Abstract:
Disclosed is a portable wireless device which can receive signals at a wideband with good sensitivity, and change a narrowband wherein signals are received with high sensitivity. In this device, a wireless unit ( 105 ) demodulates signals received by an antenna ( 101 ) or modulates signals to be transmitted by the antenna ( 101 ). Matching circuits ( 103 - 1  to  103 -n) are connected between the antenna ( 101 ) and the wireless unit ( 105 ) and match impedance so that the impedance of the antenna ( 101 ) and the impedance of the wireless unit ( 105 ) have a complex conjugate relation. A plurality of these are respectively provided for a plurality of different frequency bands where matching is performed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a portable radio apparatus, and especially relates to a portable radio apparatus that enables matching in a wideband, as well as varying frequency by which matching is enabled in a narrowband. 
       2. BACKGROUND ART 
       [0002]    Conventionally, a portable radio apparatus provided with a plurality of matching circuits for matching characteristic impedances of 50Ω, and that adapts to a wideband by switching the plurality of matching circuits is known (see e.g., Patent Literature 1). According to Patent Literature 1, by switching connections of two types of matching circuits and one antenna element by using diode switches, a matched state for two types of frequency characteristics is obtained, and an adaptation thereof to a radio system of the wideband is performed. Further, in Patent Literature 1, it has a premise that the antenna and a radio section are connected by the characteristic impedance of 50Ω. 
         [0003]    Further, conventionally, a portable radio apparatus that performs matching such that an impedance of the antenna and an input impedance of an amplifier have a complex conjugate relationship is known (see e.g., Patent Literature 2). According to Patent Literature 2, matching in the wideband is enabled by providing an impedance converting circuit that connects in parallel by ground connection between the antenna and a transistor. 
       Citation List 
     Patent Literature 
     PTL 1 
       [0000]    
       
         Japanese Patent Application Laid-Open No. 2007-325147 
       
     
       PTL 2 
       [0000]    
       
         Japanese Patent Application Laid-Open No. 2007-295459 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, since Patent Literature 1 uses the plurality of matching circuits that performs the characteristic impedance matching of 50Ω by switching the same, the frequency to be matched by the respective matching circuits is a narrowband. Consequently, Patent Literature 1 has problems that the number of the matching circuits needs to be increased to cover the wideband characteristics, and in addition, the wideband characteristics have to be obtained by the antenna element. Further, in Patent Literature 1, in a case where frequency that cannot be matched due to the limitation on the number of the matching circuits that can be installed, etc. existing, there is a problem that it is not possible to operate the radio system using the frequency that cannot be matched. Further, in Patent Literature 2, since it is not possible to change the frequency by which the matching can be obtained, there is a problem that it is not possible to deal with cases in which the frequency having a large matching loss or a scarce matching loss changes. 
         [0007]    The present invention aims to provide a portable radio apparatus that can receive signals in the wideband with satisfactory sensitivity, and change the narrowband by which the signals are received with high sensitivity. 
       Solution to Problem 
       [0008]    A portable radio apparatus of the present invention employs a configuration including an antenna; a radio section that performs demodulation of a signal received by the antenna or modulation of a signal to be sent by the antenna; and a plurality of matching circuits, each of which is connected between the antenna and the radio section, performs matching such that an impedance of the antenna and an impedance of the radio section have a complex conjugate relationship, and is provided for each of the different frequency bands in which the matching is to be performed. 
       Advantageous Effects of Invention 
       [0009]    According to the present invention, it is possible to receive signals with satisfactory sensitivity in the wideband, and it is possible to change the narrowband by which the signals are received with high sensitivity. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 1 of the present invention; 
           [0011]      FIG. 2  is a block diagram showing the first example of a configuration of a matching circuit of Embodiment 1 of the present invention; 
           [0012]      FIG. 3  is a block diagram showing the second example of a configuration of the matching circuit of Embodiment 1 of the present invention; 
           [0013]      FIG. 4  is a block diagram showing the third example of a configuration of the matching circuit of Embodiment 1 of the present invention; 
           [0014]      FIG. 5  is a block diagram showing the fourth example of a configuration of the matching circuit of Embodiment 1 of the present invention; 
           [0015]      FIG. 6  is a block diagram showing the fifth example of a configuration of the matching circuit of Embodiment 1 of the present invention; 
           [0016]      FIG. 7  is a diagram showing an operation of the portable radio apparatus of Embodiment 1 of the present invention; 
           [0017]      FIG. 8  is a diagram for explaining matching by which a complex conjugate relationship can be obtained in a Smith chart of Embodiment 1 of the present invention; 
           [0018]      FIG. 9  is a diagram showing a relationship of frequency and loss in the case of providing a plurality of conventional matching circuits for matching characteristic impedances of 50Ω; 
           [0019]      FIG. 10  is a diagram showing a relationship of frequency and loss in Embodiment 1 of the present invention; 
           [0020]      FIG. 11  is a diagram showing a conventional relationship of mismatch loss and frequency in viewing two channels of digital television broadcast; 
           [0021]      FIG. 12  is a diagram showing a relationship of mismatch loss and frequency in viewing two channels of digital television broadcast in Embodiment 1 of the present invention; 
           [0022]      FIG. 13  is a diagram showing a conventional relationship of number of matching circuits and bands by which matching can be obtained; 
           [0023]      FIG. 14  is a diagram showing a relationship of the number of matching circuits and bands by which matching can be obtained in Embodiment 1 of the present invention; 
           [0024]      FIG. 15  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 2 of the present invention; 
           [0025]      FIG. 16  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 3 of the present invention; 
           [0026]      FIG. 17  is a diagram showing a relationship of frequency and loss in the first radio system and the second radio system that are capable of receiving signals in Embodiment 3 of the present invention; 
           [0027]      FIG. 18  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 4 of the present invention; 
           [0028]      FIG. 19  is a diagram showing changes in an impedance matching point of the first radio system and the second radio system in a Smith chart in Embodiment 4 of the present invention; 
           [0029]      FIG. 20  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 5 of the present invention; 
           [0030]      FIG. 21  is a block diagram showing a configuration of a matching circuit of Embodiment 5 of the present invention; 
           [0031]      FIG. 22  is a block diagram showing a configuration of a portable radio apparatus of Embodiment 6 of the present invention; 
           [0032]      FIG. 23  is a block diagram showing the first example of a configuration of a matching circuit of Embodiment 6 of the present invention; 
           [0033]      FIG. 24  is a block diagram showing the second example of a configuration of the matching circuit of Embodiment 6 of the present invention; 
           [0034]      FIG. 25  is a block diagram showing the third example of a configuration of the matching circuit of Embodiment 6 of the present invention; 
           [0035]      FIG. 26  is a block diagram showing the fourth example of a configuration of the matching circuit of Embodiment 6 of the present invention; and 
           [0036]      FIG. 27  is a block diagram showing the fifth example of a configuration of the matching circuit of Embodiment 6 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0037]    Hereinbelow, the embodiments of the present invention will be described in detail with reference to the drawings. 
       Embodiment 1 
       [0038]      FIG. 1  is a block diagram showing a configuration of portable radio apparatus  100  of Embodiment 1 of the present invention. 
         [0039]    Portable radio apparatus  100  is configured primarily with antenna  101 , switch section  102 , matching circuits  103 - 1  to  103 - n  (n being an arbitrary natural number), switch section  104 , and radio section  105 . Hereinbelow, each configuration will be described in detail. 
         [0040]    Antenna  101  functions e.g. as a monopole antenna, and includes an antenna element with an electrical length of a quarter wavelength or less. Further, antenna  101  receives a signal from a specific radio system, and outputs the same to switch section  102 . Further, antenna  101  sends the signal of the specific radio system input from switch section  102 . 
         [0041]    Switch section  102  switches output of the signal input from antenna  101  to specific one of matching circuits  103 - 1  to  103 - n . Further, switch section  102  selects one of matching circuits  103 - 1  to  103 - n , and switches output of the signal input from the selected one of matching circuits  103 - 1  to  103 - n  to antenna  101 . 
         [0042]    Matching circuits  103 - 1  to  103 - n  are connected serially between switch section  102  and switch section  104 , and match impedances of antenna  101  and radio section  105 . Specifically, matching circuits  103 - 1  to  103 - n  perform matching such that the impedance of antenna  101  and the input impedance of radio section  105  have a complex conjugate relationship. At this occasion, each of matching circuits  103 - 1  to  103 - n  performs matching so that the complex conjugate relationship can be obtained in the respective, different frequencies. Accordingly, by switching matching circuits  103 - 1  to  103 - n , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Further, matching circuits  103 - 1  to  103 - n  convert the impedance of the signal input from switch section  102  and output the same to switch section  104 . Similarly, matching circuits  103 - 1  to  103 - n  match the impedance of antenna  101  and the output impedance of radio section  105  to have the complex conjugate relationship, convert the impedance of the signal input from switch section  104  and output the same to switch section  102 . 
         [0043]    Switch section  104  selects one of matching circuits  103 - 1  to  103 - n , and switches output of the signal input from the selected one of matching circuits  103 - 1  to  103 - n  to radio section  105 . Further, switch section  104  switches output of the signal input from radio section  105  to specific one of matching circuits  103 - 1  to  103 - n . Further, switch section  104  selects one of matching circuits  103 - 1  to  103 - n  that is identical to the one of matching circuits  103 - 1  to  103 - n  selected by switch section  102 . The method of selecting matching circuits  103 - 1  to  103 - n  will be described later. 
         [0044]    Radio section  105  obtains data that is superimposed at a specific frequency by demodulating the signal input from switch section  104 . Further, radio section  105  modulates the signal to superimpose data at the specific frequency, and outputs the modulated signal to switch section  104 . At this occasion, at radio section  105 , the input impedance and the output impedance at switch section  104  side are complex impedances and are at the same time high impedances. 
         [0045]    Next, the configuration of matching circuits  103 - 1  to  103 - n  will be described. In the explanation of the configuration of matching circuits  103 - 1  to  103 - n  hereinbelow, only matching circuit  103 - 1  will be described; since the configuration of matching circuits  103 - 2  to  103 - n  is identical to that of matching circuit  103 - 1 , the explanation of the configuration of matching circuits  103 - 2  to  103 - n  will not be repeated. 
         [0046]      FIG. 2  is a block diagram showing the first example of the configuration of matching circuit  103 - 1 . 
         [0047]    As shown in  FIG. 2 , matching circuit  103 - 1  is configured with element  201 , element  202 , and element  203 . Elements  201  to  203  are inductors or capacitors. 
         [0048]    Element  201  has its one end connected to switch section  102  and its other end connected to switch section  104 . 
         [0049]    Element  202  is connected by ground connection in parallel between switch section  102  and element  201 . 
         [0050]    Element  203  is connected by ground connection in parallel between switch section  104  and element  201 . 
         [0051]      FIG. 3  is a block diagram showing the second example of a configuration of matching circuit  103 - 1 . 
         [0052]    As shown in  FIG. 3 , matching circuit  103 - 1  is configured with element  301  and element  302 . Elements  301  and  302  are inductors or capacitors. 
         [0053]    Element  301  has its one end connected to switch section  102  and its other end connected to switch section  104 . 
         [0054]    Element  302  is connected by ground connection in parallel between switch section  102  and element  301 . 
         [0055]      FIG. 4  is a block diagram showing the third example of a configuration of matching circuit  103 - 1 . 
         [0056]    As shown in  FIG. 4 , matching circuit  103 - 1  is configured with element  401  and element  402 . Elements  401  and  402  are inductors or capacitors. 
         [0057]    Element  401  has its one end connected to switch section  102  and its other end connected to switch section  104 . 
         [0058]    Element  402  is connected by ground connection in parallel between element  401  and switch section  104 . 
         [0059]      FIG. 5  is a block diagram showing the fourth example of a configuration of matching circuit  103 - 1 . 
         [0060]    As shown in  FIG. 5 , matching circuit  103 - 0 . 1  is configured with element  501  and element  502 . Elements  501  and  502  are inductors or capacitors. 
         [0061]    Element  501  is connected by ground connection in parallel between switch section  102  and switch section  104 . 
         [0062]    Element  502  is connected by ground connection in parallel between switch section  102  and switch section  104 , and is connected by ground connection in parallel with element  501 . 
         [0063]      FIG. 6  is a block diagram showing the fifth example of a configuration of matching circuit  103 - 1 . 
         [0064]    As shown in  FIG. 6 , matching circuit  103 - 1  is configured with element  601 . Element  601  is an inductor or a capacitor. 
         [0065]    Element  601  is connected by ground connection in parallel between switch section  102  and switch section  104 . The configuration of portable radio apparatus  100  has been described above. 
         [0066]    Next, an operation of portable radio apparatus  100  will be described with reference to  FIG. 7 .  FIG. 7  is a diagram showing the operation of portable radio apparatus  100 .  FIG. 7  shows the operation of portable radio apparatus  100  in the case of receiving digital television broadcast. 
         [0067]    Portable radio apparatus  100  retains in advance a table storing the matching loss in using each of matching circuits  103 - 1  to  103 - n  in all of the channels of the digital television broadcast. 
         [0068]    Firstly, portable radio apparatus  100  starts an operation of receiving digital television broadcast (step ST 701 ). 
         [0069]    Next, switch section  102  and switch section  104  switch to connect to matching circuits  103 - 1  to  103 - n  in which the average matching loss becomes minimum in all of the bands of each channel of the digital television broadcast (step ST 702 ). 
         [0070]    Next, in the case of viewing only one channel (step ST 703 ), switch section  102  and switch section  104  switch to connect to matching circuits  103 - 1  to  103 - n  in which the average matching loss becomes minimum in the frequency of the viewing channel (step ST 704 ). 
         [0071]    Next, in the case of stopping the viewing (step ST 705 ), switch section  102  and switch section  104  switch to connect to matching circuits  103 - 1  to  103 - n  in which the average matching loss becomes minimum in all of the bands of each channel of the digital television broadcast (step ST 706 ). 
         [0072]    Further, in the case of viewing two channels (step ST 707 ), switch section  102  and switch section  104  switch to connect to matching circuits  103 - 1  to  103 - n  in which the matching loss in the frequency of the channel that is mainly viewed is smaller than the matching loss in the frequency of the other channel being viewed, and in addition to this, the total of the matching losses of both channels becomes minimum (step ST 708 ). 
         [0073]    Next, in the case of stopping the viewing (step ST 709 ), switch section  102  and switch section  104  switch to connect to matching circuits  103 - 1  to  103 - n  in which the average matching loss becomes minimum in all of the bands of each channel of the digital television broadcast (step ST 706 ). 
         [0074]    Further, after having switched to connect to matching circuits  103 - 1  to  103 - n  in which the average matching loss becomes minimum in all of the bands of each channel of the digital television broadcast in step ST 706 , portable radio apparatus  100  ends the digital television broadcast operation (step ST 710 ). The operation of portable radio apparatus  100  has been described above. 
         [0075]      FIG. 8  is a diagram for explaining matching by which the complex conjugate relationship can be obtained in a Smith chart. The matching by which the complex conjugate relationship can be obtained means that, with respect to the characteristic impedance of 50Ω, in an impedance range where VSWR is 5 or more (a range r 1  hatched in  FIG. 8 ), a matching point of the input impedance or the output impedance of radio section  105  and the impedance of antenna  101  exists in a desired frequency. 
         [0076]    Next, advantages of the present embodiment compared to the conventional art will be described with reference to  FIGS. 9 to 14 .  FIG. 9  is a diagram showing a relationship of frequency and loss in the case of providing a plurality of conventional matching circuits for matching characteristic impedances of 50Ω.  FIG. 10  is a diagram showing a relationship of frequency and loss in the present embodiment.  FIG. 11  is a diagram showing a conventional relationship of mismatch loss and frequency in viewing two channels of digital television broadcast.  FIG. 12  is a diagram showing a relationship of mismatch loss and frequency in viewing digital television broadcasts of two channels in the present embodiment.  FIG. 13  is a diagram showing a conventional relationship of the number of matching circuits and bands by which matching can be obtained.  FIG. 14  is a diagram showing a relationship of the number of matching circuits  103 - 1  to  103 - n  and bands by which matching can be obtained in the present embodiment. 
         [0077]    Conventionally, as shown in  FIG. 9 , since it had been impossible to change the frequency characteristic, it was difficult to appropriately correspond to frequencies with large matching loss and frequencies with small matching loss. On the other hand, as shown in  FIG. 10 , in the present embodiment it is possible to obtain the matching in the wideband, and it is possible to change at least one of the narrowband frequencies by which the matching can be obtained, from frequency f 1  to frequency f 2 , or from frequency f 2  to frequency f 1 . 
         [0078]    Further, conventionally, as shown in  FIG. 11 , frequency by which the matching of X channel and Y channel can be obtained had been a narrowband. Accordingly, conventionally the sensitivity was significantly deteriorated in the case of a mismatched state in which the impedances change due to an object having approached around the antenna, etc. On the other hand, as shown in  FIG. 12 , the frequency by which matching of the X channel and the Y channel can be obtained in the present embodiment is a wideband. Accordingly, the sensitivity is prevented from being significantly deteriorated in a case an object approaches near the antenna, etc. Further, the present embodiment can maintain predetermined matching loss (sensitivity) for all of the bands of the digital television broadcast. By this means, it is possible to prevent an extreme degrading in displaying the broadcast for all of the channels, in zapping to sequentially change channels within a short period of time, in scanning all of the channels, or in simultaneously operating two tuners. Further, in the present embodiment, by performing a frequency tuning to coincide a peak of the matching to the frequency of the channel that is primarily being viewed, it is possible to perform an optimal sensitivity distribution for all of the bands of the channel that is primarily being viewed and the digital television broadcast. 
         [0079]    Further, as shown in  FIG. 13 , conventionally in 470 MHz to 770 MHz, which are the entire bands of the digital television broadcast, in order to have mismatching loss of 10 dB or lower, seven matching circuits are needed to obtain matchings ( 1 ) to ( 7 ). On the other hand, as shown in  FIG. 14 , under the same condition, the present embodiment merely needs to provide three matching circuits in order to obtain matchings ( 1 ) to ( 3 ). 
         [0080]    Consequently, according to the present embodiment, by providing a plurality of matching circuits that matches so as to have a complex conjugate relationship and differing frequency by which the matching can be performed in each of the matching circuits, it is possible to receive signals with satisfactory sensitivity in the wideband, and change the narrowband by which the receipt can be made with high sensitivity. Therefore, according to the present embodiment, in receiving signals of a plurality of channels such as the digital television broadcast, it is possible to receive the signals of all of the channels with satisfactory sensitivity, and receive the signal of the channel that is primarily viewed, with high sensitivity. Further, according to the present embodiment, in performing matching in the wideband, since it is possible to decrease the number of the matching circuits compared to the conventional art, it is possible to cut down the manufacturing cost, and make the portable radio apparatus compact and thin. 
       Embodiment 2 
       [0081]      FIG. 15  is a block diagram showing a configuration of portable radio apparatus  1500  of Embodiment 2 of the present invention. 
         [0082]    Portable radio apparatus  1500  is configured primarily with antenna  1501 , switch section  1502 , matching circuits  1503 - 1  to  1503 - n , switch section  1504 , amplifier  1505 , and radio section  1506 . Portable radio apparatus  1500  functions exclusively as a receiver by providing amplifier  1505 . Hereinbelow, each configuration will be described in detail. 
         [0083]    Antenna  1501  functions e.g. as a monopole antenna, and includes an antenna element with an electrical length of a quarter wavelength or less. Further, antenna  1501  receives a signal from a specific radio system, and outputs the same to switch section  1502 . 
         [0084]    Switch section  1502  switches output of the signal input from antenna  1501  to specific one of matching circuits  1503 - 1  to  1503 - n.    
         [0085]    Matching circuits  1503 - 1  to  1503 - n  are connected serially between switch section  1502  and switch section  1504 , and match impedances of antenna  1501  and amplifier  1505 . Specifically, matching circuits  1503 - 1  to  1503 - n  perform matching such that the impedance of antenna  1501  and the input impedance of amplifier  1505  have a complex conjugate relationship. At this occasion, each of matching circuits  1503 - 1  to  1503 - n  performs matching so that the complex conjugate relationship can be obtained in the respective, different frequencies. Accordingly, by switching matching circuits  1503 - 1  to  1503 - n , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Then, matching circuits  1503 - 1  to  1503 - n  convert the impedance of the signal input from switch section  1502  and output the same to switch section  1504 . 
         [0086]    Switch section  1504  selects one of matching circuits  1503 - 1  to  1503 - n , and switches output of the signal input from the selected one of matching circuits  1503 - 1  to  1503 - n  to amplifier  1505 . Further, switch section  1504  selects one of matching circuits  1503 - 1  to  1503 - n  that is identical to the one of matching circuits  1503 - 1  to  1503 - n  selected by switch section  1502 . 
         [0087]    Amplifier  1505  amplifies a signal input from switch section  1504  and outputs the same to radio section  1506 . At this occasion, in amplifier  1505 , an input impedance is a complex impedance, and an output impedance is a characteristic impedance. Further, amplifier  1505  preferably has high gain and low noise figure (low NF) in the frequency used in portable radio apparatus  1500 . 
         [0088]    Radio section  1506  obtains data that is superimposed at a specific frequency by demodulating the signal input from amplifier  1505 . The configuration of portable radio apparatus  1500  has been described above. 
         [0089]    An operation of portable radio apparatus  1500  is identical to that of  FIG. 7 , and advantages of the present embodiment compared to the conventional art are also identical to those explained in  FIGS. 9 to 14 . Thus, explanations thereof will not be repeated. 
         [0090]    Consequently, according to the present embodiment, by providing a plurality of matching circuits that snatches so as to have a complex conjugate relationship and differing frequency by which the matching can be performed in each of the matching circuits in a portable radio apparatus that is an exclusive receiver, it is possible to receive signals with satisfactory sensitivity in the wideband, and realize the receipt with satisfactory sensitivity even when the desired specific narrowband changes. Further, according to the present embodiment, in performing matching in the wideband, since it is possible to decrease the number of the matching circuits compared to the conventional art, it is possible to cut down the manufacturing cost, and make the portable radio apparatus compact and thin. 
       Embodiment 3 
       [0091]      FIG. 16  is a block diagram showing a configuration of portable radio apparatus  1600  of Embodiment 3 of the present invention. 
         [0092]    Portable radio apparatus  1600  shown in  FIG. 16  omits radio section  1506  and adds first radio section  1601  and second radio section  1602  with respect to portable radio apparatus  1500  in Embodiment 2 shown in  FIG. 15 . In  FIG. 16 , parts having identical configurations as in  FIG. 15  will be given the same reference signs, and explanation thereof will not be repeated. 
         [0093]    Portable radio apparatus  1600  is configured primarily with antenna  1501 , switch section  1502 , matching circuits  1503 - 1  to  1503 - n , switch section  1504 , amplifier  1505 , first radio section  1601  and second radio section  1602 . Portable radio apparatus  1600  functions exclusively as a receiver by providing amplifier  1505 . Hereinbelow, the present embodiment will be described in detail regarding configurations that are different from the above Embodiment 2. 
         [0094]    Amplifier  1505  amplifies a signal input from switch section  1504  and outputs the same to first radio section  1601  and second radio section  1602 . At this occasion, in amplifier  1505 , an input impedance is a complex impedance, and an output impedance is a characteristic impedance. Further, amplifier  1505  preferably has high gain and low noise figure (low NF) in the frequency used in portable radio apparatus  1600 . 
         [0095]    First radio section  1601  obtains data of a first radio system by demodulating the signal input from amplifier  1505 . For example, first radio section  1601  demodulates a signal of a GPS system that is the first radio system and obtains position data. 
         [0096]    Second radio section  1602  demodulates a signal input from amplifier  1505 , and obtains data of the second radio system that is different from the first radio system. For example, second radio section  1602  demodulates a signal of a digital television broadcast that is the second radio system and obtains data of the digital television broadcast. 
         [0097]      FIG. 17  is a diagram showing a relationship of frequency and loss in the first radio system and the second radio system that are capable of receiving signals in portable radio apparatus  1600 . In  FIG. 17 , a case where the first radio system is a GPS system, and the second radio system is a digital television broadcast (DTV) will be described. 
         [0098]    As shown in  FIG. 17 , portable radio apparatus  1600  can obtain matching in a wideband including both of frequency f 10  used in the GPS system and frequency f 20  used in the digital television broadcast, and can vary the band in which the matching can be performed for the digital television broadcast. 
         [0099]    An operation of portable radio apparatus  1600  is identical to that of  FIG. 7 , and advantages of the present embodiment compared to the conventional art are also identical to those explained in  FIGS. 9 to 14 . Thus, explanations thereof will not be repeated. 
         [0100]    Consequently, according to the present embodiment, by providing a plurality of matching circuits that matches so as to have a complex conjugate relationship and differing frequency by which the matching can be performed in each of the matching circuits in a portable radio apparatus that can use a plurality of radio systems, it is possible to receive signals with satisfactory sensitivity in the wideband, and realize the receipt with satisfactory sensitivity even when the desired specific narrowband changes. Further, according to the present embodiment, in performing matching in the wideband, since it is possible to decrease the number of the matching circuits compared to the conventional art, it is possible to cut down the manufacturing cost, and make the portable radio apparatus compact and thin. 
         [0101]    In the present embodiment, although an exclusive receiver was exemplified by providing an amplifier, the present invention is not limited hereto, and may be configured to be capable of performing both the sending and receiving by omitting the amplifier. 
       Embodiment 4 
       [0102]      FIG. 18  is a block diagram showing a configuration of portable radio apparatus  1800  of Embodiment 4 of the present invention. 
         [0103]    Portable radio apparatus  1800  is configured primarily with antenna  1801 , switch section  1802 , matching circuits  1803 - 1  to  1803 - n , switch section  1804 , amplifier  1805 , first radio section  1806 , and second radio section  1807 . Hereinbelow, each configuration will be described in detail. 
         [0104]    Antenna  1801  functions e.g. as a monopole antenna, and includes an antenna element with an electrical length of a quarter wavelength or less. Further, antenna  1801  receives signals from the first radio system and the second radio system, and outputs the same to switch section  1802 . Further, antenna  1801  sends a signal of the second radio system input from switch section  1802 . 
         [0105]    Switch section  1802  switches output of the signal input from antenna  1801  to specific one of matching circuits  1803 - 1  to  1803 - n . Further, switch section  1802  selects one of matching circuits  1803 - 1  to  1803 - n , and switches output of the signal input from the selected one of matching circuits  1803 - 1  to  1803 - n  to antenna  1801 . 
         [0106]    Matching circuits  1803 - 1  to  1803 - n  are connected serially between switch section  1802  and switch section  1804 , and match impedances of antenna  1801  and amplifier  1805 , as well as antenna  1801  and second radio section  1807 . Specifically, matching circuits  1803 - 1  to  1803 - n  perform matching such that the impedance of antenna  1801  and the input impedance of amplifier  1805  have a complex conjugate relationship, and the impedance of antenna  1801  and the input impedance of second radio section  1807  have a complex conjugate relationship. At this occasion, each of matching circuits  1803 - 1  to  1803 - n  performs matching so that the complex conjugate relationship can be obtained in the respective, different frequencies. Accordingly, by switching matching circuits  1803 - 1  to  1803 - n , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Further, matching circuits  1803 - 1  to  1803 - n  convert the impedance of the signal input from switch section  1802  and output the same to switch section  1804 . Similarly, matching circuits  1803 - 1  to  1803 - n  match the impedance of antenna  1801  and the output impedance of second radio section  1807  to have the complex conjugate relationship, convert the impedance of the signal input from switch section  1804  and output the same to switch section  1802 . 
         [0107]    Switch section  1804  selects one of matching circuits  1803 - 1  to  1803 - n , and switches output of the signal input from the selected one of matching circuits  1803 - 1  to  1803 - n  to amplifier  1805  and second radio section  1807 . Further, switch section  1804  switches output of the signal input from second radio section  1807  to specific one of matching circuits  1803 - 1  to  1803 - n . Further, switch section  1804  selects one of matching circuits  1803 - 1  to  1803 - n  that is identical to the one of matching circuits  1803 - 1  to  1803 - n  selected by switch section  1802 . 
         [0108]    Amplifier  1805  amplifies a signal input from switch section  1804  and outputs the same to first radio section  1806 . At this occasion, in amplifier  1805 , an input impedance is a complex impedance, and an output impedance is a characteristic impedance. Further, amplifier  1805  preferably has high gain and low noise figure (low NF) in the frequency used in portable radio apparatus  1800 . 
         [0109]    First radio section  1806  obtains data of the first radio system by demodulating the signal input from amplifier  1805 . For example, first radio section  1806  demodulates a signal of the digital television broadcast that is the first radio system and obtains data of the digital television broadcast. 
         [0110]    Second radio section  1807  obtains data of the second radio system by demodulating the signal input from switch section  1804 . Further, second radio section  1807  modulates the signal to superimpose data at the frequency of the second radio system, and outputs the modulated signal to switch section  1804 . At this occasion, at second radio section  1807 , the input impedance and the output impedance at switch section  1804  side are complex impedances and are at the same time high impedances. For example, second radio section  1807  demodulates a signal of the GPS system that is the second radio system and obtains position data. The configuration of portable radio apparatus  1800  has been described above. 
         [0111]      FIG. 19  is a diagram showing changes in the impedance matching point of the first radio system and the second radio system. 
         [0112]    As shown in  FIG. 19 , the change v 1  of the matching point # 1901  of the first radio system is larger compared to the change v 2  of the matching point # 1902  of the second radio system. 
         [0113]    An operation of portable radio apparatus  1800  is identical to that of  FIG. 7 , and advantages of the present embodiment compared to the conventional art are also identical to those explained in  FIGS. 9 to 14 . Thus, explanations thereof will not be repeated. Further, a diagram showing a relationship of frequency and loss in the first radio system and the second radio system that are capable of receiving signals in portable radio apparatus  1800  is identical to  FIG. 17 , so the explanation thereof will not be repeated. 
         [0114]    Consequently, according to the present embodiment, by providing a plurality of matching circuits that matches so as to have a complex conjugate relationship and differing frequency by which the matching can be performed in each of the matching circuits in a portable radio apparatus that can use a plurality of radio systems, it is possible to receive signals with satisfactory sensitivity in the wideband, and make the receipt with satisfactory sensitivity even when the desired specific narrowband changes. Further, according to the present embodiment, in performing matching in the wideband, since it is possible to decrease the number of the matching circuits compared to the conventional art, it is possible to cut down the manufacturing cost, and make the portable radio apparatus compact and thin. 
         [0115]    In the present embodiment, although an exclusive receiver was exemplified for the first radio system by providing an amplifier, the present invention is not limited hereto, and may be configured to be capable of performing both the sending and receiving for the first radio system by omitting the amplifier. 
       Embodiment 5 
       [0116]      FIG. 20  is a block diagram showing a configuration of portable radio apparatus  2000  of Embodiment 5 of the present invention. 
         [0117]    Portable radio apparatus  2000  is configured primarily with antenna  2001 , switch section  2002 , matching circuits  2003 - 1  and  2003 - 2 , switch section  2004 , amplifier  2005 , and radio section  2006 . Portable radio apparatus  2000  functions exclusively as a receiver by providing amplifier  2005 . Hereinbelow, each configuration will be described in detail. 
         [0118]    Antenna  2001  functions e.g. as a monopole antenna, and includes an antenna element with an electrical length of a quarter wavelength or less. Further, antenna  2001  receives a signal from a specific radio system, and outputs the same to switch section  2002 . 
         [0119]    Switch section  2002  switches output of the signal input from antenna  2001  to matching circuit  2003 - 1  or  2003 - 2 . 
         [0120]    Matching circuit  2003 - 1  is connected serially between switch section  2002  and switch section  2004 , and matches impedances of antenna  2001  and amplifier  2005 . Specifically, matching circuit  2003 - 1  performs matching such that the impedance of antenna  2001  and the input impedance of amplifier  2005  have a complex conjugate relationship. At this occasion, matching circuit  2003 - 1  performs matching so as to have the complex conjugate relationship in frequency that is different from matching circuit  2003 - 2 . Accordingly, by switching matching circuit  2003 - 1  and matching circuit  2003 - 2 , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Further, matching circuit  2003 - 1  can vary the frequency by which the complex conjugate relationship can be obtained. Then, matching circuit  2003 - 1  converts the impedance of the signal input from switch section  2002  and output the same to switch section  2004 . The detailed configuration of matching circuit  2003 - 1  will be described later. 
         [0121]    Matching circuit  2003 - 2  is connected serially between switch section  2002  and switch section  2004 , and matches impedances of antenna  2001  and amplifier  2005 . Specifically, matching circuit  2003 - 2  performs matching such that the impedance of antenna  2001  and the input impedance of amplifier  2005  have the complex conjugate relationship. At this occasion, matching circuit  2003 - 2  performs matching so as to have the complex conjugate relationship in frequency that is different from matching circuit  2003 - 1 . Accordingly, by switching matching circuit  2003 - 2 , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Then, matching circuit  2003 - 2  converts the impedance of the signal input from switch section  2002  and outputs the same to switch section  2004 . 
         [0122]    Switch section  2004  selects matching circuit  2003 - 1  or matching circuit  2003 - 2 , and switches output of the signal input from the selected matching circuit  2003 - 1  or matching circuit  2003 - 2  to amplifier  2005 . Further, switch section  2004  selects one of matching circuits  2003 - 1  to  2003 - n  that is identical to the one of matching circuits  2003 - 1  to  2003 - n  selected by switch section  2002 . 
         [0123]    Amplifier  2005  amplifies a signal input from switch section  2004  and outputs the same to radio section  2006 . At this occasion, in amplifier  2005 , an input impedance is a complex impedance, and an output impedance is a characteristic impedance. Further, amplifier  2005  preferably has high gain and low noise figure (low NF) in the frequency used in portable radio apparatus  2000 . 
         [0124]    Radio section  2006  obtains data that is superimposed at a specific frequency by demodulating the signal input from amplifier  2005 . 
         [0125]    Next, the configuration of matching circuit  2003 - 1  will be described with reference to  FIG. 21 .  FIG. 21  is a block diagram showing the configuration of matching circuit  2003 - 1 . 
         [0126]    As shown in  FIG. 21 , matching circuit  2003 - 1  is configured with element  2101 , element  2102 , and element  2103 . Elements  2101  to  2103  are inductors or capacitors. 
         [0127]    Element  2101  has its one end connected to switch section  2002  and its other end connected to switch section  2004 . Further, element  2101  is configured with a variable inductor or a variable capacitor (variable condenser or varactor diode, etc.). 
         [0128]    Element  2102  is connected by ground connection in parallel between switch section  2002  and element  2101 . 
         [0129]    Element  2103  is connected by ground connection in parallel between element  2101  and switch section  2004 . 
         [0130]    An operation of portable radio apparatus  2000  is identical to that of  FIG. 7 , and advantages of the present embodiment compared to the conventional art are also identical to those explained in  FIGS. 9  to  14 . Thus, explanations thereof will not be repeated. 
         [0131]    According to the present embodiment, in addition to the effect of the above-mentioned Embodiment 1, it is possible to further decrease the number of the matching circuits by varying the frequency by which the matching can be obtained in at least one matching circuit, thus it is possible to further cut down the manufacturing cost, and make the portable radio apparatus more compact and thinner. 
         [0132]    In the present embodiment, although just one matching circuit that can vary the frequency by which the matching can be obtained was provided, the present embodiment is not limited hereto; and a plurality of matching circuits may vary the frequency by which the matching can be obtained. Further, in the present embodiment, although the number of the matching circuits was two, the present embodiment is not limited hereto; and it is possible to determine an arbitrary number of the matching circuits. 
       Embodiment 6 
       [0133]      FIG. 22  is a block diagram showing a configuration of portable radio apparatus  2200  of Embodiment 6 of the present invention. 
         [0134]    Portable radio apparatus  2200  is configured primarily with antenna  2201 , matching circuits  2202 - 1  to  2202 - n , and radio section  2203 . Hereinbelow, each configuration will be described in detail. 
         [0135]    Antenna  2201  functions e.g. as a monopole antenna, and includes an antenna element with an electrical length of a quarter wavelength or less. Further, antenna  2201  receives a signal from a specific radio system, and outputs the same to matching circuits  2202 - 1  to  2202 - n . Further, antenna  2201  sends signals from matching circuits  2202 - 1  to  2202 - n . 
         [0136]    Matching circuits  2202 - 1  to  2202 - n  are connected serially between antenna  2201  and radio section  2203 , and match impedances of antenna  2201  and radio section  2203 . Specifically, matching circuits  2202 - 1  to  2202 - n  perform matching such that the impedance of antenna  2201  and the input impedance of radio section  2203  have a complex conjugate relationship. At this occasion, each of matching circuits  2202 - 1  to  2202 - n  performs matching by switching using an internal switch based on matching loss information of each of matching circuits  2202 - 1  to  2202 - n  e.g. in all of the channels in the digital television broadcast that is stored in a switch control section, etc. that is not shown so that the complex conjugate relationship can be obtained in the respective, different frequencies. By switching matching circuits  2202 - 1  to  2202 - n , it is possible to vary the frequency by which the complex conjugate relationship can be obtained. Further, matching circuits  2202 - 1  to  2202 - n  convert the impedance of the signal input from antenna  2201  and output the same to radio section  2203 . Similarly, matching circuits  2202 - 1  to  2202 - n  match the impedance of antenna  2201  and the output impedance of radio section  2203  to have the complex conjugate relationship, convert the impedance of the signal input from radio section  2203  and output the same to antenna  2201 . The detailed configuration of matching circuits  2202 - 1  to  2202 - n  will be described later. 
         [0137]    Radio section  2203  obtains data that is superimposed at a specific frequency by demodulating the signal input from matching circuits  2202 - 1  to  2202 - n . Further, radio section  2203  modulates the signal to superimpose data at the specific frequency, and outputs the modulated signal to matching circuits  2202 - 1  to  2202 - n . At this occasion, at radio section  2203 , the input impedance and the output impedance at matching circuits  2202 - 1  to  2202 - n  side are complex impedances and are at the same time high impedances. 
         [0138]    Next, the configuration of matching circuits  2202 - 1  to  2202 - n  will be described. In the explanation of the configuration of matching circuits  2202 - 1  to  2202 - n  hereinbelow, only matching circuit  2202 - 1  will be described; since the configuration of matching circuits  2202 - 2  to  2202 - n  is identical to that of matching circuit  2202 - 1 , the explanation of the configuration thereof will not be repeated. 
         [0139]      FIG. 23  is a block diagram showing the first example of the configuration of matching circuit  2202 - 1 . 
         [0140]    As shown in  FIG. 23 , matching circuit  2202 - 1  is configured with element  2301 , element  2302 , element  2303 , switch section  2304 , and switch section  2305 . Elements  2301  to  2303  are inductors or capacitors. 
         [0141]    Element  2301  has its one end connected to antenna  2201  and its other end connected to radio section  2203 . 
         [0142]    Element  2302  is connected by ground connection in parallel between antenna  2201  and element  2301 . 
         [0143]    Element  2303  is connected by ground connection in parallel between element  2301  and radio section  2203 . 
         [0144]    Switch section  2304  connects and disconnects an electrical connection between antenna  2201 , element  2301  and element  2302 . 
         [0145]    Switch section  2305  connects and disconnects an electrical connection between element  2301 , radio section  2203  and element  2303 . 
         [0146]      FIG. 24  is a block diagram showing the second example of a configuration of matching circuit  2202 - 1 . 
         [0147]    As shown in  FIG. 24 , matching circuit  2202 - 1  is configured with element  2401 , element  2402 , and switch section  2403 . Elements  2401  and  2402  are inductors or capacitors. 
         [0148]    Element  2401  has its one end connected to antenna  2201  and its other end connected to radio section  2203 . 
         [0149]    Element  2402  is connected by ground connection in parallel between antenna  2201  and element  2401 . 
         [0150]    Switch section  2403  connects and disconnects an electrical connection between antenna  2201 , element  2401  and element  2402 . Specifically, switch section  2403  turns on if matching is performed by matching circuit  2202 - 1 , and turns off if matching is not performed by matching circuit  2202 - 1 . 
         [0151]      FIG. 25  is a block diagram showing the third example of a configuration of matching circuit  2202 - 1 . 
         [0152]    As shown in  FIG. 25 , matching circuit  2202 - 1  is configured with element  2501 , element  2502 , and switch section  2503 . Elements  2501  and  2502  are inductors or capacitors. 
         [0153]    Element  2501  has its one end connected to antenna  2201  and its other end connected to radio section  2203 . 
         [0154]    Element  2502  is connected by ground connection in parallel between element  2501  and radio section  2203 . 
         [0155]    Switch section  2503  connects and disconnects an electrical connection between element  2501 , radio section  2203  and element  2502 . Specifically, switch section  2503  turns on if matching is performed by matching circuit  2202 - 1 , and turns off if matching is not performed by matching circuit  2202 - 1   
         [0156]      FIG. 26  is a block diagram showing the fourth example of a configuration of matching circuit  2202 - 1 . 
         [0157]    As shown in  FIG. 26 , matching circuit  2202 - 1  is configured with element  2601 , element  2602 , switch section  2603 , and switch section  2604 . Elements  2601  and  2602  are inductors or capacitors. 
         [0158]    Element  2601  is connected by ground connection in parallel between antenna  2201  and radio section  2203 . 
         [0159]    Element  2602  is connected by ground connection in parallel between antenna  2201  and radio section  2203 , and is connected by ground connection in parallel with element  2601 . 
         [0160]    Switch section  2603  connects and disconnects an electrical connection between antenna  2201 , radio section  2203 , and element  2601 . Specifically, switch section  2603  turns on if matching is performed by matching circuit  2202 - 1 , and turns off if matching is not performed by matching circuit  2202 - 1   
         [0161]    Switch section  2604  connects and disconnects an electrical connection between antenna  2201 , radio section  2203 , and element  2602 . Specifically, switch section  2604  turns on if matching is performed by matching circuit  2202 - 1 , and turns off if matching is not performed by matching circuit  2202 - 1 . 
         [0162]      FIG. 27  is a block diagram showing the fifth example of a configuration of matching circuit  2202 - 1 . 
         [0163]    As shown in  FIG. 27 , matching circuit  2202 - 1  is configured with element  2701  and switch section  2702 . Element  2701  is an inductor or a capacitor. 
         [0164]    Element  2701  is connected by ground connection in parallel between antenna  2201  and radio section  2203 . 
         [0165]    Switch section  2702  connects and disconnects an electrical connection between antenna  2201 , radio section  2203 , and element  2701 . 
         [0166]    Specifically, switch section  2702  turns on if matching is performed by matching circuit  2202 - 1 , and turns off if matching is not performed by matching circuit  2202 - 1 . The configuration of portable radio apparatus  2200  has been described above. 
         [0167]    An operation of portable radio apparatus  2200  is identical to that of  FIG. 7 , and advantages of the present embodiment compared to the conventional art are also identical to those explained in  FIGS. 9 to 14 . Thus, explanations thereof will not be repeated. 
         [0168]    Consequently, according to the present embodiment, by providing a plurality of matching circuits that matches so as to have a complex conjugate relationship and differing frequency by which the matching can be performed in each of the matching circuits, it is possible to receive signals with satisfactory sensitivity in the wideband, and realize the receipt with satisfactory sensitivity even when the desired specific narrowband changes. Further, according to the present embodiment, in performing matching in the wideband, since it is possible to decrease the number of the matching circuits compared to the conventional art, it is possible to cut down the manufacturing cost, and make the portable radio apparatus compact and thin. 
         [0169]    In the present embodiment, although an amplifier was not provided, the present invention is not limited hereto, and may be configured as an exclusive receiver by serially providing the amplifier between the matching circuit and the radio section. Further, in the present embodiment, of the plurality of matching circuits, it is possible to vary the frequency by which the matching can be obtained in at least one matching circuit. Further, in the present embodiment, although a case of dealing with one radio system has been described, the present embodiment is not limited hereto; and it is possible to deal with a plurality of radio systems by providing a plurality of radio sections. 
         [0170]    The disclosure of Japanese Patent Application No. 2009-159839 filed on Jul. 6, 2009, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0171]    The portable radio apparatus of the present invention can obtain matching especially in the wideband, as well as can vary the frequency by which the matching is enabled in the narrowband.