Abstract:
The object of the present invention is to provide a high-frequency signal receiving apparatus using a high-frequency signal receiver which performs diversity control by using tuners, wherein the first tuner comprises a first high frequency amplifier gain-controlled by the first gain controller, and a first amplifier gain-controlled by the second gain controller, and the second tuner comprises a second high frequency amplifier gain-controlled by the third gain controller, and a second amplifier gain-controlled by the fourth gain controller, and there is provided a receiving quality detector capable of detecting receiving quality, to which the outputs of the first gain controller, second gain controller, the third gain controller, and the fourth gain controller are connected, and single receiving or diversity receiving is selected by using the detection signal outputted from receiving quality detector.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a high-frequency signal receiver using a diversity antenna, and a high-frequency signal receiving apparatus using the same. 
       BACKGROUND ART 
       [0002]      FIG. 4  is a block diagram of a conventional high-frequency signal receiving apparatus. In  FIG. 4 , high-frequency signal receiving apparatus  1  comprises high-frequency signal receiver  2 , and receiving quality controller  3  connected to high-frequency signal receiver  2 . Also, high-frequency signal receiver  2  comprises tuners  6 ,  7 . 
         [0003]    Tuners  6 ,  7  comprise high-frequency amplifiers  8 ,  9  to which TV broadcasting signals from antennas  4 ,  5  are respectively inputted, mixers  10 ,  11  to which output signals from these high-frequency amplifiers  8 ,  9  are respectively supplied, and demodulators  12 ,  13  to which output signals from these mixers  10 ,  11  are respectively supplied. 
         [0004]    Receiving quality controller  3  comprises diversity section  15  to which the output from demodulators  12 ,  13  is supplied, error corrector  16  to which the output of diversity section  15  is supplied, output terminal  18  to which the output of error corrector  16  is supplied, and diversity controller  19  connected between diversity section  15 , error corrector  16 , and tuners  6 ,  7 . 
         [0005]    The operation of high-frequency signal receiving apparatus  1  having the above configuration will be described in the following. TV broadcasting signals inputted from antennas  4 ,  5  are respectively supplied to tuners  6 ,  7 , and controlled to a stable signal level and converted to a predetermined frequency. The converted signals are inputted to demodulators  12 ,  13  respectively for the purpose of demodulation. The demodulated signals respectively outputted from demodulators  12 ,  13  are separately inputted to diversity section  15 . 
         [0006]    In diversity section  15 , a sub-carrier signal forming a digital signal is detected, and the sub-carrier signal is supplied to diversity controller  19 . Diversity controller  19  activates either one of tuners  6 ,  7  to create a single receiving mode when the sub-carrier detection signal is normal. Also, when the sub-carrier detection signal is abnormal, both of tuners  6 ,  7  are activated to create a diversity receiving mode. In this way, it is possible to assure the receiving quality. 
         [0007]    Also, in the case of detecting the receiving quality, the bit error rate (hereinafter called BER) signal of the error corrector can be used. As preceding technical document information related to this invention, for example, Japanese Laid-open Patent 2001-156738 is commonly known. 
         [0008]    In such a conventional high-frequency signal receiving apparatus, the receiving quality is detected by using BER or sub-carrier detection signal. However, much time is required for signal processing with use of BER or sub-carrier signal. As a result, for example, single receiving and diversity receiving cannot be smoothly changed over during high-speed travel, and it is unable to assure the receiving quality. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention smoothly performs in a short time between single receiving and diversity receiving. 
         [0010]    The high-frequency signal receiver of the present invention comprises a receiving quality detector to which the outputs of the first and third gain controllers are connected, and a third output terminal to which the detection signal from the receiving quality detector is outputted, wherein a single receiving or diversity receiving is selected by the detection signal outputted from the third output terminal. 
         [0011]    In this way, it is possible to immediately detect the receiving quality by using the gain control voltages respectively outputted from the first and third gain controllers. Accordingly, even in case the receiving condition varies during at a high speed travel, it is possible to smoothly perform changeover between single receiving and diversity receiving. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a block diagram of a high-frequency signal receiving apparatus in the preferred embodiment 1 of the present invention. 
           [0013]      FIG. 2  is an explanatory diagram showing the relationship between the desired signal and interference signal input levels and BER in the preferred embodiment 1 of the present invention. 
           [0014]      FIG. 3  is a flow chart showing the selecting operation of the diversity controller in the high-frequency signal receiving apparatus in the preferred embodiment 1 of the present invention. 
           [0015]      FIG. 4  is a block diagram of a conventional high-frequency signal receiving apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred Embodiment 1 
       [0016]      FIG. 1  is a block diagram of a high-frequency signal receiving apparatus in the preferred embodiment 1 of the present invention. In  FIG. 1 , high-frequency signal receiving apparatus  20  comprises high-frequency signal receiver  21  and receiving quality controller  22 . 
         [0017]    High-frequency signal receiver  21  is provided with tuner  31 , tuner  32 , and receiving quality detector  33  connected between tuner  31  and tuner  32 . 
         [0018]    Tuner  31  is provided with high frequency amplifier  50 , mixer  51 , intermediate frequency filter  52 , amplifier  53 , amplifier  54 , A/D converter  55 , filter  56 , and demodulator  57  in the order from input terminal  35  to which antenna  34  is connected toward output terminal  36 . 
         [0019]    Also, the output of oscillator  51   a  is connected to the other input of mixer  51 . Further, demodulation section  59  is formed by A/D converter  55 , filter  56 , demodulator  57 . 
         [0020]    And, gain controller  50   b  for gain control is connected between the output of mixer  51  and gain control input  50   a  disposed in high frequency amplifier  50 . Gain controller  53   b  for gain control is connected between the output of amplifier  53  and gain control input  53   a  disposed in amplifier  53 . Gain controller  54   b  is connected between the output of filter  56  and gain control input  54   a  for gain control which is disposed in amplifier  54 . 
         [0021]    Also, tuner  32  is provided with high frequency amplifier  64 , mixer  65 , intermediate frequency filter  66 , amplifier  67 , amplifier  68 , A/D converter  69 , filter  70 , and demodulator  71  in the order from input terminal  62  to which antenna  61  is connected toward output terminal  63 . The output of oscillator  65   a  is connected to the other input of mixer  65 . Demodulation section  77  is formed by A/D converter  69 , filter  70 , demodulator  71 . 
         [0022]    And, gain controller  64   b  for gain control is connected between the output of mixer  65  and gain control input  64   a  disposed in high frequency amplifier  64 . Gain controller  67   b  for gain control is connected between the output of amplifier  67  and gain control input  67   a  disposed in amplifier  67 . Gain controller  68   b  is connected between the output of filter  70  and gain control input  68   a  for gain control which is disposed in amplifier  68 . 
         [0023]    And, receiving quality detector  33  is provided with input terminals  33   a ,  33   b ,  33   c ,  33   d ,  33   e ,  33   f . These terminals  33   a ,  33   b ,  33   c ,  33   d ,  33   e ,  33   f  are respectively connected with gain control inputs  50   a ,  53   a ,  54   a ,  64   a ,  67   a ,  68   a.    
         [0024]    Receiving quality controller  22  comprises diversity section  80 , error corrector  81 , BER detector  82 , and diversity controller  83 . 
         [0025]    Diversity section  80  comprises input terminal  80   a  to which output terminal  36  is connection, input terminal  80   b  to which output terminal  63  is connected, and output terminal  80   c  connected to input terminal  81   a  of error corrector  81 . 
         [0026]    Diversity section  80  is provided with sub-carrier detector  84  connected between input terminals  80   a  and  80   b , and sub-carrier selector/synthesizer  85  to which input terminals  80   a ,  80   b  are respectively connected. Also, output  84   a  of sub-carrier detector  84  is connected to input  85   a  of sub-carrier selector/synthesizer  85 . And, the output of sub-carrier selector/synthesizer  85  is connected o input terminal  81   a  of error corrector  81  via output terminal  80   c  of diversity section  80 . 
         [0027]    Output terminal  81   b  of error corrector  81  is connected to TS output terminal  22   a . Also, BER output from output terminal  81   c  of error corrector  81  is inputted to input terminal  82   a  of BER detector  82 . Also, input  86   b  of BER detector  82  is connected to BER reference input terminal  22   b  to which external reference signal is inputted. Due to BER reference signal input terminal  22   b , setting to optional value of reference signal can be made, and it is possible to optimize the receiving quality detection standard. 
         [0028]    Further, diversity controller  83  is provided with input terminals  83   a ,  83   b ,  83   c . Detection signal outputted from BER detector  82  is supplied to input terminal  83   a . Sub-carrier detection signal outputted from output terminal  80   d  is supplied to input terminal  80   b  of diversity section  80 . Detection signal outputted from output terminal  33   g  of receiving quality detector  33  is supplied to input terminal  83   c.    
         [0029]    Also, diversity controller  83  is provided with output terminals  83   d ,  83   e ,  83   f . Output terminals  83   d ,  83   e  are respectively connected to power input terminals  31   a ,  32   a  for supply voltage application which are disposed in tuners  31 ,  32 . The signal outputted from output terminal  83   f  for controlling diversity section  80  is supplied to input terminal  80   e  of diversity section  80 . 
         [0030]    The operation of high-frequency signal receiving apparatus  20  having the above configuration will be described with reference to  FIG. 1 . 
         [0031]    Digital broadcasting signal recently introduced is lowered in transmission output level so as to avoid influences to the existing analog broadcasting signal. For example, there is a possibility such that digital broadcasting signal being an desired signal causes the received signal level to become higher by nearly 40 dB than analog broadcasting signal being an interference signal. For example, when the received signal level of 13ch for digital broadcast is −50 dBm, the received signal level of 25ch for analog broadcast may sometimes become −10 dBm. 
         [0032]    That is, when a digital broadcasting signal is received, it is interfered by an analog broadcasting signal of higher level, causing distortion to be generated at high-frequency receiver  21  for example, and it is unable to obtain normal signal receiving. 
         [0033]    Particularly, since the interference signal is not sufficiently suppressed before filter  52 , distortion is generated due to an interference signal of higher level in amplifier circuit  50 , mixer  51 . 
         [0034]    On the other hand, when a digital broadcasting signal is received in a suburb, there arises a problem of receiving sensitivity of high-frequency signal receiving apparatus  20 , that is, it is unable to obtain normal signal reception. 
         [0035]    For improving the receiving quality, it is possible to realize the improvement by performing changeover from single receiving to diversity receiving. 
         [0036]    Diversity receiving is such that both of tuners  31 ,  32  are operated and, at the same time, demodulation signals respectively outputted from tuners  31 ,  32  are synthesized in diversity section  80  before signal receiving. Also, single receiving is such that either one of tuner  31  and tuner  32  is operated before signal receiving. 
         [0037]    Firstly, diversity receiving is described. Supply voltages from output terminals  83   d ,  83   e  of diversity controller  83  are supplied to power input terminals  31   a ,  32   a  of tuners  31 ,  32 . And, same tuning data is delivered to tuners  31 ,  32  before start of receiving operation. 
         [0038]    And, TV broadcasting signal inputted from antenna  34  is inputted to high frequency amplifier  50  via input terminal  35  of tuner  31 . In high frequency amplifier  50 , gain control is performed so that the output level of mixer  51  is kept constant by gain controller  50   b.    
         [0039]    The output signal from high frequency amplifier  50  and the output of oscillator  51   a  are inputted to mixer  51 . For the intermediate frequency signal outputted from mixer  51 , interference signal is suppressed by interference frequency filter  52 . The output signal from intermediate frequency filter  52  is inputted to amplifier  53 . In amplifier  53 , gain control is performed so that the output level of amplifier  53  is kept constant by gain controller  53   b.    
         [0040]    The intermediate frequency signal outputted from amplifier  53  is inputted to amplifier  54 . In amplifier  54 , gain control is performed by gain controller  54   b  so that the input level to demodulator  57  is kept constant. 
         [0041]    Further, the output signal from amplifier  54  is converted from analog signal to digital signal by A/D converter  55 . For the digital signal, interference signal is suppressed by filter  56 . The output signal of filter  56  is demodulated by demodulator  57 . The transport stream (hereinafter called TS) signal outputted from amplifier  57  is outputted from output terminal  36 . 
         [0042]    Similarly, the TV broadcasting signal inputted from antenna  61  is inputted to high frequency amplifier  64  via input terminal  62  of tuner  32 . In high frequency amplifier  64 , gain control is performed so that the output level of mixer  65  is kept constant by gain controller  64   b.    
         [0043]    Also, both of the output signal from high frequency amplifier  64  and the output of oscillator  65   a  are inputted to mixer  65 . For the intermediate frequency signal outputted from mixer  65 , interference signal is suppressed by intermediate frequency filter  66 . The output signal from intermediate frequency filter  66  is inputted to amplifier  67 . For amplifier  67 , gain control is performed so that the output level of amplifier  67  is kept constant by gain controller  67   b.    
         [0044]    The intermediate frequency signal outputted from amplifier  67  is inputted to amplifier  68 . For amplifier  68 , gain control is performed by gain controller  68   b  so that the input level to demodulator  71  is kept constant. 
         [0045]    Further, the output signal of amplifier  68  is converted from analog signal to digital signal by A/D converter  69 . For the digital signal, interference signal is suppressed by filter  70 . The output signal from filter  70  is demodulated by demodulator  71 . The demodulation signal outputted from demodulator  71  is outputted from output terminal  63 . 
         [0046]    Demodulation signals outputted from output terminals  36 ,  63  are respectively inputted to input terminals  80   a ,  80   b  of diversity section  80 . 
         [0047]    In diversity section  80 , the signal quality of sub-carrier contained in two demodulation signals is detected by sub-carrier detector  84 . In accordance with the signal quality information then detected, the weighting coefficient is calculated with respect to each sub-carrier. The weighting efficiency is inputted from output  84   a  of sub-carrier detector  84  to input  85   a  of sub-carrier selector/synthesizer  85 . 
         [0048]    Further, as to each sub-carrier, in sub-carrier selector/synthesizer  85 , the sub-carrier synthesized signal with it multiplied by the weighting coefficient is outputted from output terminal  80   c . Thus, the synthesized signal is improved in C/N two times max. by the weighting coefficient. 
         [0049]    And, the sub-carrier synthesized signal is inputted to input terminal  81   a  of error corrector  81 . The error-corrected TS signal is outputted from output terminal  81   b  of error corrector  81 . In this way, the error-corrected signal improved in C/N two times max. is outputted from output terminal  22   a , thereby improving the receiving quality. 
         [0050]    It is preferable to use C/N detector which can detect C/N (carrier vs. noise) in place of BER detector  82 . 
         [0051]    Next, changeover from diversity receiving to single receiving through control of diversity controller  83  will be described in the following. In single receiving, for example, tuner  31  is in a state of operation, and tuner  32  is in a state of non-operation. 
         [0052]    The operation of changeover from diversity receiving to single receiving is controlled by diversity controller  83 . That is, input terminals  83   a ,  83   b ,  83   c  of diversity controller  83  respectively receive the BER detection signal outputted from BER detector  82 , sub-carrier detection signal outputted from diversity section  80 , and receiving quality detection signal outputted from receiving quality detector  33  (described later). It is possible to detect the receiving quality by using at least one of the three detection signals. 
         [0053]    In accordance with the receiving quality detection, the supply voltage is outputted from only one of output terminals  83   d ,  83   e  of diversity controller  83 , and therefore, for example, one tuner  32  is shifted from operation mode to non-operation mode, and the other tuner  31  is shifted to operation mode. 
         [0054]    As a result, demodulation signal outputted from tuner  31  is inputted to terminal  80   a  of diversity section  80 . On the other hand, no demodulation signal is inputted to input terminal  80   b . Demodulation signal outputted from output terminal  80   c  of diversity section  80  is inputted to input terminal  81   a  of error corrector  81 , and corrected TS signal is outputted from output terminal  22   a.    
         [0055]      FIG. 2  is an explanatory diagram showing the relationship between the desired signal, interference signal input level, and BER of a high-frequency signal receiving apparatus in the preferred embodiment 1 of the present invention. That is, the diagram shows the relationship between input signal level  101  and BER  102  in input terminal  35  of high-frequency signal receiving apparatus  20  for single receiving. In  FIG. 2 , BER  102   a  stands for error-free (generating no error). BER  103  is a reference value (2×10 −4 ) for determining the receiving quality, and when greater than this reference value, it is determined that the receiving quality is bad. 
         [0056]    In this high-frequency signal receiving apparatus  20 , for example, the gain control of high frequency amplifier  50  ranges from 0 to −50 dBm (value at input terminal  35 ). The gain control of amplifier  53  ranges from −50 dBm to −90 dBm (value at input terminal  35 ). The gain control range of amplifier  54  less than −90 dBm (value at input terminal  35 ). Also, the ranges of gain control can be changed to optimum ranges according to the gain and distortion of high frequency amplifier  50 , amplifiers  53 ,  54 , mixer  51  and the like. 
         [0057]    Characteristic curve  104  represents BER in the case of receiving only the desired signal. In characteristic curve  104 , when a desired signal of input signal level  101   b  (around −10 dBm) is inputted, it is regarded as extra-strong electric field receiving level, that is, receiving condition D 1 . When a desired signal of higher than input signal level  101   e  (−50 dBm) is inputted, it is regarded as strong electric field receiving level, that is, receiving condition D. When a desired signal of input signal level  101   e  (−50 dBm) to input signal level  101   c  (−90 dBm) is inputted, it is regarded as medium electric field receiving level, that is, receiving condition E. When a desired signal of input signal level  101   c  (−90 dBm) to input signal level  101   g  (−100 dBm) is inputted, it is regarded as weak electric field receiving level, that is, receiving condition F. When a desired signal of input signal level  101   a  (around −110 dBm) is inputted, it is regarded as very weak electric field receiving level, that is, receiving condition F 1 . 
         [0058]    For example, in the case of input signal level  101   c  (−90 dBm) of receiving condition F, the BER is  102   b , and in the case of input signal level  101   a  (−110 dBm), the BER is further deteriorated. This is due to the fact that the signal received by antenna  34  is very weak, and further, due to the noise index of tuner  31 . 
         [0059]    Also, in the case of input signal level higher than input signal level  101   d  (−20 dBm) of receiving condition D, the BER is deteriorated. This is because a very high level of desired signal is inputted to tuner  31 , resulting in generation of distortion. Particularly, in case a signal of higher than input signal level  101   b  (−10 dBm) is inputted, the influence of distortion due to high frequency amplifier  50  or mixer  51  will be very great. 
         [0060]    Characteristic curve  105  represents BER in the case of receiving a desired signal and an interference signal nearly 40 dB greater than the desired signal. Characteristic  105  is described in the following. 
         [0061]    In receiving condition C, great interference signal (−50 dBm) is inputted along with a desired signal of input signal level  101   c  (around −90 dBm). In this case, it is deteriorated from BER  102   b  to BER  102   c  due to the interference signal (−50 dBm). 
         [0062]    In receiving condition B, great interference signal (−20 dBm) is inputted along with a desired signal of input signal level  101   f  (−60 dBm). In this case, it is deteriorated from BER  102   a  or less to BER  102   e  due to the interference signal (−20 dBm). 
         [0063]    In receiving condition A, great interference signal (−10 dBm) is inputted along with a desired signal of input signal level  101   e  (−50 dBm). In this case, it is deteriorated to BER  102   d  due to the interference signal (−10 dBm). 
         [0064]    That is, since an interference signal greater by 40 dB than the desired signal is inputted, the gain is controlled by the interference signal in high frequency amplifier  50 , and the gain is controlled with respect to the desired signal as well. Consequently, the noise index of high frequency amplifier  50  becomes extremely great, and it causes deterioration of the ratio of noise signal level to desired signal level. Or, distortion is generated in high frequency amplifier  50  and mixer  51  due to such a great interference signal. 
         [0065]    As described above, the BER worsens in the cases of receiving condition F 1  for desired signal input of a very weak electric field receiving level, receiving condition D 1  for desired signal input of strong electric field receiving level, and receiving conditions A, B for great interference signal input to the desired signal. The BER can be compared with the reference value for BER (2×10 −4 ) by using BER detector  82 . 
         [0066]    However, for the detection of BER by using BER detector  82 , it requires a long length of time for signal processing although the detection accuracy is very high. Also, in the case of detecting the quality of sub-carrier signal in diversity section  80 , it requires a long length of time for signal processing. 
         [0067]    As a result, in the conventional high-frequency signal receiving apparatus, it is unable to perform sufficient detection during high-speed travel. Also, it is difficult to detect whether the receiving quality is deteriorated due to great desired signal, very weak desired signal, or great interference signal. 
         [0068]    On the other hand, the high-frequency signal receiving apparatus of the present invention comprises receiving quality detector  33  capable of detecting whether the receiving quality is deteriorated due to a specific receiving condition even during high-speed travel. The operation of receiving quality detector  33  is described in the following. 
         [0069]    Table 1 shows the status of gain control of high frequency amplifier  50 , amplifier  53 ,  54  of high-frequency signal receiving apparatus  20  in the cases of receiving conditions A to F, D 1 , F 1 . 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 High 
                   
                   
               
               
                   
                 frequency 
               
               
                 Receiving conditions 
                 amplifier 50 
                 Amplifier 53 
                 Amplifier 54 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 A 
                 Interference signal 
                 Minimum 
                 Maximum 
                 Minimum 
               
               
                   
                 −10 dBm 
                 gain 
                 gain 
                 gain 
               
               
                   
                 Desired signal 
               
               
                   
                 −50 dBm 
               
               
                 B 
                 Interference signal 
                 Medium 
                 Maximum 
                 Minimum 
               
               
                   
                 −20 dBm 
                 gain 
                 gain 
                 gain 
               
               
                   
                 Desired signal 
                 (−30 dB) 
               
               
                   
                 −60 dBm 
               
               
                 C 
                 Interference signal 
                 Maximum 
                 Maximum 
                 Minimum 
               
               
                   
                 −50 dBm 
                 gain 
                 gain 
                 gain 
               
               
                   
                 Desired signal 
               
               
                   
                 −90 dBm 
               
               
                 D1 
                 Desired signal 
                 Minimum 
                 Minimum 
                 Minimum 
               
               
                   
                 −10 dBm or over 
                 gain 
                 gain 
                 gain 
               
               
                 D 
                 Desired signal 
                 Maximum 
                 Minimum 
                 Minimum 
               
               
                   
                 −10 to −50 dBm 
                 gain-Minimum 
                 gain 
                 gain 
               
               
                   
                   
                 gain 
               
               
                 E 
                 Desired signal 
                 Maximum 
                 Maximum 
                 Minimum 
               
               
                   
                 −50 to −90 dBm 
                 gain 
                 gain- 
                 gain 
               
               
                   
                   
                   
                 Minimum 
               
               
                   
                   
                   
                 gain 
               
               
                 F 
                 Desired signal 
                 Maximum 
                 Maximum 
                 Maximum 
               
               
                   
                 −90 to −100 dBm 
                 gain 
                 gain 
                 gain-Minimum 
               
               
                   
                   
                   
                   
                 gain 
               
               
                 F1 
                 Desired signal 
                 Maximum 
                 Maximum 
                 Maximum 
               
               
                   
                 −100 dBm or less 
                 gain 
                 gain 
                 gain 
               
               
                   
               
             
          
         
       
     
         [0070]    In receiving condition A, interference signal of −10 dBm and desired signal of −50 dBm are inputted to input terminal  35 . Interference signal of −10 dBm and desired signal of −50 dBm are inputted to high frequency amplifier  50 . The gain control range of high frequency amplifier  50  is −10 dBm to −50 dBm (value at input terminal  35 ). In high frequency amplifier  50  to which interference signal of −10 dBm is inputted, the amount of gain control is 40 dB that is minimum gain obtained by subtracting the gain control of −50 dBm from the interference signal of −10 dBm. 
         [0071]    The interference signal output from high frequency amplifier  50  is greatly attenuated by filter  52 , and the desired signal output from high frequency amplifier  50  is inputted to amplifier  53 . The desired signal inputted to amplifier  53  is −90 dBm (value at input terminal  35 ) obtained by subtracting the amount of gain control 40 dB from desired signal −50 dBm. The gain control range of amplifier  53  is −50 dBm to −90 dBm (value at input terminal  35 ). Therefore, the gain of amplifier  53  is maximum gain due to the gain control voltage of gain controller  53   b.    
         [0072]    Further, the gain-controlled output signal from amplifier  53  is inputted to amplifier  54 . The desired signal inputted to amplifier  54  is −90 dBm (value at input terminal  35 ). The gain control of amplifier  54  is −90 dBm or less (value at input terminal  35 ). Therefore, obtained in amplifier  54  is minimum gain due to the gain control voltage of gain controller  54   b.    
         [0073]    Next, in receiving condition B, interference signal of −20 dBm and desired signal of −60 dBm are inputted to input terminal  35 . Interference signal of −20 dBm and desired signal of −60 dBm are inputted to high frequency amplifier  50 . The gain control range of high frequency amplifier  50  is −10 dBm to −50 dBm (value at input terminal  35 ). In high frequency amplifier  50  to which interference signal of −20 dBm is inputted, the amount of gain control is 30 dB that is medium gain obtained by subtracting the gain control of −50 dBm from the interference signal of −20 dBm. 
         [0074]    The interference signal output from high frequency amplifier  50  is greatly attenuated by filter  52 , and the desired signal output from high frequency amplifier  50  is inputted to amplifier  53 . The desired signal inputted to amplifier  53  is −90 dBm obtained by subtracting the amount of gain control 30 dB from desired signal −60 dBm (value at input terminal  35 ). The gain control range of amplifier  53  is −50 dBm to −90 dBm (value at input terminal  35 ). Therefore, the gain of amplifier  53  is maximum gain due to the gain control voltage of gain controller  53   b.    
         [0075]    Further, the gain-controlled output signal from amplifier  53  is inputted to amplifier  54 . The desired signal inputted to amplifier  54  is −90 dBm (value at input terminal  35 ). The gain control range of amplifier  54  is −90 dBm or less (value at input terminal  35 ). Therefore, the gain of amplifier  54  is minimum gain due to the gain control voltage of gain controller  54   b.    
         [0076]    Next, in receiving condition C, interference signal of −50 dBm and desired signal of −90 dBm are inputted to input terminal  35 . Interference signal of −50 dBm and desired signal of −90 dBm are inputted to gain controller  50   b , and the gain control voltage output from gain controller  50   b  is inputted to gain control input  50   a . Therefore, the gain of high frequency amplifier  50  is maximum gain. Further the interference signal output from mixer  51  is mainly greatly attenuated by filter  52 . 
         [0077]    On the other hand, the desired signal of −90 dBm (value at input terminal  35 ) is outputted from high frequency amplifier  50  obtaining maximum gain. Further, the desired signal of −90 dBm (value to input terminal  35 ) is inputted to amplifier  53 . The gain of amplifier  53  is maximum gain due to gain controller  53   b . Further, the desired signal of −90 dBm (value at input terminal  35 ) is inputted to amplifier  54 . The gain of amplifier  54  is minimum gain due to gain controller  54 . 
         [0078]    In the case of receiving condition C where the interference signal of −50 dBm and desired signal of −90 dBm are inputted to the input terminal, the receiving quality is not deteriorated because the level of interference signal is as low as −50 dBm. 
         [0079]    Next, in receiving condition D, only desired signal of −10 to −50 dBm is inputted to input terminal  35 . Desired signal of −10 to −50 dBm is inputted to high frequency amplifier  50 . The gain control range of high frequency amplifier  50  is −10 dBm to −50 dBm (value at input terminal  35 ). Therefore, due to the gain control voltage of gain controller  50   b , the gain of high frequency amplifier  50  is minimum gain˜maximum gain. 
         [0080]    The gain-controlled output signal from high frequency amplifier  50  is inputted to amplifier  53 . The desired signal inputted to amplifier  53  is −90 dBm (value at input terminal  35 ). The gain control range of amplifier  53  is −50 dBm to −90 dBm (value at input terminal  35 ). Therefore, the gain of amplifier  53  is minimum gain due to the gain control voltage of gain controller  53   b.    
         [0081]    Further, the gain-controlled output signal from amplifier  53  is inputted to amplifier  54 . The desired signal inputted to amplifier  54  is −90 dBm (value at input terminal  35 ). The gain control range of amplifier  54  is −90 dBm or less (value at input terminal  35 ). Therefore, the gain of amplifier  54  is minimum gain due to the gain control voltage of gain controller  54   b.    
         [0082]    In receiving condition D 1 , only the desired signal of −10 dBm is inputted to input terminal  35 . That is, it is included in receiving condition D. 
         [0083]    Next, in receiving condition E, only the desired signal of −50 to −90 dBm is inputted to input terminal  35 . The desired signal of −50 to −90 dBm is inputted to high frequency amplifier  50 . The gain control range of high frequency amplifier  50  is 0 dBm to −50 dBm (value at input terminal  35 ), the gain of high frequency amplifier  50  is maximum gain. 
         [0084]    The desired signal output from amplifier  50  is inputted to amplifier  53 . The gain control range of amplifier  53  is −50 dBm to −90 dBm (value at terminal  35 ). Therefore, the gain of amplifier  53  is minimum gain˜maximum gain due to the gain control voltage of gain controller  53   b.    
         [0085]    Further, the desired signal output from amplifier  53  is inputted to amplifier  54 . The gain control range of amplifier  54  is −90 dBm or less (value at input terminal  35 ). Therefore, the gain of amplifier  54  is minimum gain due to the gain control voltage of gain controller  54   b.    
         [0086]    Next, in receiving condition F, only the desired signal of −90 dBM to −100 dBm is inputted to input terminal  35 . The desired signal of −90 dBm to −100 dBm is inputted to high frequency amplifier  50 . Since the gain control range of high frequency amplifier  50  is 0 dBm to −50 dBm (value at input terminal  35 ), the gain of high frequency amplifier  50  is maximum gain. 
         [0087]    The desired signal output from high frequency amplifier  50  is inputted to amplifier  53 . The gain control range of amplifier  53  is −50 dBm to −90 dBm (value at input terminal  35 ). Therefore, the gain of amplifier  53  is maximum gain due to the gain control voltage of gain controller  53   b.    
         [0088]    Further, the desired signal output from amplifier  53  is inputted to amplifier  54 . The gain control range of amplifier  54  is −90 dBm or less (value at input terminal  35 ). Therefore, the gain of amplifier  54  is minimum gain due to the gain control voltage of gain controller  54   b.    
         [0089]    In receiving condition F 1 , only the desired signal of around −110 dBm is inputted to input terminal  35 . Therefore, all the gains of high frequency amplifiers  50 ,  53 ,  54  are maximum gains. 
         [0090]    As described above, for example, in receiving condition D, E, F where only the desired signal is inputted, the gain control voltage output from gain controller  50   b ,  53 ,  54   b  varies in accordance with the level of desired signal. 
         [0091]    That is, in the case of desired signal −90 dBm or less (value at input terminal  35 ), the gain control voltage of gain controller  54   b  changes to maximum gain˜minimum gain. Further, in the case of desired signal −50 to −90 dBm (value at input terminal  35 ), the gain control voltage of gain controller  53   b  changes to maximum gain˜minimum gain. And, in the case of desired signal −10 to −50 dBm (value at input terminal  35 ), the gain control voltage of gain controller  50   b  changes to maximum gain˜minimum gain. 
         [0092]    On the other hand, in receiving condition A where interference signal −10 dBm and desired signal −50 dBm are inputted, or in receiving condition B where interference signal −20 dBm and desired signal −60 dBm are inputted, the gains of high frequency amplifier  50  become minimum gain and medium gain respectively due to the high level of interference signal, while the gain of amplifier  53  is maximum gain. 
         [0093]    Thus, in each of receiving conditions C, D, E, F, as the level of desired signal being the received signal becomes higher, the gain control is performed in the order of amplifiers  54 ,  53 ,  50 . On the other hand, in receiving condition A, B, as the level of interference signal becomes higher, the gain control is performed in the order of high frequency amplifiers  50 , amplifier  53 . 
         [0094]    As is obvious in the above description, the gain control voltage of high frequency amplifier  50  and the gain control voltage of amplifier  53  are compared and detected by receiving quality detector  33 , and thereby, the respective differences between receiving conditions C, D, E, F and receiving conditions A, B, D 1 , F 1  can be detected. 
         [0095]    That is, in receiving conditions C, D, E, F, the gain of amplifier  53  is set to same or smaller gain as compared with the gain of high frequency amplifier  50 . Also, the difference in receiving conditions C, D, E, F is such that high frequency amplifier  50  and amplifier  53  are different from each other in gain control amount. Further, the difference in receiving conditions A, B is such that high frequency amplifier  50  and amplifier  53  are different from each other in gain control amount. 
         [0096]    Accordingly, the receiving condition can be detected in accordance with the difference in gain control voltage corresponding to the gain control amount of high frequency amplifier  50  and amplifier  53 . 
         [0097]    In the case of detecting the receiving condition, it is preferable to use the gain control voltage by which high frequency amplifier  50 , amplifiers  53 ,  54  are controlled. In this way, it is possible to correctly detect the levels of desired signal and interference signal. 
         [0098]    Further, in the case of detecting the receiving condition, it is preferable to use both of the gain control voltage by which high frequency amplifier  50 , amplifiers  53 ,  54  and the gain control voltage by which high frequency amplifier  64 , amplifiers  67 ,  68  are controlled. Thus, it is possible to select a tuner of good receiving quality by comparing the gain control voltage of tuner  31  or  32 . 
         [0099]    Further, receiving quality detector  33  is provided with reference voltage input terminal  21   a . The upper limit value and the lower limit value of the reference voltage value can be inputted from the reference voltage input terminal  21   a . Accordingly, the standard voltage value of receiving quality detector  33  can be easily externally set in accordance with the gain share and interference characteristic in tuner  31 ,  32 . 
         [0100]    As described above, receiving conditions C, D, E, F of good receiving quality and receiving conditions A, B, D 1 , F 1  of gad receiving quality can be detected by receiving quality detector  33  by using the gain control voltage by which high frequency amplifier  50  and amplifier  53  are controlled. Due to diversity controller  83  to which the detection signal is inputted, it is possible to realize single receiving in receiving conditions C, D, E, F of good receiving quality, and diversity receiving in receiving conditions A, B, D 1 , F 1  of bad receiving quality. 
         [0101]    In this way, receiving quality is detected by using receiving quality detector  33  which compares and detects each gain control voltage. The gain control voltage is very excellent in follow-up characteristic for detection with voltage even in case the receiving condition changes during mobile receiving. 
         [0102]    Accordingly, for example, even in case of high-speed travel during which time the receiving condition changes every second, it is possible to smoothly perform the changeover between single receiving and diversity receiving without affecting the receiving quality. 
         [0103]    It is preferable to insert A/D converter (analog digital converter) (not shown) for converting voltage to digital between gain controller  50   b ,  53   b ,  54   b  and the receiving quality detector, and to process the signal of digital value outputted from the A/D converter by using I 2 C bus line. In this case, the wiring is simplified because it is possible to process the signal by using a common I 2 C bus line. 
         [0104]    Further, in the preferred embodiment 1 of the present invention, as an example, BER input from error corrector  81  is inputted to BER detector  82 , but it is also preferable to use C/N detector (not shown) capable of detecting C/N value in place of BER detector  82 . 
         [0105]    Furthermore, in the preferred embodiment 1, the gain control voltages from two tuners, tuners  31 ,  32  are detected by receiving quality detector  33 , but it is also preferable to use n (n is natural number, 3 or over) pieces of tuners and to connect the gain control voltages of n pieces of tuners to a receiving quality detector (not shown) for the detection of receiving quality. 
         [0106]      FIG. 3  is a flow chart showing the operation of selection by diversity controller in the high-frequency signal receiving apparatus in the preferred embodiment 1 of the present invention. That is, the flow chart shows the method of selecting single receiving and diversity receiving by diversity controller  83  of high-frequency signal receiving apparatus  20 . 
         [0107]    In  FIG. 3 , first at start of signal receiving, diversity receiving is executed in diversity receiving step S 111 . In signal level detection step S 112 , the receiving condition can be detected by receiving quality detector  33  with use of the gain control voltages of high frequency amplifier  50 , amplifier  53 ,  54 , or high frequency amplifier  64 , amplifier  67 ,  68 . 
         [0108]    As a result of the detection, in the case of receiving condition A, B, D 1 , F 1 , it returns to diversity receiving step S 111  to execute diversity receiving. On the other hand, in the case of receiving condition C, D, E, F, it goes to single receiving step S 113  to execute single receiving. 
         [0109]    During the single receiving, it goes to receiving quality detection step S 114 , and diversity controller  83  detects the receiving quality by using the detection signal of BER detector  82  or diversity section  80 . When the receiving quality is good, it returns to the single receiving in single receiving step S 113 . On the other hand, when the receiving quality is bad, it returns to diversity receiving step S 111 . 
         [0110]    In this case, the detection standard in receiving quality detector  33  used in signal level detection step S 112  is to be set stricter than the detection standard in BER detector  82  or diversity section  80  used in receiving quality detection step S 114 . 
         [0111]    This is because the detection accuracy of receiving quality detector  33  is rather lower than the detection accuracy of BER detector  82  or diversity section  80 . However, the detection time of receiving quality detector  33  is faster as compared with the detection time of BER detector  82  or diversity section  80 . 
         [0112]    Because of the operation as described above, it is possible to instantaneously detect the receiving quality by using gain control voltages outputted from gain controllers  50   b ,  53   b ,  54   b  or gain controllers  64   b ,  67   b ,  68   b  respectively. Accordingly, single receiving and diversity receiving can be smoothly changed over even when the receiving condition changes during high-speed travel. 
         [0113]    As to the input to gain controller  50   b ,  64   b , it is preferable to connect the output of filter  52 ,  66  instead of connecting the output of mixer  51 ,  65 . In this case, since the interference signal is suppressed by filter  52 ,  66 , the influence of interference signal is suppressed for gain control in high frequency amplifier  50 ,  64 . 
         [0114]    Further, as to the input to gain controller  53   b ,  67   b , it is preferable to connect the output of filter  56 ,  70  respectively. In this case, since the interference signal can be suppressed by filter  56 ,  70 , the influence of interference signal is suppressed for gain control in high frequency amplifier  54 ,  68 . 
         [0115]    Furthermore, in tuners  31 ,  32 , mixers  51 ,  65  are used in single super, but same effects can be obtained even in case of using them in direct conversion. Thus, in the case of direct conversion, the frequency after direct conversion becomes a low frequency signal of I, Q signal. That is, the signal is processed at a low frequency, and it becomes easier to integrate the circuit. Also, interference with other signals hardly takes place. 
         [0116]    As the receiving condition, not only in the relationship between the signal levels of digital broadcasting signal and analog broadcasting signal, but also in the relation of digital broadcasting signal levels with each other or the relation of digital broadcasting signal levels with each other, the effects of preferred embodiment 1 remain unchanged. 
         [0117]    The high-frequency signal receiver of the present invention is able to smoothly perform the changeover between single receiving and diversity receiving, and it can be applied to mobile portable equipment and the like.