Patent Publication Number: US-2009221243-A1

Title: Portable wireless device

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to a portable wireless device such as tor example a cellular phone and a mobile wireless device, and more particularly to a wideband antenna of a portable wireless device for performing wireless communication in two or more frequency bands close to each other. 
     DESCRIPTION OF THE RELATED ART 
     As a wideband antenna for a wireless device, there has been known a band sharing dipole antenna and the like. 
       FIG. 19  is a block diagram showing the construction of the conventional wideband composite antenna device comprising a monopole antenna and an inverted F antenna. 
     As shown in  FIG. 19 , the wideband composite antenna device comprises a monopole antenna  61  having a length substantially equal to ½ of a wavelength of a frequency band, an inverted F antenna  62  having a length substantially equal to ½ of a wavelength of the frequency band. The inverted F antenna  62  is disposed in spaced and parallel relationship with a base plate  63 , provided with a shorting section  64  at one of its corners and a feeding section  65  distant from the shorting section  64 . 
     In the above-mentioned wideband composite antenna device, the monopole antenna  61  and the inverted F antenna  62  collectively function as a wideband composite polarization antenna under the condition that the monopole antenna  61  is electrically connected to one end of the inverted F antenna  62  on the base plate  63 , the feeding section  65  feeding a radio frequency signal to both of the monopole antenna  61  and the inverted F antenna  62  (see patent document 1). 
       FIG. 20(   a ) is a front view showing the construction of the multiband dipole antenna, while  FIG. 20(   b ) is a right side view showing the construction of the multiband dipole antenna. The multiband dipole antenna is constituted by elements resonating in respective bands. 
     In the multiband dipole antenna shown in  FIG. 20 , the first and second antenna elements  73  and  74  for the first and second frequency bands are arranged on a second base plate  72  located in the close vicinity of the upper part of a base plate  71 . The transceiving circuit  75  is arranged on the lower part of the base plate  71 , and electrically connected to the first and second antenna elements  73  and  74  through a coaxial cable  78 . The bazooka balun  79  arranged on the second base plate  72  includes a first resonating conductor  79 A for performing the balanced to unbalanced transformation in the first frequency band and a second resonating conductor  79 B for performing the balanced to unbalanced transformation in the second frequency band. 
     In this multiband dipole antenna, two regions of 800 MHz and 2000 MHz are respectively defined as the first and second frequency bands. The first and second resonant conductors  79 A and  79 B perform the balanced to unbalance transformation in the respective regions of 800 MHz and 2000 MHz, while the first and second antenna elements  73  and  74  function as respective balanced dipole antennas tor two regions of 800 MHz and 2000 MHz (see patent document 2), 
     Patent document 1: Jpn. unexamined patent publication No. 2002-64324 
     Patent document 2: Jpn. unexamined patent publication No. 2003-8330 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the recent years, we have been received many requests from customers who wishes us to develop an ultra wideband and muitiband antenna having not only two bands of 800 MHz and 2.0 GHz but also an ultra wideband, of 1.7 GHz-2.2 GHz. 
     We have been further received many requests from customers who wish us to develop an ultra wideband and multiband antenna which can reduce an influence from an operator&#39;s body. 
     The portable wireless device provided with the above-mentioned composite antenna can allow the above-mentioned antenna to function as a wideband balanced antenna by using unbalanced antennas, and reduce the influence from the operator&#39;s body. The fractional bandwidth is approximately 7.5%. 
     On the other hand, the portable wireless device provided with the above-mentioned antenna elements can allow the above-mentioned antenna to function as a balanced antenna by using a bazooka balun  79 , and reduce the influence from the operator&#39;s body. The first antenna element  73  operates in the region of 800 MHz, while the second antenna element  74  operates in the region of 2200 MHz. 
     The portable wireless device provided with the above-mentioned antenna elements can be applied to a multiband system in which the second frequency band is twice or so as high as the first frequency band. On the other hand, the first and second antenna elements interfere with each other under the condition that the first and second frequency bands are close to each other. 
     It is therefore an object of the present invention to provide a portable wireless device that can be applied to an ultra wideband system, and reduce the influence from the operator&#39;s body. 
     Means for Solving the Problems 
     The portable wireless device according to the present invention comprises: a first monopole antenna section having a length substantially equal to ¾ of a wavelength of a first frequency band; an open sleeve section having a length substantially equal to ¼ of a wavelength of the first frequency band; a feeding section for feeding a radio frequency signal to the first monopole antenna section and the open sleeve section at the same time; a grounded base plate made of conductive material; and a wireless circuit arranged on the grounded base plate, wherein each of the first monopole antenna section and the open sleeve section has an open end and a feed end through which the radio frequency signal is fed, the first monopole antenna section and the open sleeve section are parallel to each other, and each of the first monopole antenna section and the open sleeve section is perpendicular to a line extending through the feed end of the first monopole antenna section and the feed end of the open sleeve section. 
     The portable wireless device thus constructed can obtain advantageous effects of having the first monopole antenna section function as a balanced antenna, and reducing influence from the operator&#39;s body by reason that the current distribution of the open sleeve section is opposite in phase to the current distribution of the corresponding part of the first monopole antenna section. The portable wireless device can function as a high gain and wideband antenna by reason that the first monopole antenna section has a length substantially equal to ¾ of a wavelength of the first frequency band. 
     The portable wireless device may further comprise a parasitic element section having a length shorter than ½ of a wavelength of a second frequency band higher than the first frequency band, the parasitic element section being parallel to the first monopole antenna section, and arranged under the condition that the open sleeve section is not in an area between planes defined at respective ends of the parasitic element section, perpendicular to the first monopole antenna section. 
     In the portable wireless device thus constructed, the parasitic element section can act as a wideband element to the first monopole antenna section, and reduce the influence from the operator&#39;s body. 
     The portable wireless device may further comprise a second monopole antenna section having a length substantially equal to ¾ of a wavelength of a second frequency band higher than the first frequency band, the open sleeve section being arranged between first and second monopole antenna sections, the second monopole antenna section being parallel to each of the first monopole antenna section and the open sleeve section, the open sleeve section being arranged between the first and second monopole antenna sections, the feeding section feeding the radio frequency signal to the first monopole antenna section, the open sleeve section, and the second monopole antenna section at the same time. 
     The portable wireless device thus constructed can be simple in construction, and function as a high gain and wideband antenna, in addition to advantageous effects of allowing each of the first and second monopole antenna sections to function as a balanced antenna and reducing influence from the operator&#39;s body by reason that the current distribution of the open sleeve section is opposite in phase to the current distribution of the corresponding part of the first monopole antenna section in the first frequency band, the current distribution of the open sleeve section is opposite in phase to the current distribution of the corresponding part of the second monopole antenna section in the second frequency band. 
     The portable wireless device may further comprise a second monopole antenna section having a length substantially equal to ¾ of a wavelength of a second frequency band higher than the first frequency band, the second monopole antenna section being parallel to each of the first monopole antenna section and the open sleeve section, and has a feed end through which the radio frequency signal is fed, the open sleeve section being arranged between first and second monopole antenna sections, and having a node electrically connected to a feed end of the second monopole antenna section, the length between the open end and the node being substantially equal to ¼ of the wavelength of the second frequency band, each of the second monopole antenna section and the open sleeve section being perpendicular to a line extending through the feed end of the second monopole antenna section and the node of the open sleeve section, the feeding section feeding the radio frequency signal to the first monopole antenna section, the open sleeve section, and the second monopole antenna section at the same time. 
     The portable wireless device thus constructed can be constituted as a wideband and high gain antenna device which is small in size and simple in construction by reason that the position of the maximum value of the current distribution of the first monopole antenna section is in the close vicinity of the position of the maximum value of the current distribution of the open sleeve section. 
     The portable wireless device may further comprise a third monopole antenna section having a length substantially equal to ¼ of a wavelength of a third frequency band lower than the first and second frequency bands, the third monopole antenna section arranged in the vicinity of the feeding section extending from one end of the grounded base plate under the condition that the third monopole antenna section is parallel to each of the first monopole antenna section and the open sleeve section. 
     The portable wireless device thus constructed can allow the third monopole antenna section to function as a parasitic element in the third frequency band, and can function as an antenna having a more wide frequency band. 
     In the portable wireless device according to the present invention, at least one of the first monopole antenna section, the second monopole antenna section, the third monopole antenna section, the open sleeve section, and the parasitic element section may be constituted by a meander shaped element. 
     The portable wireless device thus constructed can be constituted as an antenna device which is small in size and simple in construction, and which is used in each of the first to third frequency bands. 
     ADVANTAGEOUS EFFECT OF THE INVENTION 
     The portable wireless device according to the present invention can allow the first monopole antenna section to function as a balanced antenna without being affected by the operator&#39;s body by reason that the first monopole antenna section has a length substantially equal to ¾ of a wavelength of a first frequency band, the open sleeve section has a length substantially equal to ¼ of a wavelength of the first frequency band, the current distribution of the open sleeve section is opposite in phase to that of the corresponding part of the first monopole antenna section, the first monopole antenna section and the open sleeve section are parallel to each other, and perpendicular to a line extending through the feed end of the first monopole antenna section and the feed end of the open sleeve section. 
     Further, the portable wireless device according to the present invention can function as a high gain and wideband antenna by reason that the first monopole antenna section has a length substantially equal to ¾ of a wavelength of a first frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a block diagram showing the construction of the portable wireless device according to the first embodiment of the present invention. 
         FIG. 2  is a diagram showing a current distribution of the portable wireless device according to the first embodiment of the present invention. 
         FIG. 3  is a block diagram showing the construction of the portable wireless device according to the second embodiment of the present invention. 
         FIG. 4  is a diagram showing a current distribution of the portable wireless device according to the second embodiment of the present invention. 
         FIG. 5  is a diagram showing impedance characteristic of the portable wireless device according to the second embodiment of the present invention. 
         FIG. 6  is a block diagram showing the construction of the portable wireless device according to the third embodiment of the present invention. 
         FIG. 7  is a diagram showing a current distribution of the portable wireless device according to the third embodiment of the present invention. 
         FIG. 8  is a diagram showing impedance characteristic of the portable wireless device according to toe third embodiment of the present invention. 
         FIG. 9  is a block diagram showing the construction of the portable wireless device according to the fourth embodiment of the present invention. 
         FIG. 10  is a diagram showing a current distribution of the portable wireless device according to the fourth embodiment of the present invention. 
         FIG. 11  is a diagram showing impedance characteristic of the portable wireless device according to the fourth embodiment of the present invention. 
         FIG. 12  is a block diagram showing the construction of the portable wireless device according to the fourth embodiment of the present invention, applied as a downsized element. 
         FIG. 13(   a ) is a diagram showing a downsized element to which the portable wireless device according to the fourth embodiment of the present invention is applied.  FIG. 13(   b ) is a diagram showing a downsized element to which the portable wireless device according to the fourth embodiment of the present invention is applied.  FIG. 13(   c ) is a diagram showing a downsized element to which the portable wireless device according to the fourth embodiment of the present invention is applied. 
         FIG. 14  is a diagram showing a radiation characteristic, in the frequency band of 1800 MHz, of the downsized device to which the portable wireless apparatus according to the fourth embodiment of the present invention is applied. 
         FIG. 15  is a diagram showing a radiation characteristic, in the frequency band of 2000 MHz, of the downsized device to which the portable wireless apparatus according to the fourth embodiment of the present invention is applied. 
         FIG. 16  is a block diagram showing the construction of the portable wireless device according to the fifth embodiment of the present invention. 
         FIG. 17  is a diagram showing the construction of the downsized device to which the portable wireless apparatus according to the fifth embodiment of the present invention is applied. 
         FIG. 18  is a diagram showing a radiation characteristic, in the frequency band of 800 MHz, of the downsized device to which the portable wireless apparatus according to the fifth embodiment of the present invention is applied. 
         FIG. 19  is a block diagram showing the construction of the conventional wideband composite antenna. 
         FIG. 20(   a ) is a front view showing the conventional band sharing dipole antenna.  FIG. 20(   b ) is a right side view showing the conventional band sharing dipole antenna. 
     
    
    
     EXPLANATION OF THE REFERENCE NUMERALS 
       11 : first monopole antenna section 
       12 : open sleeve section 
       13 : feeding section 
       14 : grounded base plate 
       15 : wireless circuit 
       16 : antenna housing 
       21 : parasitic element section 
       31 : second monopole antenna section 
       32 : feeding section 
       41 : second monopole antenna section 
       42 : first meander shaped monopole antenna section 
       43 : meander shaped open sleeve section 
       44 : second meander shaped monopole antenna section 
       45 : downsized element 
       46   a : upper housing 
       46   b : lower housing 
       51 : third monopole antenna section 
       52 : third meander shaped monopole antenna section 
       61 : monopole antenna 
       62 : inverted F antenna 
       63 : base plate 
       64 : short circuit section 
       65 : feeding section 
       71 : base plate 
       72 : second grounded base plate 
       73 : first antenna device 
       74 : second antenna device 
       75 : transceiving circuit 
       76 ,  77 : feed end 
       78 : coaxial cable 
       79 : bazooka balun (balanced to unbalanced transformer) 
       79 A: first resonant conductor 
       79 B: second resonant conductor 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first to fifth embodiments of the portable wireless device according to the present invention will be described hereinafter with reference to accompanying drawings. 
     First Embodiment 
       FIG. 1  is a block diagram showing the construction of the portable wireless device according to the first embodiment of the present invention. 
     As shown in  FIG. 1 , the portable wireless device according to the first embodiment of the present invention comprises a first monopole antenna section  11  having a length substantially equal to ¾ of a wavelength of a first frequency band, an open sleeve section  12  parallel to the first monopole antenna section  11 , and aligned in a longitudinal direction wind respect to the first monopole antenna section  11 , the open sleeve section  12  having a length substantially equal to ¼ of a wavelength of the first frequency band, a feeding section  13  for feeding a radio frequency signal to the first monopole antenna section  11  and the open sleeve section  12  at the same time, a grounded base plate  14  made of conductive material, and a wireless circuit  15  arranged on the grounded base plate  14 . The first monopole antenna section  11 , the open sleeve section  12 , and the feeding section  13  are in an antenna housing  16 . In this embodiment each of the first monopole antenna section  11  and the open sleeve section  12  has a feed end and an open end. The feeding section  13  feeds the radio frequency signal to each of the first monopole antenna section  11  and the open sleeve section  12  through its feed end. Each of the first monopole antenna section  11  and the open sleeve section  12  is substantially perpendicular to a line extending through the feed end of the first monopole antenna section  11  and the feed end of the open sleeve section  12 . 
       FIG. 2  is a diagram showing a current distribution of each section of the portable wireless device according the first embodiment of the present invention. The current distribution of the first monopole antenna section  11  is indicated by a broken thin line A, while the open sleeve section  12  is indicated by a broken thick line B. 
     The current distribution of the first monopole antenna section  11  reaches maximum at the feed end of the first monopole antenna section  11 , and changes in sign at a point on the first monopole antenna section  11 . The length between the point and the open end is substantially equal to ½ of the wavelength of the first frequency band. 
     On the other hand, the current distribution of the open sleeve section  12  reaches maximum at the feed end distant from the open end on the open sleeve section  12 . 
     As a result of the fact that the current distribution of the open sleeve section  12  is opposite in phase to that of the corresponding part of the first monopole antenna section  11 , that part of the first monopole antenna section  11  can not contribute to an emission of the radio wave in the first frequency band. The first monopole antenna section  11  can function as a dipole antenna having a length substantially equal to ½ of a wavelength of the first frequency band by reason that the remaining part of the first monopole antenna section  11  contributes to the emission of the radio wave in the first frequency band. 
     The portable wireless device according to the present invention can function as high gain and wideband antenna by reason that the first monopole antenna section  11  has a length substantially equal to ¾ of a wavelength of the first frequency band. 
     Second Embodiment 
       FIG. 3  is a block diagram showing the construction of the portable wireless device according to the second embodiment of the present invention. The elements of the portable wireless device according to the second embodiment the same as those of the portable wireless device according to the first embodiment will not be described but bear the same reference numbers as those of the portable wireless device according to the first embodiment. 
     As shown in  FIG. 3 , the portable wireless device according to the second embodiment of the present invention further comprises, in comparison with the portable wireless device according to the first embodiment, a parasitic element section  21  parallel to the first monopole antenna section  11 . The parasitic element section  21  has a length substantially equal to ½ of a wavelength of a second frequency band higher than the first frequency band. The open sleeve section  12  is not in an area between planes defined at respective ends of the parasitic element section  21 , each of the planes being perpendicular to the first monopole antenna section  11 . 
       FIG. 4  is a diagram showing a current distribution of the portable wireless device according the second embodiment. The current distribution of the first monopole antenna section  11  is schematically shown by a broken thick line A. The current distribution of the open sleeve section  12  is schematically shown by a broken heavy line B. The current distribution of the parasitic element section  13  is schematically shown by a dashed and dotted line C. 
     As a result of the fact that the current of the open sleeve section  12  is opposite in phase to that of the corresponding segment of the first monopole antenna section  11  as shown in  FIG. 4 , the current of the corresponding segment of the first monopole antenna section  11  does not contribute to an emission of radio waves. This means that the first monopole antenna section  11  functions as a dipole antenna having a length substantially equal to ½ of a wavelength of the first frequency band. 
     The parasitic element section  21  acts as a waveguide to the first monopole antenna section  11  by reason that the parasitic element section  21  is above the open sleeve section  12 , close to the first monopole antenna section  11 , and has a length substantially equal to ½ of a wavelength of the second frequency band higher than the first frequency band, the position of the maximum value of the current distribution of the parasitic element section  21  being the same as the position of the maximum value of the current distribution of the first monopole antenna section  11 . 
       FIG. 5  is a diagram showing impedance characteristic of the portable wireless device according to the second embodiment of the present invention. In  FIG. 5 , the alphabetic characters “A”, “B”, and “C” correspond to the impedance characteristic at the frequency of 1800 MHz, 2000 MHz, and 2200 MHz. 
     As shown in  FIG. 5 , the impedance characteristic at the frequency of 1800 MHz is similar to the impedance characteristic at the frequency of 2200 MHz by reason that the parasitic element section  21  acts as a waveguide to the first monopole antenna section  11 . The circular locus of the impedance characteristic shows that the portable wireless apparatus has a wideband characteristic. 
     The portable wireless device according to the second embodiment of the present invention has advantageous effects of functioning as a wideband antenna, and reducing the influence of the operator&#39;s body by reason that the parasitic element section  21  is above the open sleeve section  12 , and parallel to the first monopole antenna section  11 . 
     Third Embodiment 
       FIG. 6  is a block diagram showing the construction of the portable wireless device according to the third embodiment of the present invention. The elements of the portable wireless device according to the third embodiment the same as those of the portable wireless device according to the first embodiment will not be described but bear the same reference numbers as those of the portable wireless device according to the first embodiment. 
     As shown in  FIG. 6 , the portable wireless device according to the third embodiment of the present invention further comprises, in comparison with the first embodiment, a second monopole antenna section  31  having a length substantially equal to ¾ of a wavelength of a second frequency band higher than the first frequency band. The open sleeve section  12  is arranged between the first and second monopole antenna sections. The feeding section  32  feeds a radio frequency signal to the first monopole antenna section  11 , the open sleeve section  12 , and the second monopole antenna section  31  at the same time. In this embodiment, the second monopole antenna section  31  is parallel to each of the first monopole antenna section  11  and the open sleeve section  12 , while the open sleeve section  12  is arranged between the first and second monopole antenna sections  11  and  31 . 
       FIG. 7  is a diagram showing a current distribution of the portable wireless device according the third embodiment. The current distribution of the first monopole antenna section  11  is schematically shown by a broken thick line A. The current distribution of the open sleeve section  12  is schematically shown by a broken heavy line B. The current distribution of the second monopole antenna section  31  is schematically shown by a dashed and dotted line D. 
     As a result of the fact that the current distribution of the open sleeve section  12  is opposite in phase to that of the corresponding part of the first monopole antenna section  11 , that part of the first monopole antenna section  11  can not contribute to an emission of the radio wave in the first frequency band as shown in  FIG. 7 . The first monopole antenna section  11  can function as a dipole antenna having a length substantially equal to ½ of a wavelength of the first frequency band by reason that the remaining part of the first monopole antenna section  11  contributes to the emission of the radio wave in the first frequency band. 
     As a result of the fact that the current distribution of the open sleeve section  12  is opposite in phase to that of the corresponding part of the second monopole antenna section  31 , that part of the first monopole antenna section  31  can not contribute to an emission of the radio wave in the second frequency band. The second monopole antenna section  31  can function as a dipole antenna having a length substantially equal to ½ of a wavelength of the second frequency band by reason that the remaining part of the second monopole antenna section  31  contributes to the emission of the radio wave in the second frequency band. 
       FIG. 8  is a diagram showing impedance characteristic of the portable wireless device according to the third embodiment of the present invention. In  FIG. 8 , the alphabetic characters “A”, “B”, and “C” correspond to the impedance characteristic at the frequency of 1800 MHz, 2000 MHz, and 2200 MHz. 
     As will be seen from the impedance characteristic shown in  FIG. 5 , the impedance characteristic at the frequency of 1800 MHz is similar to the impedance characteristic at the frequency of 2200 MHz. The circular locus of the impedance characteristic shows that the portable wireless apparatus has a wideband characteristic. 
     The portable wireless device according to the third embodiment of the present invention has advantageous effects of functioning as a wideband antenna, and reducing the influence of the operator&#39;s body by reason that the second monopole antenna section  31  has a length substantially equal to ¾ of a wavelength of a second frequency band higher than the first frequency the second monopole antenna section  31  is parallel to each of the first monopole antenna section  11  and the open sleeve section  12 , while the open sleeve section  12  is arranged between the first and second monopole antenna sections  11  and  31 . 
     Fourth Embodiment 
       FIG. 9  is a block diagram showing tire construction of the portable wireless device according to the fourth embodiment of the present invention. The elements of the portable wireless device according to the fourth embodiment the same as those of the portable wireless device according to the first embodiment will not be described but bear the same reference numbers as those of the portable wireless device according to the first embodiment. 
     As shown in  FIG. 9 , the portable wireless device according to the fourth embodiment of the present invention comprises a second monopole antenna section  41  substantially equal in length to ¾ of a wavelength of a second frequency band, an open sleeve portion  12  having a portion electrically connected to the second monopole antenna section  41 , and distant from one end. The open sleeve section  12  is arranged between first and second monopole antenna sections  11  and  41 , and has a node electrically connected to a feed end of the second monopole antenna section  41 , the length between the open end and the node being substantially equal to ¼ of the wavelength of the second frequency band. Each of the second monopole antenna section  41  and tire open sleeve section  12  is perpendicular to a line extending through the feed end of the second monopole antenna section  41  and the node of the open sleeve section  12 . The feeding section  32  feeds the radio frequency signal to the first monopole antenna section  11 , the open sleeve section  12 , and the second monopole antenna section  41  at the same time. 
       FIG. 10  is a diagram showing a current distribution of the portable wireless device according the fourth embodiment. The current distribution of the first monopole antenna section  11  is schematically shown by a broken thick line A. The current distribution of the open sleeve section  12  is schematically shown by a broken heavy line B. The current distribution of the second monopole antenna section  41  is schematically shown by a dashed and dotted line E. 
     As shown in  FIG. 10 , the position of the maximum value of the current distribution of the parasitic element section  21  being similar to the position of the maximum value of the current distribution of the first monopole antenna section  11  by reason that the open sleeve section  12  has a node electrically connected to a feed end of the second monopole antenna section  41 , the length between the open end and the node being substantially equal to ¼ of the wavelength of the second frequency band. 
     When the first and second frequency bands are 1.8 GHz and 2.0 GHz, the length of the first monopole antenna section  11  is 125 mm by reason that the first monopole antenna section  11  has a length substantially equal to ¾ of a wavelength of the first frequency band. The length of the open sleeve section  12  is 41 mm by reason that the open sleeve section  12  has a length substantially equal to ¼ of a wavelength of the first frequency band. The length of the second monopole antenna section  41  is 112 mm by reason that the second monopole antenna section  41  has a length substantially equal to ¾ of a wavelength of the first frequency band. In this embodiment, the distance between the first monopole antenna section  11  and the open sleeve section  12  is 1 mm, while the distance between the second monopole antenna section  41  and the open sleeve section  12  is 1 mm. 
     In the portable wireless device shown in  FIG. 9 , the position of the feed end of the second monopole antenna section  41  is distant from the position of the feed end of the open sleeve section  12  by 3.5 mm in an upper direction. The second monopole antenna section  41  is parallel to each of the first monopole antenna section  11  and the open sleeve section  12 . The open sleeve section  12  is arranged between the first and second monopole antenna sections  11  and  41 . 
     As shown in  FIG. 10 , the position of the maximum value of the second monopole antenna section  41  is almost the same as the position of the maximum value of the first monopole antenna section  11 . The second monopole antenna section  41  functions as a waveguide in the first frequency band. 
     From the foregoing description, it will be understood that the portable wireless device according to the fourth embodiment of the present invention can function as a high gain antenna, and reduce the influence of the operator&#39;s body. 
     The following description will be then directed to the case that the portable wireless device according to the present invention is applied to a downsized device. 
     As shown in  FIG. 12 , the downsized device  45  comprises a first meander shaped monopole antenna section  42  having a length substantially equal to ¾ of a wavelength of the first frequency band, a meander shaped open sleeve section  43 , and a second meander shaped monopole antenna section  44  having a length substantially equal to ¾ of a wavelength of the second frequency band. The meander shaped open sleeve section  43  has a nodal point electrically connected to the feed end of the second meander shaped monopole antenna section  44 . The length between the nodal point and the open end of the meander shaped open sleeve section  43  is substantially equal to ¼ of a wavelength of the second frequency band. In this embodiment, the meander shaped open sleeve section  43  has a node electrically connected to a feed end of the second meander shaped monopole antenna section  44 , the length between the open end and the node being substantially equal to ¼ of the wavelength of the second frequency band. Each of the second meander shaped monopole antenna section  44  and the meander shaped open sleeve section  43  is perpendicular to a line extending through the feed end of the second meander shaped monopole antenna section  44  and the node of the meander shaped open sleeve section  43 . The feeding section  32  feeds the radio frequency signal to the first meander shaped monopole antenna section  11 , the meander shaped open sleeve section  43 , and the second meander shaped monopole antenna section  44  at the same time. The meander shaped open sleeve section  43  is arranged between the first and second meander shaped monopole antenna sections  11  and  44 , and parallel to each of the first and second meander shaped monopole antenna sections  11  and  44 . 
     Further, the first meander shaped monopole antenna section  42 , the meander shaped open sleeve section  43 , and the second meander shaped monopole antenna section  44  are arranged in the downsized device  45 . 
     As shown in  FIG. 13(   a ), the housing is constituted by an upper side housing  46   a  and a lower side housing  46   b.  The downsized device  45  is arranged at the bottom section of the lower side housing  46   b.  As shown in  FIG. 13(   b ), the bottom section may be pivotally moved around an axis in the vicinity of the feeding section in a direction of an arrow shown in  FIG. 13(   b ). As shown in  FIG. 13(   c ), the bottom section may be moved in a direction of an arrow shown in  FIG. 13(   c ). 
     From the foregoing description, it will be understood that the downsized device  45  can reduce the influence from the operator by reason that the first meander shaped monopole antenna section  42  and the meander shaped open sleeve section  43  collectively functio as a dipole antenna having a length substantially equal to ½ of the wave length of the first frequency band, the second meander shaped monopole antenna section  44  and the meander shaped open sleeve section  43  collectively function as a dipole antenna having a length substantially equal to ½ of the wave length of the second frequency band. 
     When the operator doesn&#39;t touch the antenna during a voice call, the antenna characteristic of the portable wireless device can be further improved in the fist and second frequency band. 
       FIG. 14  is a diagram showing a radiation characteristic, in the frequency band of 1800 MHz, of the downsized device to which the portable wireless apparatus according to the fourth embodiment of the present invention is applied.  FIG. 15  is a diagram showing a radiation characteristic, in the frequency band of 2000 MHz, of the downsized device to which the portable wireless apparatus according to the fourth embodiment of the present invention is applied. The alphabetic characters “V” and “H” correspond to horizontal and vertical polarized component of the radiation characteristic at the frequency of 1800 MHz and 2000 MHz. 
     Fifth Embodiment 
       FIG. 16  is a block diagram showing the construction of the portable wireless device according to the fifth embodiment of the present invention. The elements of the portable wireless device according to the fifth embodiment the same as those of the portable wireless device according to the fourth embodiment will not be described but bear the same reference numbers as those of the portable wireless device according to the fourth embodiment. 
     As shown in  FIG. 16 , the portable wireless device according to the fifth embodiment of the present invention further comprises, in comparison with the fourth embodiment, a third monopole antenna section  51  parallel to each of the first monopole antenna section  11 , the open sleeve section  12 , the second monopole antenna section  41 . The third monopole antenna section  51  has a length substantially equal to ¼ of a wavelength of a third frequency band lower than the first frequency band. 
     From the foregoing description, it&#39;ll be understood that those sections collectively function as a wideband antenna device by reason that the third monopole antenna section  51  functions as a passive device having a length substantially equal to ¼ of a wavelength of the third frequency band lower than the first and second frequency bands. As shown in  FIG. 16 , the current distribution of the third monopole antenna section  51  is indicated by a dashed thick line F. The portable wireless device according to the fifth embodiment of the present invention can function as a wideband antenna in a frequency band lower than the first frequency band. 
     The following description will be then directed to the case that the portable wireless device according the fifth embodiment of the present invention is applied to a downsized element. 
     As shown in  FIG. 17 , the downsized element  45  comprises a third meander shaped monopole antenna section  52  in addition to the first meander shaped monopole antenna section  42 , the meander shaped open sleeve section  43 , and the second meander shaped monopole antenna section  44 . 
     As shown in  FIG. 13(   a ), the downsized device  45  is arranged at the bottom section of the lower side housing  46   b.  As shown in  FIG. 13(   b ), the bottom section may be pivotally moved around an axis in the vicinity of the feeding section in a direction of an arrow shown in  FIG. 13(   b ). As shown in  FIG. 13(   c ), the bottom section may be moved in a direction of an arrow shown in  FIG. 13(   c ). 
       FIG. 18  is a diagram showing a radiation characteristic, in the frequency band of 800 MHz, of the downsized device to which the portable wireless apparatus according to the fourth embodiment of the present invention is applied. The alphabetic characters “V” and “H” correspond to horizontal and vertical polarized component of the radiation characteristic at the frequency of 800 MHz. From the foregoing description, it will he understood that the portable wireless device can function as a wideband antenna in a frequency band of 800 MHz smaller than the first frequency band. When the operator doesn&#39;t touch the antenna during a voice call, the antenna characteristic of the portable wireless device can be further improved in the first to third frequency bands. 
     In this embodiment, each of the distance between the feeding section and the feed end of the first monopole antenna section, the distance between the feeding section and the feed end of the open sleeve section, and the distance between the feeding section and the feed end of the second monopole antenna section is negligibly small in comparison with the length of each section. When each of the distance between the feeding section and the feed end of the first monopole antenna section, the distance between the feeding section and the feed end of the open sleeve section, and the distance between the feeding section and the feed end of the second monopole antenna section is not negligibly small, the distance between the feeding section and the feed end of the first monopole antenna section, the distance between the feeding section and the feed end of the open sleeve section, and the distance between the feeding section and the feed end of the second monopole antenna section may be respectively added to tire first monopole antenna section, the open sleeve section, and the second monopole antenna section. 
     INDUSTRIAL APPLICABILITY OF THE PRESENT INVENTION 
     From the foregoing description, it will be understood that the portable wireless device according to the present invention can be applied to an ultra wideband system, and reduce the influence from the operator&#39;s body, and is useful as a portable wireless device provided with antennas corresponding to two or more frequency bands close to each other.