Patent Publication Number: US-6670925-B2

Title: Inverted F-type antenna apparatus and portable radio communication apparatus provided with the inverted F-type antenna apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inverted F-type antenna apparatus and a potable radio communication apparatus provided with the inverted F-type antenna apparatus, and in particular, to an inverted F-type antenna apparatus for portable radio communication apparatuses mainly for mobile communications, such as a portable telephone, and to a portable radio communication apparatus provided with the above-mentioned inverted F-type antenna apparatus. 
     2. Description of the Prior Art 
     In recent years, a mobile communication system using portable radio communication apparatuses, such as a portable telephone, has been rapidly developed. This portable telephone has been changed from the positioning thereof as a conventional audio terminal apparatus to an information terminal apparatus for performing transmission of data and images. In accordance with this, a folding type portable telephone, which is more suitable for increasing the size of the screen, has been widely used. 
     FIG. 31A is a plan view showing a construction of a portable radio communication apparatus  1001 , which is a straight type portable telephone according to a prior art, and FIG. 31B is a plan view schematically showing a construction of a dielectric substrate  1004  provided with an inverted F-type antenna apparatus  1005  of FIG.  31 A. 
     Referring to FIG. 31A, a liquid crystal display section  1003  is provided near the upper side of the center portion of a housing  1002  of the portable radio communication apparatus  1001 , while a dielectric substrate  1004  is provided throughout the entire space inside of the housing  1002 . In this case, the built-in antenna  1005  is arranged above the dielectric substrate  1004 . As shown in FIG. 31B, this built-in antenna  1005  is constructed of a rectangular flat-plate-shaped antenna element  1006 , a columnar pin-shaped short-circuit conductor  1007  for connecting the antenna element  1006  with a grounding conductor (not shown) and a columnar pin-shaped feeding conductor  1008  for connecting the antenna element  1006  with a feeding coaxial cable (not shown) at a feeding point. The built-in antenna  1005  is normally constructed of a low-height small-size inverted F-type antenna apparatus called a planar inverted F antenna (PIFA). This inverted F-type antenna apparatus, which is an unbalanced type antenna, therefore operates as an antenna with a large current flowing through the grounding conductor formed on the rear surface of the dielectric substrate  1004 . In this case, current standing waves are generated when a dimension obtained by adding the length in the direction of the longer side of the grounding conductor to the length in the direction of the shorter side of the grounding conductor is greater than ¼ with respect to the wavelength 1 of the frequency band of the radio wave which is used, and therefore, a wideband characteristic can be obtained. 
     However, in the case of the built-in inverted F-type antenna apparatus of the folding type portable radio communication apparatus, the dimension of the dielectric substrate, i.e., the dimension of the grounding conductor is disadvantageously reduced in comparison with that of the built-in inverted F-type antenna apparatus of the straight type portable radio communication apparatus  1001 . In this case, when the frequency band of the radio wave which is used is comparatively low, the dimension obtained by adding the length in the direction of the longer side of the grounding conductor and the length in the direction of the shorter side of the grounding conductor becomes smaller than ¼ with respect to the wavelength 1 of the frequency band of the radio wave which is used. Consequently, there has been such a problem that the grounding conductor stops contributing to the excitation of the antenna, disadvantageously leading to a narrow-band characteristic. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to solve the aforementioned problems and provide an inverted F-type antenna apparatus which is built in a folding type portable radio communication apparatus, the antenna apparatus being capable of achieving a comparatively wideband characteristic even when the frequency band of the radio wave which is used is comparatively low and the grounding conductor does not contribute to the excitation of the antenna, as well as a portable radio communication apparatus that employs the antenna apparatus. 
     Another object of the present invention is to provide an antenna apparatus which is built in a folding type portable radio communication apparatus, the antenna apparatus being capable of reducing the influence from a human body and reducing the radiation loss of the antenna apparatus, as well as a portable radio communication apparatus that employs the antenna apparatus. 
     In order to achieve the aforementioned objective, according to one aspect of the present invention, there is provided an inverted F-type antenna apparatus including a grounding conductor, an antenna element arranged on the grounding conductor so as to face the grounding conductor, and at least one coupling element provided between the grounding conductor and the antenna element so as to face the grounding conductor and the antenna element. The inverted F-type antenna apparatus further includes first connection means for electrically connecting the antenna element with the grounding conductor at least in one place. 
     In the above-mentioned inverted F-type antenna apparatus, the grounding conductor, the antenna element and the coupling element are arranged so as to be substantially parallel to each other. 
     In the above-mentioned inverted F-type antenna apparatus, the antenna element and the grounding conductor are preferably arranged so that a distance between the antenna element and the grounding conductor in an end portion where the antenna element and the grounding conductor are electrically connected with each other by the first connection means is different from a distance between the antenna element and the grounding conductor in another end portion located opposite to the end portion. 
     In the above-mentioned inverted F-type antenna apparatus, the coupling element is preferably arranged so as to be inclined with respect to the grounding conductor. 
     In the above-mentioned inverted F-type antenna apparatus, the antenna element preferably has a shape curved along a configuration of a housing for accommodating the inverted F-type antenna apparatus. 
     In the above-mentioned inverted F-type antenna apparatus, at least one of the coupling element and the antenna element is preferably provided with a bent portion. 
     In the above-mentioned inverted F-type antenna apparatus, the grounding conductor is preferably provided with a bent portion. 
     In the above-mentioned inverted F-type antenna apparatus, a length of a sum total of lengths of two mutually different sides of the grounding conductor is preferably equal to or smaller than a quarter of a wavelength corresponding to a lowest frequency band among frequency bands which are used by a portable radio communication apparatus that employs the inverted F-type antenna apparatus. 
     The above-mentioned inverted F-type antenna apparatus preferably further includes second connection means for electrically connecting the antenna element with the coupling element at least in one place. 
     In the above-mentioned inverted F-type antenna apparatus, a connecting point of the second connection means is preferably arranged near a connecting point of the first connection means. 
     In the above-mentioned inverted F-type antenna apparatus, dimensions of the antenna element and the coupling element are preferably set so that the connecting point of the second connection means is located substantially in a portion of an anti-node of a current standing wave generated in the antenna element and the coupling element, and the coupling element operates as a quarter-wave length resonator when the inverted F-type antenna apparatus is excited by a radio signal of a predetermined wavelength. 
     In the above-mentioned inverted F-type antenna apparatus, the antenna element and the coupling element are preferably electrically connected with each other by a common feeding conductor. 
     In the above-mentioned inverted F-type antenna apparatus, the antenna element and the coupling element are preferably electrically connected with each other by a common short-circuit conductor. 
     In the above-mentioned inverted F-type antenna apparatus, a resonance frequency of the inverted F-type antenna apparatus is preferably adjusted by forming a slit in the antenna element. 
     In the above-mentioned inverted F-type antenna apparatus, a resonance frequency of the inverted F-type antenna apparatus is preferably adjusted by forming a slit in the coupling element. 
     In the above-mentioned inverted F-type antenna apparatus, a resonance frequency of the inverted F-type antenna apparatus is preferably adjusted by forming a slot in the antenna element. 
     In the above-mentioned inverted F-type antenna apparatus, a resonance frequency of the inverted F-type antenna apparatus is preferably adjusted by forming a slot in the coupling element. 
     In the above-mentioned inverted F-type antenna apparatus, an amount of electromagnetic coupling between the antenna element and the grounding conductor is preferably adjusted by changing an area of at least one of the antenna element and the coupling element. 
     In the above-mentioned inverted F-type antenna apparatus, a dielectric is preferably filled in either one of a part of internal portion and the whole portion of the inverted F-type antenna apparatus. 
     In the above-mentioned inverted F-type antenna apparatus, dimensions of the antenna element and the coupling element are preferably set so that the inverted F-type antenna apparatus resonates in a plurality of frequency bands. 
     According to another aspect of the present invention, there is provided a portable radio communication apparatus including an upper housing, a lower housing, a hinge portion for coupling the upper housing with the lower housing, and the above-mentioned inverted F-type antenna apparatus. In the portable radio communication apparatus, the inverted F-type antenna apparatus is arranged inside of the upper housing. 
     The above-mentioned portable radio communication apparatus preferably further includes a monopole antenna. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings throughout which like parts are designated by like reference numerals, and in which: 
     FIG. 1A is a plan view showing a construction of an inverted F-type antenna apparatus  101  according to a first preferred embodiment of the present invention; 
     FIG. 1B is a longitudinal sectional view taken along the line A-A′ of FIG. 1A; 
     FIG. 2A is a graph showing a frequency characteristic of the reflection coefficient S 11  of a first antenna apparatus in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B; 
     FIG. 2B is a graph showing a frequency characteristic of the reflection coefficient S 11  of a second antenna apparatus in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B; 
     FIG. 2C is a graph showing a frequency characteristic of the reflection coefficient S 11  when the first and second antenna apparatuses are combined with each other in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B; 
     FIG. 3A is a plan view showing a construction of an inverted F-type antenna apparatus  102  according to a second preferred embodiment of the present invention; 
     FIG. 3B is a longitudinal sectional view taken along the line B-B′ of FIG. 3A; 
     FIG. 4 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   a  according to a first modification of the second preferred embodiment of the present invention; 
     FIG. 5 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   b  according to a second modification of the second preferred embodiment of the present invention; 
     FIG. 6 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   c  according to a third modification of the second preferred embodiment of the present invention; 
     FIG. 7 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   d  according to a fourth modification of the second preferred embodiment of the present invention; 
     FIG. 8A is a plan view showing a construction of an inverted F-type antenna apparatus  103  according to a third preferred embodiment of the present invention; 
     FIG. 8B is a longitudinal sectional view taken along the line C-C′ of FIG. 8A; 
     FIG. 9 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   a  according to a first modification of the third preferred embodiment of the present invention; 
     FIG. 10 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   b  according to a second modification of the third preferred embodiment of the present invention; 
     FIG. 11 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   c  according to a third modification modified of the third preferred embodiment of the present invention; 
     FIG. 12 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   d  according to a fourth modification of the third preferred embodiment of the present invention; 
     FIG. 13A is a plan view showing a construction of an inverted F-type antenna apparatus  104  according to a fourth preferred embodiment of the present invention; 
     FIG. 13B is a longitudinal sectional view taken along the line D-D′ of FIG. 13A; 
     FIG. 14A is a plan view showing a construction of an inverted F-type antenna apparatus  105  according to a fifth preferred embodiment of the present invention; 
     FIG. 14B is a longitudinal sectional view taken along the line E-E′ of FIG. 14A; 
     FIG. 15A is a plan view showing a construction of an inverted F-type antenna apparatus  105   a  according to a modification of the fifth preferred embodiment of the present invention; 
     FIG. 15B is a longitudinal sectional view taken along the line F-F′ of FIG. 15A; 
     FIG. 16A is a plan view showing a construction of an inverted F-type antenna apparatus  106  according to a sixth preferred embodiment of the present invention; 
     FIG. 16B is a longitudinal sectional view taken along the line G-G′ of FIG. 16A; 
     FIG. 17A is a plan view showing a construction of an inverted F-type antenna apparatus  106   a  according to a first modification of the sixth preferred embodiment of the present invention; 
     FIG. 17B is a longitudinal sectional view taken along the line H-H′ of FIG. 17A; 
     FIG. 18 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  106   b  according to a second modification of the sixth preferred embodiment of the present invention; 
     FIG. 19 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  106   c  according to a third modification of the sixth preferred embodiment of the present invention; 
     FIG. 20A is a plan view showing a construction of an inverted F-type antenna apparatus  107  according to a seventh preferred embodiment of the present invention; 
     FIG. 20B is a plan view of an antenna element  12   e  of FIG. 20A; 
     FIG. 20C is a plan view of a coupling element  13   e  of FIG. 20A; 
     FIG. 20D is a plan view of a coupling element  14   e  of FIG. 20A; 
     FIG. 21 is a longitudinal sectional view taken along the line I-I′ of FIG. 20A; 
     FIG. 22 is a Smith chart showing a frequency characteristic of the input impedance of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21; 
     FIG. 23 is a graph showing a frequency characteristic of the voltage standing wave radio (VSWR) of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21; 
     FIG. 24 is a plan view showing a construction of an antenna element  12   f  according to a first modification of the seventh preferred embodiment, or a modified preferred embodiment of the antenna element of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21; 
     FIG. 25 is a plan view showing a construction of a coupling element  13   f  according to a second modification of the seventh preferred embodiment, or a modified preferred embodiment of the coupling element of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21; 
     FIG. 26A is a plan view showing a construction of an inverted F-type antenna apparatus  108  according to an eighth preferred embodiment of the present invention; 
     FIG. 26B is a longitudinal sectional view taken along the line J-J′ of FIG. 26A; 
     FIG. 27A is a plan view showing a construction of a portable radio communication apparatus  1101  according to a ninth preferred embodiment of the present invention; 
     FIG. 27B is a side view of FIG. 27A; 
     FIG. 28A is a plan view showing a construction of a portable radio communication apparatus  1101  a according to a modification of the ninth preferred embodiment of the present invention; 
     FIG. 28B is a side view of FIG. 28A; 
     FIG. 29A is a plan view showing a construction of a portable radio communication apparatus  2100  according to a tenth preferred embodiment of the present invention with part removed; 
     FIG. 29B is a side view of FIG. 29A; 
     FIG. 30A is a plan view showing a construction of a built-in antenna apparatus  2200  according to an eleventh preferred embodiment of the present invention; 
     FIG. 30B is a side view showing a construction of the built-in antenna apparatus  2200  of FIG. 30A; 
     FIG. 31A is a plan view showing a construction of a portable radio communication apparatus  1001  according to a prior art; and 
     FIG. 31B is a plan view schematically showing a construction of a dielectric substrate  1004  provided with the inverted F-type antenna apparatus  1005  of FIG.  31 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various preferred embodiments of the present invention will be described below with reference to the drawings. It is to be noted that the same components are denoted by the same reference numerals in the drawings, and no detailed description is provided therefor. 
     First Preferred Embodiment 
     FIG. 1A is a plan view showing a construction of an inverted F-type antenna apparatus  101  according to the first preferred embodiment of the present invention, and FIG. 1B is a longitudinal sectional view taken along the line A-A′ of FIG.  1 A. As shown in FIGS. 1A and 1B, the inverted F-type antenna apparatus  101  according to the present preferred embodiment is characterized in that a coupling element  13  is inserted between a grounding conductor  11  and an antenna element  12  which are arranged so as to be parallel to each other, and the coupling element  13  is electrically connected with the antenna element  12  via a connection conductor  23 . 
     Referring to FIGS. 1A and 1B, the inverted F-type antenna apparatus  101  is provided with a rectangular plate-shaped grounding conductor  11  and a feeding point  25  provided in a predetermined portion of the grounding conductor  11 , and further includes the antenna element  12  constructed of a rectangular plate-shaped conductor, a columnar pin-shaped short-circuit conductor  22 , a columnar pin-shaped feeding conductor  21 , a coupling element  13  constructed of a rectangular plate-shaped conductor and a columnar pin-shaped connection conductor  23 . 
     The antenna element  12  is arranged while being supported by the connection conductor  23 , the short-circuit conductor  22  and the feeding conductor  21  so as to become substantially parallel to the grounding conductor  11  and the coupling element  13 , and the antenna element  12  is electrically connected with the grounding conductor  11  via the short-circuit conductor  22 . One end of the feeding conductor  21  is electrically connected with the antenna element  12 , and another end of the feeding conductor  21  is electrically connected with the feeding point  25  on the grounding conductor  11 . Further, the coupling element  13  is arranged between the grounding conductor  11  and the antenna element  12  so as to become substantially parallel to the grounding conductor  11  and the antenna element  12 , and the coupling element  13  is electrically connected with the antenna element  12  via the connection conductor  23 . In this case, it is important that the connection conductor  23  is arranged in the vicinity of the short-circuit conductor  22  or the feeding conductor  21 . 
     A feeding coaxial cable  30  is constructed of a central conductor  31  and a grounding conductor  32  wound around the central conductor  31  via a dielectric  33 , and the feeding coaxial cable  30  is wired from a radio equipment (not shown) of a portable radio communication apparatus to the feeding point  25  of the inverted F-type antenna apparatus  101 . Although a protective sheathing is formed around the grounding conductor  32  of the feeding coaxial cable  30 , the sheathing is not shown in the drawings. At the feeding point  25 , the central conductor  31  of the feeding coaxial cable  30  is connected with one end of the feeding conductor  21 , while the grounding conductor  32  of the feeding coaxial cable  30  is connected with the grounding conductor  11 . 
     The principle of operation of the inverted F-type antenna apparatus  101  of the present preferred embodiment will be described next. This inverted F-type antenna apparatus  101  has a structure such that the coupling element  13  is inserted between the grounding conductor  11  and the antenna element  12  in a PIFA portion constructed of the antenna element  12 , the short-circuit conductor  22  and the feeding conductor  21 , electrically connecting the antenna element  12  with the coupling element  13  via the connection conductor  23 . It is important that the connection conductor  23  is arranged in the vicinity of a portion where an anti-node of the an current standing wave generated on the antenna element  12  is located when the inverted F-type antenna apparatus  101  is excited with a radio signal of a predetermined wavelength. In other words, it is important that one end of the connection conductor  23  is connected with the antenna element  12  in the vicinity of either the short-circuit conductor  22  or the feeding conductor  21 . With this arrangement, the coupling element  13  has the anti-node of the current standing wave (maximum current point) in the vicinity of the connecting point to the connection conductor  23 , and then, operates as a ¼ resonator where  1  denotes a wavelength of a frequency which is used in the antenna apparatus. In other words, it is preferable to set the lengths of the antenna element  12  and the coupling element  13  so as to operate in a manner as described above. 
     That is, the inverted F-type antenna apparatus  101  has the following first and second antenna apparatus each having a loop circuit: 
     (a) A first antenna apparatus having a first loop circuit whose length is a half-wave length, where the first loop circuit starts from the feeding point  25  via the feeding conductor  21 , the connection conductor  23 , the coupling element  13  to reach the terminal end portion (located on the lower side in FIG. 1B) of the coupling element  13  and further starts therefrom via the coupling element  13 , the connection conductor  23 , a part of the antenna element  12  and the short-circuit conductor  22  to the grounding conductor  11 ; and 
     (b) A second antenna apparatus having a second loop circuit whose length is a half-wave length, where the second loop circuit starts from the feeding point  25  via the feeding conductor  21  and the antenna element  12  to reach the terminal end portion of the antenna element  12  (located on the lower side in FIG. 1B) and further starts therefrom via the antenna element  12  and the short-circuit conductor  22  to the grounding conductor  11 . 
     Therefore, each of the antenna element  12  and the coupling element  13  preferably constitutes a quarter-wavelength resonator at the resonance frequencies of these two first and second antenna apparatuses. 
     The radio signal inputted via the feeding point  25  is mainly radiated from the antenna element  12  and the coupling element  13  via the feeding conductor  21 . At this time, by providing a slight frequency difference between the resonance frequency of the first antenna apparatus and the resonance frequency of the second antenna apparatus, a wideband frequency characteristic can be obtained. 
     In the graph of FIG. 2A, the reference numeral  201  indicates a frequency characteristic curve of a reflection coefficient S 11  of the first antenna apparatus in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B. In the graph of FIG. 2B, the reference numeral  202  indicates a frequency characteristic curve of the reflection coefficient S 11  of the second antenna apparatus in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B. In the graph of FIG. 2C, the reference numeral  203  indicates a frequency characteristic curve of the reflection coefficient S 11  of the combination of the first and second antenna apparatuses in the inverted F-type antenna apparatus  101  of FIGS. 1A and 1B. 
     It is herein considered the case where the frequency characteristic of the first antenna apparatus including the coupling element  13  has a minimum amount of reflection loss at a resonance frequency f 1  as indicated by  201  of FIG.  2 A and the frequency characteristic of the second antenna apparatus including the antenna element  12  has a minimum amount of reflection loss at a resonance frequency f 2  as indicated by  202  of FIG.  2 B. In this case, by adjusting not only the areas of the antenna element  12  and the coupling element  13  but also the distances from the grounding conductor  11  to these elements  12  and  13  so that the resonance frequency f 1  and the resonance frequency f 2  are slightly different from each other, the frequency characteristic of the amount of reflection loss of the present antenna apparatus when being seen from the feeding point  25  has two peaks at the resonance frequency f 1  and resonance frequency f 2 , as indicated by  203  of FIG.  2 C. As a result, with regard to the frequency characteristic of the amount of reflection loss of the whole antenna apparatus, there can be obtained a very wideband frequency characteristic in comparison with the characteristic of each of the antenna apparatuses. 
     Although the coupling element  13  operates as a ¼ resonator according to the above description of the present preferred embodiment, the present invention is not limited to this. It is acceptable to operate the coupling element  13  as a resonator that has a resonance wavelength of any of odd multiples of ¼. It is also acceptable to operate the coupling element  13  as a resonator that has a resonance wavelength of any of even multiples of ¼. Most preferably, the coupling element  13  is operated as a ½ resonator. In this case, it is preferable to connect the connection conductor  23  with the antenna element  12  in a portion of a node (minimum current point) of the current distribution of the antenna element  12 , i.e., at the open end thereof. 
     Furthermore, by filling a region surrounded by the grounding conductor  11  and the antenna element  12  partially or totally with a dielectric, namely, by filling the dielectric in a part of the internal portion or the whole portion of the region, the resonance frequency can be reduced, and the antenna apparatus is allowed to have a small size and a reduced weight with respect to an identical resonance frequency. Moreover, the shape of the antenna apparatus can be stably fixed, and therefore, characteristic variations in mass production can be suppressed. 
     In the aforementioned preferred embodiment, the feeding conductor  21 , the short-circuit conductor  22  and the connection conductor  23  are fixedly supported by pressing and inserting respective end portions thereof into respective holes formed in the grounding conductor  11 , the antenna element  12  and the coupling element  13  so that respective end portions thereof are electrically connected with the grounding conductor  11 , the antenna element  12  and the coupling element  13 , respectively. However, the present invention is not limited to this, and it is acceptable to fixedly support these conductors  21 ,  22  and  23  by soldering these conductors  21 ,  22  and  23  with the grounding conductor  11 , the antenna element  12  and the coupling element  13 . These modified preferred embodiments can be also applied to respective preferred embodiments which will be described later. 
     The feeding conductor  21 , the short-circuit conductor  22  and the connection conductor  23  are formed so as to have a columnar pin-like shape in the above-mentioned preferred embodiment. However, the present invention is not limited to this, and it is acceptable to make them have a rectangular columnar pin-like shape, a rectangular plate-like shape, a strip plate-like shape or the like. These modified preferred embodiments can be also applied to respective preferred embodiments which will be described later. 
     Second Preferred Embodiment 
     FIG. 3A is a plan view showing a construction of an inverted F-type antenna apparatus  102  according to the second preferred embodiment of the present invention, and FIG. 3B is a longitudinal sectional view taken along the line B-B′ of FIG.  3 A. As shown in FIGS. 3A and 3B, the inverted F-type antenna apparatus  102  of the present preferred embodiment is provided with a grounding conductor  11  and a feeding point  25  and further includes an antenna element  12  constructed of a rectangular plate-shaped conductor, a short-circuit conductor  22 , a feeding conductor  21  and a coupling element  13  made of a rectangular plate-shaped conductor. 
     Referring to FIGS. 3A and 3B, the antenna element  12  and the grounding conductor  11  are arranged so as to be substantially parallel to each other and to face each other, and the antenna element  12  is electrically connected with the grounding conductor  11  via the short-circuit conductor  22 . One end of the feeding conductor  21  is electrically connected with the antenna element  12 . Another end of the feeding conductor  21  is connected with the feeding coaxial cable  30  at the feeding point  25  on the grounding conductor  11 , in a manner similar to that of the first preferred embodiment. Moreover, the coupling element  13  is inserted between the antenna element  12  and the grounding conductor  11  and electrically connected with the feeding conductor  21 . 
     Also, in the inverted F-type antenna apparatus  102  of the present preferred embodiment constructed as above, by adjusting the areas of the antenna element  12  and the coupling element  13 , the distance from the grounding conductor  11  to the antenna element  12  and/or the distance from the grounding conductor  11  to the coupling element  13  so as to make the resonance frequencies of the antenna apparatuses of the two loop circuits which are slightly different from each other, a wideband frequency characteristic can be obtained. Further, by making the feeding conductor  21  function as the connection conductor  23  of the first preferred embodiment, the antenna structure can be simplified and made suitable for mass production. 
     Modified Preferred Embodiments of Second Preferred Embodiment 
     FIG. 4 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   a  according to the first modification of the second preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment, this inverted F-type antenna apparatus  102   a  is characterized by being constituted by a grounding conductor  11  and a coupling element  13  formed on two mutually different surfaces on a dielectric substrate  41  and an antenna element  12  formed on a dielectric substrate  42 , and further, a feeding conductor  21  and a short-circuit conductor  22  are each made of a through hole conductor formed by filling a through hole, which penetrates the dielectric substrates  41  and  42  in the direction of thickness, with a metallic conductor. In this case, the coupling element  13  is electrically connected with the feeding conductor  21  but not electrically connected with the short-circuit conductor  22 . It is to be noted that the coupling element  13  may be formed on the dielectric substrate  42 . The inverted F-type antenna apparatus  102   a  constructed as above has operation and advantageous effects similar to those of the first and second preferred embodiments. By changing the thickness of each of the dielectric substrates  41  and  42 , the distance between the grounding conductor  11  and the coupling element  13  and the distance between the coupling element  13  and the antenna element  12  can be changed, and the amount of electromagnetic field coupling between these elements can be adjusted. 
     FIG. 5 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   b  according to the second modification of the second preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment, this inverted F-type antenna apparatus  102   b  can reliably fix and support the respective components of the inverted F-type antenna apparatus  102   b  by filling a space between the grounding conductor  11  and the antenna element  12  with a dielectric  45 . 
     FIG. 6 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   c  according to the third modification of the second preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment, this inverted F-type antenna apparatus  102   c  is constructed of a grounding conductor  11  formed on a dielectric substrate  43 . Further, by filling a space between a region of a part of the left-side flat surface of the coupling element  13  in the figure, and the dielectric substrate  43  with a dielectric  46 , and also by filling a space between a region of a part of the right-side flat surface of the coupling element  13  in the figure, and the antenna element  12  with a dielectric  47 , the respective components of the inverted F-type antenna apparatus  102   c  can be reliably fixed and supported. 
     FIG. 7 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  102   d  according to the fourth modification of the second preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment, this inverted F-type antenna apparatus  102   d  can reliably fix and support the respective components of the inverted F-type antenna apparatus  102   d  by filling a space between a region of a part of the left-side flat surface of the coupling element  13  in the figure, and the grounding conductor  11  with a dielectric  46  and by filling a space between a region of a part of the right-side flat surface of the coupling element  13  in the figure, and the antenna element  12  with a dielectric  47 . 
     Third Preferred Embodiment 
     FIG. 8A is a plan view showing a construction of an inverted F-type antenna apparatus  103  according to the third preferred embodiment of the present invention, and FIG. 8B is a longitudinal sectional view taken along the line C-C′ of FIG.  8 A. As shown in FIGS. 8A and 8B, the inverted F-type antenna apparatus  103  of the present preferred embodiment is provided with a grounding conductor  11  and a feeding point  25 , and further includes an antenna element  12  constructed of a rectangular plate-shaped conductor, a short-circuit conductor  22 , a feeding conductor  21  and a coupling element  13  constructed of a rectangular plate-shaped conductor. This antenna apparatus  103  is characterized in that the short-circuit conductor  22  is used as a connection conductor. 
     Referring to FIGS. 8A and 8B, the antenna element  12  and the grounding conductor  11  are arranged so as to be substantially parallel to each other and to face each other, and the antenna element  12  is electrically connected with the grounding conductor  11  via the short-circuit conductor  22 . One end of the feeding conductor  21  is electrically connected with the antenna element  12 , while another end of the feeding conductor  21  is connected with the feeding coaxial cable  30  at the feeding point  25  on the grounding conductor  11 , in a manner similar to that of the first preferred embodiment. Moreover, the coupling element  13  is inserted between the antenna element  12  and the grounding conductor  11  and electrically connected with the short-circuit conductor  22 . 
     Also, in the inverted F-type antenna apparatus  103  of the present preferred embodiment constructed as above, by adjusting the areas of the antenna element  12  and the coupling element  13 , the distance from the grounding conductor  11  to the antenna element  12  and/or the distance from the grounding conductor  11  to the coupling element  13  so as to make the resonance frequencies of the antenna apparatuses of the two loop circuits which are slightly different from each other, a wideband frequency characteristic can be obtained. Further, by making the short-circuit conductor  22  function as the connection conductor  23  of the first preferred embodiment, the antenna structure can be simplified and made suitable for mass production. 
     Modified Preferred Embodiments of Third Preferred Embodiment 
     FIG. 9 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   a  according to the first modification of the third preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  103  of the third preferred embodiment, this inverted F-type antenna apparatus  103   a  is characterized in that the antenna apparatus  103  includes a grounding conductor  11  and a coupling element  13  formed on two different surfaces on a dielectric substrate  41  and an antenna element  12  formed on a dielectric substrate  42 , and further, a feeding conductor  21  and a short-circuit conductor  22  are each constructed of a through hole conductor formed by filling a through hole, which penetrates the dielectric substrates  41  and  42  in the direction of thickness, with a metallic conductor. In this case, the coupling element  13  is electrically connected with the short-circuit conductor  22 , but is not electrically connected with the feeding conductor  21 . It is to be noted that the coupling element  13  may be formed on the dielectric substrate  42 . The inverted F-type antenna apparatus  103   a  constructed as above has operation and advantageous effects similar to those of the first to third preferred embodiments. By changing the thickness of each of the dielectric substrates  41  and  42 , the distance between the grounding conductor  11  and the coupling element  13  and the distance between the coupling element  13  and the antenna element  12  can be changed, and the amount of electromagnetic field coupling between these elements can be adjusted. 
     FIG. 10 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   b  according to the second modification of the third preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  103  of the third preferred embodiment, this inverted F-type antenna apparatus  103   b  can reliably fix and support the respective components of the inverted F-type antenna apparatus  103   b  by filling a space between the grounding conductor  11  and the antenna element  12  with a dielectric  45 . 
     FIG. 11 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   c  according to the third modification of the third preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  103  of the third preferred embodiment, this inverted F-type antenna apparatus  103   c  is constituted by a grounding conductor  11  formed on a dielectric substrate  43 , and is able to reliably fix and support the respective components of the inverted F-type antenna apparatus  103   c  by filling a space between a region of a part of the left-side flat surface of the coupling element  13  in the figure, and the dielectric substrate  43  with a dielectric  46 , and by filling a space between a region of a part of the right-side flat surface of the coupling element  13  in the figure and the antenna element  12  with a dielectric  47 . 
     FIG. 12 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  103   d  according to the fourth modification of the third preferred embodiment of the present invention. In comparison with the inverted F-type antenna apparatus  103  of the third preferred embodiment, this inverted F-type antenna apparatus  103   d  can reliably fix and support the respective components of the inverted F-type antenna apparatus  103   d  by filling a space between a region of a part of the left-side flat surface of the coupling element  13  in the figure, and the grounding conductor  11  with a dielectric  46 , and also by filling a space between a region of a part of the right-side flat surface of the coupling element  13  in the figure and the antenna element  12  with a dielectric  47 . 
     Fourth Preferred Embodiment 
     FIG. 13A is a plan view showing a construction of an inverted F-type antenna apparatus  104  according to the fourth preferred embodiment of the present invention, and FIG. 13B is a longitudinal sectional view taken along the line D-D′ of FIG.  13 A. In comparison with the inverted F-type antenna apparatus  103  of the second preferred embodiment shown in FIGS. 3A and 3B, this inverted F-type antenna apparatus  104 , as shown in FIGS. 13A and 13B, is characterized in that a further coupling element  14  is inserted between the coupling element  13  and the grounding conductor  11 . In this case, the coupling element  14  is electrically connected with the feeding conductor  21 , but is not electrically connected with the short-circuit conductor  22 . 
     In the inverted F-type antenna apparatus  104  constructed as above, by adjusting not only the areas of the antenna element  12  and the coupling elements  13  and  14  but also the respective distances from the grounding conductor  11  to the coupling elements  13  and  14  or the antenna element  12  so as to make the resonance frequencies of the plurality of antenna apparatuses of a plurality of loop circuits be slightly different from each other, a wideband characteristic can be obtained. Moreover, it is enabled to perform impedance matching between the antenna apparatus  104  and the feeding coaxial cable  30  so as to cover a plurality of frequency bands by means of the plurality of coupling elements  13  and  14 . Furthermore, it is acceptable to fill a space between the grounding conductor  11  and the antenna element  12  partially or totally with a dielectric, namely, to fill the dielectric in a part of the internal portion or the whole portion of the space, or to arrange a dielectric substrate, in a manner similar to those of the first to fourth modification of the second preferred embodiment. In this case, the advantageous effect of reducing the resonance frequency can be expected, and characteristic variations in mass production can be suppressed by stably fixing the shape of the antenna apparatus. 
     Fifth Preferred Embodiment 
     FIG. 14A is a plan view showing a construction of an inverted F-type antenna apparatus  105  according to the fifth preferred embodiment of the present invention, and FIG. 14B is a longitudinal sectional view taken along the line E-E′ of FIG.  14 A. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment, this inverted F-type antenna apparatus  105 , as shown in FIGS. 14A and 14B, is characterized by including an antenna element  12   a  whose lower portion in the figure is formed in a meandering configuration with a plurality of slits  12   s  arranged parallel to the shorter side direction and a coupling element  13   a  whose lower portion in the figure is formed in a meandering configuration with a plurality of slits  13   s  arranged parallel to the shorter side direction. 
     In the inverted F-type antenna apparatus  105  constructed as above, by forming the plurality of slits  12   s  and  13   s  in the antenna element  12   a  and the feeding element  13   a,  respectively, there can be obtained such advantageous effects as reducing the resonance frequencies and increasing the reactance component by virtue of their increased path lengths and the advantageous effect of increasing the reactance component by virtue of the reduced amount of coupling accompanied by their reduction in area. Taking advantage of these effects, in addition to the fact that impedance matching between the antenna apparatus  105  and the feeding coaxial cable  30  and the adjustment of the resonance frequency of the antenna apparatus  105  can be easily done, the reduction in the resonance frequency of the antenna apparatus  105  can be achieved to allow the antenna apparatus  105  to have a small size and a reduced weight. That is, when the capacitive coupling between the antenna element  12   a  and the coupling element  13   a  and the capacitive coupling between the coupling element  13   a  and the grounding conductor  11  are comparatively large, by adjusting the areas of the slits  12   s  and  13   s  so that the opposing area therebetween is reduced with the path length maintained constant, the capacitive coupling between these elements can be reduced to allow impedance matching to be achieved. Further, by adjusting not only the distance between the antenna element  12   a  and the coupling element  13   a  but also the distance between the coupling element  13   a  and the grounding conductor  11 , the adjustment of impedance matching can easily be performed. 
     In the aforementioned preferred embodiment, the structural example in which both the antenna element  12   a  and the coupling element  13   a  are provided with the slits  12   s  and  13   s  has been described. However, the present invention is not limited to this, and at least one of the antenna element  12   a  and the coupling element  13  a may be provided with the slits  12   s  and  13   s.  Moreover, by providing at least one of the antenna element  12   a  and the coupling element  13   a  with a slot and by adjusting the amount of electromagnetic field coupling between the antenna element  12   a  and the coupling element  13   a  and the amount of electromagnetic field coupling between the coupling element  13   a  and the grounding conductor  11 , the adjustment of impedance matching between the input impedance of the antenna apparatus  105  and the feeding coaxial cable  30  can be easily done. Moreover, by providing at least one of the antenna element  12   a  and the coupling element  13   a  with a slot, the resonance frequency of the antenna element can be adjusted. 
     Although the aforementioned preferred embodiment is provided with one coupling element  13   a,  the present invention is not limited to this. By inserting and arranging two or more coupling elements  13   a  between the antenna element  12   a  and the grounding conductor  11 , a frequency characteristic of a wider band can be achieved. In this case, by using a plurality of coupling elements  13   a,  impedance matching can be achieved so as to cover a plurality of frequency bands. 
     Moreover, by forming a slit in the grounding conductor  11  and by adjusting the amount of electromagnetic field coupling between the grounding conductor  11  and the antenna element  12   a,  operation and advantageous effects similar to those above can be obtained. Furthermore, in the aforementioned preferred embodiment, the structural example in which the feeding conductor  21  is made to function as a connection conductor is described. However, the present invention is not limited to this, and it is acceptable to use the short-circuit conductor  22  as a connection conductor or to provide a further connection conductor for connecting the coupling element  13   a  with the antenna element  12   a.  Furthermore, the space surrounded by the grounding conductor  11  and the antenna element  12   a  may be filled partially or totally with a dielectric, namely the dielectric may be filled in a part of the internal portion or the whole portion of the space. In this case, the advantageous effect of reducing the resonance frequency can be obtained, and the shape of the antenna apparatus can be stably fixed. Therefore, electrical characteristic variations in mass production can be suppressed. 
     Modified Preferred Embodiment of Fifth Preferred Embodiment 
     FIG. 15A is a plan view showing a construction of an inverted F-type antenna apparatus  105   a  according to the modification of the fifth preferred embodiment of the present invention, and FIG. 15B is a longitudinal sectional view taken along the line F-F′ of FIG.  15 A. In comparison with the inverted F-type antenna apparatus  105  of the fifth preferred embodiment, this inverted F-type antenna apparatus  105   a,  as shown in FIGS. 15A and 15B, is characterized in that a plurality of slits  12   s  formed in the antenna element  12   b  and a plurality of slits  13   s  formed in the coupling element  13   b  face each other, respectively. In the inverted F-type antenna apparatus  105   a  constructed as above, directions  901  and  902  of the currents that flow on the antenna element  12   b  as shown in FIG. 15A can be made to coincide with directions  911  and  912 , respectively, of the currents that flow on the coupling element  13   b.  By aligning these directions of the currents, the radiation efficiency of the inverted F-type antenna apparatus  105   a  can be improved, and the antenna gain can be improved. 
     Sixth Preferred Embodiment 
     FIG. 16A is a plan view showing a construction of an inverted F-type antenna apparatus  106  according to the sixth preferred embodiment of the present invention, and FIG. 16B is a longitudinal sectional view taken along the line G-G′ of FIG.  16 A. In comparison with the inverted F-type antenna apparatus  102  shown in FIGS. 3A and 3B, this inverted F-type antenna apparatus  106 , as shown in FIGS. 16A and 16B, is constructed in such a manner that the coupling element  13   c  is perpendicularly bent in two portions parallel to the shorter side direction thereof, and the coupling element  13   c  is constructed of the following: 
     (i) a portion  13   ca  parallel to the grounding conductor  11  and the antenna element  12 ; 
     (ii) a portion  13   cb  perpendicular to the grounding conductor  11  and the antenna element  12 ; and 
     (iii) a portion  13   cc  parallel to the grounding conductor  11  and the antenna element  12 . 
     In this case, it is set such that a distance between the portion  13   cc  and the antenna element  12  becomes shorter than a distance between the portion  13   ca  and the antenna element  12  and the amount of electromagnetic field coupling between the antenna element  12  and the coupling element  13   c  is increased. 
     That is, the coupling element  13   c  has one portion bent and has a step-shaped configuration with a difference in level. With this arrangement, the distance between the grounding conductor  11  and the coupling element  13   c  and the distance between the antenna element  12  and the coupling element  13   c  are changed depending on the positions of these elements in the longitudinal direction. Consequently, the distance is changed between the portion  13   ca  located on the side where the antenna element  12  and the grounding conductor  11  are electrically connected with each other (short-circuit conductor  22  side) and the portion  13   cc  located on the opposite open end side. With this arrangement, the distance between the antenna element  12  and the coupling element  13   c  and the distance between the grounding conductor  11  and the coupling element  13   c  can be changed depending on the positions of these elements in the longitudinal direction, and this enables the adjustment of the amount of electromagnetic field coupling between the coupling element  13   c  and the antenna element  12  and the amount of electromagnetic field coupling between the coupling element  13   c  and the grounding conductor  11 . Therefore, frequency adjustment in the manufacturing stage can be easily done, and this leads to suitability for mass production. Moreover, the electrical length of the coupling element  13   c  can be made longer than that of the planar structure by bending the coupling element  13   c  with three-dimensional deformation. Therefore, the resonance frequency of the antenna apparatus  106  can be reduced to allow the antenna apparatus  106  to have a small size and a reduced weight. 
     In the present preferred embodiment, by bending a part of the coupling element  13   c  as shown in FIG. 16B to put the coupling element  13  closer to the open end and its neighborhood of the antenna element  12 , the amount of electromagnetic field coupling between the coupling element  13   c  and the antenna element  12  can be increased, and the resonance frequency of the antenna apparatus can be further reduced. Moreover, by increasing the distance between the coupling element  13   c  and the grounding conductor  11  at the end portion of the inverted F-type antenna apparatus  106  as shown in FIG. 16B, electromagnetic field coupling with components of a transceiver or the like arranged in the vicinity of the antenna apparatus  106  can be reduced, enabling the prevention of malfunction of the transceiver or the like. 
     Modified Preferred Embodiments of Sixth Preferred Embodiment 
     FIG. 17A is a plan view showing a construction of an inverted F-type antenna apparatus  106   a  according to the first modification of the sixth preferred embodiment of the present invention, and FIG. 17B is a longitudinal sectional view taken along the line H-H′ of FIG.  17 A. In comparison with the inverted F-type antenna apparatus  106  of the sixth preferred embodiment shown in FIG. 16B, this inverted F-type antenna apparatus  106   a  is constructed in such a manner that the coupling element  13  is not bent, and the antenna element  12   c  is perpendicularly bent in two portions parallel to the shorter side direction thereof. The antenna element  12   c  is constructed of the following: 
     (i) a portion  12   ca  parallel to the grounding conductor  11  and the coupling element  13 ; 
     (ii) a portion  12   cb  perpendicular to the grounding conductor  11  and the coupling element  13 ; and 
     (iii) a portion  12   cc  parallel to the grounding conductor  11  and the coupling element  13 . 
     It is set such that a distance between the portion  12   cc  and the coupling element  13  becomes shorter than a distance between the portion  12   ca  and the coupling element  13 , and the amount of electromagnetic field coupling between the antenna element  12   c  and the coupling element  13   c  is increased. The inverted F-type antenna apparatus  106   a  of the first modification of the sixth preferred embodiment constructed as above has operation and advantageous effects similar to those of the inverted F-type antenna apparatus  106  of the sixth preferred embodiment. 
     FIG. 18 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  106   b  according to the second modification of the sixth preferred embodiment of the present invention. 
     Referring to FIG. 18, a liquid crystal display section  41  is arranged on the top surface side in the center portion in the longitudinal direction of an upper housing  40  of a folding type portable radio communication apparatus. A dielectric substrate  43  is arranged on the rear side of this liquid crystal display section  41 , and a grounding conductor  11  is formed on a flat surface of the dielectric substrate  43 , which is located on the liquid crystal display section  41  side. An inverted F-type antenna apparatus  106   b  having the following construction is provided on the upper side of this dielectric substrate  43 . This inverted F-type antenna apparatus  106   b  is basically provided with the grounding conductor  11  and a feeding point  25  in a manner similar to that of the structure of the inverted F-type antenna apparatus  102  of the second preferred embodiment shown in FIG. 3B, and further includes an antenna element  12   d  constructed of a rectangular plate-shaped conductor, a short-circuit conductor  22 , a feeding conductor  21  and a coupling element  13  constructed of a rectangular plate-shaped conductor. In this case, the antenna element  12   d  is characterized by being bent in a curved shape along the housing configuration of the upper housing  40 . With this arrangement, there is such a unique advantageous effect that the inverted F-type antenna apparatus  106   b  can be compactly accommodated in the upper housing  40 . 
     FIG. 19 is a longitudinal sectional view showing a construction of an inverted F-type antenna apparatus  106   c  according to the third modification of the sixth preferred embodiment of the present invention. 
     Referring to FIG. 19, a liquid crystal display section  41  is arranged on the top surface side in the center portion in the longitudinal direction of the upper housing  40  of a folding type portable radio communication apparatus. A grounding conductor  11   a  constructed of, for example, a rectangular metal plate, is arranged on the rear side of this liquid crystal display section  41  while being bent along the configuration of the liquid crystal display section  41 . An inverted F-type antenna apparatus  106   c  having the following construction is provided on the upper side of the upper housing  40  with this grounding conductor  11   a.  This inverted F-type antenna apparatus  106   c  is basically provided with a grounding conductor a  11  and a feeding point  25  in a manner similar to that of the structure of the inverted F-type antenna apparatus  102  of the second preferred embodiment shown in FIG. 3B, and further includes an antenna element  12   d  constructed of a rectangular plate-shaped conductor, a short-circuit conductor  22 , a feeding conductor  21  and a coupling element  13  constructed of a rectangular plate-shaped conductor. In this case, the antenna element  12   d  is characterized by being bent in a curved shape along the housing configuration of the upper housing  40 . With this arrangement, there is such a unique advantageous effect that the inverted F-type antenna apparatus  106   c  can be compactly accommodated in the upper housing  40 . 
     In the sixth preferred embodiment and the modified preferred embodiments described above, by arranging at least either the antenna elements  12 ,  12   c  and  12   d  or the coupling elements  13  and  13   c  so as to be inclined from the grounding conductor  11 , the amount of electromagnetic field coupling between the antenna elements  12 ,  12   c  and  12   d  and the coupling elements  13  and  13   c,  and the amount of electromagnetic field coupling between the coupling elements  13  and  13   c  and the connection conductors  11  and  11   a  can be adjusted. Also, in this case, impedance matching and resonance frequency adjustment can be performed. 
     Although the sixth preferred embodiment and the modified preferred embodiments thereof are provided with one coupling element  13  or  13   c,  the present invention is not limited to this. By providing two or more coupling elements  13  and  13   c,  a frequency characteristic of a wider band can be achieved. In this case, by employing a plurality of coupling elements  13  and  13   c,  impedance matching can be performed so as to cover a plurality of frequency bands. 
     In the sixth preferred embodiment and the modified preferred embodiments thereof, it is acceptable to form a slit or slot in at least any one of the antenna elements  12 ,  12   c  and  12   d,  the coupling elements  13  and  13   c  and the grounding conductors  11  and  11   a.  In this case, operation and advantageous effects similar to those described above can be obtained. Moreover, although the feeding conductor  21  has such a function as the connection conductor in the sixth preferred embodiment and the modified preferred embodiments thereof as described above, it is acceptable to provide the short-circuit conductor  21  having the function of the connection conductor or to provide a further connection conductor in place of this. 
     Furthermore, in a manner similar to those of the various modified preferred embodiments of the second preferred embodiment shown in FIGS. 4 to  7 , the space surrounded by the grounding conductor  11  and one of the antenna elements  12 ,  12   c  and  12   d  may be filled partially or totally with a dielectric, namely, the dielectric may be filled in a part of the internal portion or the whole portion of the space. In this case, the advantageous effect of reducing the resonance frequency of the antenna apparatus can be obtained, and the respective components of the antenna apparatus can be stably fixed. Therefore, electrical characteristic variations in mass production can be suppressed. 
     Seventh Preferred Embodiment 
     FIG. 20A is a plan view showing a construction of an inverted F-type antenna apparatus  107  according to the seventh preferred embodiment of the present invention, FIG. 20B is a plan view of an antenna element  12   e  of FIG. 20A, FIG. 20C is a plan view of a coupling element  13   e  of FIG. 20A, and FIG. 20D is a plan view of a coupling element  14   e  of FIG.  20 A. FIG. 21 is a longitudinal sectional view taken along the line I-I′ of FIG.  20 A. This inverted F-type antenna apparatus  107  is related to an implemental example produced for a trial purpose by the present inventor and others. In these FIGS. 20A to  20 D, the dimensions of the respective components are shown using a unit of millimeters. 
     Referring to FIGS. 20A to  20 D and FIG. 21, there is provided an the inverted F-type antenna apparatus  107 , which has a feeding point  25  on a grounding conductor  11  having a length of 70 mm and a width of 43 mm. This inverted F-type antenna apparatus  107  further includes the following: 
     (i) the antenna element  12   e  having a length of 17 mm and a width of 43 mm shown in FIG. 20B; 
     (ii) the coupling element  13   e  shown in FIG. 20C; 
     (iii) the coupling element  14   e  shown in FIG. 20D; 
     (iv) a short-circuit conductor  22  for electrically connecting the antenna element  12   e  with the grounding conductor  11 ; and 
     (v) a feeding conductor  21  for electrically connecting the central conductor  31  of the feeding coaxial cable  30  with the antenna element  12   e  via two coupling elements  13   e  and  14   e.    
     In this case, an L-figured strip-shaped slit  12   es  is formed in the antenna element  12   e,  and a linear type strip-shaped slit  13   es  is formed in the coupling element  13   e.  The element length and the amount of electromagnetic field coupling of the antenna apparatus are changed by adjusting the lengths and areas of these slits  12   es  and  13   es,  and impedance matching between the input impedance of the antenna apparatus and the characteristic impedance of the feeding coaxial cable  30  can be easily adjusted. 
     Moreover, as shown in FIG. 21, the antenna element  12   e  is arranged to be inclined from the grounding conductor  11  so that the height thereof from the grounding conductor  11  located on the feeding conductor  21  side becomes 9.2 mm and the height thereof from the grounding conductor  11  located on the open-end side becomes 7.9 mm. Likewise, the coupling elements  13   e  and  14   e  are also arranged so as to be inclined from the grounding conductor  11 . In the coupling elements  13   e  and  14   e,  their heights from the grounding conductor  11  located on the feeding conductor  21  side are 8.1 mm and 6.6 mm, respectively, and their heights from the grounding conductor  11  located on the open end side are 6.7 mm and 4.7 mm, respectively. By changing the distance from each of the antenna element  12   e  and the coupling elements  13   e  and  14   e  to the grounding conductor  11  according to their positions in the longitudinal direction, the amount of electromagnetic field coupling between the antenna element  12   e,  each of the coupling elements  13   e  and  14   e  and the grounding conductor  11  can be adjusted. In addition to the fact that the resonance frequency of the antenna apparatus  107  can be adjusted so as to be reduced, impedance matching between the antenna apparatus  107  and the feeding coaxial cable  30  can be easily adjusted, and this leads to achievement of a frequency characteristic of a wider band. 
     In the aforementioned seventh preferred embodiment, one end of the feeding conductor  21  is electrically connected with the antenna element  12   e,  and another end of the feeding conductor  21  is electrically connected with the central conductor  31  of the feeding coaxial cable  30  via the feeding point  25  on the grounding conductor  11 . It is important that the coupling elements  13   e  and  14   e  are each electrically connected with the feeding conductor  21 , however, is not electrically connected with the short-circuit conductor  22 . That is, the diameter of the short-circuit conductor  22  is smaller than the through holes  13   eh  and  14   eh  formed through the coupling elements  13   e  and  14   e,  respectively, and the short-circuit conductor  22  passes through the center portions of these through holes  13   eh  and  14   eh.  Therefore, the short-circuit conductor  22  is not electrically connected with the coupling elements  13   e  and  14   e.    
     FIG. 22 is a Smith chart showing a frequency characteristic of the input impedance of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21, and FIG. 23 is a graph showing a frequency characteristic of the voltage standing wave ratio (VSWR) of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21. 
     As is apparent from FIG. 22, it can be understood that a plurality of resonance circles exist and the antenna apparatus is in a state of multiple resonance. Referring to FIG. 23, a frequency range, in which VSWR was equal to or smaller than three, ranged from 905 to 1024 MHz, and the ratio of the range to the band was 12.3%. In other words, a wideband frequency characteristic was able to be obtained. 
     In the aforementioned preferred embodiment, even when a dimension obtained by adding the shorter side to the longer side of the grounding conductor  11  has an extremely small value which is equal to or smaller than a quarter of the wavelength, a wideband characteristic can be achieved. Moreover, the impedance characteristic of the antenna apparatus  107  can be easily adjusted. Therefore, this arrangement is suitable for constituting an antenna apparatus on the grounding conductor  11  that has comparatively small dimensions with respect to the wavelength in a portable radio communication apparatus such as a folding type portable telephone. 
     In the above-mentioned preferred embodiment, the space surrounded by the grounding conductor  11  and the antenna element  12   e  may be filled partially or totally with a dielectric, namely, the electric may be filled in a part of the internal portion or the whole portion of the space. In this case, the advantageous effect of reducing the resonance frequency of the antenna apparatus can be obtained, and the shape of the antenna apparatus can be stably fixed. Therefore, variations in mass production can be suppressed. 
     Modified Preferred Embodiments of Seventh Preferred Embodiment 
     FIG. 24 is a plan view showing a construction of an antenna element  12   f  according to the first modification of the seventh preferred embodiment, or a modified preferred embodiment of the antenna element of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21. As shown in FIG. 24, the antenna element  12   f  is formed so as to have a slot  12   ss  of a predetermined shape. The antenna element  12   f  is constructed of a rectangular ring-shaped conductor portion  12   fa,  a rectangular patch-shaped conductor portion  12   fc  and a strip-shaped conductor portion  12   fb  for coupling the conductor portion  12   fa  and the conductor portion  12   fc  with each other. The antenna element  12   f  of the above-mentioned configuration has such a unique advantageous effect that it is able to have a long substantial element length and have an increased amount of electromagnetic field coupling with other conductors. Moreover, by forming the slot  12   ss  in the antenna element  12   f,  the resonance frequency of the antenna apparatus can be adjusted. 
     FIG. 25 is a plan view showing a construction of a coupling element  13   f  according to the second modified preferred embodiment of the seventh preferred embodiment, or a modified preferred embodiment of the coupling element of the inverted F-type antenna apparatus  107  shown in FIGS. 20A and 21. As shown in FIG. 25, the coupling element  13   f  is formed so as to have a slot  13   ss  of a predetermined shape. The coupling element  13   f  is constructed of a rectangular ring-shaped conductor portion  13   fa,  a rectangular patch-shaped conductor portion  13   fc  and a strip-shaped conductor portion  13   fb  for coupling these conductor portions  13   fa  and the conductor portion  13   fc  to each other. The coupling element  13   f  of the above-mentioned configuration has such a unique advantageous effect that it is able to have a long substantial element length and have an increased amount of electromagnetic field coupling with other conductors. Moreover, by forming the slot  13   ss  in the coupling element  13   f,  the resonance frequency of the antenna apparatus can be adjusted. 
     Eighth Preferred Embodiment 
     FIG. 26A is a plan view showing a construction of an inverted F-type antenna apparatus  108  according to the eighth preferred embodiment of the present invention, and FIG. 26B is a longitudinal sectional view taken along the line J-J′ of FIG.  26 A. In comparison with the inverted F-type antenna apparatus  102  of the second preferred embodiment shown in FIGS. 3A and 3B, this inverted F-type antenna apparatus  108  is characterized in that the antenna element  12  is inserted between the grounding conductor  11  and the coupling element  13 , and the other construction is similar to that of the second preferred embodiment. One end of the feeding conductor  21  is electrically connected with the coupling element  13  and electrically connected with the antenna element  12  roughly in the center portion of the feeding conductor  21 . Another end of the feeding conductor  21  is connected with the central conductor  31  of the feeding coaxial cable  30 . Moreover, one end of the short-circuit conductor  22  is connected with the antenna element  12 , and another end thereof is electrically connected with the grounding conductor  11 . 
     The inverted F-type antenna apparatus  108  according to the eighth preferred embodiment constructed as above has operation and advantageous effects similar to those of the inverted F-type antenna apparatus  102  of the second preferred embodiment. Moreover, also in this inverted F-type antenna apparatus  108 , the space between the coupling element  13  and the grounding conductor  11  may be filled partially or totally with a dielectric, as described in connection with the modified preferred embodiments of the second preferred embodiment. In this case, the advantageous effect of reducing the resonance frequency of the antenna apparatus and the advantageous effect of restraining variations in mass production can be obtained. 
     Ninth Preferred Embodiment 
     FIG. 27A is a plan view showing a construction of a portable radio communication apparatus  1101  according to the ninth preferred embodiment of the present invention, and FIG. 27B is a side view of FIG.  27 A. 
     Referring to FIGS. 27A and 27B, a portable radio communication apparatus  1101  is a structural example of a folding type portable telephone and is constructed of an upper housing  1102 , a lower housing  1103  and a hinge portion  1104  that is a mechanical section for coupling the upper housing  1102  with the lower housing  1103  and making the upper and lower housings  1102  and  1103  be superimposed on each other when the hinge portion  1104  is folded. In this case, a liquid crystal display section  1105  is provided roughly in the center portion of the upper housing  1102 , and an upper dielectric substrate  1108  is arranged on the lower side in the thickness direction, and a built-in antenna  1110  is provided in the upper portion in the figure of the dielectric substrate  1108  where a transmitting signal is supplied from a feeding section of a radio transmitter (not shown) to the built-in antenna  1110 . Moreover, a ten-key section  1106  is provided roughly in the center portion of the lower housing  1103 , and a lower dielectric substrate  1109  is arranged on the lower side in the thickness direction. A whip antenna  1107  constructed of a helical antenna  1107   a  and a monopole antenna  1107   b  is provided on the lower housing  1103  retractably along the longitudinal direction of the lower housing  1103  on the left side in FIG.  27 A and then, a transmitting signal is fed from a feeding section of a radio transmitter (not shown) to the whip antenna  1107 . 
     In the present preferred embodiment, the built-in antenna  1110  can be constructed of any one of the aforementioned first to eighth preferred embodiments or their modified preferred embodiments. In this case, the built-in antenna  1110  and the whip antenna  1107  can be controlled so that at least one of these two antennas is used by a space diversity technology during transmission and reception of a radio signal. 
     In the portable radio communication apparatus  1101  constructed as above, the built-in antenna  1110  can achieve a wideband characteristic even when the dimension of the grounding conductor formed on the rear surface of the upper dielectric substrate  1108  is equal to or smaller than a quarter of the wavelength. Therefore, satisfactory communication quality can be obtained. Moreover, by arranging the built-in antenna  1110  in the upper portion of the inside of the upper housing  1102 , it is enabled to make the antenna apparatus less susceptible to the influence of the human body, such as fingers of the user, during a telephone conversation. With this arrangement, the radiation loss of the radio wave from the portable radio communication apparatus  1101  can be reduced, and the antenna gain of the built-in antenna  1110  can be improved. 
     In the aforementioned preferred embodiment, the whip antenna  1107  is provided on the lower housing  1103 . However, the present invention is not limited to this, and the whip antenna may be provided on the upper housing  1102 . Moreover, the built-in antenna  1110  may be arranged in the lower portion of the upper housing  1102  or in the lower portion of the lower housing  1103 . 
     Modified Preferred Embodiment of Ninth Preferred Embodiment 
     FIG. 28A is a plan view showing a construction of a portable radio communication apparatus  1101   a  according to the modification of the ninth preferred embodiment of the present invention, and FIG. 28B is a side view of FIG.  28 A. 
     Referring to FIGS. 28A and 28B, this portable radio communication apparatus  1101   a  is characterized in that the whip antenna  1107  on the lower housing  1103  is removed in comparison with the portable radio communication apparatus  1101  of the ninth preferred embodiment. 
     Tenth Preferred Embodiment 
     FIG. 29A is a plan view showing a construction of a portable radio communication apparatus  2100  according to the tenth preferred embodiment of the present invention with part removed, and FIG. 29B is a side view of FIG.  29 A. In these FIGS. 29A and 29B, the same components as those of FIGS. 28A and 28B are denoted by same reference numerals. 
     Referring to FIGS. 29A and 29B, the built-in antenna  1110  formed on the dielectric substrate  1108  of the upper housing  1102  is provided, and a flexible dielectric substrate  2702  on which conductor patterns  2702   a  and  2702   b  are formed is provided in a hinge portion  1104 . One end of each of the conductor patterns  2702   a  and  2702   b  is connected with a connector  2109  formed on the upper dielectric substrate  1108 , while another end of each of the conductor patterns  2702   a  and  2702   b  is connected with a connector  2110  formed on the lower dielectric substrate  1109 . 
     In this case, a strip-shaped conductor pattern  2703  formed on the upper dielectric substrate  1108  is connected with the conductor pattern  2702   a  via a connector  2109 . The conductor pattern  2702   a  is further connected with a feeding point  2111  via a connector  2110 . One monopole antenna is constructed of a conductor pattern extended from this conductor pattern  2703  to the feeding point  2111 . Then, the monopole antenna and the built-in antenna  1110  can be controlled so that at least one of these two antennas is used by the space diversity technology during transmission and reception of a radio signal. 
     Eleventh Preferred Embodiment 
     FIG. 30A is a plan view showing a construction of a built-in antenna apparatus  2200  according to the eleventh preferred embodiment of the present invention, and FIG. 30B is a side view showing a construction of a built-in antenna apparatus  2200  of FIG.  30 A. 
     The built-in antenna  2200  of this eleventh preferred embodiment is employed in place of the aforementioned built-in antenna  1110 , and is provided with a bent grounding conductor  11   a,  an antenna element  12   g  (operating in a manner similar to that of the aforementioned antenna element  12  or the like) formed in a meandering configuration on a dielectric substrate  42 , and a strip-shaped antenna element  12   h  that is formed while being connected with the antenna  12   g  on the dielectric substrate  42  and operates as a monopole antenna. The built-in antenna  2200  further includes a coupling element  13  arranged while being inserted between the antenna element  12   g  and the grounding conductor  11   a,  a feeding conductor  21  for connecting a feeding point with the antenna element  12   g,  and a connection conductor  22  for connecting the antenna element  12   g  with the coupling element  13 . In this case, the feeding conductor  21  is electrically connected with the coupling element  13  and the antenna element  12   g,  while the short-circuit conductor  22  is electrically connected with the antenna element  12   g  in a state in which the short-circuit conductor  22  is not connected with the coupling conductor  13 . Then, by making the resonance frequency of the antenna element  12   g  provided with the coupling element  13  be different from the resonance frequency of the antenna element  12   h,  the antenna apparatus can be used as a wideband built-in antenna apparatus  2200 , which can cover a plurality of frequency bands. 
     In the preferred embodiment constructed as above, by arranging the built-in antenna apparatus  2200  in the upper portion of the inside of the upper housing  1102 , it is enabled to make the antenna apparatus less susceptible to the influence of the human body, such as fingers, during a telephone conversation. With this arrangement, the radiation loss of the radio wave from the portable radio communication apparatus can be reduced, and the antenna gain of the built-in antenna  2200  can substantially be improved. 
     Advantageous Effects of Preferred Embodiments 
     As described in detail above, the inverted F-type antenna apparatus according to the preferred embodiments of the present invention is characterized in that the coupling element is inserted between the unbalanced type antenna element and the grounding conductor, and the connecting means for electrically connecting the antenna element with the grounding conductor in at least one place is provided. 
     By adjusting the amount of coupling between the antenna element and the coupling element, the amount of coupling between the antenna element and the grounding conductor or the amount of coupling between coupling element and the grounding conductor by means of the coupling element, the resonance frequency of the antenna element provided with the coupling element is made to be different from the resonance frequency of the antenna element provided with no coupling element. With this arrangement, a wideband frequency characteristic can be obtained. Moreover, the resonance frequency of the antenna apparatus can be adjusted by shifting in correspondence with a plurality of frequency bands. Moreover, by providing the connecting means common to either the feeding conductor or the short-circuit conductor, structural simplification can be achieved, and this leads to suitability for mass production. 
     Furthermore, by providing the slit or the slot, the resonance frequency can be reduced, and the amount of coupling between the antenna element and the coupling element and/or the grounding conductor can be adjusted. By inclining the coupling element with respect to the antenna element or the connection conductor or by providing the coupling element or the antenna element with a stepped portion, the amount of coupling between the antenna element and the grounding conductor can be adjusted. 
     By arranging the antenna apparatus constructed as above inside of the upper housing of the folding type portable radio communication apparatus, it can be expected to make the antenna apparatus less susceptible to the influence from the human body, such as during a telephone conversation, and the radiation loss due to the human body can be reduced. 
     Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.