Abstract:
The present invention relates to a portable communication device arrangement comprising a main unit and an auxiliary unit. The main unit includes an electrical interface to an auxiliary unit, a ground plane dimensioned for antenna operation at a multiple of a quarter of a wavelength of a desired frequency, and a radio communication unit connected to the ground plane and to the electrical interface. The auxiliary unit comprises at least one electrical conductor to be connected to the electrical interface and including a first radio frequency trap, where the distance between the first radio frequency trap and an end of the conductor that is to be connected to the electrical interface corresponds to an odd multiple of a quarter of a wavelength of the desired frequency. The invention provides a good antenna through reuse of elements already provided in relation to a portable communication device.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates to antennas and, more particularly, to a portable communication device. 
       DESCRIPTION OF RELATED ART 
       [0002]    Portable communication devices, such as cellular phones, tend to be provided with ever increasing ancillary functionality, for example, MP3 technology, camera arrangements, and radio reception. At the same time, such phones are being manufactured at increasingly smaller dimensions. Accordingly, phone manufacturers make continued efforts to place devices that provide such functionality in quite limited available space within the phone. 
         [0003]    Additionally, an interest in receiving various types of radio signals exists. Receiving UHF radio signals, for instance, DVB-H mobile TV, often presents cell phone manufacturers with a number of challenges. Space is limited and cell phones often already have a number of built-in antennas, for instance, GSM and Bluetooth antennas. In some cases, additional antennas are present, such as WLAN and GPS antennas. Accordingly, additional space required for yet another antenna is limited, if not non-existent. Some solutions for built-in UHF antennas exist, but such antennas typically only provide low antenna gain or limited bandwidth. Proximity to the ground plane is also an issue with in-built antennas; when a phone is handheld by a user, performance is often degraded. 
         [0004]    In the field of FM radio as it relates to cellular phones, space considerations have led to attempts to use a cord of an accessory, for instance, the cord of a portable hands-free device, as an antenna for the cellular phone, where the cellular phone is a main unit and the portable hands-free device is an auxiliary unit. The use of such a cord as an antenna, however, could be improved upon. 
         [0005]    Implementations of the present invention provide an improved antenna solution for a portable communication device arrangement that includes a main unit and an auxiliary unit. 
       SUMMARY OF THE INVENTION 
       [0006]    Implementations of the present invention provide an improved portable communication device arrangement. 
         [0007]    According to a first aspect of the present invention, a portable communication device arrangement is provided, which arrangement comprises: 
         [0000]    a main unit including:
       an electrical interface to an auxiliary unit,   a ground plane dimensioned for antenna operation at a multiple of a quarter of a wavelength of a desired frequency, and   a radio communication unit connected to the ground plane and to said electrical interface, and
 
an auxiliary unit including
   at least one electrical conductor to be connected to the electrical interface and including a first radio frequency trap, wherein the distance between said first radio frequency trap and an end of the conductor that is to be connected to said electrical interface corresponds to an odd multiple of a quarter of a wavelength of said desired frequency.       
 
         [0012]    A second aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein the main unit includes a second radio frequency trap connected to the electrical interface and the radio circuit is connected between said second radio frequency trap and said electrical interface. 
         [0013]    A third aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein the radio circuit is connected to the electrical interface via a matching unit. 
         [0014]    A fourth aspect of the present invention is directed towards a portable communication device arrangement including the features of the third aspect, wherein the matching unit is a capacitor. 
         [0015]    A fifth aspect of the present invention is directed towards a portable communication device arrangement including the features of the third aspect, wherein the matching unit is a matching network. 
         [0016]    A sixth aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein the ground plane includes a main element and an extension element in order to be dimensioned for operation at said multiple of a quarter of a wavelength of said desired frequency. 
         [0017]    A seventh aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein a radio frequency trap is provided through ferrite beads provided for each conductor of the auxiliary unit. 
         [0018]    An eighth aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein a radio frequency trap is provided through a parallel resonant LC network provided for each conductor of the auxiliary unit. 
         [0019]    A ninth aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein at least one of the multiples is an odd multiple of a quarter of a wavelength of said desired frequency. 
         [0020]    A tenth aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein one conductor of the auxiliary unit is a shield and the radio communication unit is connected to this shield. 
         [0021]    An eleventh aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein the desired frequency lies in the UHF frequency range. 
         [0022]    A twelfth aspect of the present invention is directed towards a portable communication device arrangement including the features of the first aspect, wherein the main unit is a portable communication device and the auxiliary unit is an accessory to this portable communication device. 
         [0023]    A thirteenth aspect of the present invention is directed towards a portable communication device arrangement including the features of the twelfth aspect, wherein the portable communication device is a cellular phone and the accessory is a portable hands-free device. 
         [0024]    Implementations of the invention have several advantages, for example, an antenna that is suitable for receiving UHF signals, such as digital television signals, but also radio, such as FM radio, having superior gain and bandwidth. Implementations are inexpensive and relatively easy to produce, in part, because components and units that are provided in existing portable communication devices and accessories may be utilized. In some implementations, the conductor associated with the auxiliary unit is extended in the process of being used by a user, which may enable superior antenna properties when, for instance, using the auxiliary unit while watching mobile TV. 
         [0025]    It should be emphasized that the terms, “comprises/comprising” and “includes/including,” when used herein, are intended to denote the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present invention will now be described in more detail in relation to the enclosed drawings, in which: 
           [0027]      FIG. 1  schematically shows a front view of an exemplary communication device arrangement in which systems and methods described herein may be implemented; 
           [0028]      FIG. 2  schematically shows a cross-sectional side view of an exemplary circuit board associated a device in which systems and methods described herein may be implemented; 
           [0029]      FIG. 3  schematically shows a front view of the circuit board of  FIG. 2  together with relevant elements of an associated device in which systems and methods described herein may be implemented; and 
           [0030]      FIG. 4  schematically shows a variation of a ground plane that enables operation at a desired frequency. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0031]    A portable communication device arrangement will now be described in relation to a main unit that is a portable communication device in the form of a cellular phone, which may be a variation of such a unit. The portable communication device may include another type of device, such as a cordless phone, a PDA or any other type of portable device configured to communicate using radio waves. The portable communication device arrangement may include an auxiliary unit in the form of an accessory to the main unit. The accessory may include a portable hands-free device. However it is not limited to this type of device, but may include any auxiliary unit that electrically connects to the main unit, for example, via at a conductor. 
         [0032]      FIG. 1  schematically shows a front view of a phone  10 , which may include the main unit of the portable communication device arrangement according to one implementation. Phone  10  may include a casing  12 , a keypad  14 , and a display  16 . Phone  10  may include an electrical interface to auxiliary units in the form of a system connector  18 , which may be provided at a bottom end of phone  10 . To system connector  18 , a first auxiliary unit in the form of a portable hands-free device  20  may connect. Portable hands-free device  20  may include ear phones  22  and  24  for wearing by a user, as well as a central unit  26 , which may include a microphone. To central unit  26 , a cord  28  may connect, which in turn may connect to a plug  30  for insertion in system connector  18 . Cord  28  may include a number of conductors, which may transport signals to and from microphone and ear phones  22  and  24  of portable hands-free device  20 . 
         [0033]      FIG. 2  shows a side view of a circuit board  32  that may be provided in casing  12  of phone  10 . Casing  12  is shown as a dashed box and may include some of the elements of implementations of the present invention. On one side of circuit board  32  a radio communication unit  36  and a sound processing unit  38  may be provided, where radio communication unit  36  is arranged to receive radio frequency signals in one or more frequency ranges, which may include the UHF frequency range. Sound processing unit  38  may be arranged to process various audio signals for the microphone and ear phones  22 ,  24  of hands-free device  20 . In a middle layer of circuit board  32  there may be provided a ground plane  34 , which, in one embodiment of the present invention, may extend substantially entirely throughout circuit board  32 . 
         [0034]      FIG. 3  schematically shows cord  28  with plug  30  connected to system connector  18 , which are all shown as dashed boxes.  FIG. 3  also shows some units of phone  10  that are relevant for the present invention. Cord  28  may include a first, a second, and a third conductor  40 ,  42 , and  44 , where third conductor  44  may act as a shield of cord  28 . At a distance d from the connection point to system connector  18 , a first radio frequency trap  46  may be provided in cord  28 . Beyond first trap  48 , cord  28  may have any desired length. This first radio frequency trap  48  is a trap that is effective for each of conductors  40 ,  42 ,  44  of cord  28 , which will be described in more detail below. Conductors  40 ,  42 , and  44  of cord  28  may mate when plug  30  is inserted in system connector  18 , with corresponding conductors leading to sound processing unit  38 . In the mating conductors, between sound processing unit  38  and system connector  18 , a second radio frequency trap  48  may be provided. Second trap  48  may be provided as close as possible to system connector  18 . Radio communication unit  36  may connect to one of the mating conductors, for example, the one that mates with third conductor  44  of cord  28 , via a capacitor  50 . Radio communication unit  36  may connect to ground plane  34 . 
         [0035]    According one embodiment, the part of conductors  40 ,  42 , and  44  of cord  28  between system connector  18  and first radio frequency trap  46 , which is here denoted active length d, may function as a first leg of a dipole antenna, while ground plane  34  may functions as the second leg of the dipole antenna. reasoning this regard, ground plane  34  may be dimensioned for antenna operation, i.e., for being most efficient, at a multiple of a quarter of a wavelength of a desired frequency within a frequency band that is of interest, which, in this example, may be a frequency in the UHF frequency band. The placing of first radio frequency trap  46  may be chosen so that distance d between the ends of conductors  40 ,  42  and  44  of cord  28  that connect to system connector  18  and the first radio frequency trap  46 , i.e., active length d, is essentially equal to a multiple of a quarter of the same wavelength. In its simplest form, for example, the multiple associated with the active length and the multiple associated with ground plane  34  may be chosen as one, which means that both active length d and ground plane are dimensioned for a quarter of a wavelength of the desired frequency. Traps  46  and  48  may have dual functions. They may both stop radio signals received via cord  28  from influencing the signals provided to sound processing unit  38  and ear phones  22 ,  24  and the microphone of hands free device  20 . First trap  46  may enable the first leg of the dipole antenna to have the chosen length d. 
         [0036]    Each of radio frequency traps  46  and  48  may function as a parallel resonance circuit, i.e., like a capacitor and inductor connected in parallel, and thus filter out the radio frequency signals that are received by the antenna. Radio frequency traps  46  and  48  may be provided in the form of ferrite beads, one for each conductor in cord  28  and one for each mating conductor on circuit board  32 . The ferrite beads may have a high impedance for the frequency of interest, for instance, UHF, and perhaps also for FM radio frequencies, but a low impedance for audio frequencies. A suitable ferrite bead, for example, may include the ferrite bead of the type, Murata BLM15HD182SN1, which has an impedance above 3.3 kΩ at UHF and about 1.8 kΩ at FM frequencies. 
         [0037]    Capacitor  50 , for example, may be a matching unit that will block any difference in DC levels between the audio signal and the antenna input, and can also provide impedance matching. This capacitor and its leads may be surrounded by a low capacitance area between radio communication unit  36  and conductors  40 ,  42 , and  44  of cord  28 . This may act to minimize RF losses. The capacitor can also be part of or replaced by an impedance matching network, which is thus another form of matching unit. 
         [0038]    Implementations thus provide an antenna that may be suitable for receiving UHF signals such as digital television signals, but may also be applied to radio such as FM radio. 
         [0039]    Implementations of the present invention have a number of advantages, for example, a superior gain (˜2 dBi or 0 dBd) and bandwidth, where no high Q tuning is needed. The impedance matching, which may be made around 50-750, is incomplex. The antenna is inexpensive and simple to produce since it utilizes components and units that are present in existing portable communication devices and accessories. According to one implementation, the phone itself may be used as a part of the antenna, which is possible since it is electrically ‘floating.’ The cord of the hands-free device is normally naturally extended when in use. T his furthermore provides good antenna properties, when using the hands-free device while watching mobile TV. The hands-free device can furthermore still be used as radio antenna, for instance, for FM radio, if the RF trap in the cord is designed with suitable impedance at FM frequencies. 
         [0040]    In implementations in which the circuit board may not have sufficient size for dimensioning the ground plane to the desired multiple of a quarter of a wavelength of a desired frequency, an extension element may be provided, as is schematically shown in  FIG. 4 , which shows a ground plane having a main element  52 , which is here rectangular, to which an extension element  54  is connected. Extension element  54  is here provided as an added bar-shaped element. It should be realized that extension element  54  may have any desired regular or irregular shape to provide an additional length of the ground plane. Extension element  54  may, for instance be curved or of meandering shape. Likewise, main element  52  may have any suitable shape. 
         [0041]    The above-described implementations may be varied in a number of ways. For example, the active length of the cord and the ground plane may be dimensioned for different multiples of the same wavelength. Each may separately be dimensioned for both even and odd multiples. The second trap may be omitted, and as such, the audio signal processing may have to be designed for better noise handling. The traps may be provided in ways other than that described above. A trap may be provided as only an inductor provided in a conductor, only a capacitor provided in a conductor or as a parallel resonance LC circuit (capacitor in parallel with inductor) in a conductor. The capacitor via which the radio communication unit may connect to a conductor, may, as has been explained above, be omitted. The radio communication unit need not connect to a shield of the cord, but may connect to any of the conductors. It should be appreciated that the number of conductors can be varied and range, for example, from only one to several. Additional capacitors may connect between the conductors of the cord. Implementations have been described in relation to the UHF and the FM bands. Other radio frequency bands, for instance, VHF, are possible. The radio communication unit can be disposed anywhere relative to the circuit board. The electrical interface described above need not be provided in the form of a system connector. The electrical interface may include a separate connection, for instance, an ear phone jack. This electrical interface need not be disposed at the bottom of the phone, but may be disposed anywhere relative to the casing of the phone. 
         [0042]    The invention is therefore only to be limited by the accompanying claims.