conductive material. The feeding element can be a double loop antenna with an outer 313 and an inner 314 loop both having an approximately quadratic shape with dimensions 12x12 mm for the outer loop and 8x8 mm for the inner loop. A separation between the two loops can be about 1 ,5-2 mm and can vary along the extension of the loops as will be shown in the example of figure 4. This separation distance between the loops can vary considerably and the only requirement is that the inner loop runs inside the outer loop.

In this example the distance between the first and the second ground connection points is about 35 mm. Moving them closer will shift resonance frequency towards lower frequencies. Increasing the distance between the ground connection points, the antenna will become electrically shorter and the resonance frequency will move to higher frequencies and low band matching, e.g. at GSM-900, will get worse. Figure 3b schematically illustrates relative locations between different parts of the conductive element 300, with the planar part 309 and the side parts 310, and the ground plane 317 located at a PCB. There is a first distance 318 between the ground plane and an edge of the side part most distal from the planar part and a second distance 319 between the extension plane of the planar area and the extension plane of the ground plane. The first distance in the example of figure 3a is about 0,5-2 mm and the second distance about 8 mm. These distances can however vary depending on the application, but typically the first distance is within 0,1 - 10 mm and the second distance within 1 - 20 mm.

Figures 3a and 3b show the conductive element made in a metal sheet or the other alternative material and formed as a rectangular box with a planar part 309 and planar side parts 310 being approximately perpendicular to the planar part. The conductive element can however be designed to the desired shape of at least a part of an external cover of a mobile device. This means e.g. that the planar parts can be curved in a third dimension and the rectangular shape can e.g. be more oval. In the general case the metal sheet or the other alternative material of the conductive element can have a free form surface. The surface form is then described using e.g. Non Uniform Rational B-spline (NURBS). There can also be more than two ground connection points, as are schematically illustrated in figure 3c showing a perspective view of a radiating element 320 with a first 321 , a second 322 and a third 323 ground connection to the ground plane of a Printed Circuit Board (PCB) 324. Each ground connection is galvanically connected to a corresponding ground connection point at the inner second surface of the conductive element, in this case the part of the inner second surface belonging to the first radiating element. The ground connection to the radiating elements can also be made non- galvanically through e.g. a ground matching network as explained in association with figure 10. A galvanic RF connection 326 is arranged between the RF circuits of the PCB and the feeding element 325. By introducing the third ground connection it will be possible e.g. to create a wider band width including e.g. also UMTS frequencies around 2,2 GHz in addition to the coverage of GSM- 900, GSM-1800 and GSM-1900 as shown in the example of figure 3a. In figure 3c the side parts of the radiating element have been left out for clarity reasons. By introducing one or several ground connections to the feeding element it is also possible to affect the impedance matching of the antenna arrangement to the RF-circuits.

The ground connections to the radiating and feeding elements and the RF connections to the feeding elements can also be connected through switching means preferably located at the PCB, 324. The operation of the radiating element can be configured to cover different frequency bands by selecting certain ground connections to be connected or disconnected to the ground plane through said switching means. The switching means can comprise e.g. switches realized with Microelectromechanical systems (MEMS) or Field Effect Transistors (FET) or PIN (P-type Intrinsic and N-type of semiconductor) diodes.

The connection of the radiating element to the ground plane can also be realized via a ground matching network as will be explained in association with figure 10.

The feeding element with the first side and the second side as shown in figure 3, and also in figure 2, may be manufactured as a stamped metal part shaped to a desired conductive pattern of the feeding element. The feeding element can be applied to the interior of the mobile device by conventional means such as non-conductive spacers. Other examples of feeding elements will be described in association with figure 4.

The feeding element can preferably be an H-field antenna such as a helix connected to ground or a single or multiple loop antenna. Other types of feeding elements are however possible within the scope of the invention as long as electromagnetic energy is transferred between the feeding element and the conductive element. Some examples of feeding elements are shown in figure 4. An H-field antenna is defined as an antenna with an electromagnetic field having a dominating H-field. A typical example of an H- field antenna is a loop antenna. Normally at least one of the feeding elements is an H-field antenna. Typically at least one of the feeding elements is a single loop or a double loop antenna.

Figures 4a to 4e schematically show some examples of different configurations of conductive patterns for loop antennas, the loop antennas being used as feeding elements. Figure 4f shows a helix antenna with a ground connection and figure 4g a capacatively loaded radiating element using a patch antenna as feeding element. All feeding elements described below have a conductive pattern manufactured of a conductive material such as copper or other metal or metal alloy or other suitable conductive material. The conductive pattern can be shaped as rectangular, circular or triangular loops or as helixes or patches as will be described below. The loops can be of single-, double- or triple-type as will be illustrated. The conductive patterns are applied to a non-conductive substrate such as a rigid or flexible PCB. The non-conductive substrate is not shown in figures 4a-4f for clarity reasons. A flexible PCB is also called a flexfilm. All illustrated examples of loop antennas have an RF pad 402 for connection to the RF circuits and a ground pad 403 for connection to the ground plane of the mobile device. The conductive pattern can thus be applied to a first surface of the non-conductive substrate, the second surface of which can be applied to the conductive element for feeding at least one radiating element from each feeding element. The feeding element in the examples in figures 4a - 4f below thus comprises the non-conductive substrate (although not shown in the figures 4a-4f) with the conductive pattern. The second surface of the non-conductive substrate can also be applied to an internal non-conductive structure. Alternatively the conductive pattern of the feeding element is applied directly to the internal non-conductive structure, the internal non-conductive structure in this case functioning also as a non-conductive substrate for the feeding element. In the examples above, one side of the feeding element, which can be the first or the second side of the feeding element, thus comprises the first surface of the non-conductive substrate with the conductive pattern. The opposite side of the feeding element comprises the second surface of the non-conductive substrate. Choice of type of non-conductive substrate will affect the matching of the antenna arrangement. The internal non-conductive structure is described in association with figure 7. Figure 4a shows an example of a single loop antenna 401 with the RF pad 402 and the ground pad 403. The location of the RF and ground connection to the feeding element does not necessarily have to be as shown in the examples in figures 4a to 4g. For matching purposes it can be suitable to make these connections at other points at the feeding element. RF matching networks and/or ground matching networks, as described in association with figures 9 and 10, can also be used between the RF pad and the RF circuits and between the ground pad and the ground plane.

Fig 4b shows an example of a double loop antenna 404 with a first loop 405 and a second loop 406. The distance d between the loops can vary along the loop as illustrated.

Figure 4c shows an example of a triple loop antenna 407 with a first loop 408, a second loop 409 and a third loop 410.

The loop examples shown in figures 4a-4c have a mainly rectangular or quadratic shape. A loop can also have any other shape as exemplified in figure 4d with a triangular loop 41 1 and in figure 4e with a circular loop 412. Different parts of the loop or loops can have different widths. An example of this is shown in figure 4d where the different sides in the triangle have different widths. This is an advantage because different widths can create more resonances which is a way to increase the band width or create a multiple band antenna. The widest part of the loop can e.g. be responsible for a first resonance, the widest and second widest in series for a second resonance and all widths in series for a third frequency. The first resonance can e.g. be a ½-wave resonance for a high GSM frequency and the second and third resonance frequency can e.g. be ¼-wave resonances for lower frequencies.

The conductive pattern of the feeding element can also be a helix 413 where a short 414 is connected to the ground pad 403. The short can be connected to the helix at a location along the helix giving a good matching between the RF-circuits and the feeding element according to principles well known to the skilled person. The helix can e.g. be realized as a flat helix on two layers of a non-conductive substrate such as a PCB. The conductive pattern of the helix pattern starts at a first layer of the PCB, runs through a first plated hole to a second layer, continuous on the second layer, runs through a second plated hole to the first layer, continuous on the first layer, runs through a third plated hole to the second layer, continuous on the second layer, and so on. The feeding element in this case comprises the PCB with the conductive helix pattern. In this particular case the gap distance is the distance from the radiating element to the conductive pattern in the layer being closest to the radiating element.

Figure 4g shows a further example of a feeding element with a conductive pattern shaped as a patch 415 connected to the RF circuits via the RF connection 416. The radiating element 417 is connected via a ground connection 418 to the ground plane of the mobile device. The ground plane is located at a PCB 419, holding also the RF circuits. With this feeding arrangement RF energy is transferred between the feeding element and the conductive element through a capacitive coupling via a gap 420 between the conductive pattern and the radiating element. Gap distances are discussed in association with figure 6. In this example the feeding element is ungrounded. Other ungrounded feeding elements such as helixes or monopoles are also possible within the scope of the invention. In this example the feeding element with its two sides is a patch-shaped metal sheet. The conductive pattern is thus patch shaped. In order to broaden the bandwidth of the antenna arrangement the feeding element can also comprise a parasitic element.

Figure 5 is a perspective view of one example of the invention showing a conductive element 500 from the outside of a mobile device. The conductive element is in this example an external cover of a mobile phone divided in three radiating elements, a first radiating element 501 , a second radiating element 502 and a third radiating element 503. The three radiating elements are physically separated from each other by isolation means, in this example comprising a first slit 504 and a second slit 505. The conductive element, and thus also the radiating elements, are manufactured of a well conductive metal such as aluminium, copper, silver, titan, gold or suitable metal alloys (like stainless steel) or other alternative material like plastics plated with a well conductive metal surface using e.g. Vacuum Metallization (VM) or Physical Vapour Deposition (PVD). A further alternative material for manufacturing the conductive element can be metals like iron, zinc and magnesium being plated with a well conductive metal as aluminium, copper, silver, titan, gold or suitable metal alloys using VM or PVD. The isolation means in this example two slits are filled with a non-conductive material such as e.g. plastics of type ABS (Acrylonitrile Butadiene Styrene), PC (Polycarbonate) or PA (Polyamide) or plastic compounds or glass fibre reinforced plastics. This non- conductive material can be the same material as used for the internal non- conductive structure as will be discussed in association with figure 7. In the example of figure 5 the external cover also includes an opening 506 to be used for a camera lens and in this case the number of slits is one less than the number of radiating elements. The plastic materials mentioned above and other non-conductive materials are also dielectric materials, as is well known to the skilled person. The internal non-conductive structure and the non- conductive substrate, manufactured of non-conductive materials, can thus also be said to be manufactured of dielectric materials. The dielectric material chosen for the internal non-conductive structure and the non-conductive substrate shall have good, low loss, RF-properties, as is well known to the skilled person.

The non-conductive substrate is typically a non-conductive material as known in the art, used for manufacturing of Printed Circuit Boards and flexfilms or any suitable non-conductive material, e.g. plastics mentioned above for use as slit filling. In one example of the invention the conductive element of the housing element comprises three radiating elements. The first radiating element 501 is in this example dedicated to the frequencies of GSM bands GSM-850, GSM-900, GSM-1800 and GSM-1900 (operating from about 850 to 1900 MHz) as well as the UMTS band (1920 - 2170 MHz). The second radiating element 502 is dedicated for FM-radio frequencies (operating at 30-300 MHz). The third radiating element 503 is dedicated to WLAN frequencies (e.g. 2,4 or 5 GHz band). The second radiating element is located between the first and the third radiating elements.

Figure 6 shows a part of a housing element 600 with the part of the conductive element shown in figure 5 comprising the first radiating element 601 . The first radiating element has a outer first surface 602 and a inner second surface 603. The outer first surface of the conductive element in this example is an outer surface of a part of an external cover to the mobile device. The inner second surface is facing one side of the feeding element and is an interior surface of a part of the external cover. A feeding element 604, in this case a double loop antenna, is applied to the inner second surface 603 of the mobile device. The conductive pattern of the feeding element comprises a double loop with a first loop 606 and a second loop 607. The conductive pattern of the loops are of conductive material, such as copper, and can e.g. be printed or plated to a first surface of a flexible or rigid non-conductive substrate 605 such as a flexfilm or PCB. A second surface of the non-conductive substrate is then applied to the first radiating element by any conventional means such as gluing. The feeding element thus comprises the conductive pattern and the non-conductive substrate. The gap between the conductive pattern of the feeding element and the radiating element is in this example equal to the thickness of the non-conductive substrate. The first radiating element has an opening 610 for e.g. a camera lens.

In the example of figure 6 the feeding between the feeding element and the radiating element is arranged with a non-galvanic coupling. This means that the RF energy fed to the feeding element from the RF circuits is electromagnetically coupled to the radiating element. This is accomplished by locating the feeding element in the vicinity of the radiating element. The gap distance between the conductive pattern of the feeding element and the radiating element is normally within 0,1 -7 mm, preferably within 0,1 -5 mm but most preferably within 0,1 -3 mm. The gap distance can be used as a parameter for matching of the radiating element to a certain frequency band.

The feeding between the RF-circuits of the mobile device and the feeding element is preferably arranged with a galvanic coupling. This can be arranged by any conventional means such as a spring contact or pogo pin placed on the PCB of the mobile device and contacting RF pad 608 and ground pad 609 on the loop antenna. The feeding between the RF-circuits of the mobile device and the feeding element can also be arranged with a non- galvanic coupling, e.g. through a capacitance arranged between the RF- circuits and the feeding element. The feeding between the RF-circuits of the mobile device and said feeding element/s can thus be arranged with at least one galvanic and/or at least one non-galvanic coupling. There is at least one RF connection to each feeding element.

The feeding between the RF-circuits and the feeding element can also be arranged via an RF matching network to further improve the number of matching possibilities. An example of such a matching possibility is shown in figure 9.

In the example of figure 6 the loop antenna is conveniently arranged around the opening 610. This is not a necessary requirement but the feeding element just has to be in the vicinity of the radiating element as described above.

The radiating element is normally arranged to be connected, galvanically or non-galvanically, to the ground plane of the mobile device at, at least, one point. This is schematically illustrated with the ground connection point 61 1 . In certain realizations of the invention the radiating element can be unconnected to the ground plane. This can be advantageous, but not necessary, for radiating elements operating at higher frequencies such as e.g. WLAN frequencies.

Figure 7 is an exploded perspective view of one example of how to assemble the conductive element comprising the first 701 , the second 702 and the third 703 radiating element. The three radiating elements are applied to the internal non-conductive structure 704. This can be accomplished by adhesive moulding or insert moulding as will be further explained in association with figure 1 1 , describing one example of a manufacturing method of the housing element. The non-conductive material used in the moulding process will then fill up the slits between the radiating elements such that the filling will become flush with the outer first surface of the conductive element. Figure 7 also shows an internal slit 705 which can be used in any of the radiating elements to facilitate the possibility to cover two or more frequency bands or for broadening the bandwidth of a certain frequency band. For tuning purposes the edges of the internal slit can be straight, curved or even meandered. The width of the internal slit can also vary along the slit. The internal slit is not an isolation means.

Figure 8 shows an example of an assembled housing element comprising the first, second and third radiating elements, 801 -803, with a first and second slit 804-805. The housing element in this example also comprises the internal non-conductive structure and the feeding element/s. The internal non- conductive structure 806 is moulded to the radiating elements. The material of the internal non-conductive structure fills the slits and the filled slit functions as the isolation means between the radiating elements. The number of slits is one less than the number of radiating elements in the examples of the invention when the slit is physically separating one radiating element from another. This is not valid in the case a slit is also made internally within a radiating element as shown in figure 7.

The housing element 800 of figure 8 for a mobile device comprises an antenna arrangement according to any one of claims 1 -17 and the internal non-conductive structure 704, 806 wherein the outer first surface of the conductive element is an outer surface of at least a part of an external cover to the mobile device and the inner second surface of the conductive element is facing one side of the feeding element/s. The internal non-conductive structure is in this example located between the conductive element and the feeding element/s. The conductive element and the internal non-conductive structure are integrated into one unit. In this example the feeding element/s is/are also attached to the internal non-conductive structure. This is however not necessary as will be explained. Figure 8 also shows a first feeding element 807 comprising a double loop antenna as described in association with figure 6. This double loop antenna is used to excite the first radiating element 801 through a non-galvanic coupling.

A second feeding element 808 realized as a single loop antenna is feeding the third radiating element 803 non-galvanically. The feeding elements realized as e.g. a conductive pattern on a non-conductive substrate or a conductive pattern of stamped metal can be applied to the internal non- conductive structure through any conventional means such as gluing or they can be applied during a moulding process. The feeding element/s is/are thus integrated with the internal non-conductive structure and the internal non- conductive structure is attached to the conductive element thus forming a one-piece housing element. Each radiating element normally has at least one ground connection arranging contact between the ground plane of the mobile device and the radiating element (not shown in figure 8). In certain applications, as described in association with figure 6, the ground connection for the radiating element is not necessary. The first radiating element can be matched for use in the GSM frequency bands and the third radiating element can be matched for use in WLAN applications or as a GPS antenna. The second radiating element can e.g. be used for FM (Frequency Modulation) radio. A feeding element for FM radio is not shown in figure 8. A suitable feeding element for a radiating element covering FM frequencies can be a loop antenna with an RF and/or a ground matching network. An extension coil can be used in series with the loop, between the RF pad of the loop and the RF circuits, to decrease the dimensions of the loop. By a combination of the sizes for the loop antenna and the radiating element, the configuration of the matching network and choice of extension coil a resonance frequency in the FM band can be achieved.

The conductive element of the housing element can be at least a part of an external cover to a mobile device, e.g. the back cover of a mobile phone. Figure 9 schematically shows an example of the RF matching network mentioned above. The feeding element 901 , is illustrated with a loop antenna with the ground pad 914 and the RF pad 915, connected from the ground pad 914 to the ground plane 902 of the mobile device. The RF pad 915 of the loop antenna is connected to a first terminal 910 of an RF generator 907 through a first connection point 903, a first capacitor 904, a second connection point 905 and a first inductor 906. The second terminal 91 1 of the RF generator is connected to ground 902 through a third connection point 908 and a fourth connection point 909. A second capacitor 912 is connected between the second and third connection points and a second inductor 913 is connected between the first and fourth connection points. The matching network in this example comprises the first and second capacitor and the first and second inductor. The matching components can be located at a PCB of the mobile device holding also the RF circuits. Alternatively the matching components can be located at the non-conductive substrate, such as a flexfilm, holding the feeding element. The RF generator is part of the RF circuits of the mobile device. The matching between the RF circuits and the antenna arrangement can now be tuned by varying the component values of the matching components. Typical values in the frequency bands GSM-900 and GSM-1800/1900 for the first and second capacitor can be around 1 -100 pF and for the first and second inductor around 1 -100 nH, but also values below 1 pF and 1 nH are possible. This is just one example of a configuration for a ground matching network. The matching network can comprise more or less components than shown in this example. In its simplest form it can e.g. comprise just one capacitor or one inductor. In more complicated configuration active components like switching means can also be used. The configuration and dimensioning principles of the matching components to achieve matching at different frequencies are well known to the skilled person and therefore not further discussed here.

Figure 10 schematically shows an example of a ground matching network where the feeding element 1001 or the radiating element (not shown in figure 10) is connected to the ground plane 1002 of the mobile device via two parallel connection paths. The feeding element 1001 is illustrated with a loop antenna with the ground pad 1010 and the RF pad 101 1 . The two parallel connection paths start at the ground pad 1010 and ends at the ground plane 1002. The RF pad is connected to the RF circuits. The first connection path comprises a third capacitor 1003 and the second connection path comprises a third 1004 and fourth 1005 inductor in series. This ground matching network adds a further possibility to match the antenna arrangement to the desired frequency band or bands. Typical values in the frequency bands GSM-900 and GSM-1800/1900 for the third capacitor can be around 1 -100 pF and for the third and fourth inductor around 1 -100 nH, but also values below 1 pF and 1 nH are possible. This is just one example of a configuration for a ground matching network. The matching network can comprise more or less components than shown in this example. In its simplest form it can e.g. comprise just one capacitor or one inductor. In more complicated configuration active components like switching means can also be used. The configuration and dimensioning principles of the matching components to achieve matching at different frequencies are well known to the skilled person and therefore not further discussed here.

The matching or tuning of the radiating elements of the antenna arrangement to a certain frequency band can be made by adjusting one or several of following parameters:

• size of radiating element

• size and type of feeding element

· positioning of the feeding element in relation to the radiating element

• location and number of ground connection points at the radiating element

• location of RF pad and ground pad of the feeding element

• location and number of RF-connections to the feeding element

· width and shape of the slits between radiating elements

• the gap distance between the feeding element and the radiating element

• dimensioning of the RF matching network

• dimensioning of the ground matching network

· choice of dielectric material or dielectric medium in the gaps and slits (also internal ones) and choice of dielectric material for the internal non-conductive structure and the non-conductive substrate.

These tuning parameters are examples of tuning parameters that can be used to create e.g. ¼-wave, ½-wave or full wave resonances. Other types of resonances, well known to the skilled person, are also possible within the scope of the invention. The term resonance frequency for an antenna is also well known to the skilled person and therefore not further discussed here. A ¼ -wave resonance is preferably used at low frequencies as GSM-850 and GSM-900 as this will require a radiating element with smaller dimensions than when using e.g. ½-wave or full wave resonances. The dimensions of the radiating elements are roughly proportional to the wavelength at the resonating frequency divided by 4, 2 or 1 for ¼-wave, ½-wave and full wave resonances respectively. However it is the combination of tuning parameters mentioned above and in the description that decides the resonance frequency/ies of the antenna arrangement. This means that the radiating element itself does not necessarily have to have a dimension of ¼-wave, a ½-wave or a full wave of the resonance frequency/ies.

Figure 1 1 is a block diagram showing one example of a manufacturing method of the housing element. In a forming step 1 101 the conducting element is formed in a deep drawn sheet metal process. Also other process can be used such as stamping or hydro forming of sheet metal. When the conductive element is manufactured using other alternative material with a metal plating realized with VM or PVD, the forming of the conductive element can be made in a conventional moulding process. The conductive element is at least a part of an external cover of the mobile device. The conductive element is henceforth exemplified with a back cover to a mobile phone. In the forming step, the metal back cover will obtain its free form outer surface according to the chosen industrial design. The conductive element is thus a free form sheet of metal or the other type of the alternative material as mentioned above.

In a cutting step 1 102 the back cover is cut into 2 or more radiating elements by one or more slits physically separating the back cover into the radiating elements. Holding means are attached to the radiating elements to hold the back cover together in one unit during moulding. The holding means can be point welded metal strips across the slits at each side of each slit, holding the radiating parts together in one piece. The holding means extend outside the outer outline of the back cover in order not to disturb the subsequent moulding step. As variations in the slit width can cause variations in tuning, the holding means are preferred in order to keep the variations in slit width low during the manufacturing process. The cutting step also includes cutting of e.g. holes for cameras and/or speaker openings. The cutting step can also include cutting of internal slits. The cutting can be performed with water jet cutting or alternative methods as laser cutting or stamping and bending. Variations in the width and shape of the slit will affect the tuning of the radiating elements. The width can e.g. vary along the slit; the edges of the slit can be straight, curved or even meandered. This tuning feature can preferably be used during development and early test run phases for final matching of the antenna arrangement. In a moulding step 1 103 the internal non-conductive structure is formed and the radiating elements of the conductive element are applied to the internal non-conductive structure. This can be accomplished with adhesion moulding or insert moulding which are well known moulding processes to the skilled person. In the moulding process the slits are filled with the resin used in the moulding process. The resin forms the internal non-conductive structure and fills the slits such that the slit filling becomes flush with the outer first surface of the conductive element. Typical resins are non-conductive materials such as plastics like e.g. ABS, PC, PA and other polymers used for handheld devices and compounds of different polymers and also glass fiber reinforced polymers (well known to the skilled person). The slit filling can also be applied in a separate step using any type of suitable non-conductive material or the slit can be left open, i.e. without any filling in the slit but with the internal non-conductive structure under the slit sealing the interior of the mobile device from the outside of the mobile device. This separate filling step can e.g. be used when there is a desire to use the slit for decorative purposes. For decorative or other purposes the slit filling can also extend outside the outer first surface of the conductive element, i.e. the slit filling does not necessarily have to be flush with the outer first surface of the conductive element. Internal slits can be with or without filling in the same way as described for slits above. The internal non-conductive structure is preferably also arranged to include holding features like screw towers, battery holding features, bumpers and ribs for improving the rigidity of the housing element. The feeding element can also be applied to the internal non-conductive structure in the insert moulding process. If adhesive moulding or insert moulding is used the feeding element can be applied during moulding process, which is also a process well known to the skilled person. The feeding element can also be applied as a separate production step later in the manufacturing process, using any conventional means, such as gluing or Pressure Sensitive Adhesive Process (PSA).

The internal non-conductive structure can also be manufactured as a separate component using a conventional plastic tool. In a separate step the radiating elements are then assembled to the internal non-conductive structure by conventional means such as glue, adhesive or ultrasonic welding. An example of an internal non-conductive structure is shown in figure 7. In this example the internal non-conductive structure is covering a main part of the inner second surface of the conductive element except for holes for e.g. camera lenses or minor holes e.g. for allowing contact between ground connection points at the inner second surface of the conductive element and the ground plane of the mobile device. In other examples the internal non-conductive structure can have more holes and cover a smaller part of the inner second surface of the conductive element. In one example the internal non-conductive structure can comprise a plastic frame along the side parts of the conductive element and a structure to fit into the slits between the radiating elements. The radiating elements are applied to the plastic frame type of internal non-conductive structure. When the internal non-conductive structure is of plastic frame type a large part of the inner second surface of the conductive element will not be covered by the internal non-conductive structure. The conductive pattern of the feeding element can then e.g. be applied to the first surface of the non-conductive substrate such as a flexfilm, the second surface of which is applied by an adhesive to the inner second surface of the conductive element, in this case a part of the back cover of a mobile phone. The gap between the conductive pattern of the feeding element and the conductive element is in this example equal to the thickness of the flexfilm. When the internal non-conductive structure is of the plastic frame type the feeding element can be applied to the inner second surface of the conductive element via the non-conductive substrate or some other non-conductive element. An example of this frame-type of internal non- conductive structure is described in association with figures 12 and 13. In a removal step 1 104 the holding means are removed to disconnect any galvanic contact between the radiating elements.

Holes in the internal non-conductive structure have been arranged during the moulding process in order to be able to contact suitable ground connection points at the radiating elements intended for connection to the ground plane of the mobile device, in the examples of the invention when the radiating element is connected to ground. In these examples at least one ground connection point at the inner second surface of at least one of the radiating elements is/are arranged to be connected in a contacting step 1 105 to the ground plane of the mobile device. The area around these ground connection points at the inner second surface of the conductive element, in this case the back cover, can, in a separate process, be plated with e.g. gold in order to improve contacting to the ground plane. In the contacting step 1 105 contact springs are laser or point welded to the ground connection points. Holes in the internal non-conductive structure can also be arranged for other purposes such as for attaching metal snaps to the inside of the back cover.

Paint, such as clear lacquer or coloured clear lacquer is applied to the outer first surface 315 of the back cover in a surface treatment step 1 106. In a marking process, using e.g. printing or laser marking, a logotype, name, camera type/size can be applied to the outer first surface of the back cover. This surface treatment step can also be used to conceal the slits.

In a final testing step 1 107 the antenna arrangement, now integrated in the housing element, is tested to check that the performance of the antenna over the bandwidth is according to specification. The testing is performed by introducing the housing element into a test arrangement. An advantage with this procedure is that the antenna performance is checked when the antenna is integrated in the housing element, thus avoiding mismatches caused by an antenna cover being assembled to an antenna arrangement after testing of the antenna.

The above described manufacturing process is just one example of a possible manufacturing process for a housing element and the production steps do not necessarily have to be performed in the order described above.

In an alternative realization of the invention, the feeding element is not integrated to the housing element but is located separated from the housing element e.g. on a PCB of the mobile device. The gap between the conductive pattern of the feeding element and the conductive element will then typically be filled with air or a combination of air and a non-conductive material such as the internal non-conductive structure.

In the manufacturing process described above all radiating elements are applied to the internal non-conductive structure in the moulding step 1 103. In an alternative process, one or several of the radiating elements are applied to the internal non-conductive structure in a separate process. In this process the radiating elements can be applied permanently by conventional means such as gluing or the radiating elements are applied by conventional arrangements such as snapping means to allow the radiating elements to be removed by the user. This can be advantageous if one of the radiating elements e.g. is used also as a battery hatch. Figure 12 is an exploded perspective view of one example of a housing element 1200 with the frame type of internal non-conductive structure 1204 and the first 1201 , second 1202 and third 1203 radiating elements. The first radiating element has a first hole 1207 which can be used as an opening for a camera lens. The feeding element with its first and second sides comprises in this example a flexfilm 1206 having a first surface and a second surface and the conductive pattern 1205 plated to the first surface of the flexfilm 1206. In this example the non-conductive substrate thus is a flexfilm. The conductive pattern is in this example a double loop. The feeding element is located in a first recess 1210 at a surface of the frame type of internal non- conductive structure 1204 facing the interior of the mobile device, this surface being defined as the interior frame side. The second surface of the flexfilm is in the example of figure 12 applied at the interior frame side around a second hole 1208 in the frame type of internal non-conductive structure. The flexfilm has a third hole 1215. The second and third holes have substantially the same size and shape as the first hole. The double loop is thus located around the second hole 1208 and the third hole 1215 in the same manner illustrated in figure 6. When the first radiating element and the feeding element is assembled to the frame type of internal non-conductive structure the first hole 1207, the second hole 1208 and the third hole 1215 are aligned. The feeding element can either be applied to the frame type of the internal non-conductive structure in a separate process or during the moulding step 1 103. In an alternative realization of the invention (not shown in figure 12) the first surface of the flexfilm with the conductive pattern can be applied to the first recess 1210.

Alternatively the second surface of the flexfilm can be applied via an adhesive layer or glue directly to the inner second surface of the first radiating element 1201 around the first hole 1207. The frame type of internal non-conductive structure 1204 has a large third hole 1209. The second radiating element 1202 is applied to the surface of the frame type of internal non-conductive structure facing the exterior of the mobile device, this surface being defined as the exterior frame side, and is covering the third hole 1209. This solution can be advantageous when the second radiating element is used as a detachable hatch covering e.g. a battery. The second radiating element is attached to the frame type of internal non-conductive structure in a separate process by e.g. snapping means. The feeding element for the second radiator can in this example be applied directly to the radiating element as described in association with figure 6.

The third radiating element 1203 can be applied to the frame type of internal non-conductive structure in the moulding step 1 103 as described earlier. A second recess 121 1 at the interior frame side is intended for location of a feeding element for the third radiating element. The second recess 121 1 can be replaced with a hole with the same or larger dimensions as the recess and the feeding element can then be applied directly at the inner second surface of the third radiating element as described in association with figure 6.

Figure 12 also shows a first rib 1212 and a second rib 1213 making the frame type of internal non-conductive structure more rigid. Screw towers 1214 are also integrated into the frame type of internal non-conductive structure. The screw towers can be used to fasten e.g. a PCB.

Figure 13 shows a frame type of internal non-conductive structure 1300 with the second 1208 and the third 1209 holes as seen from the exterior of the mobile device. First 1301 and second 1302 slit ribs are integrated into the exterior frame side. The first slit rib is filling the slit between the first and second radiating element and the second slit rib is filling the slit between the second and third radiating element when the radiating elements are applied to the frame type of internal non-conductive structure. In the example of figure 13 the isolation means thus comprises the slit filled with the slit rib. Small holes 1303-1305 in the frame type of the internal non-conductive structure can be used to allow ground connections between the ground plane and the ground connection points at the radiating elements.

As mentioned above the manufacturing method described is just one example of how the housing element can be accomplished. A common feature for manufacturing of the housing element for the mobile device according to any one of the claims 18-21 of the invention is that the radiating elements are applied 1 103 to the internal non-conductive structure.

In one example of the method at least one ground connection point at the inner second surface of at least one of the radiating elements is/are arranged to be connected in a contacting step 1 105 to the ground plane of the mobile device.

In one example of the method the internal non-conductive structure is filling the gaps between the radiating elements. In one example of the method said feeding element is applied to the internal non-conductive structure for feeding at least one radiating element from each feeding element.

In one example of the method said feeding element is applied to a first surface of a non-conductive substrate, the second surface of which is applied to the conductive element for feeding at least one radiating element from each feeding element.

In one example of the method the outer first surface of the conductive element is an outer surface of at least a part of an external cover to the mobile device and the inner second surface is facing one side of said feeding element, the conductive element, the internal non-conductive structure and said feeding element being integrated into one unit.

In one example of the method said radiating elements are applied to the internal non-conductive structure in a moulding process.

In one example of the method said radiating elements are attached to each other during the moulding step 1 103 by holding means located across the slits at each side of each slit, holding the radiating elements together in a one piece conductive element.

In one example of the method the holding means are removed in a removal step 1 104 to disconnect any galvanic contact between the radiating elements.

In one example of the method the internal non-conductive structure is manufactured as a separate component and said radiating elements are assembled to the internal non-conductive structure. In a further embodiment of the antenna arrangement for the mobile device it is possible that the conductive element comprises just one radiating element. In this case there is no need for an isolation means. An internal slit in the radiating element as described in association with figure 7 is however possible. This also means that the manufacturing method as described in figure 1 1 can be simplified. The cutting step 1 102 does not have to include holding means and cutting of slits and the removal step 1 104 can be deleted. In this embodiment the mobile device comprises radio frequency circuits and a ground plane. The antenna arrangement comprises a conductive element and at least one feeding element, said feeding element comprise a conductive pattern being arranged to be connected to the radio frequency circuits wherein the conductive element is a sheet having an outer first surface and an inner second surface. The conductive element comprises one radiating element. The radiating element is arranged to be fed through said feeding element and said feeding element having an extension plane with one side of said feeding element facing the inner second surface of the conductive element with a gap between the conductive element and the conductive pattern of said feeding element.

The invention is not limited solely to the examples described above, but instead many variations are possible within the scope of the inventive concept defined by the appended claims. Within the scope of the inventive concept the attributes of different examples and applications can be used in conjunction with or replace the attributes of another example or application.