Abstract:
A portable communications device such as an integrated hands-free mobile telephone includes an antenna cavity which doubles as an audio cavity for an integrated hands-free speaker. By using the antenna cavity as an audio cavity, space within the telephone can be saved and the telephone made smaller overall without compromising audio performance.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a portable communications device which includes a speaker and an antenna, particularly but not exclusively to a device having an antenna cavity which forms the audio cavity for a hands-free speaker.  
         BACKGROUND  
         [0002]    The demand for new features in portable communications equipment, such as mobile telephones, continues to rise, while the size of these devices remains the same or is required to become even smaller. Some of these new features relate to the audio aspects of mobile telephones. For example, integrated hands-free devices require a significant improvement in speaker quality compared with the earphone speaker arrangement provided in conventional mobile telephones. Similarly, an improvement in speaker quality is required as mobile telephone speakers are increasingly used to play polyphonic ring-tones, downloaded midi files, FM radio and so on.  
           [0003]    An increase in speaker performance can be brought about by the use of an audio cavity, in much the same way as a conventional audio system loudspeaker requires a speaker enclosure. However, an audio cavity inevitably takes up space within the body of the telephone.  
           [0004]    One of the objects of the present invention is to improve the usage of space within a portable communications device.  
         SUMMARY OF THE INVENTION  
         [0005]    According to the invention, there is provided a portable communications device including a speaker and an antenna, the antenna being associated with an antenna cavity which is arranged to form an audio cavity for the speaker.  
           [0006]    By sharing the volume which results from the presence of an antenna, for example in an internal antenna arrangement, with the speaker, the need for a separate audio cavity is removed, so saving space and allowing the overall size of the device to be minimised, without adverse effects on audio performance.  
           [0007]    The antenna can be a patch antenna, for example a planar inverted-F antenna having a radiating conductor and a ground plane, the antenna cavity resulting from the required separation between the radiating conductor and the ground plane. Alternatively, the antenna can be a planar or meander antenna having a radiating conductor but not using a ground plane, the antenna cavity resulting from the need to avoid metallic objects in the vicinity of the radiating conductor.  
           [0008]    The antenna may be internal to the antenna cavity. The antenna may be external to the antenna cavity. The antenna cavity may be defined partially/wholly by antenna support means. Preferably, the antenna support means defines a sealed volume which is used as an audio cavity.  
           [0009]    The speaker can be located outside the antenna cavity and coupled to the cavity, for example by an audio duct. By locating the speaker outside the antenna cavity, adverse effects on antenna performance, caused by metal components in the speaker, can be avoided, while still making effective use of the antenna cavity as an audio cavity.  
           [0010]    According to the invention, there is also provided a portable communications device including a speaker and an antenna, said antenna forming an antenna cavity within said device, said device including an audio cavity for the speaker, wherein the audio cavity and the antenna cavity are shared by said speaker and said antenna.  
           [0011]    The invention further provides an antenna module for a portable communications device, said device including a housing portion and said antenna module including an antenna and an audio outlet for a speaker, the module being configured such that, when it is connected to said housing portion of the device, a sealed cavity is formed which comprises an audio cavity for a speaker mounted to the device.  
           [0012]    In accordance with the invention, there is still further provided a method of assembling a portable communications device, the device comprising a housing, a speaker and an antenna module including an antenna, the method comprising the steps of mounting the speaker to the housing and mounting the antenna module to the housing to form a sealed volume between the antenna and the housing, said sealed volume including the speaker and said sealed volume comprising an audio cavity. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0014]    [0014]FIG. 1 is a perspective view of a mobile telephone handset;  
         [0015]    [0015]FIG. 2 is an exploded view of the rear of the handset of FIG. 1 illustrating an internal antenna module with an audio outlet;  
         [0016]    [0016]FIG. 3 is a schematic diagram of mobile telephone circuitry for use in the telephone handset of FIG. 1;  
         [0017]    [0017]FIG. 4 is a simplified cross-sectional view of the rear of the handset shown in FIG. 2, when assembled;  
         [0018]    [0018]FIG. 5 is a schematic diagram illustrating an antenna/audio cavity in a PIFA antenna arrangement;  
         [0019]    [0019]FIGS. 6 a - c  illustrate various forms of internal meander antennas;  
         [0020]    [0020]FIG. 7 is a schematic diagram illustrating an antenna/audio cavity in a meander antenna arrangement;  
         [0021]    [0021]FIG. 8 is a schematic diagram illustrating a speaker arrangement in which an audio cavity is used as a front volume for a speaker;  
         [0022]    [0022]FIG. 9 is a schematic diagram illustrating a speaker arrangement in which an audio duct connects a speaker to an audio cavity; and  
         [0023]    [0023]FIG. 10 is a schematic diagram illustrating a further embodiment of the invention, in which a speaker is located in the centre of an antenna arrangement. 
     
    
     DETAILED DESCRIPTION  
       [0024]    Referring to FIGS. 1 and 2, a mobile station in the form of a mobile telephone handset  1  includes a microphone  2 , keypad  3 , a hands-free mode selection key  4 , an LCD display  5 , an earphone speaker  6 , a hands-free speaker  7  and an internal antenna  8 . The location of the hands-free speaker  7  and antenna  8  are illustrated in FIG. 2, which shows the back of the handset  1  with a rear cover (not shown) removed.  
         [0025]    The back of the handset  1  comprises a chassis  9  having a recessed portion  10  for receiving an antenna module  11 . The recessed portion includes a speaker clip arrangement  12  for receiving the hands-free speaker  7 . The recessed portion  10  has a lip  13 , so that when the antenna module  11  is fitted to the chassis  9 , the recessed portion  10  and antenna module  11  form a sealed cavity between them, which will be described in more detail below with reference to FIG. 4.  
         [0026]    The antenna module  11  comprises an integrally moulded plastic substrate  14  with an antenna pattern  15  plated onto it to form part of the antenna  8 , for example by using the moulded interconnect device (MID) moulding process. A feed duct  16  on the chassis mates with a corresponding outlet  17  in the antenna module  11  to permit the antenna to be connected to the PCB  18 , which is mounted to the underside of the chassis  9 . The antenna module  11  also includes an integrally moulded audio outlet  19  for the hands-free speaker  8 .  
         [0027]    The antenna module  11  is assembled to the chassis  9  by clipping the speaker  7  into the speaker clip arrangement  12  and fitting the antenna module  11  onto the recessed portion  10 . In an alternative embodiment, there is a speaker clip arrangement in the antenna module  11  and the speaker  7  is clipped into the antenna module  11  prior to assembly to the chassis  9 .  
         [0028]    The mobile station  1  is operable to communicate through cellular radio links with individual PLMNs (public land mobile network) shown schematically in FIG. 1 as PLMN A, for example a GSM 1800 MHz network.  
         [0029]    [0029]FIG. 3 illustrates the major circuit components of the telephone handset  1 . Signal processing is carried out under the control of a digital micro-controller  20  which has an associated flash memory  21 . Electrical analogue audio signals are produced by microphone  2  and amplified by pre-amplifier  22 . Similarly, analogue audio signals are fed to the earphone speaker  6  through an amplifier  23  or to the hands-free speaker  7  through an amplifier  24 , depending on which speaker is selected. The micro-controller  20  receives instruction signals from the keypad  3  and hands-free mode selection key  4  and controls operation of the LCD display  5 . The hands-free mode selection key  4  is used to instruct the micro-controller  20  to switch between the earphone and hands-free speakers  6 ,  7 .  
         [0030]    Information concerning the identity of the user is held on a smart card  25  in the form of a GSM SIM card which contains the usual GSM international mobile subscriber identity (IMSI) and an encryption key K i  that is used for encoding the radio transmission in a manner well known per se. The SIM card is removably received in a SIM card reader  26 .  
         [0031]    The mobile telephone circuitry includes a codec  27  and an rf stage  28  feeding the antenna  7 .  
         [0032]    [0032]FIG. 4 is a simplified cross-sectional view of the handset  1  along the line A-A′ in FIG. 2, not showing the speaker clip arrangement or other incidental details. When the antenna module  11  is assembled to the chassis  9 , a cavity  29  is formed, which acts as an audio cavity for the speaker  7 , in this case a sealed back volume. A common or shared antenna and audio cavity is therefore provided. To avoid adverse effects on antenna operation caused by metal components within the hands-free speaker  7 , the speaker is not mounted directly underneath the antenna  8 , but adjacent to it. The antenna pattern  15  together with a ground plane  18  formed by the PCB, together form the antenna  8 , which is known as a patch antenna and more specifically a planar inverted-F antenna (PIFA).  
         [0033]    [0033]FIG. 5 illustrates the general configuration of an antenna of the PIFA type, comprising a radiating conductive plate  30  mounted on a dielectric support  31  and a ground plane  32 , for example the PCB to which the handset components are mounted or the surface of the RF screening cans mounted to the PCB. For correct operation, a separation of around 6-7 mm is required between the conductive plate  30  and the ground plane  32 . Therefore, with a typical dielectric thickness of 1 mm, the gap of 5-6 mm between the dielectric  31  and the ground plane  32  is available to be used as an audio cavity  33 . The smaller cavity  34  above the speaker  7  acts as a duct to port the audio signal into the larger audio cavity  33  between the antenna plates  30 ,  32 .  
         [0034]    Many different types of internal antenna are suitable to implement the invention, including plate antennas and meander type antennas, three examples of which are shown in FIGS. 6 a - c . A meander type antenna comprises an antenna element  40  arranged within a handset casing  41  in such a way that the handset PCB  42  does not act as a ground plane for the antenna. With this type of antenna, it is therefore important that there are no metallic components within the casing beneath the antenna element, since such elements would act as a ground plane and affect antenna operation. This makes the space beneath the antenna element suitable for use as an audio cavity.  
         [0035]    A meander antenna arrangement analogous to the PIFA antenna arrangement shown in FIG. 5 is illustrated in FIG. 7, comprising an antenna pattern  50  above an audio cavity  51 .  
         [0036]    [0036]FIG. 8 illustrates a speaker arrangement in a telephone handset  60  in which a speaker  7  is mounted against a battery  61 . An audio outlet  62  is located so that an audio cavity  63  beneath an antenna  64  forms a front volume for the speaker  7 , rather than a back volume. In alternative embodiments, combined front and back volumes are envisaged.  
         [0037]    The various alternative embodiments described are not intended to be limiting; the particular arrangement used in any case by which the audio and antenna cavities are shared depends on the layout and requirements of the particular communications device in question. For example, in the embodiment shown in FIG. 9, the speaker  7  can be separated from the antenna  8  and an audio duct  71  used to port the audio signal to the antenna/audio cavity  72 . In a further embodiment shown in FIG. 10, the speaker  7  is located in the centre of a plate antenna, with active antenna elements  80  surrounding it, over an antenna/audio cavity  81 .