Abstract:
An antenna system for a portable transceiver device comprises an antenna structure for transmitting and receiving RF signals. The antenna structure includes multiple feeding ports having a common structure fully coupling multiple antennas together. This antenna structure is made of a conductor that can be surface mounted over a nonplanar surface. When the conductor is mounted on a nonplanar surface, the antenna structure extends in three dimensional space around the portable communications device.

Description:
FIELD OF THE INVENTION 
     The present invention relates to antennas that can send and receive signals from a radio frequency device. In particular the present invention relates to antennas that are used in portable hand held devices. 
     BACKGROUND OF THE INVENTION 
     An antenna is a transforming device that converts circuit currents into electromagnetic energy. Conversely, the antenna can convert electromagnetic energy into circuit currents. The frequency to which the antenna responds is based on characteristics of the antenna such as width and length. Changes in the width and length of the antenna affect the resistance of the antenna and shape the current densities along the length of the antenna. The antenna field can be affected by nearby objects, such as other antennas, which distort the performance of the antenna. 
     There remains a need for a portable hand-held communications device that implements an antenna in at least a transmitting or a receiving configuration. Ideally, the antenna conforms to the housing of the device and is positioned so that the antenna will transmit and receive regardless of the orientation of the device relative to the communications station. 
     SUMMARY OF THE INVENTION 
     An antenna system for a portable transceiver device comprises an antenna structure for transmitting and receiving RF signals. The antenna structure includes multiple feeding ports having a common structure fully coupling multiple antennas together. This antenna structure is made of a conductor that can be surface mounted over a nonplanar surface. When the conductor is mounted on a nonplanar surface, the antenna structure extends in three-dimensional space around the portable hand held communications device. 
     More accordingly, as a principal feature of the invention, an antenna system comprises an antenna structure, a first feeding port, and a second feeding port. The first and second feeding ports connect the antenna structure to communications circuitry. The antenna structure forms a first antenna structure connected to the first feeding port and further forms a second antenna structure connected to the second feeding port. Importantly, a portion of the first antenna structure is also a portion of the second antenna structure. 
     According to the present invention, there is also provided a portable communications device comprising: a transmitting circuit; a receiving circuit; and an antenna system, wherein the antenna system comprises a first antenna structure and a second antenna structure which has a common portion of a radiation element fully coupling the first antenna structure to the second antenna structure. Preferably, the first antenna structure and the second antenna structure include a monopole antenna, a dipole antenna, and a top loaded member wherein the top loaded member is a portion of the first antenna structure and the second antenna structure. Preferred applications of the present invention include portable communication devices, wireless PDAs, and two-way paging devices. 
     Some of the advantages provided by the present invention include: high efficiency, high gain, wide bandwidth, and low SAR. In addition, the present invention allows for use of one piece of wire to realize two different antenna functions simultaneously. Further still, the present invention&#39;s use of two feeding points will allow optimization of the radio board layout to minimize EMI problems. Further and advantageously, there is no performance issue regarding coupling between antennas in the present invention as in traditional separate two antenna solutions wherein the coupling between the antennas degrades the antenna performance. Another advantage of the present invention is the simple layout. In the present invention a folded dipole is used as a transmitting antenna to raise the antenna radiation resistance thereby increasing efficiency. Traditional dipoles and monopoles that are widely used in wireless devices are very sensitive to a change in the environment. In contrast, the present invention is less sensitive to the environment by taking advantage of the environment by reducing the effects of the same. Further still, the present invention allows the potential for increasing bandwidth by appropriately changing wire lengths. Finally, the present invention allows for lower manufacturing cost due to simpler layout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of an antenna system comprising a preferred embodiment of the invention; 
     FIG. 2 is an orthogonal view of the antenna system of FIG. 1 mounted on a telecommunications device housing; 
     FIG. 3 is a partial view of the antenna system of FIG. 1; and 
     FIG. 4 also is a partial view of the antenna system of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An antenna system  10  comprising a preferred embodiment of the present invention is shown in FIG.  1 . The antenna system  10  comprises a backing substrate  12 , and an antenna structure  14 . The backing substrate  12  is made of a thin, flexible material. Preferably, the antenna structure  14  is made of a low resistance conductor and affixed to the backing substrate  12 . In this manner, the antenna system  10  is a laminate with layers of the antenna structure  14  and the backing substrate  12 . 
     The antenna structure  14  has distinct portions defining a radiating element, a top loading member  22 , a monopole feeding port  24 , and a dipole feeding port  26 . The radiating element is a conductor that extends from the feeding ports  24  and  26  to the top loading member  22 . Portions of the radiating element include: a monopole portion  30 , a common portion  32 , and a dipole portion  34 . These portions  30 - 34  are configured so that the radiating member includes a first antenna structure  40 (as shown in FIG. 3) that functions as an effective monopole antenna and a second antenna structure  44 (as shown in FIG. 4) that functions as an effective dipole antenna. 
     When the antenna system  10  is excited from the monopole feeding port  24 , the dipole feeding port  26  and the dipole portion  34  of the antenna structure  14  are a load on the effective monopole antenna  40  (indicated as XX and YY on FIG.  3 ). When the system is excited from the dipole feeding port  26 , the monopole feeding port  24  and the monopole portion  30  of the antenna structure  14  are a load on the effective dipole antenna  44 (indicated as ZZ on FIG.  4 ). 
     The effective monopole antenna  40  includes a current path along the radiating element between the monopole feeding port  24  and the top loading member  22 . As shown in FIG. 3, the primary path of the effective monopole antenna  40  is defined by the monopole portion  30 , the common portion  32  and the top loading member  22 . The loads XX and YY between the monopole feeding port  24  and the top loading member  22  have a high impedance, and consequently, very small amounts of current are delivered through the loads. The effective dipole antenna  44  includes a current path along the radiating element between the dipole feeding port  26  and the top loading member  22 . As shown in FIG. 4, the path of the effective dipole antenna  44  comprises the dipole portion  30 , the common portion  32 , and the top loading member  22 . The load ZZ between the dipole feeding port  26  and the top loading member  22  has a high impedance, and consequently, a very small amount of current is delivered through the load. 
     A dielectric housing  46  is a box-shaped container made of a dielectric material. The dielectric housing  46  has a top and bottom surface  52  and  54 , a front and back surface  56  and  58 , and opposite side surfaces  60  and  62 . Within the dielectric housing  46  is a transmitting circuit  70  and a receiving circuit  74 . The dielectric housing  46  holds the electronics of the transmitting circuit  70  and the receiving circuit  74 . 
     The antenna system  10  is folded from the original, flat configuration of FIG. 1 to the configuration in which it is mounted on the inside of the dielectric housing  46 , as shown in FIG.  2 . The antenna system  10  then extends around the dielectric housing  46  to orient the antenna structure  14  in multiple perpendicular planes. The top loading member  22  and the common portion  32  of the radiating element are mounted on the side surface  60 . The common portion  32  and the dipole portion  34  of the radiating element extend around a front comer  78  from the side surface  60  to the front surface  56 . The common portion  32  extends fully along the front surface  56  to the opposite comer  80 . The dipole portion  34  turns upward from the front surface  56  to the top surface  52  and extends along the top surface  52 . The dipole feeding port  26  also is located on the top surface  52  of the dielectric housing  46 . Near the comer  80 , the dipole portion  34  turns down from the top surface  52  back onto the front surface  56 . The monopole portion  30  turns around the far front comer  80  from the front surface  56  to the far side surface  62  and again turns from the side surface  62  upward onto the top surface  52 . The effective monopole antenna  40  and the effective dipole antenna  44  each extend in a plane parallel to the front surface  56 , and planes parallel to the top surface  52 , and the side surface  60 . This orientation of the antenna system  10  makes the portable communications device  56  an omnidirectional transmit and receive device. 
     The monopole feeding port  24  is connected to the receiving circuit  74 . The dipole feeding port  26  is connected to the transmitting circuit  70 . Importantly, the current distributed from the monopole feeding port  24  mainly flows along the effective monopole antenna  40  while a small amount of current travels along the loads XX and YY. Since these loads are the high impedances of the dipole portion  34 , dipole feeding port  26  and transmitting circuitry  70 , the current distribution along the effective monopole antenna  40  is minimally changed. Similarly, when current is distributed from the dipole feed port  26 , the current mainly flows along the effective dipole antenna  44  while a small amount of current travels along the load ZZ. Since the load ZZ is the high impedance of the monopole portion  30 , monopole feeding port  24  and receiving circuit  74 , the current distribution along the effective dipole antenna  44  is minimally changed. This configuration is important in the operation of the antenna system  10  in its transmit and receive states. 
     The effective monopole antenna  40  is sized to receive signals from a radio wave at a particular frequency by defining the length and width of its radiating element appropriately. Since the loads XX and YY have a high impedance, most of the current generated along the antenna structure  14  from the received radio signal is distributed along the effective monopole antenna  40 . The length of the common portion  32  of the radiating element is sized so that the antenna is tuned to the chosen frequency for receiving signals. 
     The effective dipole antenna  44  is sized to transmit a signal at a specified frequency by defining the length and width of its radiating element appropriately. The high impedance of the load ZZ of the antenna structure  14  forces the current from the transmitting circuit  70  to flow along the effective dipole antenna  44 . The length of the effective dipole antenna  44  is the length of both the common portion  32  and the dipole portion  34 . The dipole portion  34  can thus be sized with the prior knowledge of the length of the common portion  32  to convert the circuit currents of the transmitting antenna to an electromagnetic signal at the desired frequency. 
     The top loading member  22  of the antenna structure  14  further alters the current distribution of each effective antenna  40  and  44 . The top loading member thus further shapes the characteristics of each effective antenna  40  and  44  by adding perceived length to the antenna structure  14 . 
     The invention has been described with reference to a preferred embodiment. Those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes, and modifications are intended to be within the scope of the claims.