Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010-038584, filed on Feb. 24, 2010, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed here are related to an antenna apparatus and to a radio terminal apparatus. 
       BACKGROUND 
       [0003]    In conventional technology, diversity antennas is used as antenna apparatuses in which the same radio signals are received by for example two antennas, and reception signals from the antenna with superior radio wave conditions are preferentially used. 
         [0004]    Further, a multimode antenna structure is known in which, by for example connecting a conductive connection element between two antenna elements, bypassing by the current flowing to the feed point of one of the antenna elements is caused, and the two antenna elements are electrically insulated. 
         [0005]    Furthermore, an integrated-type flat-plate multi-element and electronic equipment are also known in which, by for example forming a cutout unit in an end unit of a ground pattern, the coupling between the antenna elements is reduced. 
         [0006]    In addition, a compact-type portable terminal apparatus for radio reception is also known in which, for example, a variable reactance or switch is provided in a cut-out depressed unit of the rim unit of an upper ground conductor, and by means of the switch or similar, the correlation factors between antenna elements provided at the tip units of a plurality of protrusions in the upper ground conductor are reduced.
   Patent Document 1: WO 2008/131157 A1   Patent Document 2: Japanese Laid-open Patent Publication No. 2007-13643   Patent Document 3: Japanese Laid-open Patent Publication No. 2007-243455   
 
         [0010]    However, in the above-described techniques of the prior art, when a connection element is directly connected between antenna elements, the characteristics of the antenna elements change. Consequently by further arranging a matching circuit in the antenna apparatus, the reception frequency or transmission frequency can be kept in a prescribed range, accommodating the change in characteristics. However, if a matching circuit is arranged in the antenna apparatus, the number of components increases to this extent, and installation space for various elements and similar within the antenna apparatus is decreased. An increase in the number of components and decrease in installation space make it difficult to achieve reduced space usage or greater compactness of the antenna apparatus. 
         [0011]    Further, in the above-described techniques of the prior art, when a cutout is provided in an end unit of a ground pattern, or a depressed unit is provided in an upper ground conductor, if the area of the cutout or depressed unit is equal to or greater than a specific size, the installation space for various elements and similar installed on the ground pattern is diminished by the amount of the cutout or similar. 
         [0012]    On the other hand, by making the coupling, correlation or similar between antenna elements, or other antenna element characteristics equal to or greater than a specific value, the reception characteristics and similar of an antenna apparatus can be improved. 
       SUMMARY 
       [0013]    According to an aspect of the invention, an antenna apparatus, including: a substrate; an antenna element which is arranged on the substrate and transmits or receives a radio signal; a feed point which is connected to the antenna element and feeds a current or a voltage to the antenna element; and a wiring pattern, one end of which is connected to a ground pattern formed on a portion of the substrate, wherein two or more sets of the antenna element, the feed point, and the wiring pattern is included if the antenna element, the feed point, and the wiring pattern form one set. 
         [0014]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a perspective view of an antenna apparatus; 
           [0017]      FIG. 2A  is a partial enlarged view of an antenna apparatus,  FIG. 2B  and  FIG. 2   c  are cross-sectional views of the antenna apparatus; 
           [0018]      FIG. 3  illustrates an example of simulation results for S 11 ; 
           [0019]      FIG. 4  illustrates an example of simulation results for antenna efficiency; 
           [0020]      FIG. 5A  and  FIG. 5B  each illustrate an example of simulation results for a radiation pattern; 
           [0021]      FIG. 6  illustrates an example of simulation results for correlation factors; 
           [0022]      FIG. 7  illustrates an example of simulation results for S 21 ; 
           [0023]      FIG. 8  is a partial enlarged view of an antenna apparatus for simulation; 
           [0024]      FIG. 9  illustrates an example of current distribution; 
           [0025]      FIG. 10A  illustrates an example of simulation results for S 11 , and  FIG. 10B  illustrates an example of simulation results for reactance; 
           [0026]      FIG. 11  illustrates an example of a Smith chart; 
           [0027]      FIG. 12A  is a partial enlarged view of an antenna apparatus when there are no stubs, and  FIG. 12B  is a partial enlarged view of the antenna apparatus when there is one stub fold; 
           [0028]      FIG. 13  is a partial enlarged view of an antenna apparatus; 
           [0029]      FIG. 14  illustrates an example of simulation results for S 11  and S 21 ; 
           [0030]      FIG. 15A  illustrates an example of simulation results for S 11 , and  FIG. 15B  illustrates an example of simulation results for S 21 ; 
           [0031]      FIG. 16  illustrates an example of simulation results for correlation factors; 
           [0032]      FIG. 17A  and  FIG. 17B  each illustrate an example of current distribution; 
           [0033]      FIG. 18  is a partial enlarged view of an antenna apparatus; 
           [0034]      FIG. 19A  illustrates an example of simulation results for S 11  and S 21 , and 
           [0035]      FIG. 19B  illustrates an example of simulation results for correlation factors; 
           [0036]      FIG. 20  illustrates an example of simulation results for current distribution; 
           [0037]      FIG. 21A  is a perspective view of an antenna apparatus, and  FIG. 21B  and  FIG. 21C  are cross-sectional views of the antenna apparatus; 
           [0038]      FIG. 22A  illustrates an example of simulation results for S 11 , and  FIG. 22B  illustrates an example of simulation results for S 21 ; 
           [0039]      FIG. 23  illustrates an example of simulation results for correlation factors; 
           [0040]      FIG. 24  is a perspective view of an antenna apparatus; 
           [0041]      FIG. 25A  is an enlarged view of an antenna apparatus, and  FIG. 25B  and  FIG. 25C  are cross-sectional views of the antenna apparatus; 
           [0042]      FIG. 26  is a front view of an antenna apparatus; 
           [0043]      FIG. 27  is a front view of an antenna apparatus; 
           [0044]      FIG. 28A  illustrates an example of simulation results for S 11 , and  FIG. 28B  illustrates an example of simulation results for S 21 ; 
           [0045]      FIG. 29A  and  FIG. 29B  are perspective views of a radio terminal apparatus; 
           [0046]      FIG. 30A  and  FIG. 30B  are perspective views of an antenna apparatus; 
           [0047]      FIG. 31  is a perspective view of an antenna apparatus; 
           [0048]      FIG. 32A  and  FIG. 32B  each illustrate an example of a radio terminal apparatus; 
           [0049]      FIG. 33  is a partial enlarged view of an antenna apparatus; 
           [0050]      FIG. 34A  illustrates an example of simulation results for S 11  and S 21 , and 
           [0051]      FIG. 34B  illustrates an example of simulation results for correlation factors; 
           [0052]      FIG. 35  is a partial enlarged view of an antenna apparatus; and 
           [0053]      FIG. 36A  illustrates an example of simulation results for S 11  and S 21 , and 
           [0054]      FIG. 36B  illustrates an example of simulation results for correlation factors. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0055]    Embodiments of the invention are explained below. 
       First Example 
       [0056]    A first example is explained.  FIG. 1  is a perspective view of an antenna apparatus  10 . The antenna apparatus  10  is for example a card-type antenna apparatus, and can be loaded into or accommodated in a personal computer, a portable telephone, or another radio terminal apparatus.  FIG. 32A  and  FIG. 32B  illustrate a radio terminal apparatus  100 ;  FIG. 32A  and  FIG. 32B  illustrate examples of a portable telephone and a personal computer respectively as radio terminal apparatuses  100 . The antenna apparatus  10  is accommodated within the housing  101  of the portable telephone  100 , and can transmit and receive radio signals with a radio base station or similar. Further, the antenna apparatus  10  can be loaded into the housing  101  of a personal computer  100 , and can transmit and receive radio signals with a radio base station or similar. 
         [0057]    A configuration example of the antenna apparatus  10  is explained.  FIG. 1  is a perspective view of the antenna apparatus  10 , and  FIG. 2A  is a partial enlarged view of the antenna apparatus  10 . Also,  FIG. 2B  is a cross-sectional view seen from the Cy direction upon sectioning the antenna apparatus  10  at line segment K-K′ in  FIG. 2A , and  FIG. 2C  is a cross-sectional view, seen from the same direction Cy, upon sectioning the antenna apparatus  10  at line segment M-M′. 
         [0058]    As illustrated in  FIG. 1 , the antenna apparatus  10  has a dielectric substrate (hereafter “substrate”)  12 ; two antenna elements  14 - 1  and  14 - 2  (or, first and second antenna elements  14 - 1  and  14 - 2 ); two feed points  16 - 1  and  16 - 2  (or, first and second feed points  16 - 1  and  16 - 2 ); and two stubs  18 - 1  and  18 - 2  (or, first and second stubs  18 - 1  and  18 - 2 ). 
         [0059]    The substrate  12  has length “V+h” (for example, “80 mm”) in the y-axis direction, has length “H” (for example, “30 mm”) in the x-axis direction, and has length (or thickness) “d 1 ” (for example, “1 mm”) in the z-axis direction. The substrate  12  has, on a portion of the top surface, a metal flat plate (or metal flat surface), such as for example a copper layer  13 , and on the bottom surface, various elements. 
         [0060]    The copper layer  13  has area V×H and thickness d 2  (for example, “35 μm”), and forms a ground pattern  15  for the various elements and similar on the substrate  12 . The antenna elements  14 - 1  and  14 - 2  are also formed from a conductive metal flat plate, such as for example a copper layer  13 . 
         [0061]    The antenna elements  14 - 1  and  14 - 2  receive radio signals transmitted from another antenna apparatus, and transmit radio signals to another antenna apparatus. The antenna elements  14 - 1  and  14 - 2  respectively have fixed units  14 - 1   a  and  14 - 2   a  (or first and second fixed units  14 - 1   a  and  14 - 2   a ) fixed on the substrate  12 , and bent units  14 - 1   b  and  14 - 2   b  (or, first and second bent units  14 - 1   b  and  14 - 2   b ) bent into an L shape from the fixed units  14 - 1   a  and  14 - 2   a.    
         [0062]    The bent units  14 - 1   b  and  14 - 2   b  can be rotated about the y 1  axis and y 2  axis respectively, and can be accommodated within the width H of the substrate  12  (or antenna apparatus  10 ). Details of the bent units  14 - 1   b  and  14 - 2   b  are described below. 
         [0063]    The feed points (or feed units)  16 - 1  and  16 - 2  are respectively arranged on the substrate  12  so as to be in contact with the fixed units  14 - 1   a  and  14 - 2   a  between the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2  and the ground pattern  15 . The feed points  16 - 1  and  16 - 2  are connected to a power supply or similar via a feed line (for example a coaxial cable, stripline, or similar), and feed a current or voltage to the antenna elements  14 - 1  and  14 - 2 . 
         [0064]    The stubs  18 - 1  and  18 - 2  are for example conductive wiring patterns, and are distributed constant lines in a high-frequency circuit. As illustrated in  FIG. 2A , the stubs  18 - 1  and  18 - 2  have meander units (or meander lines, or first and second meander units)  18 - 1   a  and  18 - 2   a.    
         [0065]    The meander units  18 - 1   a  and  18 - 2   a  are formed such that the copper layer  13  is bent alternately in concave or in convex shapes. The length in the y-axis direction (or the long-side direction) of the meander units  18 - 1   a  and  18 - 2   a  is “h” in the example of  FIG. 2  and similar. Further, the meander units  18 - 1   a  and  18 - 2   a  are connected to the ground pattern  15  in the connection units  18 - 1   b  and  18 - 2   b , and are formed to the tip units  18 - 1   c  and  18 - 2   c . The tip units  18 - 1   c  and  18 - 2   c  are mutually separated, and are also separated from the ground pattern  15 . The meander units  18 - 1   a  and  18 - 2   a  closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2  are at a distance in the x-axis direction from the fixed units  14 - 1   a  and  14 - 2   a  which is equal to or less than a threshold value href. 
         [0066]    As illustrated in  FIG. 1  and  FIG. 2A , in the antenna apparatus  10  are further arranged slits  21 - 1  and  21 - 2  (or, first and second slits  21 - 1  and  21 - 2 ) in a portion of the ground pattern  15 . By means of the slits  21 - 1  and  21 - 2 , the coupling between the antenna elements  14 - 1  and  14 - 2  and other characteristics are further improved. 
         [0067]    In this way, the antenna apparatus  10  has, as two sets one set of a first antenna element  14 - 1 , first feed point  16 - 1 , and first stub  18 - 1 , and one set of a second antenna element  14 - 2 , second feed point  16 - 2  and second stub  18 - 2 . 
         [0068]    The inventor of this application performed various simulations for such an antenna apparatus  10 . The results of simulations of the antenna apparatus  10  are explained below.  FIG. 3  through  FIG. 12B  illustrate examples of simulation results and similar. 
         [0069]    Of these,  FIG. 3  illustrates an example of simulation results for the parameter S 11  (or the “reflection coefficient” or “matching”) among the S parameters. 
         [0070]    In the simulations illustrated in  FIG. 3 , for example an AC voltage is applied from the first feed point  16 - 1  in the antenna apparatus  10  of  FIG. 1  and similar. These simulation results were obtained by measuring this voltage and the voltage reflected at the first feed point  16 - 1  (or the first antenna element  14 - 1 ) at this time, when the frequency of the AC voltage is varied. The voltage supply is for example between the ground pattern  15  and the first feed point  16 - 1 . In  FIG. 3 , the horizontal-axis indicates the frequency, and the vertical axis indicates the parameter S 11  (in decibels); dashed lines and solid lines are simulation results for an antenna apparatus  10  without stubs  18 - 1  and  18 - 2  and for an antenna apparatus  10  with stubs  18 - 1  and  18 - 2 , respectively. 
         [0071]    As illustrated in  FIG. 3 , simulation results were obtained indicating that for frequencies from “1.7 GHz” to “2.5 GHz”, the parameter S 11  was lower for the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  than for the antenna apparatus  10  without stubs  18 - 1  and  18 - 2 . Hence compared with the case without stubs  18 - 1  and  18 - 2 , the antenna apparatus  10  having the stubs  18 - 1  and  18 - 2  has lower reflected voltage, and the parameter S 11  can be improved, over this frequency range. From these simulation results, when for example the frequency of transmitted or received radio signals is between “1.5 GHz” and “2.5 GHz”, with respect to matching, characteristics for the antenna apparatus  10  equal to or greater than a specific value can be obtained. 
         [0072]      FIG. 4  illustrates an example of simulation results for antenna efficiency. Antenna efficiency represents for example the ratio of radiation power to the power applied to the antenna elements  14 - 1  and  14 - 2 . For example, simulation is performed in which, when an AC voltage is applied to the first feed point  16 - 1 , the frequency of the applied AC voltage is varied, and the power radiated into space in the first antenna element  14 - 1  is measured or otherwise determined. Simulations were performed, in cases in which there is a “single” “antenna element”, in which there are “two antenna elements” “without stubs”, and in which there are “two antenna elements” “with stubs”, with the frequency of the AC voltage varied between “1.7 GHz”, “2.0 GHz”, and “2.3 GHz”. 
         [0073]    As illustrated in  FIG. 4 , simulation results were obtained indicating that the antenna efficiency is higher for an antenna apparatus  10  with stubs  18 - 1  and  18 - 2  than an antenna apparatus  10  without stubs  18 - 1  and  18 - 2  at each frequency, including the frequency “1.7 GHz”. From these simulation results, the antenna efficiency of this antenna apparatus  10  can be raised, compared with that of an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , when the frequency of radio signals transmitted and received by the antenna elements  14 - 1  and  14 - 2  is for example “1.7 GHz”. 
         [0074]      FIG. 5A  and  FIG. 5B  illustrate radiation patterns, and  FIG. 6  illustrates an example of simulation results for correlation factors. 
         [0075]    The radiation pattern illustrated in  FIG. 5A  illustrates, for example, the directional distribution when an AC voltage is applied at frequency “2.2 GHz” to the first feed point  16 - 1  in the antenna apparatus  10 , and no voltage is applied to the second feed point  16 - 2 . Further, the radiation pattern illustrated in  FIG. 5B  illustrates, for example, the directional distribution when an AC voltage is applied at frequency “2.2 GHz” to the second feed point  16 - 2 , and no voltage is applied to the first feed point  16 - 1 . 
         [0076]    When an AC voltage is applied to the first feed point  16 - 1 , a portion with higher power compared with elsewhere is distributed in the W 1  direction, which is in the y axis second quadrant, as illustrated in  FIG. 5A . On the other hand, when an AC voltage is applied to the second feed point  16 - 2 , a portion with higher power compared with elsewhere is distributed in the W 2  direction, which is in the y axis second quadrant, as illustrated in  FIG. 5B . 
         [0077]    In this way, simulation results were obtained indicating that the two radiation patterns are directed in opposite directions (the W 1  direction and the W 2  direction). 
         [0078]      FIG. 6  illustrates simulation results for the correlation factors, based on radiation patterns and similar when the frequency of the applied AC voltage was varied. The correlation factors are an index indicating the extent of coincidence between, for example, the radiation pattern when feeding from the first feed point  16 - 1  (for example,  FIG. 5A ) and the radiation pattern when feeding from the second feed point  16 - 2  (for example,  FIG. 5B ). In  FIG. 6 , the horizontal axis indicates the frequency and the vertical axis indicates the correlation factors; the solid line and the dashed line are simulation results when there are stubs  18 - 1  and  18 - 2 , and when there are no stubs  18 - 1  and  18 - 2 , respectively. 
         [0079]    As illustrated in  FIG. 6 , simulation results were obtained indicating that, compared with the case of no stubs  18 - 1  and  18 - 2 , the correlation factors of the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  is low from “1.5 GHz” to “1.7 GHz”, from “2.2 GHz” to “2.5 GHz”, and similar. Hence improved simulation results for this antenna apparatus  10  could be obtained for the correlation factors as well, compared with an antenna apparatus without stubs  18 - 1  and  18 - 2 , over these frequency ranges. From these simulation results, characteristics relating to correlation equal to or greater than a specific value can be obtained for this antenna apparatus  10  for frequencies of the radio signals transmitted or received from “1.5 GHz” to “1.7 GHz” and for “2.2 GHz” to “2.5 GHz”. 
         [0080]      FIG. 7  illustrates simulation results for the parameter S 21  (or “coupling” or “isolation”) among the S parameters. In these simulations, in for example the antenna apparatus  10  illustrated in  FIG. 1  and similar, an AC voltage is applied from the first feed point  16 - 1  to the first antenna element  14 - 1 , and the frequency of the voltage is varied. At this time, this simulation simulates the parameter S 21  by measuring or otherwise determining this voltage and the voltage output from the second feed point  16 - 2 . The voltage supply is for example between the ground pattern  15  and the first feed point  16 - 1 . In  FIG. 7 , the horizontal axis indicates the frequency and the vertical axis indicates S 21  (in decibels). In the figure, the dashed line and the solid line indicate simulation results for an antenna apparatus  10  with stubs  18 - 1  and  18 - 2  and for an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , respectively. 
         [0081]    As illustrated in  FIG. 7 , the parameter S 21  of the antenna apparatus  10  with stubs  18 - 1  and  18 - 2 , and the parameter S 21  of the antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , both remain at lower numerical values than a reference threshold (for example, “−6 dB”). This reference threshold indicates for example the maximum parameter S 21  which can be allowed with respect to coupling of the antenna elements  14 - 1  and  14 - 2 . As illustrated in  FIG. 7 , the parameter S 21  of the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  remains equal to or below this reference threshold for frequencies from “1.5 GHz” to “2.5 GHz”. 
         [0082]    From these simulation results, characteristics, for example, relating to coupling equal to or greater than a specific value can be obtained for this antenna apparatus  10  for frequencies of the radio signals transmitted and received by the antenna elements  14 - 1  and  14 - 2  from “1.5 GHz” to “2.5 GHz”. 
         [0083]    Simulation results for the stubs  18 - 1  and  18 - 2  illustrated in  FIG. 1  and similar are further explained below.  FIG. 8  through  FIG. 11B  illustrate examples and similar of simulation results. 
         [0084]      FIG. 8  is a partial enlarged view of an antenna apparatus  10  for simulation. In order to simulate the characteristics of the stubs  18 - 1  and  18 - 2 , the first feed point  16 - 1  is arranged at the first connection unit  18 - 1   b.    
         [0085]      FIG. 9  illustrates an example of current distribution when an AC voltage is applied from the first feed point  16 - 1 . The figure illustrates an example of simulation results when the frequency of the AC voltage is “1.4 GHz”; the sizes and thicknesses of arrows indicate the current magnitude. 
         [0086]    As illustrated in  FIG. 9 , because feeding is from the first feed point  16 - 1 , a large current flows at the first stub  18 - 1  compared with the second stub  18 - 2  and similar. In this antenna apparatus  10 , by shaping the stubs  18 - 1  and  18 - 2  as illustrated in  FIG. 1  and similar, simulation results were obtained in which a large current flows at an AC voltage frequency of “1.4 GHz” compared with at other frequencies. Next, the reason for the flowing of a large current at frequency “1.4 GHz” is explained. 
         [0087]      FIG. 10A  illustrates simulation results for the parameter S 11  in the first antenna element  14 - 1  in the antenna apparatus  10  illustrated in  FIG. 8 , when an AC voltage is fed from the first feed point  16 - 1 . Further,  FIG. 10B  illustrates simulation results for the imaginary part of the combined impedance (reactance) of the stubs  18 - 1  and  18 - 2 .  FIG. 10A  and  FIG. 10B  are both simulation results when the frequency of the fed AC voltage is varied from “0.5 GHz” to “2.5 GHz”. 
         [0088]    As illustrated in  FIG. 10A , simulation results were obtained in which the parameter S 11  is much lower at the frequency “1.4 GHz” compared with at other frequencies. Further, as illustrated in  FIG. 10B , simulation results were obtained in which the reactance was “0” at frequency “1.4 GHz”. 
         [0089]    From this, by making the stub shape as in  FIG. 2  and  FIG. 8 , the stubs  18 - 1  and  18 - 2  enter a parallel resonance state at frequency “1.4 GHz”. Because of this state, simulation results could be obtained in which a large current equal to or greater than a specific value flows when the frequency of the AC voltage fed from the first feed point  16 - 1  is “1.4 GHz”, as illustrated in  FIG. 9 . 
         [0090]    As explained above, relating to matching (parameter S 11 ), improved simulation results were obtained for this antenna apparatus  10  (for example,  FIG. 3  and similar); next, the reason for this improvement is explained. 
         [0091]      FIG. 11  is a Smith chart illustrating an example of impedance changes in each of an antenna apparatus  10  with stubs  18 - 1  and  18 - 2 , an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , and an antenna apparatus  10  having a meander line without folds. 
         [0092]    As the antenna apparatus  10  having stubs  18 - 1  and  18 - 2  which was to be simulated, for example the antenna apparatus  10  of  FIG. 8  was selected. This selection was made in order to confirm the characteristics of the stubs  18 - 1  and  18 - 2  similarly to the above-described examples. 
         [0093]    Further,  FIG. 12A  is a configuration example of an antenna apparatus  10  without stubs  18 - 1  and  18 - 2  which is to be simulated, and  FIG. 12B  is a configuration example of an antenna apparatus  10  having a meander line without folds which is to be simulated. As illustrated in  FIG. 12B , an antenna apparatus  10  having a meander line without folds has, for example, a structure with a straight-line shape in which the meander units  18 - 11   a  and  18 - 21   a  closest to the antenna elements  14 - 1  and  14 - 2  are not folded. 
         [0094]    In these simulations, for example an AC voltage is applied from the first feed point  16 - 1  of the antenna apparatus  10 , and the change in impedance of the first antenna element  14 - 1  when the frequency of the AC voltage is varied from “1.5 GHz” to “2.5 GHz” is measured. The horizontal axis in  FIG. 11  indicates the real part of the impedance (or the pure resistance), the upper half of the vertical axis indicates the inductive region, and the lower half indicates the capacitive region. In  FIG. 11 , the solid line and the dashed line are simulation results for the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  (for example,  FIG. 8 ) and for the antenna apparatus  10  without stubs  18 - 1  and  18 - 2  (for example,  FIG. 12A ), respectively. The dot-dash line indicates simulation results for the antenna apparatus  10  having a meander line without folds (for example,  FIG. 12B ). 
         [0095]    As illustrated in  FIG. 11 , the simulation results for the antenna apparatus  10  without stubs  18 - 1  and  18 - 2  (“no stubs”) indicate that the pure resistance remains at the position farthest from point “1” compared with the others. Next, the pure resistance for the antenna apparatus  10  having a meander line without folds (“stub having a meander line without folds”) remains at a position far from point “1”. The simulation results for the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  (“with stubs”) indicate that the pure resistance is closest to “1”. 
         [0096]    From these simulation results, the pure resistance for the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  is closest to “1” compared with others, so that the best matching is possible. Hence as illustrated in  FIG. 3 , simulation results can be obtained for the antenna apparatus  10  having two stubs  18 - 1  and  18 - 2  with lower reflection coefficient and lower parameter S 11  than an antenna apparatus without stubs  18 - 1  and  18 - 2 . 
         [0097]    As illustrated in  FIG. 2  and similar, it is known that by providing a metal surface in proximity to the antenna elements  14 - 1  and  14 - 2  (for example, within a distance href), the radiation resistance and similar assume low values equal to or less than a specific value, and the graph on a Smith chart moves in the W 3  direction in  FIG. 11 . In this antenna apparatus  10  also, the meander units  18 - 1   a  and  18 - 2   a  of the stubs  18 - 1  and  18 - 2  are installed in proximity to the antenna elements  14 - 1  and  14 - 2  (within threshold value href), so that the radiation resistance is a low value equal to or less than a specific value, and matching and similar are also improved. 
         [0098]    In this way, the antenna apparatus  10  of this first example is provided with first and second stubs  18 - 1  and  18 - 2  between the antenna elements  14 - 1  and  14 - 2 , and with the first stub  18 - 1  and first feed point  16 - 1 , and the first antenna element  14 - 1  as one set, has two sets. By means of such a configuration, characteristics equal to or above specific values for matching, coupling, and correlation factors can be obtained for antenna apparatus  10  when the frequency of radio signals transmitted or received is “1.7 GHz”, or is from “2.2 GHz” to “2.5 GHz”. 
         [0099]    Further, because this antenna apparatus  10  does not have cutouts, slits or similar of size equal to or greater than a specific value as indicated in Japanese Laid-open Patent Publication No. 2007-13643 or in Japanese Laid-open Patent Publication No. 2007-243455, greater compactness or reduced space usage can be achieved for this antenna apparatus  10 . Moreover, the stubs  18 - 1  and  18 - 2  are not directly connected to the antenna elements  14 - 1  and  14 - 2 , but one end thereof is directly connected to the ground pattern  15 . Hence a separate matching circuit or similar need not be provided, without changing the characteristics of the antenna elements  14 - 1  and  14 - 2 . Hence this antenna apparatus  10  can attain cost reductions and similar. 
       Second Example 
       [0100]    Next a second example is explained. In the first example, an explanation was given in which the lengths (or heights) in the y-axis direction of the meander units  18 - 1   a  and  18 - 2   a  in the stubs  18 - 1  and  18 - 2  were the same. For example, the lengths may be made short compared with others at places closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2 , and may be made longer in moving from the antenna elements  14 - 1  and  14 - 2 . By this means, the length from the connection units  18 - 1   b  and  18 - 2   b  of the stubs  18 - 1  and  18 - 2  to the tip units  18 - 1   c  and  18 - 2   c  can be shortened. 
         [0101]      FIG. 13  is a partial enlarged view of this antenna apparatus  10 . In the example illustrated in  FIG. 13 , the height in the y-axis direction of the meander units  18 - 11   a  and  18 - 21   a  closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2  is “h 1 ”, and the height in the y-axis direction of the meander units  18 - 1   a  and  18 - 2   a  near the middle is “h 2 ” (h 1 &lt;h 2 ). The height of the meander units  18 - 13   a  and  18 - 23   a  farthest from the fixed units  14 - 1   a  and  14 - 2   a  is “h” (h 2 &lt;h). 
         [0102]    Next, simulation results for an antenna apparatus  10  configured in this way are explained.  FIG. 14  illustrates an example of simulation results for the parameters S 11  (or “matching”) and S 21  (or “coupling”). Similarly to the first example,  FIG. 14  describes simulations in which an AC voltage is fed from the first feed point  16 - 1  for example, and the radiation voltage from the first feed point  16 - 1  is measured, or the output voltage from the second feed point  16 - 2  is measured, or similar. In  FIG. 14 , the solid and dashed lines indicate simulations of the parameter S 11  and of the parameter S 21  respectively. 
         [0103]    As illustrated in  FIG. 14 , the two parameters S 11  and S 21  both remain at low numerical values equal to or less than the reference threshold “−6 dB”, similarly to the first example, at frequencies of “1.7 GHz” or higher. Further, simulation results were obtained in which the two parameters S 11  and S 21  were much lower at the frequency “1.7 GHz” than at other frequencies. 
         [0104]      FIG. 15A  illustrates simulation results for parameter S 11 , compared with an antenna apparatus  10  without stubs  18 - 1  and  18 - 2  (for example,  FIG. 12A ). Further,  FIG. 15B  illustrates simulation results for parameter S 21 , compared with an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 . In  FIG. 15A  and  FIG. 15B , the graphs indicated as “with stubs” are the same as the respective graphs “S 11 ” and “S 21 ” in  FIG. 14 . 
         [0105]    As illustrated in  FIG. 15A , simulation results were obtained for this antenna apparatus  10  (for example,  FIG. 13 ) indicating, for the parameter S 11 , a low value compared with an antenna apparatus without stubs  18 - 1  and  18 - 2  at frequencies equal to or above “1.7 GHz”. Further, as illustrated in  FIG. 15B , simulation results for the parameter S 21  were obtained indicating that the value at frequency “1.7 GHz” is much lower for an antenna apparatus  10  with stubs  18 - 1  and  18 - 2  than for an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 . 
         [0106]    From these simulation results, characteristics can be obtained for matching and coupling of the antenna apparatus  10  of the second example which, when the frequency of radio signals transmitted or received is “1.7 GHz” or higher, are on average a specific value, or are equal to or greater than a specific value. 
         [0107]      FIG. 16  illustrates an example of simulation results for correlation factors. Similarly to the first example,  FIG. 16  illustrates simulation results for the degree of coincidence between the radiation pattern when feeding is performed from the first feed point  16 - 1  and the radiation pattern when feeding is performed from the second feed point  16 - 2 , when the frequency of the AC current fed was varied. 
         [0108]    As illustrated in  FIG. 16 , results were obtained indicating that the correlation factors for the antenna apparatus  10  of the second example is low, compared with an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , at frequencies of “1.7 GHz” or higher. 
         [0109]    With respect to antenna efficiency also, similarly to the first example, simulation results indicated that at frequency “1.7 GHz” a numerical value of “−1.45 dB” was obtained. In the case of “two antenna elements with no stubs” of  FIG. 4 , at frequency “1.7 GHz” the value was “−1.59 dB”; compared with this, simulation results indicated a high antenna efficiency for this antenna apparatus  10 . Simulation results obtained for the antenna efficiency of the antenna apparatus  10  of this second example were further improved over the antenna apparatus  10  of the first example. 
         [0110]    From simulation results for the correlation factors and antenna efficiency, characteristics for the coupling and antenna efficiency of the antenna apparatus  10  of the second example equal to or greater than a specific value could be obtained when the frequency of radio signals transmitted or received was “1.7 GHz” or above. 
         [0111]    Next, the reason for this improvement in the antenna efficiency and coupling is explained.  FIG. 17A  and  FIG. 17B  each illustrate simulation results for current distribution when the frequency of the AC voltage fed is “1.7 GHz”.  FIG. 17A  is the current distribution for an antenna apparatus  10  without stubs  18 - 1  and  18 - 2 , and  FIG. 17B  is the current distribution for the antenna apparatus  10  of this second example. These simulations, similar to those of the first example ( FIG. 9 ), are for a case in which feeding is performed from the first feed point  16 - 1 , and no feeding from the second feed point  16 - 2  is performed. In both  FIG. 17A  and  FIG. 17B , the magnitudes of arrows indicate the strength of the current. 
         [0112]    Focusing on the second antenna element  14 - 2  which is not being fed, a larger current is flowing in the antenna apparatus  10  without stubs  18 - 1  and  18 - 2  ( FIG. 17A ) than in the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  ( FIG. 17B ). Due to this large current, coupling of the second antenna element  14 - 2  and the first antenna element  14 - 1  of the antenna apparatus  10  without stubs  18 - 1  and  18 - 2  becomes equal to or larger than a specific value. Further, due to this large current, the antenna efficiency of the antenna apparatus  10  without stubs  18 - 1  and  18 - 2  deteriorates to be equal to or less than a specific value, as electric power (or energy) equal to or greater than a specific value is consumed at the second feed point  16 - 2 . 
         [0113]    On the other hand, in the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  ( FIG. 17B ), a large current equal to or greater than a specific value flows in the stubs  18 - 1  and  18 - 2 , and in the second antenna element  14 - 2  not being fed, a small current compared with that with stubs  18 - 1  and  18 - 2  flows. Due to this small current, coupling between the first and second antenna elements  14 - 1  and  14 - 2  in the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  weakens to be equal to or less than a specific value. Further, due to this small current, in the antenna apparatus  10  with stubs  18 - 1  and  18 - 2  the electric power consumed at the second feed point  16 - 2  becomes equal to or less than a specific value, and the antenna efficiency is improved to be equal to or greater than a specific value. 
         [0114]    From the above, characteristics equal to or greater than a specific value for matching, coupling, and correlation factors can be obtained for the antenna apparatus  10  of this second example when the frequency of radio signals transmitted or received is for example from “1.7 GHz” to “2.5 GHz”. Further, similarly to the first example, costs can be reduced for the antenna apparatus  10  of this second example, without providing a separate matching circuit or similar to obtain satisfactory characteristics for the antenna elements  14 - 1  and  14 - 2 . Moreover, because the antenna apparatus  10  of this second example does not have cutouts, slits or similar of size equal to or greater than a specific value as indicated in Japanese Laid-open Patent Publication No. 2007-13643 or in Japanese Laid-open Patent Publication No. 2007-243455, greater compactness or reduced space usage can be achieved. 
         [0115]    As illustrated in  FIG. 14 ,  FIG. 17  and similar, when the frequency of the fed AC voltage is “1.7 GHz”, the stubs  18 - 1  and  18 - 2  are in a resonant state. Hence as illustrated in  FIG. 17B , the current flowing in the stubs  18 - 1  and  18 - 2  is a large current equal to or greater than a specific value. The length of the stubs  18 - 1  and  18 - 2  of the antenna apparatus  10  in the second example is shorter than the length of the stubs  18 - 1  and  18 - 2  in the first example. In this way, by adjusting the lengths of the stubs  18 - 1  and  18 - 2 , the resonance frequency could be adjusted from the “1.4 GHz” of the first example to the “1.7 GHz” of the second example. From this, by adjusting the length of the stubs  18 - 1  and  18 - 2 , it is also possible to change the frequency band in which characteristics relating to coupling, correlation factors and similar which are equal to or greater than a specific value can be obtained. 
       Third Example 
       [0116]    Next, a third example is explained. In the antenna apparatus  10  of the second example, the length in the y-axis direction of the meander units  18 - 1   a  and  18 - 2   a  was made longer with increasing distance from the antenna elements  14 - 1  and  14 - 2 . For example, the length in the y-axis direction of the meander units  18 - 11   a  and  18 - 21   a  closest to the antenna elements  14 - 1  and  14 - 2  can be made longer than the length of the meander units  18 - 12   a  and  18 - 22   a  with the shortest length in the y-axis direction. 
         [0117]      FIG. 18  is a partial enlarged view of the antenna apparatus  10  of the third example. As illustrated in  FIG. 18 , of the meander units  18 - 1   a  and  18 - 2   a , the length in the y-axis direction of the meander units  18 - 11   a  and  18 - 21   a  closest to the antenna elements  14 - 1  and  14 - 2  is made “h′”. At this time, if the length in the y-axis direction of the meander units  18 - 12   a  and  18 - 22   a  which have the shortest length in the y-axis direction is “h 1 ”, then the meander units  18 - 11   a  and  18 - 21   a  are installed such that h′&gt;h 1 . In the example of  FIG. 18 , the length h′ is the same length as the length “h” of the stubs  18 - 13   a  and  18 - 23   a  with the longest length in the y-axis direction. Other than the meander units  18 - 11   a  and  18 - 21   a  closest to the antenna elements  14 - 1  and  14 - 2 , meander units are arranged such that the length in the y-axis direction increases with increasing distance from the antenna elements  14 - 1  and  14 - 2 . 
         [0118]    Simulation results for the antenna apparatus  10  in this third example are explained.  FIG. 19A  illustrates examples of simulation results for the parameter S 11  (matching) and the parameter S 21  (coupling). For example, similarly to the first example and similar, simulations were performed in which an AC voltage with different frequencies was fed to the first feed point  16 - 1 , and the reflected voltage of the first feed point  16 - 1  or the output voltage from the second feed point  16 - 2  was measured or otherwise determined. 
         [0119]    As illustrated in  FIG. 19A , simulation results were obtained in which the two parameters S 11  and S 21  were less than a reference threshold “−6 dB” over frequencies from “1.6 GHz” to “2.5 GHz”. 
         [0120]      FIG. 19B  illustrates an example of simulation results for the correlation factors. Similarly to the first example and similar, simulations were performed based on the radiation pattern when feeding to the first feed point  16 - 1  and the radiation pattern when feeding to the second feed point  16 - 2 . 
         [0121]    As illustrated in  FIG. 19B , the correlation factors of the antenna apparatus  10  with stubs  18 - 1  and  18 - 2 , illustrated in  FIG. 18 , also remains at a lower numerical value than an antenna apparatus without stubs  18 - 1  and  18 - 2  at frequencies from “1.6 GHz” to “2.5 GHz”. 
         [0122]    From the above simulation results, characters for matching, coupling, and correlation factors of the antenna apparatus  10  of the third example equal to or greater than a specific value can be obtained when the frequency of radio signals transmitted or received is from “1.6 GHz” to “2.5 GHz”. 
         [0123]    Characteristics equal to or above a specific value could be obtained for the antenna apparatus  10  of the second example at frequencies of “1.7 GHz” or above; but in the antenna apparatus  10  of this third example, by further adjusting the lengths of the stubs  18 - 1  and  18 - 2 , characteristics equal to or greater than a specific value can be obtained for radio signals in a still broader band. 
         [0124]      FIG. 20  illustrates an example of simulation results for current distribution in this antenna apparatus  10 . This simulation is also an example of current distribution for a case in which, similarly to the second example, an AC voltage having a frequency of “1.7 GHz” is applied from the first feed point  16 - 1 . 
         [0125]    Upon comparison with  FIG. 17A  illustrating an example of simulation of current distribution without stubs  18 - 1  and  18 - 2 , in the example of  FIG. 20  a small current is flowing in the second antenna element  14 - 2  on the side not being fed. Similarly to the second example, because of this small current, coupling between the two antenna elements  14 - 1  and  14 - 2  is less than a specific value, and the antenna efficiency is also improved to be equal to or greater than a specific value. 
         [0126]    The antenna efficiency of the antenna apparatus  10  in this third example is “−1.29 dB”, so that a still higher numerical value than in the first example and similar was obtained. 
         [0127]    Similarly to the first example and similar, a matching circuit for the antenna elements  14 - 1  and  14 - 2  is not provided in the antenna apparatus  10  in this third example, so that cost reductions and similar are also possible. Further, similarly to the first example and similar, because the antenna apparatus  10  of this third example does not have cutouts, slits or similar of size equal to or greater than a specific value as indicated in Japanese Laid-open Patent Publication No. 2007-13643 or in Japanese Laid-open Patent Publication No. 2007-243455, reduced space usage and greater compactness can be achieved. 
       Fourth Example 
       [0128]    Next, a fourth example is explained. The fourth example is an example of a case in which the antenna apparatus  10  of the first example or similar is loaded into or accommodated within a personal computer or other radio terminal apparatus  100 . 
         [0129]      FIG. 21A  is a perspective view of a case in which the antenna apparatus  10  is loaded into a radio terminal apparatus  100  or similar,  FIG. 21B  is a cross-sectional view as seen from the Cy direction of the radio terminal apparatus  100  illustrated in  FIG. 21A , and  FIG. 21C  is a cross-sectional view as seen from the Cx direction of the radio terminal apparatus  100 . 
         [0130]    As illustrated in  FIG. 21A  and similar, the radio terminal apparatus  100  have a conductor (for example, a metal flat plate)  102 , with length “H′” in the x-axis direction, length “V” in the y-axis direction, and length (thickness) “d 3 ” in the z-axis direction. The conductor  102  forms a ground pattern for the antenna elements  14 - 1  and  14 - 2  of the antenna apparatus  10 . 
         [0131]    The length (thickness) in the z-axis direction of the antenna apparatus  10  is the same “d 3 ” as the conductor  102 , and as indicated by the dot-dash line in  FIG. 21A , the antenna apparatus  10  is loaded onto a portion of the conductor  102  or similar. 
         [0132]    When the antenna apparatus  10  is loaded into the radio terminal apparatus  10  or similar, the antenna elements  14 - 1  and  14 - 2  of the antenna apparatus  10  protrude by a distance “a” from the conductor  102 . Further, the antenna elements  14 - 1  and  14 - 2  are installed at an interval a distance “d” in the x-axis direction. The antenna elements  14 - 1  and  14 - 2  also are configured from conductors. 
         [0133]    The feed points  16 - 1  and  16 - 2  in the antenna apparatus  10  are arranged at the connection points of the antenna elements  14 - 1  and  14 - 2  respectively with the conductor  102 . 
         [0134]    Similarly to the first example and similar, the antenna apparatus  10  of this fourth example has two stubs  18 - 1  and  18 - 2 ; but as illustrated in  FIG. 21A  and similar, the stubs  18 - 1  and  18 - 2  are arranged to as to extend in the z-axis direction a distance “b” (for example, b&lt;a) from the conductor  102 . The interval “d′” between the first and second stubs  18 - 1  and  18 - 2  is for example shorter than the interval “d” between the antenna elements  14 - 1  and  14 - 2 . In this way, the stubs  18 - 1  and  18 - 2  may be installed so as to extend a prescribed length within a plane (for example, within the yz plane) perpendicular to the xy plane in which the ground pattern  15  is formed. 
         [0135]    Simulation results for a radio terminal apparatus  100  including such an antenna apparatus  10  are explained below.  FIG. 22A ,  FIG. 22B , and  FIG. 23  respectively illustrate examples of simulation results for the parameter S 11 , the parameter S 21 , and the correlation factors. 
         [0136]    Similarly to the first example and similar, in these simulations, for example an AC voltage with different frequencies is applied from the first feed point  16 - 1 , and the reflected voltage from the first feed point  16 - 1  is measured, or the output voltage from the second feed point  16 - 2  is measured or otherwise determined. All simulations were performed for a radio terminal apparatus  100  including an antenna apparatus  10  with stubs  18 - 1  and  18 - 2  as illustrated in  FIG. 21A  and similar, and for a radio terminal apparatus  100  without stubs  18 - 1  and  18 - 2 . 
         [0137]    As illustrated in  FIG. 22A , upon comparing the radio terminal apparatus  100  with stubs  18 - 1  and  18 - 2  with the radio terminal apparatus  100  without stubs  18 - 1  and  18 - 2  with respect to the parameter S 11 , the value remains substantially the same numerical value for frequencies from “600 MHz” to “750 MHz”. However, at frequencies of “750 MHz” and above, the value is a lower numerical value for the case with stubs  18 - 1  and  18 - 2  than for the case without stubs. 
         [0138]    Further, with respect to the parameter S 21 , as illustrated in  FIG. 22B , simulation results were obtained indicating that on average the value remains same numerical value for both the radio terminal apparatus  100  with stubs  18 - 1  and  18 - 2  and for the radio terminal apparatus without stubs  18 - 1  and  18 - 2  for frequencies from “600 MHz” to “1 GHz”. 
         [0139]    With respect to the correlation factors, as illustrated in  FIG. 23 , simulation results were obtained indicating that while there is some degradation at frequency “850 MHz”, the value is lower at frequencies from “700 MHz” to “900 MHz” compared with the radio terminal apparatus  100  without stubs  18 - 1  and  18 - 2 . 
         [0140]    From the above, characteristics can be obtained for matching, coupling and correlation factors of the radio terminal apparatus  100  illustrated in  FIG. 21  which, when the frequency of radio signals transmitted or received is from “700 MHz” to “900 MHz”, are on average a specific value, or are equal to or greater than a specific value. 
         [0141]    Further, similarly to the first example, costs can be reduced for the antenna apparatus  10  of the fourth example, without providing a separate matching circuit or similar to obtain satisfactory characteristics for the antenna elements  14 - 1  and  14 - 2 . Moreover, because similarly to the first example and similar the antenna apparatus  10  does not have cutouts, slits or similar of size equal to or greater than a specific value as indicated in Japanese Laid-open Patent Publication No. 2007-13643 or in Japanese Laid-open Patent Publication No. 2007-243455, reduced space usage and greater compactness can be achieved. 
       Fifth Example 
       [0142]    Next, a fifth example is explained. In the first example and similar, an antenna apparatus  10  having two stubs  18 - 1  and  18 - 2  was explained. An antenna apparatus  10  may have for example three or more stubs. This fifth example is an example of an antenna apparatus  10  which likewise has three or more stubs. 
         [0143]      FIG. 24  is a perspective view of the antenna apparatus  10  of the fifth example;  FIG. 25A  is a partial enlarged view.  FIG. 25B  is a cross-sectional view seen from the Cy direction upon sectioning the antenna apparatus  10  at line segment P-P′ in  FIG. 25A , and  FIG. 25C  is a cross-sectional view seen from the Cy direction upon sectioning at line segment Q-Q′. 
         [0144]    This antenna apparatus  10  also has third through sixth stubs  18 - 3  through  18 - 6 , as illustrated in  FIG. 24  and similar. 
         [0145]    As illustrated in  FIG. 24  and similar, the third and fourth stubs  18 - 3  and  18 - 4  are each provided so as to extend a prescribed length in the z-axis direction from the end units G 1  and G 2  of the ground pattern  15  closest to the feed points  16 - 1  and  16 - 2 . 
         [0146]    Further, the fifth and sixth stubs  18 - 5  and  18 - 6  similarly are each provided so as to extend a prescribed length in the x-axis direction from the end units G 1  and G 2  of the ground pattern  15 . 
         [0147]    The third through sixth stubs  18 - 3  to  18 - 6 , similarly to the first and second stubs  18 - 1  and  18 - 2 , are also configured using for example the copper layer  13 . Further, the length in the x-axis direction and the length in the y-axis direction of the third and fourth stubs  18 - 3  and  18 - 4  can for example be made the same “d 2 ” as the copper layer  13 . Further, the length in the z-axis direction of the fifth and sixth stubs  18 - 5  and  18 - 6  can also for example be made “d 2 ”. 
         [0148]    The first and second stubs  18 - 1  and  18 - 2  are connected to the ground pattern  15  at the connection units  18 - 1   b  and  18 - 2   b , similarly to the first example and similar. As illustrated in  FIG. 25A  and similar, the first stub  18 - 1  extends in a straight-line shape in an oblique direction in the xy plane toward the second bent unit  14 - 2   b  of the second antenna element  14 - 2  with increasing distance from the first antenna element  14 - 1 . Moreover, the second stub  18 - 2  extends in a straight-line shape in an oblique direction in the xy plane toward the first bent unit  14 - 1   b  of the first antenna element  14 - 1  with increasing distance from the second antenna element  14 - 2 . The first and second stubs  18 - 1  and  18 - 2  are provided mutually separated at the farthest tip units  18 - 1   c  and  18 - 2   c  from the connection units  18 - 1   b  and  18 - 2   b.    
         [0149]    The example illustrated in  FIG. 24  and similar is one example, and for example the number of stubs connected to the ground pattern  15  can be four. In this case, if the third and fourth stubs  18 - 3  and  18 - 4 , or the fifth and sixth stubs  18 - 5  and  18 - 6  are deleted, such an antenna apparatus  10  can be configured. Further, by deleting the third stub  18 - 3  and fourth stub  18 - 4 , and the sixth stub  18 - 6 , an antenna apparatus  10  having a total of three stubs  18 - 1 ,  18 - 2 , and  18 - 5  can be obtained. In this way, this antenna apparatus  10  can be made to have an arbitrary number of two or more stubs  18 - 1 ,  18 - 2 , . . . . 
       Sixth Example 
       [0150]    Next, a sixth example is explained. In the sixth example, characteristics are explained when in the above-described first through fifth examples the shapes of the antenna elements  14 - 1  and  14 - 2  are made L-shapes. 
         [0151]      FIG. 26  and  FIG. 27  illustrate examples of the configuration of the antenna apparatus  10  for simulation; of these,  FIG. 26  is an example of the configuration of an antenna apparatus  10  in which the shape of the antenna elements  14 - 1  and  14 - 2  is a straight-line shape, and  FIG. 27  is an example of the configuration of an antenna apparatus  10  in which the shape of the antenna elements  14 - 1  and  14 - 2  explained in the first example and similar is an L-shape. 
         [0152]    The straight-line shape antenna elements  14 - 1  and  14 - 2  have fixed units  14 - 1   a  and  14 - 2   a , and straight-line units  14 - 1   c  and  14 - 2   c  directed in the y-axis direction from the fixed units  14 - 1   a  and  14 - 2   a , as illustrated in  FIG. 26 . 
         [0153]    On the other hand, the L-shape antenna elements  14 - 1  and  14 - 2  have fixed units  14 - 1   a  and  14 - 2   a , and bent units  14 - 1   b  and  14 - 2   b , as illustrated in  FIG. 27  and  FIG. 2A  and similar. 
         [0154]    The shapes of the stubs  18 - 1  and  18 - 2  are both similar to those in the third example; the length in the y-axis direction of the meander units  18 - 11   a  and  18 - 21   a  closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2  are longer than the shortest thereof. Further, the length in the y-axis direction of the meander units  18 - 1   a  and  18 - 2   a  gradually increases with increasing distance from the fixed units  14 - 1   a  and  14 - 2   a.    
         [0155]      FIG. 28A  and  FIG. 28B  respectively illustrate simulation results for parameter S 11  and for parameter S 21 . In both cases, the simulation method is similar to that of the first example or similar. 
         [0156]    As illustrated in  FIG. 28A , with respect to the parameter S 11 , when the frequency of the AC voltage fed from the first feed point  16 - 1  was from “1.9 GHz” to “2.5 GHz”, the numerical value was lower for the L-shape antenna elements  14 - 1  and  14 - 2  than for the straight-line shape antenna elements  14 - 1  and  14 - 2 . Moreover, at frequencies equal to or greater than “1.7 GHz”, the parameter S 11  was equal to or less than the reference threshold “−6 dB”. 
         [0157]    As illustrated in  FIG. 28B , with respect to the parameter S 21 , a lower numerical value was obtained for the L shape than for the straight-line shape at frequencies from “1.5 GHz” to “2.3 GHz”. With respect to coupling, simulation results could be obtained indicating the L-shape was more improved over the straight-line shape than matching over a broad frequency band. Further, the parameter S 21  remained at a numerical value equal to or less than the reference threshold “−6 dB” from “1.5 GHz” to “2.5 GHz”. 
         [0158]    Hence characteristics for the antenna apparatus  10  including L-shape antenna elements  14 - 1  and  14 - 2  could be obtained for matching which, when the frequency of radio signals transmitted or received is from “1.7 GHz” to “2.5 GHz”, are on average a specific value, or are equal to or greater than a specific value. Further, characteristics for the antenna apparatus  10  including L-shape antenna elements  14 - 1  and  14 - 2  could be obtained for coupling, when the frequency of radio signals transmitted or received is from “1.5 GHz” to “2.5 GHz”, which are on average a specific value, or are equal to or greater than a specific value. 
       Seventh Example 
       [0159]    Next, a seventh example is explained. The seventh example is an example relating to a radio terminal apparatus  100  including an antenna apparatus  10 . 
         [0160]      FIG. 29A  and  FIG. 29B  are perspective views of the radio terminal apparatus  100 , and illustrate the manner of rotation. The radio terminal apparatus  100  has a housing  103  and antenna units  24 - 1  and  24 - 2 . 
         [0161]    The housing  103  accommodates the antenna apparatus  10  therein. 
         [0162]    The antenna units  24 - 1  and  24 - 2  (or the first antenna unit  24 - 1  and second antenna unit  24 - 2 ) accommodate, among the housing  103 , the bent units  14 - 1   b  and  14 - 2   b  of the antenna elements  14 - 1  and  14 - 2 . The antenna units  24 - 1  and  24 - 2  can rotate in the W 4  direction and the W 5  direction about the y 1  axis and the y 2  axis (or the fixed units  14 - 1   a  and  14 - 1   b ) respectively, as illustrated in  FIG. 29A . Further, as illustrated in  FIG. 29B , the antenna units  24 - 1  and  24 - 2  can be housed within the width H 1  of the radio terminal apparatus  100  by rotating. For this reason, the length in the y-axis direction h 3  of the first antenna unit  24 - 1  is longer than the length in the y-axis direction h 4  of the second antenna unit  24 - 2 . Because it is sufficient that the antenna units  24 - 1  and  24 - 2  can be housed within the width H 1 , the length h 4  of the second antenna unit  24 - 2  may be longer than the length h 3  of the first antenna unit  24 - 1 . 
         [0163]      FIG. 30A  and  FIG. 30B  are perspective views of the antenna apparatus  10 , and illustrate the manner of rotation. The bent units  14 - 1   b  and  14 - 2   b  of the antenna elements  14 - 1  and  14 - 2  can rotate in the direction W 4  and the direction W 5  about the y 1  axis and y 2  axis, respectively, accompanying rotation of the antenna units  24 - 1  and  24 - 2 , as illustrated in  FIG. 30A . The bent units  14 - 1   b  and  14 - 2   b  can be housed within the width H of the antenna apparatus  10  by rotation, as illustrated in  FIG. 30B . For this reason, the length h 5  in the y-axis direction of the first fixed unit  14 - 1   a  is longer than the length h 6  in the y-axis direction of the second fixed unit  14 - 2   a . It is sufficient that the bent units  14 - 1   b  and  14 - 2   b  can be housed within the width H, so that the length h 6  in the y-axis direction of the second fixed unit  14 - 2   a  may be longer than the length h 5  of the first fixed unit  14 - 1   a.    
       Eighth Example 
       [0164]    Next, an eighth example is explained. The above-described examples were examples in which the antenna apparatus  10  had two sets, where one set includes a first antenna element  14 - 1 , first feed point  16 - 1 , and first stub  18 - 1 . In addition, the antenna apparatus  10  may have three or more sets. 
         [0165]      FIG. 31  is a perspective view of an antenna apparatus  10  including four sets. The antenna apparatus  10  also has, below a ground pattern in the y-axis direction, antenna elements  14 - 1 ′ and  14 - 2 ′, feed points  16 - 1 ′ and  16 - 2 ′, and stubs  18 - 1 ′ and  18 - 2 ′. 
         [0166]    The antenna elements  14 - 1 ′ and  14 - 2 ′ are also provided to enable rotation about the y 1  axis and y 2  axis respectively. Further, the feed points  16 - 1 ′ and  16 - 2 ′ are also provided on the substrate  12  so as to be in contact with the antenna elements  14 - 1 ′ and  14 - 2 ′. Further, the stubs  18 - 1 ′ and  18 - 2 ′ also have shapes similar to those in the above-described examples. In this case, the antenna aperture  10  includes for example a connector which is connected to the housing of the radio terminal apparatus  100  in the center of the ground pattern  15 , and is loaded into or accommodated within the radio terminal apparatus  100  by this connector. 
         [0167]    The example illustrated in  FIG. 31  has four sets; but by for example deleting the antenna element  14 - 2 ′, feed point  16 - 2 ′, and stub  18 - 2 ′, an antenna apparatus  10  having three sets can be obtained. Further, an antenna element, feed point, and stub can also be provided on a side of the ground pattern  15 , so that an antenna apparatus  10  having five or more sets can be obtained. In this way, this antenna apparatus  10  can be made to have two or more sets of an antenna element, feed point, and stub. 
       Ninth Example 
       [0168]    Next, a ninth example is explained. The ninth example is another example relating to the shape of the stubs  18 - 1  and  18 - 2 .  FIG. 33  is a partial enlarged view of an antenna apparatus  10 . 
         [0169]    As illustrated in  FIG. 33 , the length h in the y-axis direction (or the long-side direction) of the meander units  18 - 11   a  and  18 - 21   a  closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2  is longer than any other meander unit. Further, the length gradually decreases with increasing distance from the antenna elements  14 - 1  and  14 - 2 , and the length h 7  in the y-axis direction of the meander units  18 - 13   a  and  18 - 23   a  farthest from the antenna elements  14 - 1  and  14 - 2  is the shortest compared with the other meander units. In the example of  FIG. 33 , the lengths in the y-axis direction are in the relation h 7 &lt;h 8 &lt;h 9 &lt;h. 
         [0170]      FIG. 34A  illustrates simulation results for the parameters S 11  and S 21  of this antenna apparatus  10 , and  FIG. 34B  illustrates simulation results for the correlation factors. Simulations were performed similarly to those of the first example. 
         [0171]    In  FIG. 34A , the solid line and dashed line illustrate simulation results for the parameter S 11  and the parameter S 21  respectively. Similarly to the first example and similar, if the allowable maximum threshold with respect to matching or coupling of the antenna elements  14 - 1  and  14 - 2  is “−6 dB” (reference threshold), then in  FIG. 34A  the values remain equal to or below this reference threshold at “1.7 GHz” and above. Hence for the antenna apparatus  10  of the ninth example, characteristics equal to or above a specific value can be obtained even when radio signals having a frequency of “1.7 GHz” or above are transmitted or received. 
         [0172]    Further, as illustrated in  FIG. 34B , with respect to the correlation factors also, simulation results were obtained in which the correlation factors was low at frequencies of “1.6 GHz” and above compared with an antenna apparatus  10  without stubs  18 - 1  and  18 - 2  (for example, the dashed line in  FIG. 6 ). Hence for the antenna apparatus  10  of the ninth example, characteristics for correlation equal to or above a specific value could be obtained when the frequency of radio signals for transmission or reception is “1.6 GHz” or higher. 
       Tenth Example 
       [0173]    Next, a tenth example is explained. The tenth example is another example relating to the shape of stubs  18 - 1  and  18 - 2 .  FIG. 35  is a partial enlarged view of an antenna apparatus  10 . 
         [0174]    As illustrated in  FIG. 35 , between the meander units  18 - 11   a  and  18 - 21   a  closest to the fixed units  14 - 1   a  and  14 - 2   a  of the antenna elements  14 - 1  and  14 - 2 , and the farthest meander units  18 - 13   a  and  18 - 23   a , are meander units  18 - 1   a  and  18 - 2   a . The length h in the y-axis direction (or long-side direction) of these meander units  18 - 14   a  and  18 - 24   a  is longer than any other meander unit. In the example of  FIG. 35 , the lengths in the y-axis direction of the meander units  18 - 11   a  and  18 - 21   a  and of the meander units  18 - 13   a  and  18 - 23   a  are the same h 10  (h 10 &lt;h), but the lengths may be different. 
         [0175]      FIG. 36A  and  FIG. 36B  illustrate examples of simulation results for the parameters S 11  and S 21  and for the correlation factors respectively. 
         [0176]    As illustrated in  FIG. 36A , the two parameters S 11  and S 21  remain equal to or below the reference threshold “−6 dB”. Further, results were obtained indicating that both of the two parameters S 11  and S 21  were at extremely low values at frequency “1.7 GHz” compared with at other frequencies. From this, characteristics equal to or greater than a specific value can be obtained for the antenna apparatus  10  of this tenth example even when radio signals of frequency “1.7 GHz” or higher are transmitted or received. Further, more satisfactory characteristics can be obtained for the antenna apparatus  10  of this tenth example when transmitting or receiving radio signals at frequency “1.7 GHz” than at other frequencies. 
         [0177]    Further, as illustrated in  FIG. 36B , with respect to the correlation factors as well, simulation results were obtained indicating low correlation factors at frequencies of “1.7 GHz” and above compared with an antenna apparatus without stubs  18 - 1  and  18 - 2  (for example, the dashed line in  FIG. 6 ). Hence characteristics for correlation equal to or above a specific value can be obtained for the antenna apparatus  10  of the tenth example when the frequency of radio signals to be transmitted or received is “1.7 GHz” or above. 
       Other Examples 
       [0178]    Further, in each of the above-described examples, an antenna apparatus  10  was explained as having a single substrate  12 . An antenna apparatus  10  may have a plurality of substrates  12 . Of these, a certain substrate  12  has for example a ground pattern  15  and antenna elements  14 - 1  and  14 - 2  and similar, as illustrated in  FIG. 1  and similar, and this ground pattern  15  forms a ground for the elements and similar on the other substrates  12 . 
         [0179]    Also, in each of the above-described examples, explanations were given in which antenna elements  14 - 1  and  14 - 2 , feed points  16 - 1  and  16 - 2 , and stubs  18 - 1  and  18 - 2  are arranged on the top surface of a substrate  12 . For example, antenna elements  14 - 1  and  14 - 2  and feed points  16 - 1  and  16 - 2  can be arranged on the top surface of the substrate  12 , and stubs  18 - 1  and  18 - 2  and the ground pattern  15  can be arranged on the bottom surface. 
         [0180]    An antenna apparatus and radio terminal apparatus with reduced space usage or greater compactness can be provided. Further, an antenna apparatus and radio terminal apparatus from which specific characteristics can be obtained can be provided. 
         [0181]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

Technology Category: h