Abstract:
In a structural arrangement for radio communication terminals comprising a casing in which are disposed at least a first sound transducer having an earpiece function and a second sound transducer having a loudspeaker function, the two transducers being respectively connected to two opposite faces of a printed circuit card, and each transducer comprising at least one resonating membrane vibrating in a front acoustical cavity and a rear acoustical cavity. The rear acoustical cavities of the transducers communicate with each other via orifices formed in the printed circuit card to form a twin rear acoustical cavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based on French Patent Application No. 02 10 969 filed Sep. 5, 2002, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a structural arrangement for radio communication terminals.  
           [0004]    2. Description of the Prior Art  
           [0005]    The current trend is to produce radio communication terminals of small size that are functionally ergonomic and user friendly. A radio communication terminal mainly comprises a casing in which equipment units are housed, in particular a radio transceiver unit comprising at least an antenna and a man-machine interface unit generally including a keypad, a screen and a sound transducer.  
           [0006]    The search for improved ergonomics and convenience has led to the antenna being accommodated inside the casing, for example, through the development of planar patch antennas. The same trend is encouraging the provision of increasingly comprehensive and increasingly larger man-machine interfaces.  
           [0007]    [0007]FIG. 1 shows diagrammatically the various component parts of a radio communication terminal. This kind of terminal generally comprises a casing  10  made of a rigid insulative material or partly of metal and in which are disposed various components connected to a printed circuit card  100 . The terminal comprises at least a screen  20 , a keypad  25 , a battery  27 , an antenna  40  for establishing radio communication, and a transducer  30  for reproducing sound able to transform electrical signals supplied to it into sound waves.  
           [0008]    The sound transducer  30  can have a number of functions, such as those of an earpiece, a loudspeaker and a ringer. The earpiece is essentially intended to be placed against the ear of a user when using the device to communicate, the ringer alerts the user to an incoming call or some other action, and the loudspeaker provides sound reproduction at a high volume, for example for hands-free applications. To reproduce the sound waves, the sound transducer  30  uses two separate acoustical resonance volumes respectively defining a front acoustical cavity  31  and a rear acoustical cavity  32  whose shapes and dimensions are chosen to achieve sound reproduction of sufficient quality for the application for which the transducer is intended. In particular, the size of the transducer  30  and the dimensions of the front and rear acoustical cavities  31  and  32  define the spectrum and the sound pressure level of the transducer. A rear cavity that is too small limits the sound spectrum at low frequencies, which reduces the sound pressure level at the bottom end of the spectrum.  
           [0009]    [0009]FIG. 2 shows diagrammatically a sound transducer. In the conventional way, a transducer  30  includes a vibrating membrane  33  secured by attachments to the walls of a diaphragm  34  so as to be able to vibrate freely when acted on by a coil  37 , to which it is attached, which is in turn caused to vibrate by a magnet  38  disposed on a metal support  39 , such as a yoke.  
           [0010]    Theoretically, the earpiece function necessitates a smaller component than a loudspeaker and ringer function, which must produce a higher sound volume. The volume used by a sound transducer  30  can be defined as the volume occupied by the component itself and the volume occupied by the acoustical cavities previously defined. The volume for correct operation of the transducer cannot be reduced below a particular limit imposed by the loudspeaker function.  
           [0011]    As previously mentioned, the current trend is to enlarge the man-machine interface and in particular the screen, for example through the use of liquid crystal screens. Because the size of the keypad cannot be reduced, for reasons of convenience of use, the present invention proposes to use the space occupied by the sound transducer to enlarge the space available to receive a screen without reducing the size of the keypad or increasing the size of the mobile terminal.  
           [0012]    The object of the invention is to eliminate the drawbacks of the prior art.  
           [0013]    To this end, the invention proposes to retain only a simple earpiece on the front face of the terminal and to transfer the loudspeaker and ringer function to the rear of the terminal. To guarantee a good quality of sound reproduction, the rear acoustical cavities of the two transducers constituting the earpiece and the loudspeaker, communicate with each other. This feature is referred to hereinafter as a twin rear acoustical cavity.  
         SUMMARY OF THE INVENTION  
         [0014]    The invention provides a structural arrangement for radio communication terminals comprising a casing in which are disposed at least a first sound transducer having an earpiece function and a second sound transducer having a loudspeaker function, the two transducers being respectively connected to two opposite faces of a printed circuit card, and each of the transducers comprising at least one resonating membrane vibrating in a front acoustical cavity and a rear acoustical cavity, in which structural arrangement the rear acoustical cavities of the transducers communicate with each other via orifices formed in the printed circuit card to form a twin rear acoustical cavity.  
           [0015]    One embodiment of the terminal further comprises a planar patch antenna connected to the printed circuit card and having a cavity delimited by a ground plane and a conductive patch disposed on a dielectric support, and the twin rear acoustical cavity is contained at least partially in the cavity of the antenna.  
           [0016]    In a different embodiment, at least one of the sound transducers is disposed in an opening in the printed circuit.  
           [0017]    The features and advantages of the invention will become more clearly apparent on reading the following description which is given by way of illustrative and non-limiting example and with reference to the appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1, already described, is a diagram showing the component parts of a radio communication terminal.  
         [0019]    [0019]FIG. 2 is a diagram showing a sound transducer.  
         [0020]    [0020]FIG. 3 is a diagram showing a planar patch antenna.  
         [0021]    [0021]FIG. 4 is a diagram showing a structural arrangement in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    The invention uses two separate transducers for the earpiece and loudspeaker/ringer functions, respectively. FIG. 4 is a diagram showing one arrangement in accordance with the present invention.  
         [0023]    As previously mentioned, the volume necessary for correct operation of the earpiece transducer is smaller than the volume necessary for correct operation of the loudspeaker transducer. An earpiece transducer  30  is therefore disposed on the front of the casing  10  of the radio communication terminal, above an enlarged screen  20 , such as a liquid crystal screen, for example. A loudspeaker/ringer transducer  30 ′ is disposed on the rear of the casing  10  of the terminal, on the opposite side of the printed circuit card  100  to the first transducer  30 .  
         [0024]    In the conventional way, each of the transducers  30  and  30 ′ has a front acoustical cavity  31 ,  31 ′ and a rear acoustical cavity  32 ,  32 ′ as previously defined. According to an essential feature of the invention, the rear acoustical cavities  32 ,  32 ′ of the transducers  30 ,  30 ′ communicate with each other to form a twin rear acoustical cavity  32 ″. In particular, orifices  101  are formed in the printed circuit card  100  to enable this communication between the rear cavities  32  and  32 ′.  
         [0025]    The orifices  101  providing for the formation of the single twin rear acoustical cavity  32 ″ can be holes in the printed circuit card  100 , with appropriate shapes and sizes, or notches in the edges of the card and forming spaces between the printed circuit card  100  and the casing  10  of the terminal.  
         [0026]    The twin rear acoustical cavity  32 ″ therefore has dimensions larger than those of each of the rear cavities  32 ,  32 ′ in isolation. This increased acoustical volume for each of the transducers  30 ,  30 ′ improves the sound quality of the transducers, and in particular widens the bandwidth and increases the sound pressure level.  
         [0027]    In one embodiment, at least one of the sound transducers can be disposed in an opening in the printed circuit card. For example, the yoke and a portion of the diaphragm of the transducer are disposed in an opening in the card. In this embodiment, the opening in the card incorporating one of the transducers replaces the orifices previously cited to provide for the formation of the twin rear acoustical cavity.  
         [0028]    The casing  10  of the terminal has openings  15 ,  15 ′ facing the front acoustical cavities  31 ,  31 ′ of the transducers  30 ,  30 ′ to allow outward propagation of sound waves.  
         [0029]    In an advantageous embodiment, shown in FIG. 4, the terminal further includes a planar patch antenna.  
         [0030]    A patch antenna is described with reference to FIG. 3. These antennas have been developed to replace the wire antennas conventionally used and are advantageously integrated into the casing of the radio communication terminal. The patch antenna  40  is disposed on one face of the printed circuit card  100  and has a cavity  45  delimited by two conductive structures, namely a ground plane  41  and a conductive patch  42  disposed on a dielectric support  43 . The ground plane  41  can be a single plane member, such as a conductive layer deposited on the card  100 , or a plurality of coplanar conductive members, possibly each formed on a different component. The conductive patch  42  is generally plane, but can be conformed as required, and held at a particular distance from the ground plane  41  by a rigid insulative support  43 . The shapes and dimensions of the dielectric support  43  are the result of dimensional and structural considerations and are decided on by the person skilled in the art according to the intended applications.  
         [0031]    In a preferred embodiment, the conductive patch  42  takes the form of a plane or quasi-plane conductive member consisting of an etched conductive layer carried by a thin substrate  43  or by a thin board. The patch  42  is extended by two bent or attached conductive patches  46 ,  47  which are positioned at its periphery so that one provides a short circuit function through its direct connection to the ground plane  41  and the other provides an antenna feeder function through its connection to a signal processing unit, not shown, of the radio transceiver equipment unit.  
         [0032]    The antenna  40  is preferably of the dual band type. To enable this mode of operation the patch  42  consists of a plane conductive member in the central portion of which there is formed a slot  44  that passes through the thickness of the patch and has a spread U-shape. The slot  44  delimits two plane areas on the surface of the patch; a first of these areas, which is called the interior area, corresponds mainly to the part of the patch that is inside the U-shape, and the second of these areas, which is called the exterior area, extends over the remainder of the patch, beyond the interior area.  
         [0033]    As the person skilled in the art knows, an arrangement of this kind achieves two resonances starting from the short circuit lug, one mostly in the interior area and the other mostly in the exterior area, and one being a substantially quarter-wave resonance in the upper band and the other a substantially quarter-wave resonance in the lower band, to enable the antenna to operate in the required two bands, the shapes and dimensions of the antenna being calculated accordingly, in a manner known to the person skilled in the art.  
         [0034]    In an advantageous embodiment of the invention, shown in FIG. 4, the twin rear acoustical cavity  32 ″ is at least partly contained in the electromagnetic cavity  45  of the patch antenna  40 , without impeding the correct operation of the antenna.  
         [0035]    The ground plane  41  must have openings in it aligned with the orifices  101  in the printed circuit card  100 , but this discontinuity of the ground plane is minimized by the small size of the orifices, which have a diameter of the order of 1 mm to 2 mm, for example.  
         [0036]    Furthermore, for better communication between the rear cavities  32  and  32 ′ of the two transducers  30 ,  30 ′, the dielectric support  43  of the antenna  40  is not completely closed in the ground plane. This kind of arrangement does not prejudice the correct operation of the antenna  40 , since the conductive patch  42  retains the required shape and disposition, as described with reference to FIG. 3.