Abstract:
There is provided an apparatus comprising: a first radiation element having a horizontal pattern extending in parallel with a ground element and having a first open end; a second radiation element having a horizontal pattern extending in parallel with the ground element and having a second open end; wherein each of said first radiation element and second radiation element connects to the ground element; wherein said second open end of the second radiation element occupies an area surrounded by a horizontal pattern of the first radiation element and the ground element; and a driven element including a first excitation pattern extending along the horizontal pattern of the first radiation element and a second excitation pattern extending along the horizontal pattern of the second radiation element. Other embodiments are disclosed.

Description:
CLAIM FOR PRIORITY 
       [0001]    This application claims priority from Japanese Application No. 2011-024597, filed on Feb. 8, 2011, and which is fully incorporated by reference as if fully set forth herein. 
       FIELD OF THE INVENTION 
       [0002]    The subject matter described herein relates to a dual band antenna mountable in a wireless terminal. 
       BACKGROUND 
       [0003]    There are frequencies for cellular phones in North America, namely the PCS (Personal Communications Service) band and the cellular band. In the PCS band, a frequency band from 1700 MHz to 2200 MHz is used as the 2 GHz band. In the cellular band, a frequency band from 820 MHz to 960 MHz has been previously used as the 800 MHz band, and recently, a mobile telecommunications service based on a communication standard called LTE (Long Term Evolution) has started as the 700 MHz band in the cellular band. 
         [0004]    In the United States, Verizon Wireless Inc. and AT&amp;T Inc. offer wireless data communication services using LTE. Verizon Wireless Inc. uses a frequency band from 747 MHz to 787 MHz, and AT&amp;T Inc. uses a frequency band from 704 MHz to 746 MHz. Cellular phones or smart phones have only to be equipped with an antenna adapted to a frequency band of either of the companies, whereas it is desired that notebook computers (hereinafter called laptop PCs) and other types of mobile computing devices, including tablets, netbooks, and ultra laptops be equipped with an antenna adapted to a range of frequencies from 704 MHz to 787 MHz to cover the frequency bands of both companies in order to use the frequency band for cellular phones in the United States. 
         [0005]    Japanese Patent No. 4121799 discloses a dual band antenna composed of an exciter and two quarter-wavelength antennas. The exciter is composed of a dipole antenna resonating with a fundamental frequency and a harmonic resonance frequency. One quarter-wavelength antenna is an inverted-L dipole antenna resonating with the fundamental frequency and the other quarter-wavelength antenna is an inverted-L dipole antenna resonating with an n-order harmonic resonance frequency. The open end of the one quarter-wavelength antenna is electrostatically coupled to the exciter in a position in which the current distribution of the fundamental frequency is minimized, and the open end of the other quarter-wavelength antenna is electrostatically coupled to the exciter in a position in which the current distribution of the n-order harmonic resonance frequency is minimized. 
         [0006]    Japanese Patent Application Publication No. 2010-288175 discloses a multiband antenna of a T monopole structure composed of a common conductor and two horizontal conductors different in length. This antenna has the common conductor and the respective horizontal conductors form a quarter-wavelength radiation conductor to resonate with two frequencies and operate in a serial resonance mode. With this antenna, it is described that the low frequencies adapt to the 800 MHz band. 
         [0007]    Japanese Patent Application Publication No. 2007-214961 discloses a multiband antenna apparatus capable of reducing electrostatic coupling among multiple antennas. A support base member includes a flat face portion and peripheral end faces orthogonal to the flat face portion. A first antenna element and a second antenna element are branched from the same power feed point. The first antenna element is laid out along the peripheral end faces and the second antenna element is provided along the peripheral end face of the flat face portion. The distal ends of the antenna elements are arranged orthogonal to each other at positions where the distal ends do not face each other. With this antenna, it is described that the low frequencies adapt to the 800 MHz band. 
         [0008]    Japanese Patent Application Publication No. 2009-135633 discloses an antenna in common use with multiple frequencies for mobile terminals, composed of an inverted-L driven element, a first radiation conductor, and a second radiation conductor. The first radiation conductor having one folded portion and the second radiation conductor having two folded portions are branched in opposite directions from a common conductor connected to the ground. The first radiation conductor is arranged partially in parallel with a horizontal portion of the driven element and capacitively coupled. The second radiation conductor is arranged partially in parallel with the first radiation conductor and capacitively coupled. With this antenna, it is described that low frequencies adapt to the 900 MHz band. 
         [0009]    “A Study of Broadband Monopole Antenna with Parasitic Elements,” Sugimoto, et. al., 2008 IEICE Tokyo Branch Student Research Conf. discloses an asymmetric monopole antenna having a size incorporable in a mobile terminal as shown in  FIG. 6A  and ultrawideband characteristics. This antenna is composed of a T-shaped feed element and inverted-L parasitic elements respectively having branch conductors parallel to each other on both sides of a common portion of the feed element. Use of the parasitic elements results in exciting two new resonances in a high frequency range, achieving a wider bandwidth from 1.9 GHz to 5 GHz. 
         [0010]    Since the antenna increases in length as the resonance frequency decreases, a large space is required to accommodate low frequencies. An inverted-F dual-band antenna as shown in  FIG. 6B  has been mounted in traditional laptop PCs. The laptop PCs are required to incorporate multiple antennas in a display case for wireless communication, such as WLAN and WiMAX, in addition to cellular phone lines. However, when the antenna structure of  FIG. 6B  is adopted for a new antenna to adapt the low-frequency side to the 700 MHz band, the length of each element increases, causing a problem that it cannot be accommodated in the limited space. 
         [0011]    Further, in order to incorporate a new antenna in a laptop PC, it is necessary to achieve a wide bandwidth capable of covering the frequency bands of both companies in the United States within the limits of space given to traditional antennas. It is also necessary to mount multiple antennas in a small space in a laptop PC, and this may not be able to secure enough distance therebetween depending on the mounting condition. Therefore, there is a need for the new antenna to have a structure that is not likely to cause radio wave interference with other antennas. 
         [0012]    The dual band antenna described in Japanese Patent No. 4121799 requires a space equal to or larger than the sum of the lengths of the horizontal portions of the two quarter-wavelength antennas in the longitudinal direction of the antenna pattern. In the T-shaped asymmetric monopole antenna described in “A Study of Broadband Monopole Antenna with Parasitic Elements,” Sugimoto, et. al., 2008 IEICE Tokyo Branch Student Research Conf., since the open ends of the two inverted-L parasitic elements extend out in opposite directions, a large space is also required in the longitudinal direction of the antenna pattern. Further, since none of the antennas described in the above-mentioned related art documents conforms to the 700 MHz band, there is a need to develop an antenna having a new structure capable of being accommodated in a small space provided in a laptop PC. 
       BRIEF SUMMARY 
       [0013]    An apparatus comprising: a first radiation element having a horizontal pattern extending in parallel with a ground element and having a first open end; a second radiation element having a horizontal pattern extending in parallel with the ground element and having a second open end; wherein each of said first radiation element and second radiation element connects to the ground element; wherein said second open end of the second radiation element occupies an area surrounded by a horizontal pattern of the first radiation element and the ground element; and a driven element including a first excitation pattern extending along the horizontal pattern of the first radiation element and a second excitation pattern extending along the horizontal pattern of the second radiation element. 
         [0014]    An apparatus comprising: an antenna pattern formed on a dielectric substrate, said antenna pattern further comprising: a horizontally extending pattern of a first radiation element; a horizontally extending pattern of a second radiation element; and a ground element; wherein both horizontally extending patterns and the ground element are attached to the dielectric substrate; and wherein the horizontally extending patterns are arranged at approximately 90 degrees from one another. 
         [0015]    Furthermore, another aspect provides an apparatus comprising: an antenna; wherein elements of said antenna comprise: a first radiation element; and a second radiation element; said first radiation element and said second radiation element being formed into a first horizontal pattern and a second horizontal pattern; wherein each of said first horizontal pattern and said second horizontal pattern has an open end and an portion extending in parallel with a ground element; wherein each of said first horizontal pattern and said second horizontal pattern is connected at the ground element such that the open end of the second radiation element enters an area surrounded by the first horizontal pattern of the first radiation element and the ground element; and a driven element comprising a first excitation element and a second excitation element, each of the first excitation element and the second excitation element having a common power source and extending along horizontal elements of the first radiation element and second radiation element. 
         [0016]    The foregoing is a summary and thus may contain simplifications, generalizations, and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting 
         [0017]    For a better understanding of the embodiments, together with other and further features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying drawings. The scope of the invention will be pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0018]      FIG. 1  is perspective view showing the basic structure of a dual band antenna according to an embodiment. 
           [0019]      FIG. 2  is a plan view of an antenna pattern excluding a ground plane and a dielectric substrate from the antenna in  FIG. 1   
           [0020]      FIG. 3  is a graph showing a current distribution of standing waves generated in a low-frequency radiation element and an excitation pattern 
           [0021]      FIG. 4  depicts fabricated antenna patterns according to embodiments. 
           [0022]      FIG. 5  is a plan view showing an antenna installed in a laptop PC. 
           [0023]      FIG. 6  depicts diagrams of conventional antenna structures. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    It will be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations in addition to the described example embodiments. Thus, the following more detailed description of the example embodiments, as represented in the figures, is not intended to limit the scope of the embodiments, as claimed, but is merely representative of example embodiments. 
         [0025]    Reference throughout this specification to “one embodiment” or “an embodiment” (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment. 
         [0026]    Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obfuscation. The following description is intended only by way of example, and simply illustrates certain example embodiments. 
         [0027]    The remainder of the disclosure begins with a general overview and proceeds to give a more detailed description of example embodiments with reference to the accompanying figures. 
         [0028]    In view of the above described conventional arrangements, an embodiment provides a compact dual band antenna capable of being incorporated in a wireless terminal Further another embodiment provides a dual band antenna having a wide frequency bandwidth in the 700 MHz band. Further another embodiment provides a dual band antenna capable of reducing radio wave interference with adjacent antennas. Further another embodiment provides a wireless terminal with such a dual band antenna incorporated therein. 
         [0029]    Embodiments provide a dual band antenna including antenna elements formed into patterns on a dielectric substrate and used with a first fundamental frequency and a second fundamental frequency. A first radiation element makes a junction with one end of a ground edge, including a horizontal pattern having an open end and extending in parallel with the ground edge. A second radiation element makes a junction with the other end of the ground edge, including a horizontal pattern having an open end and extending in parallel with the ground edge so that the open end will enter an area surrounded by the horizontal pattern of the first radiation element and the ground edge. 
         [0030]    A driven element includes a first excitation pattern extending along the horizontal pattern of the first radiation element and a second excitation pattern extending along the horizontal pattern of the second radiation element, and having a common power supply. At least part of the horizontal pattern of the second radiation element on the open end side is arranged in an area formed between the first radiation element and the ground edge. Further, the first radiation element and the second radiation element are supplied with power indirectly from the driven element. Therefore, the antenna according to the subject matter described herein can form antennas adapted to two fundamental frequencies in a small space. 
         [0031]    The horizontal pattern of the first radiation element can also include a horizontally extending pattern having an open end and arranged on a flat surface intersecting at right angles with a flat surface on which the driven element is formed. In such a structure, the open end of the horizontally extending pattern can reduce electromagnetic wave interference that may occur with the second radiation element and adjacent other antennas. Further, the length of the shorter side of the antenna pattern can be reduced. The first radiation element and the first excitation pattern can be composed of quarter-wavelength monopole antennas, respectively. 
         [0032]    The first excitation pattern resonates at a quarter wavelength with an m-order harmonic frequency relative to the first fundamental frequency, and the first radiation element resonates with the m-order harmonic frequency at a predetermined wavelength by means of an electromagnetic wave induced from the first excitation pattern and further resonates with the first fundamental frequency at the quarter wavelength. The first radiation element can establish electrostatic coupling and electromagnetic coupling with the driven element subjected to harmonic resonance to resonate with a harmonic, and further resonates with the first fundamental frequency, achieving a wide frequency bandwidth. At this time, if m is set to 3 or 5, excellent characteristics can be obtained while enabling downsizing. The frequency band of the first fundamental frequency can be set in a range from 704 MHz to 787 MHz. The horizontal pattern of the first radiation element can include an impedance adjustment portion expanded into a trapezoidal shape toward the ground edge. 
         [0033]    The second radiation element and the second excitation pattern can be composed of quarter-wavelength monopole antennas, respectively. The structure can also be such that the second excitation pattern resonates with an n-order harmonic frequency relative to the second fundamental frequency, and the second radiation element resonates with the n-order harmonic frequency at a predetermined wavelength by means of an electromagnetic wave induced from the second excitation pattern and further resonates with the second fundamental frequency at the quarter wavelength. Since the size of the antenna is roughly determined by the size of the first radiation element, if the antenna is accommodated in the size, the second radiation element may resonate at a quarter wavelength of the second fundamental frequency. The frequency band of the second fundamental frequency can be set in a range from 1700 MHz to 2200 MHz. The first radiation element and the second radiation element can be inverted-L monopole antennas. The driven element can be a linear antenna or a T monopole antenna having a power supply at the center. 
         [0034]    Embodiments also provide a compact dual band antenna mountable in a wireless terminal Embodiments also provide a dual band antenna with a wide range of frequencies in the 700 MHz band. Still other embodiments provide a dual band antenna capable of reducing radio wave interference with adjacent antennas. Other embodiments provide a wireless terminal with such a dual band antenna mounted therein. 
       Antenna Structure 
       [0035]    Referring now to the figures,  FIG. 1  is a perspective view showing the basic structure of a dual band antenna  100  (hereinafter, simply called “antenna”) according to an example embodiment.  FIG. 2  is a plan view of an antenna pattern excluding a ground plane  115  and a dielectric substrate  101  from the antenna  100 . As shown in  FIG. 1 , a flat surface on which a horizontally extending pattern  109   c  of the antenna pattern exists intersects at 90 degrees with a flat surface on which horizontal pattern  109   b  exists, but both of the patterns are illustrated in  FIG. 2  as if they exist on the same flat surface for the sake of illustration. Note that the subject matter described herein includes the case where the horizontally extending pattern  109   c  is arranged on the same flat surface as the horizontal pattern  109   b.    
         [0036]    The antenna  100  adapts to a frequency band on the low-frequency side used in a range of frequencies from 704 MHz to 787 MHz and a frequency band on the high-frequency side used in a range of frequencies from 1700 MHz to 2200 MHz. Suppose that 746 MHz (approximately the center of the frequency band on the low-frequency side) is set as fundamental frequency f H  on the low-frequency side and its wavelength is denoted as λ H . Suppose also that 1950 MHz (approximately the center of the frequency band on the high-frequency side) is set as fundamental frequency f L  of the high-frequency side and its wavelength is denoted as λ L . The antenna  100  is composed of three members, i.e., an antenna pattern formed on a principal plane  103  of the dielectric substrate  101  by performing photolithography and etching processes on a printed circuit board, the horizontally extending pattern  109   c  and the ground plane  115 , both of which are soldered to the antenna pattern of the principal plane  103 , respectively. 
         [0037]    The shape of the dielectric substrate  101  is a thin plate-like rectangular parallelepiped having the principal plane  103  for providing an area, in which the antenna pattern is formed, and four side faces  105 . On the principal plane  103 , patterns of a driven element  107 , a low-frequency radiation element  109 , a high-frequency radiation element  111 , and a ground element  113  are formed. Note that the low-frequency radiation element  109  includes the horizontally extending pattern  109   c  that is not formed on the dielectric substrate  101 . The ground element  113  provides an area in which the ground plane  115  is connected with a linear pattern extending in parallel with one linear edge of the ground plane  115 . In the ground element  113 , a power supply  121   b  on the ground side is defined almost at the center in the longitudinal direction. 
         [0038]    The driven element  107  is a linearly-formed, grounded-type quarter-wavelength monopole antenna, which is disposed in parallel with the ground element  113  with a power supply  121   a  on the voltage side defined almost at the center. In the driven element  107 , the power supply  121   a  acts as a border between a low-frequency excitation pattern  107   a  having a length of X 2  up to one open end  107   c  and a high-frequency excitation pattern  107   b  having a length of y 2  up to the other open end  107   d.    
         [0039]    The excitation patterns  107   a  and  107   b  extend in parallel with the ground element  113  with the open ends  107   c  and  107   d  facing in the opposite directions to form linear antennas, respectively. A coaxial cable connected to a wireless module including a high-frequency oscillator is connected to the power supply  121   a ,  121   b  to supply high-frequency power. The excitation patterns  107   a  and  107   b  resonate with odd-order harmonics, such as three times or five times of the fundamental frequencies f L , and f H , respectively, at predetermined wavelengths. The driven element  107  can be composed of a quarter wavelength T-shaped monopole antenna. 
         [0040]    A vertical pattern  109   a  of the radiation element  109  makes a junction with one end of the ground element  113 . The vertical pattern  109   a  extends perpendicular to the ground element  113  on the principal plane  103 . The horizontal pattern  109   b  makes a junction with the vertical pattern  109   a . The horizontal pattern  109   b  extends up to an end  109   e  in parallel with the ground element  113 . The horizontal pattern  109   b  includes the horizontally extending pattern  109   c  arranged on a flat surface intersecting at 90 degrees with the principal plane  103  on the border indicated by dashed line  119 . Note that 90 degrees is an example of an intersection angle when being housed in a laptop PC, but other cases where the horizontally extending pattern  109   c  intersects with the horizontal pattern  109   b  at other angles are also included in the scope of the subject matter described herein. 
         [0041]    The horizontally extending pattern  109   c  is formed of a flat, thin plate-like conductor, and disposed along a side face  105 . The horizontally extending pattern  109   c  is soldered to the horizontal pattern  109   b . The horizontally extending pattern  109   c  extends in parallel with the ground element  113  up to an open end  109   d  located further ahead of the end  109   e  of the horizontal pattern  109   b . In the embodiment, the horizontally extending pattern  109   c  is fabricated as a separate member from the horizontal pattern  109   b  and both are soldered together, but they may be formed as an integrated pattern and folded along the dashed line  119 . The low-frequency radiation element  109  resonates with a predetermined frequency as an inverted-L quarter-wavelength monopole antenna to radiate an electromagnetic wave. 
         [0042]    The length, x 1 , of the radiation element  109  from the ground element  113  to the open end  109   d  is so adjusted that the radiation element  109  will resonate at a quarter wavelength of the wavelength λ L . The radiation element  109  having the length of x 1  also resonates with a harmonic relative to the fundamental frequency f L . The horizontal pattern  109   b  is arranged to be parallel to at least part of the excitation pattern  107   a  on the principal plane  103  to receive electromagnetic wave energy from the excitation pattern  107   a  by means of electrostatic coupling and electromagnetic coupling. A state in which the horizontal pattern  109   b  and the excitation pattern  107   a  are electrically coupled and arranged in parallel with each other on the same flat surface so that electromagnetic wave energy can be sent and received is referred to as overlapping. 
         [0043]    A vertical pattern  111   a  of the radiation element  111  makes a junction with the other end of the ground element  113 . The vertical pattern  111   a  extends perpendicular to the ground element  113  on the principal plane  103 . A horizontal pattern  111   b  makes a junction with the vertical pattern  111   a . The horizontal pattern  111   b  extends in parallel with the ground element  113  in a direction in which an open end  111   c  faces the end  109   e . A predetermined clearance is provided between the end  109   e  and the open end  111   c  to reduce electromagnetic wave interference therebetween. 
         [0044]    The horizontal pattern  111   b  may be so formed that the open end  111   c  will extend toward the vertical pattern  109   a  in parallel with the excitation pattern  107   b . The horizontal pattern  111   b  is so arranged that the open end  111   c  will exist in an area surrounded by a vertical line drawn from the open end  109   d  to the ground element  113 , the ground element  113 , and the radiation element  109 . The radiation element  111  resonates with a predetermined frequency as an inverted-L quarter wavelength dipole antenna to radiate an electromagnetic wave. 
         [0045]    The length, y 1 , of the radiation element  111  from the ground element  113  to the open end  111   c  is so adjusted that the radiation element  111  will resonate at a quarter wavelength of the wavelength λ H . The radiation element  111  having the length of y 1  also resonates with a harmonic relative to the fundamental frequency f H . The horizontal pattern  111   b  overlaps at least part of the excitation pattern  107   b  to establish electrostatic coupling and electromagnetic coupling. The meaning of overlapping is as described above. 
         [0046]    In  FIG. 2 , it appears that the high-frequency horizontal pattern  111   b  goes inside the low-frequency horizontally extending pattern  109   c  on the same flat surface. However, since they actually exist on a flat surface on which both intersect at 90 degrees as shown in  FIG. 1 , radio wave interference therebetween does not occur. Further, since at least part of the horizontal pattern  111   b  is arranged to enter a space between the horizontally extending pattern  109   c  and the excitation pattern  107   b , the length of the longitudinal direction of the antenna pattern parallel to the ground element  113  can be shortened. In addition, since a structure in which the horizontally extending pattern  109   c  is arranged on the flat surface on which it intersects with the principal plane  103  at 90 degrees is adopted, the length of the shorter side of the antenna pattern perpendicular to the ground element  113  can also be shortened. 
       Method of Determining Antenna Pattern 
       [0047]    When a predetermined installation space is given inside a laptop PC, the pattern of the antenna  100  can be determined according to the following procedure: At first, the length, x 1 , of the radiation element  109  resonating with the quarter wavelength of the low-frequency fundamental frequency f L  is determined to be λ L /4. The length and shape of the radiation element  109  roughly determines the size of the antenna  100 . Since the physical length of the radiation element  109  to resonate is shorter than λ L /4 due to the influence of ambient permittivity and the speed of an electromagnetic wave propagating through the inside of the conductor, the optimum length for resonance at the quarter wavelength can be determined from experiment. 
         [0048]    Next, a ratio of length between the vertical pattern  109   a  and the horizontally extending pattern  109   c  is determined. The ratio is determined so that not only the antenna  100  can be fitted into the given space, but also the driven element  107  can be formed in a space inside the radiation element  109  and surrounded by the radiation element  109  and the ground element  113 . When resonating at the quarter wavelength of the wavelength λ L  of the fundamental frequency, the radiation element  109  resonates with a harmonic at a wavelength of mλ m /4, where m is an odd number and λ m  is the m-th harmonic wavelength. 
         [0049]    The phenomenon of resonating a harmonic relative to the fundamental frequency is called higher harmonic resonance, and the frequency at the time is called a harmonic resonance frequency f m . If the excitation pattern  107   a  is resonated at a quarter wavelength of wavelength λ m  of the harmonic resonance frequency f m , m=x 1 /x 2  is obtained in theory. At this time, the physical length of the excitation pattern  107   a  to resonate is shorter than λ m /4 for the same reason as the radiation element  109 . Therefore, m calculated from actual lengths x 1  and x 2  may not be an integer. Then, the harmonic resonance frequency f m  used to receive electromagnetic wave energy from the excitation pattern  107   a  is determined from among standing waves of multiple harmonic resonance frequencies f m  with which the radiation element  109  resonates. 
         [0050]    It is preferred that the order m of the harmonic resonance frequency f m  should be small to increase the transmission efficiency of electromagnetic wave energy. However, the smaller the order m, the longer the length of x 2  relative to the predetermined length of x 1 . Therefore, consideration is required to determine whether the excitation pattern  107   a  can be accommodated in an area surrounded by the radiation element  109  and the radiation element  111 . Then, a value as small as possible within a range allowed for the space given to the driven element  107  is selected as the order m. 
         [0051]    Next, the pattern of the radiation element  111  and the length of the excitation pattern  107   b  are determined for the high-frequency fundamental frequency f H  in the same procedure. It is apparent from  FIG. 2  that, since the radiation element  111  is arranged mostly in a space determined by the radiation element  109  and the ground element  113 , the lengths of the radiation element  111  and the excitation pattern  107   b  hardly affect the overall size as long as the structure as shown in  FIG. 2  is adopted. In one embodiment, it is desired to set the order m on the low-frequency side to 3 or 5. As for the high-frequency side, if the length of the excitation pattern  107   b  can be put in a predetermined space, it can resonate the fundamental frequency f H  at the wavelength of λ H /4 without higher harmonic resonance. 
       Description of Operation 
       [0052]    Next, the operation of the antenna  100  will be described.  FIG. 3  is a graph showing a current distribution of standing waves generated in the radiation element  109  and the excitation pattern  107   a . In  FIG. 3 , the radiation element  109  is illustrated as a linear antenna for the purpose of describing standing waves. A high-frequency voltage with fundamental frequency f L  is supplied from the coaxial cable to the power supply  121   a ,  121   b . The excitation pattern  107   a  having the length of x 2  resonates at a quarter wavelength with a third-order harmonic resonance frequency of a wavelength of λ L /3 to generate a standing wave  155 . Since the excitation pattern  107   a  resonates with the fundamental frequency of the third-order harmonic, a high-frequency voltage with a frequency three times the fundamental frequency f L  may be supplied from the coaxial cable. 
         [0053]    In the excitation pattern  107   a , the standing wave  155  reaches the maximum current and the minimum voltage at the position of the power supply  121   a . Further, the standing wave  155  reaches the minimum current and the maximum voltage at the open end  107   c . Since the high-frequency excitation pattern  107   b  does not resonate with higher harmonics of the fundamental frequency f L , the excitation pattern  107   b  does not resonate with the fundamental frequency f L . The standing wave  155  generated in the excitation pattern  107   a  establishes electromagnetic coupling and electrostatic coupling with part of the horizontal pattern  109   b  of the radiation element  109  to induce an electromagnetic wave in the radiation element  109  with the same frequency. The length, x 1 , of the radiation element  109  and the relative position of the excitation pattern  107   a  in the longitudinal direction of the horizontal pattern  109   b  are so determined that the radiation element  109  will resonate with the third-order harmonic frequency. 
         [0054]    For example, as indicated by the dashed lines in  FIG. 3 , if the relative position of the excitation pattern  107   a  moves along the horizontal pattern  109   b  on the side of the open end  109   d  or the opposite side, no standing wave of the third-order harmonic frequency will not be generated in the radiation element  109 . The current and voltage induced by the radiation element  109  are distributed as a standing wave  153  of the third-order harmonic frequency. The standing wave  153  reaches the minimum current and the maximum voltage at the open end  109   d . Further, the current distribution and the voltage distribution at each position of the horizontal pattern  109   b  facing the excitation pattern  107   a  match those of the standing wave  155  on the excitation pattern  107   a.    
         [0055]    Since the radiation element  109  resonates with the fundamental frequency f L , at the quarter wavelength, the standing wave  153  further generates a standing wave  151  at the wavelength λ L . The standing wave  151  reaches the minimum current and the maximum voltage at the open end  109   d . Further, the standing wave  151  reaches the maximum current and the minimum voltage at the junction with the ground. Thus, an electromagnetic wave with the fundamental frequency f L  is radiated from the radiation element  109 . 
         [0056]    Likewise, on the high-frequency side, when a high-frequency voltage with the fundamental frequency f H  is supplied to the power supply  121   a ,  121   b , the excitation pattern  107   b  resonates with a harmonic to establish electrostatic coupling and electromagnetic coupling between the excitation pattern  107   b  and the horizontal pattern  111   b  of the radiation element  111 . The radiation element  111  that received electromagnetic wave energy from the excitation pattern  107   b  radiates an electromagnetic wave with the fundamental frequency f H  on the same principle as the low-frequency side. When the excitation pattern  107   b  does not resonate with any harmonic, both the excitation pattern  107   b  and the radiation element  111  resonate the fundamental frequency f H  at the quarter wavelength. 
       Actual Conductor Pattern 
       [0057]      FIG. 4  contains diagrams showing conductor patterns of antennas actually fabricated and the availability of which was confirmed in a low-frequency band from 704 MHz to 787 MHz and a high-frequency band from 1700 MHz to 2200 MHz. The antenna patterns shown in  FIG. 4  correspond to the antenna pattern in  FIG. 2 . An antenna  200  shown in  FIG. 4A  includes a driven element  207 , a low-frequency radiation element  209 , a high-frequency radiation element  211 , and a ground element  213  to radiate electromagnetic waves by being supplied with power from power supply  221   a ,  221   b . The radiation element  211  is modified from the inverted-L basic structure to provide a length adjusting pattern  211   a  for adjusting the length to resonate with the quarter wavelength of the fundamental frequency f H . The length adjusting pattern  211   a  is formed in a space between the driven element  207  and the ground element  213  so that the overall size of the antenna pattern will not be increased. 
         [0058]    The antenna  200  can realize a wider frequency bandwidth particularly for the fundamental frequency f L , on the low-frequency side. The following reason is considered: The radiation element  209  is a parasitic element indirectly supplied with power by electrostatic coupling and electromagnetic coupling with the driven element without being directly supplied with voltage at the fundamental frequency f L . Then, the driven element  207  as a feed element resonates with a harmonic frequency relative to the fundamental frequency f L , so that the radiation element  209  resonates with the fundamental frequency by means of an electromagnetic wave induced in the radiation element  209  by an electromagnetic wave resulting from higher harmonic resonance. 
         [0059]    An antenna  300  shown in  FIG. 4B  includes a driven element  307 , a low-frequency radiation element  309 , a high-frequency radiation element  311 , and a ground element  313  to radiate electromagnetic waves by being supplied with power from a power supply  321   a ,  321   b . A bandwidth expanding pattern  307   c  is formed into an excitation pattern  307   a  of the driven element  307  to expand frequency bandwidths. The bandwidth expanding pattern  307   c  provides two passages for current flowing into the excitation pattern  307   a  to widen the frequency bandwidths for electromagnetic waves radiated from the driven element  307 . 
         [0060]    The antenna element  309  also includes a length adjusting pattern  309   f  and an impedance adjusting pattern  309   g . Like the length adjusting pattern  211   a , the length adjusting pattern  309   f  plays a role in adjusting the length so that the radiation element  309  will resonate at the quarter wavelength of the fundamental frequency f L . The impedance adjusting pattern  309   g  is formed by enlarging a horizontal pattern  309   b  into a trapezoidal shape toward the ground element  313 , playing a role in adjusting the impedance of the radiation element  309  to make impedance matching with the coaxial cable. 
       Method of Installing Antenna 
       [0061]      FIG. 5  is a plan view showing a state in which the antenna  200  is installed in a laptop PC. A display case  401  internally houses a liquid crystal display (LCD)  403 . A total of five antennas are provided in a space having a length of L 1  on the longer side and a length of L 2  on the shorter side between an upper edge  401   a  of the display case  401  and the LCD  403 . The antennas are different in structure from one another, but at least one of them is the antenna  200 . The antenna  200  is so arranged that an antenna pattern on the principal plane will become parallel to the bottom of the display case  401 , and the ground plane is arranged between the LCD  403  and the bottom of the display case  401 . 
         [0062]    The antenna  200  is so formed that the length on the shorter side of the principal plane  103  falls within L 2 . When five antennas are arranged in the length of L 1 , enough distance cannot be kept between antennas. If a radiation element with the maximum field intensity and the open end of the driven element come close to adjacent antennas, radio wave interference may occur. However, since the open end of the low-frequency radiation element  209  is located on a flat surface on which it intersects at 90 degrees with an antenna pattern of any adjacent antenna on the principal plane, the radio wave interference can be reduced. 
         [0063]    The open end of the high-frequency radiation element  211  faces inward, and this does not cause radio wave interference with adjacent antennas. Further, since both open ends of the driven element  207  are surrounded by the high-frequency radiation element  211  and the low-frequency radiation element  209 , they do not cause radio wave interference with the adjacent antennas as well. Thus, the antenna  200  has a structure suitable for cases where multiple antennas are arranged in a limited space. 
         [0064]    In the above explanation, embodiments are described with particular characteristics shown in drawings. However, the disclosure is not limited to these embodiments shown in the drawings, and as far as the advantageous effects described can be achieved, other embodiments can adopt any configuration that has been known until now. If not otherwise stated herein, it is to be assumed that all patents, patent applications, patent publications and other publications (including web-based publications) mentioned and cited herein are hereby fully incorporated by reference herein as if set forth in their entirety herein. 
         [0065]    Embodiments have been described with reference to specific examples illustrated in the drawings. However, these are simply non-limiting examples, and of course, so long as the effects are obtained, any kind of well known configuration can be employed.