Patent Publication Number: US-8988290-B2

Title: Apparatus and method of providing an apparatus

Description:
FIELD OF THE INVENTION 
     Embodiments of the present invention relate to an apparatus and method of providing an apparatus. In particular, they relate to an apparatus and method of providing an apparatus wherein the apparatus comprises a conductive cover portion. 
     BACKGROUND TO THE INVENTION 
     Apparatus for wireless communication are known. In order to communicate in a particular frequency band the apparatus must comprise an antenna arrangement which is operable within that frequency band. Efficient operation occurs when the insertion loss of the antenna arrangement is better than an operational threshold such as −6 dB. 
     There is a trend to decrease the volume of such apparatus. Consequently there is also a trend to decrease the volume of the apparatus which is taken up by antenna arrangements. However it is important to ensure that the antenna arrangement will still operate efficiently in the desired frequency bands. 
     BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising; a conductive cover portion defining at least a portion of an external surface of the apparatus; a feed element configured to capacitively couple radio circuitry to the conductive cover portion at a feed point; a ground plane galvanically connected to the conductive cover portion at a ground point; wherein the feed point and the ground point are separated along a length of the conductive cover portion and configure the conductive cover portion to resonate at a first resonant frequency so as to be operable as an antenna in a first frequency band and wherein the first resonant frequency of the conductive cover portion is controlled by the separation between the feed point and the ground point. 
     The conductive cover portion may define an aperture. 
     In some embodiments of the invention the conductive cover portion may be a bezel around an edge of an external surface of the apparatus. In other embodiments the conductive cover portion may be a bezel around an edge of a display or a user input device. 
     In some embodiments of the invention the conductive cover portion may be configured to operate as a PIFA (planar inverted F antenna) in the first frequency band. 
     In some embodiments of the invention the apparatus may also comprise a matching circuit configured to enable the conductive cover portion to resonate at the first resonant frequency and at a second resonant frequency so that the conductive cover portion is operable as an antenna in both the first frequency band and a second frequency band. 
     In some embodiments of the invention the apparatus may also comprise an antenna element within the apparatus. The antenna element may be configured to resonate at a third resonant frequency so as to be operable as an antenna in a third frequency band. The third frequency band may be a cellular frequency band. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising; a conductive cover portion defining at least a portion of an external surface of the apparatus; at least one feed element configured to capacitively couple radio circuitry to the conductive cover portion at least at one feed point; a ground plane galvanically connected to the conductive cover portion at a ground point; wherein the feed point and the ground point are separated along a length of the conductive cover portion and configure the conductive cover portion to resonate at a first resonant frequency and a second resonant frequency so as to be operable as an antenna in at least a first frequency band and a second frequency band and wherein the first resonant frequency and the second resonant frequency of the conductive cover portion are controlled by the separation between the feed point and the ground point. 
     In some embodiments of the invention the ground plane may be galvanically connected to the conductive cover portion via decoupling circuitry. 
     In some embodiments of the invention the conductive cover portion does not overlay the ground plane. In some embodiments of the invention the conductive cover portion may define a portion of the rear external surface of the apparatus. 
     In some embodiments of the invention a first feed element may be configured to resonate in conjunction with the conductive cover portion at the first resonant frequency and a second feed element may be configured to resonate in conjunction with the conductive cover portion at the second resonant frequency. 
     In some embodiments of the invention the first feed element and the second feed element may be connected to the radio circuitry by the same connection. 
     In some embodiments of the invention there is provided a portable electronic device comprising the apparatus. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: providing a conductive cover portion defining at least a portion of an external surface of an apparatus; configuring a feed element to capacitively couple radio circuitry to the conductive cover portion at a feed point; configuring a ground plane to be galvanically connected to the conductive cover portion at a ground point; positioning the feed point and the ground point such that the feed point and the ground point are separated along a length of the conductive cover portion and the conductive cover portion is configured to resonate at a first resonant frequency so as to be operable as an antenna in a first frequency band and wherein the first resonant frequency of the conductive cover portion is controlled by the separation between the feed point and the ground point. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: providing a conductive cover portion defining at least a portion of an external surface of an apparatus; configuring at least one feed element to capacitively couple radio circuitry to the conductive cover portion at a feed point; configuring a ground plane to be galvanically connected to the conductive cover portion at a ground point; positioning the feed point and the ground point such that the feed point and the ground point are separated along a length of the conductive cover portion and the conductive cover portion is configured to resonate at a first resonant frequency and a second resonant frequency so as to be operable as an antenna in a first resonant frequency band and a second resonant frequency band and wherein the first resonant frequency and the second resonant frequency of the conductive cover portion is controlled by the separation between the feed point and the ground point. 
     The apparatus may be for wireless communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  schematically illustrates an apparatus according to embodiments of the invention; 
         FIG. 2  illustrates an apparatus according to a first embodiment of the invention; 
         FIG. 3A  is a perspective view of the first embodiment of the invention; 
         FIG. 3B  is a plan view of the first embodiment of the invention; 
         FIG. 3C  is a side view of the first embodiment of the invention; 
         FIG. 4  illustrates a flow chart showing method blocks of an embodiment of the present invention; 
         FIG. 5  illustrates an apparatus according to a second embodiment of the invention. 
         FIG. 6A  is a front view of an apparatus according to a third embodiment of the invention; 
         FIG. 6B  is a rear view of an apparatus according to the third embodiment of the invention; 
         FIG. 7A  is a front view of the third embodiment of the invention; 
         FIG. 7B  is a side view of the third embodiment of the invention; and 
         FIG. 8  illustrates a flow chart showing method blocks of the third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION 
     The Figures illustrate an apparatus  10  comprising; a conductive cover portion  16  defining at least a portion of an external surface  34  of the apparatus  10 ; a feed element  20  configured to capacitively couple radio circuitry  14  to the conductive cover portion  16  at a feed point  40 ; a ground plane  44  galvanically connected to the conductive cover portion  16  at a ground point  42 ; wherein the feed point  40  and the ground point  42  are separated along a length of the conductive cover portion  16  and configure the conductive cover portion  16  to resonate at a first resonant frequency so as to be operable as an antenna in a first frequency band and wherein the first resonant frequency of the conductive cover portion  16  is controlled by the separation between the feed point  40  and the ground point  42 . 
     In the following description, unless expressly stated otherwise, the words ‘connect’ and ‘couple’ and their derivatives mean operationally connected/coupled. It should be appreciated that any number or combination of intervening components can exist (including no intervening components). Additionally, it should be appreciated that, unless expressly stated otherwise, the connection/coupling may be physical galvanic connection and/or an electromagnetic connection. 
       FIG. 1  schematically illustrates an apparatus  10  according to embodiments of the invention. Only features referred to in the following description are illustrated. It should, however, be understood that the apparatus  10  may comprise additional features that are not illustrated. The apparatus  10  comprises functional circuitry  12 , radio circuitry  14  and a conductive cover portion  16 . The apparatus  10  may also comprise an antenna arrangement  17 . 
     The apparatus  10  may be for wireless communication. The apparatus  10  may be a portable electronic device, for example, the apparatus  10  may be a hand portable electronic device which can be carried in a user&#39;s hand, handbag or jacket pocket. The apparatus  10  may be a mobile cellular telephone, a personal digital assistant (PDA), a laptop computer, a palm top computer, a portable WLAN or WiFi device, or a module for such devices. As used here, ‘module’ refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or user. 
     The conductive cover portion  16  defines a portion of the external surface  34  of the apparatus  10 . The external surface  34  is on the outside of the apparatus  10  and is visible when the apparatus  10  is in use. The external surface  34  may be touched by a user of the apparatus  10  when the apparatus  10  is in use such that the conductive cover portion  16  may come into direct contact with a part of the user, for example the user&#39;s hand or ear. 
     The conductive cover portion  16  may be part of a casing  38  which houses the electronic components of the apparatus  10 . The casing  38  and the conductive cover portion  16  may protect the electronic components from damage. For example the casing  38  may protect the electronic components from damage due to impacts or from atmospheric conditions such as water. The casing  38  may comprise non-metallic portions. A non-metallic portion of the casing  38  may be located on one or more sides of the apparatus  10 . 
     The conductive cover portion  16  may provide other functions in addition to being configured to resonate at a first resonant frequency. For example, the conductive cover portion  16  may provide an aesthetic aspect to the apparatus  10 . The conductive cover portion  16  may be a bezel or a trim around an edge  36  of an external surface  34  of the apparatus  10  or around an edge  61  of a display  32  or user input device  30  such as a keypad and may be designed to improve the aesthetic appearance of the apparatus  10 . In such embodiments the conductive cover portion  16  may protect the apparatus  10  or the casing  38  from damage, for example in embodiments where the conductive cover portion  16  is a bezel or a trim around an edge  36  of an external surface  34  of the apparatus  10  or around an edge  61  of a display  32 , or a user input device  30  such as a keypad, the conductive cover portion  16  may also be configured to protect the edges  36 ,  61  from damage. In some embodiments the conductive cover portion  16  may also assist in holding parts of the casing  38  or display  32  or a user input device such as a keypad  30  securely in position with respect to other parts of the casing  38 . 
     The conductive cover portion  16  may be made of any suitable material which is conductive and also hard wearing such as stainless steel or aluminium. 
     The conductive cover portion  16  is capacitively coupled to the radio circuitry  14  by a feed line  21  and a feed element  20  at a feed point  40 . The feed line  21  extends from the radio circuitry  14  to the feed element  20 . The feed line  21  may act as an inductor in series with the capacitance of the feed element  20 . 
     The conductive cover portion  16  is also galvanically connected to a ground plane  44  by a ground connection  18  at a ground point  42 . The feed point  40  and the ground point  42  are separated along a length of the conductive cover portion  16  and configure the conductive portion to resonate at a first resonant frequency in a first frequency band. The feed element  20  and the feed point  40  may be located so that they are positioned underneath the non-metallic portions of the casing  38 . 
     The functional circuitry  12  comprises circuitry which controls the apparatus  10 . The functional circuitry  12  may comprise a controller which may comprise a processor and a memory. In embodiments where the apparatus  10  is a mobile cellular telephone, the functional circuitry  12  may also comprise input/output devices such as a microphone, a loudspeaker, a display  32  and a user input device such as a keypad  30 . 
     The radio circuitry  14  is connected to the functional circuitry  12  and, as mentioned above, is capacitively coupled to the conductive cover portion  16 . The functional circuitry  12  is configured to provide data to the radio circuitry  14 . The radio circuitry  14  is configured to encode the data and provide it to the conductive cover portion  16  for transmission. The conductive cover portion  16  is configured to transmit the encoded data as a radio signal in a first frequency band. 
     The conductive cover portion  16  is also configured to receive a radio signal in the first radio frequency band. The antenna arrangement  12  then provides the received radio signal to the radio circuitry  14  which decodes the radio signal into data and provides the data to the functional circuitry  12 . 
     In some embodiments of the invention the radio circuitry  14  may also be configured to provide data to an antenna arrangement  17  for transmission and to decode radio signals received by the antenna arrangement  17  into data and provide the data to the functional circuitry  12 . The antenna arrangement  17  is located within the apparatus  10 . The antenna arrangement  17  may be located so that it is positioned underneath the non-metallic portion of the casing  38 . The antenna arrangement  17  is configured to transmit data as a radio signal and also receive a radio signal which is then provided to the radio circuitry  14 . 
     The antenna arrangement  17  may be configured to operate in a plurality of different operational radio frequency bands and via a plurality of different protocols. For example, the different frequency bands and protocols may include (but are not limited to) AM radio (0.535-1.705 MHz); FM radio (76-108 MHz); Bluetooth (2400-2483.5 MHz); WLAN (2400-2483.5 MHz); HLAN (5150-5850 MHz); GPS (1570.42-1580.42 MHz); US-GSM 850 (824-894 MHz); EGSM 900 (880-960 MHz); EU-WCDMA 900 (880-960 MHz); PCN/DCS 1800 (1710-1880 MHz); US-WCDMA 1900 (1850-1990 MHz); WCDMA 2100 (Tx: 1920-1980 MHz Rx: 2110-2180 MHz); PCS1900 (1850-1990 MHz); UWB Lower (3100-4900 MHz); UWB Upper (6000-10600 MHz); DVB-H (470-702 MHz); DVB-H US (1670-1675 MHz); DRM (0.15-30 MHz); Wi Max (2300-2400 MHz, 2305-2360 MHz, 2496-2690 MHz, 3300-3400 MHz, 3400-3800 MHz, 5250-5875 MHz); DAB (174.928-239.2 MHz, 1452.96-1490.62 MHz); RFID LF (0.125-0.134 MHz); RFID HF (13.56-13.56 MHz); RFID UHF (433 MHz, 865-956 MHz, 2450 MHz); LTE 700 (US) (698-716 MHz [Tx] and 728-746 MHz [Rx]); LTE 1500 (Japan) (1427.9-1452.9 MHz [Tx] and 1475.9-1500.9 MHz [Rx]); LTE 2600 (Europe) (2500-2570 MHz [Tx] and 2620-2690 MHz [Rx]). The electrical length of the antenna arrangement  17  may be tuned in order to achieve these frequencies and protocols. 
     The antenna arrangement  17  may be configured to operate in a different frequency band to the conductive cover portion  16 . 
     The electronic components that provide the functional circuitry  12  the radio circuitry  14  and the antenna arrangement  17  may be interconnected via a printed wiring board (PWB). The PWB may also function as the ground plane  44  for the antenna arrangement  17  and the conductive cover portion  16 . 
     In other embodiments of the invention the ground plane  44  may be provided by any conductive feature within the apparatus  10 . The ground plane  44  may not be planar, for example it may comprise a plurality of different components in different planes which need not necessarily include a PWB or it could include components which are not flat or planar shaped. 
       FIG. 2  illustrates an apparatus  10  according to a first example embodiment of the invention. The apparatus  10  comprises a casing  38  which defines an external surface  34  of the apparatus  10 . The electronic components of the apparatus  10  including the radio circuitry  14 , the functional circuitry  12  and the antenna arrangement  17  are housed within the casing  38  and are not shown in  FIG. 2 . 
     The casing  38  comprises a conductive cover portion  16 . In the illustrated embodiment the conductive cover portion  16  is a bezel which is a metal trim which extends around the edge  36  of the front external surface  34  of the apparatus  10 . In the particular embodiment illustrated in  FIG. 2  the conductive cover portion  16  extends around the entire perimeter of the front external surface  34  to form an aperture  31 . The part of the casing  38  which defines the front external surface  34  is securely fixed in place within the aperture  31 . 
     The conductive cover portion  16  is substantially rectangular with rounded corners. The aperture  31  defined by the conductive cover portion  16  is also substantially rectangular. In the illustrated embodiment the conductive cover portion  16  is substantially flat so that the conductive cover portion  16  is in a single plane. In other embodiments of the invention the conductive cover portion  16  may be a different shape. For example in the illustrated embodiment the conductive cover portion  16  is located on the front surface of the apparatus  10 . In other embodiments of the invention the conductive cover portion  16  may be shaped so that it is not substantially flat and is in more than one plane. For example, part of the conductive cover portion  16  may be located on the front surface of the apparatus  10  but it may also curve around the apparatus  10  so that it also extends onto the edges and possibly even rear surface of the apparatus  10 . 
     In the illustrated embodiment the conductive cover portion  16  extends around the entire perimeter of the front external surface  34  of the apparatus  10 . In other embodiments of the invention the conductive cover portion  16  may extend only part way around the perimeter of the front external surface  34  so that there is a gap in the conductive cover portion  16 . 
     In the illustrated embodiment the apparatus  10  is a mobile cellular telephone and comprises a display  32  and a user input device  30 . The display  32  and the user input device  30  are positioned on the front external surface  34 . In the illustrated embodiment the user input device  30  is a keypad. In other embodiments of the invention other types of user input device may be used such as touch sensitive portions of a display or a joystick or a roller key. The other types of user input device may be used in place of or in addition to the key pad. 
       FIGS. 3A to 3C  illustrate the first example embodiment of the invention illustrated in  FIG. 2  in more detail. In these Figs the casing  38  and the functional circuitry  12  and radio circuitry  14  are not shown for clarity.  FIG. 3A  is a perspective view of the first embodiment of the invention,  FIG. 3B  is a plan view of the first embodiment of the invention and  FIG. 3C  is a side view of the first embodiment of the invention. 
       FIGS. 3A to 3C  illustrate the conductive cover portion  16 , the ground plane  44  and the antenna arrangement  17 . The ground plane  44  and the antenna arrangement  17  would be positioned inside the casing  38 . 
     The ground plane  44  is substantially flat and is located in a first plane a distance d from the conductive cover portion  16 . In some embodiments of the invention the ground plane  44  may also be a PWB. As mentioned above, the radio circuitry  14  and the functional circuitry  12  have not been illustrated in  FIGS. 3A to 3C  for clarity but these may be mounted on the PWB and may be interconnected to the conductive cover portion  16  and the antenna arrangement  17  via the PWB. 
     The conductive cover portion  16  is a bezel which forms an aperture  31  as illustrated in  FIG. 2  and described above. 
     As can be seen in  FIGS. 3A to 3C  the conductive cover portion  16  has a length which is slightly longer than the length of the ground plane  44  and a width which is slightly wider than the width of the ground plane  44 . The conductive cover portion  16  is in a plane parallel to the ground plane  44  and is positioned a distance d from the ground plane  44 . 
     In the embodiment illustrated in  FIG. 3  a feed element  20  is positioned between the ground plane  44  and the conductive cover portion  16 . In other embodiments of the invention the feed element  20  may be mounted on the ground plane  44 . 
     The feed element  20  capacitively couples the radio circuitry  14  to the conductive portion  16  at the feed point  40 . The feed point  40  is positioned in a corner of the conductive cover portion  16 . The feed point  40  and the feed element  20  may be positioned within the apparatus  10  so that they are positioned underneath the non-metallic portion of the casing  38 . 
     A feed line  21  extends from the radio circuitry  14  to the feed element  20 . The feed line  21  may act as an inductor in series with the capacitance of the feed element  20 . The feed line  21  may extend along the ground plane  44 . 
     A ground connection  18  is also positioned between the ground plane  44  and the conductive cover portion  16 . The ground connection  18  galvanically connects the conductive cover portion  16  to the ground plane  44  at the ground point  42 . 
     The feed point  40  and the ground point  42  are separated along a length of the conductive cover portion by a distance L. In the illustrated embodiment both the feed point  40  and the ground point  42  are provided along the same side of the rectangular conductive cover portion  16 . In other embodiments the feed point  40  and the ground point  42  may be provided on different sides of the conductive cover portion  16 . The relative positions of the feed point  40  and the ground point  42  may be selected to configure the conductive cover portion  16  to resonate at a first resonant frequency in a first resonant frequency band. 
     The antenna arrangement  17  is substantially flat and is also positioned in a plane parallel to the ground plane  44 . The antenna arrangement  17  may be, for example, a PIFA. In the illustrated embodiment the antenna arrangement  17  is positioned on the opposite side of the ground plane  44  to the conductive cover portion  16 . Positioning the antenna element  17  on the opposite side of the ground plane  44  to the conductive cover portion  16  may reduce the electromagnetic coupling between the antenna element  17  and the conductive cover portion  16 . 
     The antenna arrangement  17  is coupled to the radio circuitry  14  by a feed  48  and coupled to the ground plane  44  by a ground connection  46 . The feed  48  of the antenna arrangement  17  may be positioned close to the feed element  20  of the conductive cover portion  16  so that the feed  48  of the antenna arrangement  17  and the feed element of the conductive cover portion  16  may be positioned in line with the non-metallic portion of the casing  38 . This enables the feed elements to act as radiators. 
     In the above described embodiment feed element  20  and the ground connection  18  configure the conductive cover portion  16  to operate as a slotted PIFA. The feed point  40  and the ground point  42  are separated along the length of the conductive cover portion  16 . The length L of the separation between the feed point  40  and the ground point  42  can be controlled to control the impedance of the conductive cover portion  16  and consequently control the resonant frequency so that the conductive cover portion  16  is operable as an antenna in a first frequency band. 
     The length of the feed line  21  may also be selected in order to configure the conductive cover portion  16  to resonate and be operable as an antenna in a first frequency band. The distance between the ground plane  44  and the conductive cover portion  16  may also be selected so that the conductive cover portion  16  is configured to resonate and be operable as an antenna in a first frequency band. 
     The first frequency band may be, for example, 2400-2483.5 MHz and the conductive cover portion  16  may be used as an antenna arrangement for communications in a wireless local area network (WLAN) or Bluetooth network. In such embodiments of the invention the length of the feed line  21  may be 20 mm and the distance between the ground plane  44  and the feed element  20  may be 1 mm. The feed element  20  may have an area of 4 mm 2 . The distance between the ground plane  44  and the conductive cover portion  16  may be 2.5 mm. Any ground layers associated with the ground plane  44  which may be in the form of a multi-layer printed wiring board may be removed in the region of the feed line  21  and feed element  20 , this may further allow the feed line  21  and feed element  20  to radiate through the non-metallic portion of the casing  38 . The feed line  21  and the feed element  20  may also be provided on the printed wiring board. In embodiments of the invention where the printed wiring board is a multi-layer printed wiring board the feed line  21  and feed element may be provided on one or more of the layers. 
     In other embodiments of the invention the conductive cover portion  16  may be configured to be operable as an antenna in a different frequency band via a different protocol such as HLAN (5150-5850 MHz); GPS (1570.42-1580.42 MHz); US-GSM 850 (824-894 MHz); EGSM 900 (880-960 MHz); EU-WCDMA 900 (880-960 MHz); PCN/DCS 1800 (1710-1880 MHz); US-WCDMA 1900 (1850-1990 MHz); WCDMA 2100 (Tx: 1920-1980 MHz Rx: 2110-2180 MHz); PCS1900 (1850-1990 MHz); UWB Lower (3100-4900 MHz); DRM (0.15-30 MHz); Wi Max (2300-2400 MHz, 2305-2360 MHz, 2496-2690 MHz, 3300-3400 MHz, 3400-3800 MHz, 5250-5875 MHz). 
     In some embodiments of the invention the conductive cover portion  16  may be configured to have an electrical length which is longer at the operating frequency. This causes the conductive cover portion  16  (by itself) to resonate at a frequency below the operating frequency. The feed element  20  may be configured to have a shorter electrical length at the operating frequency causing the feed element  20  (by itself) to resonate at a frequency above the operating frequency. The loading caused by the conductive cover portion  16  on the feed element  20  tunes the resonant frequency of the feed element  20  to the desired operating frequency. 
     As the conductive cover portion  16  defines part of the external surface  34  of the apparatus  10  it may make direct contact with a user. For example, in the illustrated embodiment the apparatus  10  is a mobile phone which may be held in a user&#39;s hand or positioned next to their ear. This may cause a build up of electrostatic charge on the conductive cover portion  16 . This build up of charge may then result in electrostatic discharge which could damage sensitive electronic components which may be found in the radio circuitry  14 . In embodiments of the invention the radio circuitry  14  is capacitively coupled to the conductive portion  16 . As the conductive cover portion  16  is physically separated from the radio circuitry  14  by the dielectric of the capacitor this reduces the detuning effect which occurs when the conductive cover portion  16  comes into contact with the users hand or ear. This may also prevent electrostatic discharge from being transmitted to the radio circuitry  14  and damaging the radio circuitry  14 . 
     Also the conductive cover portion  16  is galvanically connected to the ground plane  44 . This also protects the radio circuitry because any electrostatic charge which builds up on the conductive cover portion  16  can then dissipate through the ground connection  18  rather than through the feed element  20 . 
     The antenna arrangement  17  may be operable in a different frequency band to the conductive cover portion  16 . For example the antenna arrangement  17  may be operable in a cellular communications band such as EGSM 900 (880-960 MHz), PCN/DCS 1800 (1710-1880 MHz), WCDMA 2100 (Tx: 1920-1980 MHz Rx: 2110-2180 MHz). The antenna arrangement  17  may be operable in a plurality of communication bands. There may also be other antenna arrangements within the portable electronic device for use in other frequency bands. 
     As the conductive cover portion  16  defines part of an external surface  34  of the apparatus  10  it does not take up any volume inside the apparatus  10 . This enables the volume of the apparatus  10  to be reduced. Alternatively it enables an additional antenna arrangement to be added to an existing apparatus  10  without increasing the volume of the apparatus  10 , or enabling the volume which would have been taken by the antenna arrangement to be used for alternative features. 
       FIG. 4  illustrates a method of providing an apparatus according to an embodiment of the invention. At block  50  a conductive cover portion  16  is provided. As mentioned above the conductive cover portion  16  may be part of the casing  38  of the apparatus  10 . 
     At block  52  the feed element  20  is configured to capacitively couple the conductive cover portion  16  to the radio circuitry  14  and at block  54  the ground plane  44  is galvanically connected to the conductive cover portion  16  so that the conductive cover portion  16  is configured to operate as an antenna. 
     At block  56  the resonant frequency of the conductive cover portion  16  is controlled by controlling the separation between the feed point  40  and the ground point  42  so that the conductive cover portion is operable at a selected frequency within a resonant frequency band. 
     Although the blocks of the method are illustrated in a particular order in  FIG. 4  the illustration of a particular order of the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted. 
       FIG. 5  illustrates the casing  38  of an apparatus  10  according to a second example embodiment of the invention. Similar to the embodiment illustrated in  FIG. 2  the apparatus  10  is a mobile cellular telephone and comprises a display  32  and a keypad  30  positioned on the front external surface  34 . The electronic components of the apparatus  10  including the radio circuitry  14 , the functional circuitry  12  and the antenna arrangement  17  are housed within the casing  38  and not visible in the illustrated view. 
     In  FIG. 5  the conductive cover portion  16  is a bezel which is a metal trim which extends around the edge  61  of the display  32 . The conductive cover portion  16  may be configured to protect the edges of the display  32  from damage and also to hold the display  32  securely in position in with respect to other elements of the casing  38 . 
     The conductive cover portion  16  which surrounds the display  32  is capacitively coupled to a radio circuitry  14  via a feed element  20  and is galvanically connected to a ground plane  44  and operates in the same manner as the embodiment illustrated in  FIG. 2  and  FIGS. 3A to 3C  and described above. 
       FIGS. 6A and 6B  illustrate an apparatus  10  according to a third example embodiment of the invention. The apparatus  10  according to the third embodiment also comprises a casing  38  which defines an external surface  34  of the apparatus  10 . The casing  38  defines a front external surface  34 A which is illustrated in  FIG. 6A  and a rear external surface  34 B which is illustrated in  FIG. 6B . 
     As with the previous embodiments the electronic components of the apparatus  10  including the radio circuitry  14 , the functional circuitry  12  and the antenna arrangement  17  are housed within the casing  38  and are not shown in  FIGS. 6A and 6B . 
     In the third embodiment of the invention the apparatus  10  is a mobile cellular telephone and comprises a display  32  and a user input device  30 . In the illustrated embodiment the user input device  30  is a keypad. 
     The apparatus  10  has a first portion  70  and a second portion  72 . The first portion  70  is mounted on the second portion  72  so that the first portion  70  can move relative to the second portion  72  between a first position and a second position. In the illustrated embodiment the first portion  70  is mounted on slide tracks  74  so that the first portion  70  can slide relative to the second portion  72 . 
     It is to be appreciated that in other embodiments of the invention the apparatus  10  may have a different configuration. For example, the first portion  70  may be mounted on the second portion  72  by a hinge so that the first portion can rotate relative to the second portion  72  and the first portion  70  can be folded onto the second portion  72 . Other configurations may also be possible, for example, the first portion  70  may be twisted relative to the second portion  72 . In other embodiments of the invention the apparatus  10  may comprise only a single portion. 
     The display  32  is positioned on the first portion  70  and the user input device  30  is positioned on the second portion  72 . In  FIGS. 6A and 6B  the first portion  70  is illustrated in a first position in which the user input device  30  is accessible and the display  32  can be viewed. The first portion  70  may be moved to the second position by moving downwards, relative to the second portion  72 , in the direction of arrow  73  until the first portion  70  overlays the second portion  72 . When the first portion  70  is in the second position the user input device  30  is covered by the first portion  70  and cannot be actuated. 
     In the particular embodiment illustrated in  FIGS. 6A and 6B  the front external surface  34 A may comprise one or more conductive portions. The conductive portions may comprise metal or plated plastics. The front external surface  34 A may also comprise one or more non-conductive portions as well as conductive portions. In other embodiments of the invention the front external surface may only comprise non-conductive cover portions. 
     The rear external surface  34 B is illustrated in  FIG. 6B .  FIG. 6B  also illustrates the first portion  70  in the first position relative to the second portion  72  as in  FIG. 6A . The slide tracks  74  on the rear of the first portion  70 , which enable the first portion  70  to be moved relative to the second portion  72 , are illustrated in  FIG. 6B . 
     The apparatus  10  comprises a battery for powering the apparatus  10  which is mounted within the second portion  72 . The rear external surface  34 B of the second portion  72  comprises the battery cover  76 . The battery cover  76  may comprise a conductive material such as metal or a non-conductive material such as plastic. 
     The rear external surface  34 B also comprises a conductive cover portion  16 . In this third embodiment of the invention the conductive cover portion  16  is located on the second portion  72  of the apparatus  10  and defines the lower portion of the rear external surface  34 B. In the embodiment illustrated in  FIG. 6B  the conductive cover portion  16  is substantially planar so that the conductive cover portion  16  is in a single plane and forms a substantially semicircular shape. In other embodiments of the invention the conductive cover portion  16  may be a different shape and may be shaped so that it is not substantially flat and is in more than one plane. 
     The conductive cover portion  16  is galvanically connected to a ground plane  44  by a ground connection  18 . The ground connection  18  and the ground plane  44  are not illustrated in  FIG. 6B  as these are internal components of the apparatus  10 . However the location of the ground point  42  is indicated by dashed lines in  FIG. 6B . 
     The ground point  42  is located on the conductive cover portion  16  at the edge of the rear external surface  34 B. In other embodiments of the invention the ground point  42  may be in a different position. 
       FIGS. 7A and 7B  illustrate the third example embodiment of the invention illustrated in  FIGS. 6A and 6B  in more detail. In  FIGS. 7A and 7B  the casing  38 , the functional circuitry  12 , the radio circuitry  14  and the antenna arrangement  17  are not shown for clarity.  FIG. 7A  is a front view of the third embodiment of the invention and  FIG. 7B  is a side view of the third embodiment of the invention. 
       FIGS. 7A and 7B  illustrate the conductive cover portion  16 , the capacitive feed element  82  for feeding the conductive cover portion  16  and the ground plane  44 . The ground plane  44  and the capacitive feed element  82  would be positioned inside the casing  38 . The conductive cover portion  16  is indicated by dashed lines in  FIG. 7A  so that the antenna elements beneath it can be clearly illustrated. 
     In the illustrated embodiment the ground plane  44  is substantially flat and is located in a first plane. The conductive cover portion  16  is also substantially flat and is located in a second plane. The first and second planes are parallel to each other and a distance d 1  apart. 
     In some embodiments of the invention the ground plane  44  may also be a printed wiring board (PWB). As mentioned above, the radio circuitry  14  and the functional circuitry  12  have not been illustrated in  FIGS. 7A to 7B  for clarity but these may be mounted on the PWB and may be interconnected to the conductive cover portion  16  via the PWB. 
     A first capacitive feed element  82  is connected to the ground plane  44 . The first capacitive feed element  82  is connected to the radio circuitry  14  which may be mounted on the ground plane  44 . A second capacitive feed element  84  is provided adjacent to the first capacitive feed element  82 . The second capacitive feed element is also connected to the radio circuitry  14 . 
     The capacitive feed elements  82 ,  84  have lengths which configure them to resonate in conjunction with the conductive cover portion  16 . The capacitive feed elements  82 ,  84  may be configured to resonate at different frequencies. The different frequencies may be in different frequency bands. For example the first capacitive feed element  82  may be configured to resonate in conjunction with the conductive cover portion  16  at approximately 900 MHz which would be in a frequency band such as EGSM 900 (880-960 MHz) or EU-WCDMA 900 (880-960 MHz) and the second capacitive feed element  84  may be configured to resonate in conjunction with the conductive cover portion at approximately 1800 MHz which would be in a frequency band such as PCN/DCS 1800 (1710-1880 MHz) or US-WCDMA 1900 (1850-1990 MHz). 
     In the embodiment illustrated in  FIGS. 7A and 7B  the capacitive feed elements  82 ,  84  are bent so that they are not wholly in the same plane as the ground plane  44 . For example, as can been seen in the side view in  FIG. 7B  the first capacitive feed element  82  comprises a first portion  101 , a second portion  103  and a third portion  105 . The first portion  101  is in the same plane as the ground plane  44  and extends from the ground plane  44  underneath the conductive cover portion  16 . The second portion  103  is substantially perpendicular to the first portion  101  and extends out of the plane of the ground plane  44  and towards the conductive cover portion  16 . The third portion  105  is substantially perpendicular to the second portion  103  and runs parallel to the ground plane  44 , the first portion  101  of the capacitive feed element  82  and the conductive cover portion  16 . The third portion  105  is separated from the conductive cover portion  16  by a distance d 2 . The distance d 2  is less than the distance d 1 . The distance d 2  may be approximately 1 mm. The configuration of the capacitive feed element  82  may be selected so that the distance d 2  is controlled to ensure good coupling between the capacitive feed element  82  and the conductive cover portion  16 . 
     The capacitive feed elements  82 ,  84  extend from the edge of the ground plane  44  and so do not overlay the ground plane  44 . 
     The capacitive feed elements  82 ,  84  are positioned underneath the conductive cover portion  16  so that the capacitive feed elements  82 ,  84  act as feed elements which capacitively couple the radio circuitry  14  to the conductive cover portion  16  at the respective feed points  40 . 
     A feed line may extend from the radio circuitry  14  to the capacitive feed elements  82 ,  84 . The feed line may act as an inductor in series with the capacitance of the capacitive feed elements  82 ,  84 . The feed line may extend along the ground plane  44 . A single feed line may be used to connect both the first and second capacitive feed elements  82 ,  84  to the radio circuitry  14 . A diplexer may be provided to separate the feed line into two. 
     The conductive cover portion  16  is positioned overlaying the capacitive feed elements  82 ,  84  so that the conductive cover portion  16  also does not overlay the ground plane  44 . In the embodiment illustrated there is gap  85  between the edge of the ground plane  44  and the edge of the conductive cover portion  16  in the longitudinal direction so that there is no overlap between the conductive cover portion  16  and the ground plane  44 . The width of this gap  85  may be approximately 1 mm. 
     The conductive cover portion  16  is galvanically connected to the ground plane  44  by a ground connection  18 . The ground connection  18  extends between the ground plane  44  and the conductive cover portion  16  and galvanically connects the conductive cover portion to the ground plane  44  at the ground point  42 . 
     In the illustrated embodiment the ground point  42  is located at the edge of the rear external surface  34 B defined by the conductive cover portion  16 . The relative positions of the feed point  40  and the ground point  42  may be selected to configure the conductive cover portion  16  to resonate at a particular resonant frequency in a particular resonant frequency band. 
     The ground connection  18  comprises decoupling circuitry  80  located between the conductive cover portion and the ground plane  44 . The decoupling circuitry  80  may be, for example, an inductor. The decoupling circuitry  80  may be adjustable and may be used to tune the conductive cover portion  16  to resonate in one or more particular frequency bands. For example the decoupling circuitry  80  may comprise a variable inductor or may comprise a switching mechanism for switching between different inductors or different decoupling circuits. This enables the conductive cover portion  16  to be operable as an antenna in a plurality of frequency bands. 
     The decoupling circuitry  80  may be mounted on the PWB. In other embodiments of the invention the decoupling circuitry  80  and ground connection  18  may be in a different position. 
     In the embodiment illustrated in  FIGS. 6 and 7  the capacitive feed elements  82 ,  84  and the ground connection  18  configure the conductive cover portion  16  to operate as an antenna. The separation between the respective feed points  40  and the ground point  42  can be controlled to control the impedance of the conductive cover portion  16  and consequently control the resonant frequency so that the conductive cover portion  16  is operable as an antenna in a particular frequency band. 
     The length of the feed line  21  may also be selected in order to configure the conductive cover portion  16  to resonate and be operable as an antenna in a particular frequency band. The distance between the ground plane  44  and the conductive cover portion  16  may also be selected so that the conductive cover portion  16  is configured to resonate and be operable as an antenna in a particular frequency band. 
     As the conductive cover portion  16  is connected to the ground plane  44  by decoupling circuitry  80  the conductive cover portion  16  may be operable as an antenna in more than one frequency band. For example the conductive cover portion  16  may be operable as an antenna in one or more cellular frequency bands such as US-GSM 850 (824-894 MHz); EGSM 900 (880-960 MHz); EU-WCDMA 900 (880-960 MHz); PCN/DCS 1800 (1710-1880 MHz); US-WCDMA 1900 (1850-1990 MHz); WCDMA 2100 (Tx: 1920-1980 MHz Rx: 2110-2180 MHz) or PCS1900 (1850-1990 MHz). 
     As in the previously described embodiments the conductive cover portion  16  defines part of the external surface  34  of the apparatus  10  and so it may make direct contact with a user. Using capacitive feed elements  82 ,  84  to capacitively couple the conductive cover portion  16  to the radio circuitry  14  ensures that the conductive cover portion  16  is physically separated from the radio circuitry  14  which reduces the detuning effect which occurs when the conductive cover portion  16  comes into contact with the users hand or ear. This may also prevent electrostatic discharge from being transmitted to the radio circuitry  14  and damaging the radio circuitry  14 . 
     Also the conductive cover portion  16  is galvanically connected to the ground plane  44  via the decoupling circuitry  80 . This provides additional protection for the radio circuitry  14  because any electrostatic charge which builds up on the conductive cover portion  16  can then dissipate through the ground connection  18  rather than through the capacitive feed elements  82 ,  84 . 
     The third embodiment of the invention provides the same advantages as the above described embodiments. As the conductive cover portion  16  defines part of an external surface  34  of the apparatus  10  it does not take up any volume inside the apparatus  10  which enables the volume of the apparatus  10  to be reduced. Alternatively it enables an additional antenna arrangement to be added to an existing apparatus  10  without increasing the volume of the apparatus  10 , or enabling the volume which would have been taken by the antenna arrangement to be used for alternative features. 
       FIG. 8  illustrates a method of providing an apparatus according to an embodiment of the invention. At block  90  a conductive cover portion  16  is provided. The conductive cover portion  16  may be provided on the rear external surface  34 B of an apparatus  10 . 
     At block  92  a first capacitive feed element  82  is provided and configured to capacitively couple the conductive cover portion  16  to the radio circuitry  14  of the apparatus  10 . At block  94  the ground plane  44  is galvanically connected to the conductive cover portion  16  via decoupling circuitry  80  so that the conductive cover portion  16  is configured to operate as an antenna. The decoupling circuitry may also enable the electrical length of the conductive cover portion  16  to be adjusted so that the conductive cover portion is operable as an antenna at a particular frequency. 
     At block  96  the resonant frequency of the conductive cover portion  16  is controlled by controlling the separation between the feed point  40  and the ground point  42  so that the conductive cover portion is operable at a selected frequency within a resonant frequency band. 
     Although the blocks of the method are illustrated in a particular order in  FIG. 4  the illustration of a particular order of the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the blocks may be varied. Furthermore, it may be possible for some steps to be omitted. For example block  92  may be repeated so that more than one capacitive feed element is provided and configured to capacitively couple the conductive cover portion  16  to the radio circuitry  14 . 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example in the above description only one resonant mode is described for the conductive cover portion  16 . It is to be appreciated that the conductive cover portion  16  may have more than one resonant mode and may be operable in more than one frequency band. For example the conductive cover portion  16  may have a first resonant frequency in the band 2400-2483.5 MHz which is used for communications in a wireless local area network (WLAN) or Bluetooth network and a second resonant frequency in the band 1570.42-1580.42 MHz which is used for GPS. The apparatus may comprise a matching circuit and/or a switch arrangement which is configured to tune the conductive cover portion so that it is operable as an antenna in both a Bluetooth frequency band and the GPS frequency band. 
     In some embodiments of the invention the conductive cover portion  16  may be configured to be tuned to be operable as an antenna at a number of different frequencies. For example, there may be one or more switching mechanisms connected to conductive cover portion  16  which enable the electrical length of the conductive cover portion  16  to be selected so that the conductive cover portion  16  is operable at a particular frequency. The switching mechanism may be connected to the feed line or the ground connection or there may be switching mechanisms connected to both the feed line and the ground connection. 
     Also in the above described first and second example embodiments the conductive cover portion is operable as a PIFA. It is to be appreciated that other types of antenna may be used such as IFAs, or unbalanced loop antennas, or other antennas which have both a feed line and a ground connection, etc. 
     The conductive cover portion  16  is described as being a bezel or trim around the edge of the apparatus  10  or the display  32 . It is to be appreciated that the conductive cover portion  16  could be any part of the external surface  34  of the apparatus. For example, the conductive cover portion  16  may be a bezel around a user input device such as a keypad, touchpad, scrolling or rotary input device. 
     More than one embodiment of the invention may be incorporated into a single apparatus  10 . For example an apparatus  10  may comprise a conductive bezel on a front surface in accordance with the first or second example embodiments described above and also a conductive cover portion on the rear surface of the apparatus  10  in accordance with the third example embodiment described above. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.