Abstract:
Disclosed herein is a digital broadcast receiving apparatus configured to receive terrestrial digital television broadcasting and satellite digital broadcasting, including: a terrestrial digital tuner; a satellite digital tuner; a demodulating block configured to demodulate a reception signal of the terrestrial digital television broadcasting with an output supplied from the terrestrial digital tuner, and, at the same time, demodulate a reception signal of the satellite digital broadcasting with an output supplied from the satellite digital tuner; a terrestrial digital tuner control block; a satellite digital tuner control block; and a switching block configured to switch output terminals of the demodulating block in accordance with a positional arrangement of the terrestrial digital tuner and the satellite digital tuner relative to the demodulating block.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present invention contains subject matter related to Japanese Patent Application JP 2007-229476 filed in the Japan Patent Office on Sep. 4, 2007, the entire contents of which being incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to digital broadcast receiving apparatuses and, more particularly, to a digital broadcast receiving apparatus configured to receive both satellite digital broadcasting and terrestrial digital broadcasting. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, the digitization of broadcasting has been speeded up, with the satellite digital broadcasting implemented from 2000 by use of the SHF band. Also, from December 2003, the terrestrial digital television broadcasting started by use of the UHF band. In addition, the experimental broadcasting of the terrestrial digital audio broadcasting has started by use of the VHF band. 
         [0006]    In the service form of the satellite digital broadcasting, each of the programs produced by broadcasting companies A, B, and so on is transmitted to an uplink center in the form of TS (Transport Stream) of MPEG-2 (Motion Picture Experts Group-2) to be time-division multiplexed, the multiplexed program being transmitted to a transmitter station. In the transmitter station, a carrier having a predetermined frequency is modulated by the time-division multiplexed transport stream into transmission signal, which is transmitted to a BS (Broadcasting Satellite) via a transmission antenna. 
         [0007]    In the broadcasting satellite, the frequency of the transmission signal received from the transmitter station is converted into a frequency of the broadcasting band of the satellite digital broadcasting and then resultant signal is amplified to be transmitted to the ground. The transmission signal transmitted from the transmitter station is received at a reception antenna to be supplied to a satellite digital broadcast receiving apparatus. It should be noted that, at the present time (year 2004), four channels, namely, four carrier frequencies, are used for the satellite digital broadcasting in Japan. 
         [0008]    In a relation between the channel and frequency for use in the satellite digital broadcasting, channel  1  (BS 1 ), channel  3 , channel  13 , and channel  15  in the 12-GHz band allocated to the Japanese satellite broadcasting are used for digital broadcasting. 
         [0009]    In the satellite digital broadcasting, a broadcast signal is retransmitted by use of two or more transponders corresponding to channels arranged in a broadcasting satellite. Broadcast signals for one channel are transmitted from the satellite by use of one transponder. If there are eight satellite broadcasting channels, eight transponders are used for the satellite digital broadcasting. At the present, four of the eight channels are used for the satellite digital broadcasting and the remaining four channels are used for the satellite analog broadcasting. 
         [0010]    The broadcast signals for one channel of the satellite digital broadcasting include two or more broadcasting services. For the types of broadcasting services included in channel  1  (BS 1 ), the signals to be transmitted on channel  1  (BS 1 ) are divided into two or more transport streams, each transport stream being allocated to each broadcasting company for broadcasting. Channel  1  (BS 1 ) contains the television broadcasting, the audio broadcasting, and the data broadcasting at the same time. 
         [0011]    The channels of the satellite digital broadcasting have frequencies different to each other, so that, in each satellite digital broadcasting apparatus, an incorporated tuner is controlled so as for the signal having the frequency of a desired channel to be received, thereby receiving the broadcast signal of the channel  1  (BS 1 ). 
         [0012]    As described above, the transport streams of the broadcast signals of channel  1  (BS 1 ) includes the information of the television broadcast, the audio broadcasting, and the data broadcasting, so that all transport streams of the broadcast signals of channel  1  (BS 1 ) are received and only the transport streams of a predetermined portion are extracted for decoding. 
         [0013]    Consequently, any of the television broadcasting, the audio broadcasting, and the data broadcasting can be received by one type of tuner. Therefore, in the satellite digital broadcast receiving apparatus, the audio broadcasting and the data broadcasting can be received by use of a circuit configured to receive the television broadcasting. 
         [0014]    As with this satellite digital broadcast receiving apparatus, terrestrial digital broadcast receiving apparatuses for receiving the terrestrial digital broadcasting are configured to receive any of the television broadcasting, the audio broadcasting, and data broadcasting with tuners of one type. 
         [0015]    Referring to  FIG. 16 , there is shown a schematic diagram illustrating a tuner circuit and a demodulating circuit in a related-art digital broadcast receiving apparatus. The related-art digital broadcast receiving apparatus has three circuits; a terrestrial digital broadcast tuner circuit  151 , a satellite digital broadcast tuner circuit  152 , and a demodulating circuit  153  configured to demodulate an IF (Intermediate Frequency) signals  166  and  169  of the reception signals of these two schemes. 
         [0016]    The IF signals  166  and  169  of the reception signals of these two schemes are analog signals, so that these signals are converted by an A/D converting circuits  160  and  162 , respectively, into digital signals in the preprocessing of the demodulating circuit  153 . The demodulating circuit  153  demodulates there digital signals. The demodulating circuits  153  has a terrestrial digital broadcast tuner circuit control block  154  and a satellite digital broadcast tuner circuit control block  155  configured to execute control in the circuit. 
         [0017]    The terrestrial digital broadcast tuner circuit control block  154  and the satellite digital broadcast tuner circuit control block  155  have an AGC (Automatic Gain Control)  161  and an AGC  163 , respectively. AGC signals of the AGC  161  and AGC  163  are fed back to the terrestrial digital broadcast tuner circuit  151  and the satellite digital broadcast tuner circuit  152  via a terminal  156  and a terminal  158 , respectively. Control is executed such that the AGC signals are passed to an intermediate frequency amplifying circuit in the tuner circuit  151  and an intermediate frequency amplifying circuit in the tuner circuit  152  to be automatically amplified to an optimum level in these amplifying circuits. The control for optimizing the IF signal amplitude consequently widens dynamic range DR of the A/D converting circuits  160  and  162 . 
         [0018]    Serial communications signals  165  and  167 , such as various setting data, are bidirectionally communicable between the terrestrial digital broadcast tuner circuit  151  and the satellite digital broadcast tuner circuit  152  and the terrestrial digital broadcast tuner circuit control block  154  and the satellite digital broadcast tuner control block  155  via the terminals  157  and  158 , respectively. 
         [0019]    A digital demodulating circuit configured to replace terminals of a digital modulating circuit has also been proposed (refer to Japanese Patent Laid-Open No. 2003-125302, hereinafter referred to as Patent Document 1). Namely, if the reception of two broadcast programs is desired and these two broadcast programs are on different frequency channels, then baseband signals (I signal and Q signal) outputted from two lines of tuner blocks are supplied to two lines of demodulating blocks, respectively. 
         [0020]    If two broadcast programs of which reception is desired are on one frequency channel, then a signal switching circuit operates such that the baseband signals (I signal, Q signal) are switched so as to supply the baseband signals (I signal, Q signal) outputted from one line of tuner block to two lines of demodulating blocks. 
       SUMMARY OF THE INVENTION 
       [0021]    Configuring the above-mentioned digital broadcast receiving apparatus shown in  FIG. 16  has the following restrictions. Namely, terminals  156 ,  157 ,  158 , and  159  are arranged in the demodulating circuit  153  in a fixed manner for controlling two tuners, the terrestrial digital broadcast tuner circuit  151  and the satellite digital broadcast tuner  152 . 
         [0022]    Consequently, the above-mentioned configuration limits the freedom in the circuit arrangement of the terrestrial digital broadcast tuner circuit  151 , the satellite digital broadcast tuner circuit  152 , and the demodulating circuit  153 . The following describes an example in which the freedom in circuit arrangement is limited with reference to  FIGS. 17 and 18 . In another related-art digital broadcast receiving apparatus shown in  FIG. 17 , the circuit arrangements of a terrestrial digital broadcast tuner circuit  171 , a satellite digital broadcast tuner circuit  172 , and a demodulating circuit  173  are different. 
         [0023]    Consequently, IF signals  176  and  179  can be wired between opposite sides of the terrestrial digital broadcast tuner circuit  171  and the demodulating circuit  173  and the opposite sides of the satellite digital broadcast tuner circuit  172  and the demodulating circuit  173 . Serial communications signals  174  and  177  and AGC signals  175  and  178  can only be wired between the non-opposite sides of the terrestrial digital broadcast tuner circuit  171  and the demodulating circuit  173  and the non-opposite sides of the satellite digital broadcast tuner circuit  172  and the demodulating circuit  173 ; however, the signal lines do not cross each other and the length of wiring is minimized. 
         [0024]    On the other hand, in still another digital broadcast receiving apparatus shown in  FIG. 18 , the circuit arrangements of a terrestrial digital broadcast tuner circuit  181 , a satellite digital broadcast tuner circuit  182 , and a demodulating circuit  183  are different. Because the positions of the circuit terminals of the terrestrial digital broadcast tuner circuit  181 , the satellite digital broadcast tuner circuit  182 , and the demodulating circuit  183  are fixed, the arrangements of these circuits are substantially the same as in  FIG. 17 . 
         [0025]    Because the terminals are fixed in position, the wiring of serial communications signals  184  and  187  and AGC signals  185  and  188  is unnecessarily long. Because the serial communications signals  184  and  187  and AGC signals  185  and  188  are digital signal, it is not good for these signals to cross analog signal lines of IF signals  186  and  189 . Otherwise, digital signal lines of serial communications signals  184  and  187  and AGC signals  185  and  188  may interfere the analog signal lines of IF signals  186  and  189 . Therefore, in order to prevent this crossing with the IF signals, the wiring is unnecessarily long. 
         [0026]    Further, in order to prevent the crossing with the IF signal, there are crossings between the serial communications signal and AGC signal for the terrestrial digital broadcast tuner circuit and the serial communications signal and AGC signal for the satellite digital broadcast tuner circuit. Like the crossing with the IF signal, the crossing between digital signal lines may cause signal interference, so that the wiring of this kind is undesirable. 
         [0027]    Thus, a poor arrangement between the terrestrial digital broadcast tuner circuit  181 , the satellite digital broadcast tuner circuit  182 , and the demodulating circuit  183  makes it difficult to wire the signal lines for tuner control. This is because the terminals for controlling the two tuners in the demodulating circuit are arranged in a fixed manner. 
         [0028]    In addition, as with the technique disclosed in Patent Document above, the above-mentioned configuration presents following problems. Namely, the technique disclosed in Patent Document 1 above is intended for a signal switching circuit to switch the baseband signals (I signal, Q signal) to be supplied from the tuner to the demodulating circuit. 
         [0029]    However, the disclosed technique may not switch the control signal that is fed back from the demodulating circuit shown in  FIGS. 17 and 18  to the tuner. Therefore, as with the configuration described before, the wiring of the control signal line becomes unnecessarily long. The disclosed technique makes it possible for the control signal digital line to interfere the analog signal line of the baseband signal (I signal, Q signal). 
         [0030]    In the case of the technique disclosed in Patent Document 1 above, the two tuners are of the same receiving scheme (for satellite digital broadcasting). However, this configuration may not be applied to a configuration in which different receiving schemes are used, namely, the two tuners are for the terrestrial digital broadcast receiving and the satellite digital broadcast receiving, respectively. 
         [0031]    Also, in the case of the technique disclosed in Patent Document 1 above, if the baseband signals (I signal, Q signal) that are supplied from the tuner to the demodulating circuit are switched by the signal switching circuit, the freedom in the arrangement of the terrestrial digital broadcast tuner circuit  151 , the satellite digital broadcast tuner circuit  152 , and the demodulating circuit  153  shown in  FIG. 16  is also restricted. 
         [0032]    Therefore, the present invention addresses the above-identified and other problems associated with related-art methods and apparatuses and solves the addressed problems by providing a digital broadcast receiving apparatus configured to increase the freedom in the arrangement of three circuits, a terrestrial digital broadcast tuner circuit, a satellite digital broadcast tuner circuit, and a demodulating circuit and, at the same time, minimize the interference by a control signal on a reception signal. 
         [0033]    In carrying out the invention and according to one embodiment thereof, there is provided a digital broadcast receiving apparatus configured to receive terrestrial digital television broadcasting and satellite digital broadcasting. This digital broadcast receiving apparatus has a terrestrial digital tuner configured to receive terrestrial digital television broadcasting; a satellite digital tuner configured to receive satellite digital broadcasting; a demodulating block configured to demodulate a reception signal of the terrestrial digital television broadcasting with an output supplied from the terrestrial digital tuner, and, at the same time, demodulate a reception signal of the satellite digital broadcasting with an output supplied from the satellite digital tuner. 
         [0034]    The above-mentioned digital broadcast receiving apparatus also has a terrestrial digital tuner control block, included in the demodulating block, configured to control the terrestrial digital tuner; a satellite digital tuner control block, included in the demodulating block, configured to control the satellite digital tuner; and a switching block configured to switch, inside the demodulating block, output terminals of the demodulating block from which a control signal supplied from the terrestrial digital tuner control block to the terrestrial digital tuner and a control signal supplied from the satellite digital tuner control block to the satellite digital tuner are outputted in accordance with a positional arrangement of the terrestrial digital tuner and the satellite digital tuner relative to the demodulating block. 
         [0035]    In the above-mentioned digital broadcast receiving apparatus, output terminals of the demodulating block for control signals for controlling the two tuners, namely, the terrestrial digital tuner and the satellite digital tuner, can be switched by the switching block inside the demodulating block. 
         [0036]    Consequently, in configuring a system having three circuits, namely, a terrestrial digital broadcast tuner circuit, a satellite digital broadcast tuner circuit, and a demodulating circuit, the output terminals of the demodulating block for the control signals for controlling these two tuners inside the demodulating circuit can be switched. 
         [0037]    The above-mentioned novel configuration allows the wiring without waste of the control signal in accordance with a positional arrangement of the terrestrial digital tuner and the satellite digital tuner relative to the modulating block and, at the same time, the minimization of interference by the control signal against a reception signal due to crossing between the wiring of reception signal and the wiring of control signal. Consequently, the above-mentioned novel configuration significantly enhances the freedom in the arrangement of these three circuits and enables the wiring of a control signal line for tuner control regardless of the arrangement of the three circuits. 
         [0038]    As described and according to the invention, a terrestrial digital broadcast tuner circuit, a satellite digital broadcast tuner circuit, and a demodulating circuit capable of the reception signals of these two schemes can be arranged with significantly higher freedom. Consequently, the novel configuration significantly enhances the selectivity in wiring, thereby contributing to the reduced size and cost of an entire system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  is a block diagram illustrating a digital broadcast receiving apparatus practiced as one embodiment of the invention; 
           [0040]      FIG. 2  a block diagram illustrating an exemplary internal configuration of a terrestrial digital tuner; 
           [0041]      FIG. 3  is a schematic diagram illustrating a tuner circuit and a demodulating circuit in the digital broadcast receiving apparatus shown in  FIG. 1 ; 
           [0042]      FIG. 4  is a diagram illustrating a switching state of a switching circuit of the demodulating circuit; 
           [0043]      FIG. 5  is a diagram illustrating another switching state of the switching circuit of the demodulating circuit; 
           [0044]      FIG. 6  is a diagram illustrating still another switching state of the switching circuit of the demodulating circuit; 
           [0045]      FIG. 7  is a schematic diagram illustrating a tuner circuit and a demodulating circuit of another digital broadcast receiving apparatus; 
           [0046]      FIG. 8  is a diagram illustrating a switching state of another modulating circuit; 
           [0047]      FIG. 9  is a diagram illustrating another switching state of the demodulating circuit shown in  FIG. 8 ; 
           [0048]      FIG. 10  is a schematic diagram illustrating a tuner circuit and a demodulating circuit of still another digital broadcast receiving apparatus; 
           [0049]      FIG. 11  is a diagram illustrating a switching state of another demodulating circuit; 
           [0050]      FIG. 12  is a diagram illustrating another switching state of the demodulating circuit shown in  FIG. 11 ; 
           [0051]      FIG. 13  is a diagram illustrating a relation between output terminals and control signals switched by a switching signal supplied from a host CPU; 
           [0052]      FIG. 14  is a diagram illustrating a relation between output terminals and control signals switched by terminal states set by a switching signal; 
           [0053]      FIG. 15  is a diagram illustrating a relation between output terminals and control signals switched by a switching signal supplied from an I 2  I/F block by setting by the host CPU; 
           [0054]      FIG. 16  is a schematic diagram illustrating a tuner circuit and a demodulating circuit of a related-art satellite digital broadcast receiving apparatus; 
           [0055]      FIG. 17  is a schematic diagram illustrating another related-art digital broadcast receiving apparatus; and 
           [0056]      FIG. 18  is a schematic diagram illustrating still another related-art digital broadcast receiving apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0057]    This invention will be described in further detail by way of embodiments thereof with reference to the accompanying drawings. To be more specific, the following describes embodiments of the invention with reference to  FIGS. 1 through 15 . Now, referring to  FIG. 1 , there is shown a block diagram of a digital broadcast receiving apparatus practiced as one embodiment of the invention. 
         [0058]    It should be note that, although a receiving apparatus shown in  FIG. 1  can also receive analog broadcasting, this apparatus is herein referred to as a digital broadcast receiving apparatus because the function thereof is for mainly receiving digital broadcasting. For the brevity, the description of a receiving system of satellite digital broadcasting by a communications satellite (CS) is skipped herein. 
         [0059]    Terrestrial analog television broadcast signals transmitted on VHF band (90 MHz to 220 MHz) and UHF band (440 MHz to 770 MHz) are received at a VHF antenna  1  and a UHF antenna  2  to be supplied to a terrestrial digital broadcast tuner circuit  3 . A terrestrial digital television broadcast signal transmitted on UHF band is received at the UHF antenna  2  to be supplied to the terrestrial digital broadcast tuner circuit  3 . A terrestrial digital audio broadcast signal transmitted on channel  7  of VHF is received at the VHF antenna  1  to be supplied to the terrestrial digital broadcast tuner circuit  3 . 
         [0060]    Referring to  FIG. 2 , there is shown a block diagram illustrating an exemplary internal configuration of the terrestrial digital broadcast tuner circuit  3 . The terrestrial digital broadcast tuner circuit  3  has a high-frequency amplifying circuit  3   a  configured to amplify signals supplied from the VHF antenna  1  and the UHF antenna  2 , a local oscillating circuit  3   b  configured to generate a local oscillation signal, and a mixing circuit  3   c  configured to mix an output signal of the high-frequency amplifying circuit  3   a  with a local oscillation signal from the local oscillating circuit  3   b  to output an intermediate-frequency signal. 
         [0061]    The terrestrial digital broadcast tuner circuit  3  also has a variable bandwidth filter  3   i  configured to vary the passband width between 4 MHz and 6 MHz by an external control signal, an intermediate-frequency amplifying circuit  3   g  to which an output signal of the variable bandwidth filter  3   i , and a station selecting circuit  3   h  configured to control operations of the above-mentioned high-frequency amplifying circuit  3   a , the above-mentioned local oscillating circuit  3   b , and a switching block, not shown. 
         [0062]    In the terrestrial digital broadcast tuner circuit  3 , a desired channel, namely a signal having a desired frequency in the entered VHF band (90 MHz to 220 MHz) and UHF band (440 MHz to 770 MHz) is converted into an intermediate-frequency signal having a predetermined frequency, 57 MHz for example. Namely, the terrestrial digital broadcast tuner circuit  3  basically has the capabilities of the VHF/UHF tuner for use in related-art terrestrial analog television broadcast receiving. 
         [0063]    At the reception of the terrestrial digital television broadcasting transmitted in the VHF band (90 MHz to 220 MHz) and the UHF band (440 MHz to 770 MHz), an intermediate-frequency signal from the terrestrial digital broadcast tuner circuit  3  is supplied to an OFDM demodulating block  7 , in which an OFDM signal is demodulated, thereby providing transport stream TS 1  of MPEG. This transport stream TS 1  is supplied to one input of a switching block  8  configured for transport stream. 
         [0064]    A satellite digital television broadcast signal transmitted on the SHF band (12 GHZ) is received at an SHF antenna  9  and converted by an LNB (Low Noise Block) converter, not shown, into an intermediate-frequency signal of 1-GHz band to be supplied to a satellite digital broadcast tuner circuit  10 . 
         [0065]    In the satellite digital broadcast tuner circuit  10  a signal having a desired channel or frequency among the intermediate-frequency signals in the entered 1-GHz band is converted by direction conversion into an I signal and a Q signal, which are supplied to a QPSK demodulating block  11 , in which the QPSK signal is demodulated, thereby providing MPEG transport stream TS 2 . This transport stream TS 2  is supplied to the other input of the switching block  8 . 
         [0066]    A transport stream output of the switching block  8  configured for transport stream is supplied to a demultiplexer  12 , in which video data, audio data, and broadcast data that are multiplexed with the transport stream in a time division manner are separated from the transport stream. 
         [0067]    The video data and the audio data separated by the demultiplexer  12  are supplied to an MPEG decoder  13  to be decoded, thereby providing a video signal and an audio signal. The video signal from the MPEG decoder  13  is supplied to a video processing block  14  and the audio signal is supplied to an audio processing block  15 . 
         [0068]    Predetermined image processing is executed on the video signal supplied to the video processing block  14  and the resultant video signal is supplied to a video output apparatus  16 , such as a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), or a PDP (Plasma Display Panel). Predetermined audio processing is executed on the audio signal supplied to an audio processing block  15  and the resultant audio signal is supplied to an audio output apparatus  17 , such as a loudspeaker. 
         [0069]    The broadcast data for data broadcasting separated by the demultiplexer  12  is supplied to a broadcast data processing block  18 , in which user-specified predetermined processing, EPG display processing for example, is executed on the broadcast data. A control signal from the broadcast data processing block  18  is supplied to a video data generating block  19 , in which an image signal for displaying a predetermined image on the video output apparatus  16  is generated. The image signal from the video data generating block  19  is combined with the video signal of a broadcast signal in the video processing block  14 . 
         [0070]    The entire digital broadcast receiving apparatus mentioned above is controlled by a control block  4  that is implemented by a microprocessor and so on. The embodiment shown in  FIG. 1  is configured to control operations of the terrestrial digital broadcast tuner circuit  3 , the satellite digital broadcast tuner circuit  10 , and the switching block  8  by the control block  4 . Other circuit components, not shown, are also controlled by the control block  4 . 
         [0071]    The control block  4  is connected with a remote operation signal receiving block  5 . A remote control signal from a remote operation signal transmitter  6  is received by the remote operation signal receiving block  5 , which discriminates the contents of the received remote control signal. Accordingly, the control block  4  executes a user-specified control operation. 
         [0072]    From the control block  4 , station selection data is supplied to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10  for tuner switching and channel switching. Here, the above-mentioned OFDM demodulating block  7 , QPSK demodulating block  11 , switching block  8 , demultiplexer  12 , MPEG decoder  13 , and broadcast data processing block  18  provide a demodulating circuit  23  configured to demodulate an intermediate-frequency signal received by the terrestrial digital broadcast tuner circuit  3  or the satellite digital broadcast tuner circuit  10 . 
         [0073]    The following describes operations to be executed by the above-mentioned digital broadcast receiving apparatus. First, an operation to be executed when the digital broadcast receiving apparatus receives a terrestrial digital television broadcast signal is described. For example, if a terrestrial digital television broadcast signal transmitted on channel  27  of UHF is received, the user turns on a terrestrial digital broadcasting button of the remote operation signal transmitter  6  and then presses a button corresponding to channel  27  of UHF among channel selection buttons. 
         [0074]    From the remote operation signal transmitter  6 , remote control signals corresponding to the types of pressed buttons are sequentially transmitted to be received by the remote operation signal receiving block  5  shown in  FIG. 1 , in which these signals are converted into control data corresponding to the types of pressed button to be supplied to the control block  4 . 
         [0075]    The control block  4  discriminates the contents of the control data supplied from the remote operation signal receiving block  5 . If the supplied control data is found to be corresponding to the terrestrial digital broadcasting button, then the control block  4  supplies station selection data that enables the terrestrial digital broadcast tuner circuit  3  to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10 , thereby enabling only the terrestrial digital broadcast tuner circuit  3 . At the same time, the switching block  8  is switched to the side of the OFDM demodulating block  7  by a signal route switching signal supplied from the control block  4 . 
         [0076]    If the control data is found to be corresponding to the button corresponding to channel  27 , then station selection data for specifying the reception of channel  27  is supplied from the control block  4  to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10 , upon which channel  27  is received by the terrestrial digital broadcast tuner circuit  3 . 
         [0077]    The following further details the operation of the terrestrial digital broadcast tuner circuit  3 . As shown in  FIG. 2 , when station selection data for specifying the reception of channel  27  is supplied from the control block  4  to the terrestrial digital broadcast tuner circuit  3 , this station selection data is supplied to the station selecting circuit  3   h . Then, the station selecting circuit  3   h  supplies a control voltage for setting a resonance frequency suitable for the reception of channel  27  to the high-frequency amplifying circuit  3   a  and the local oscillating circuit  3   b . Therefore, from the mixing circuit  3   c , an intermediate-frequency signal corresponding to the broadcast contents of channel  27  is outputted. 
         [0078]    In an initial status, the frequency components of all bands of terrestrial digital television broadcast signals pass the variable bandwidth filter  3   i  without degradation because this filter has a passband width of 6 MHz. 
         [0079]    The signal that has passed the variable bandwidth filter  3   i  is amplified by the intermediate-frequency amplifying circuit  3   g  to a desired level to be supplied to the OFDM demodulating block  7  shown in  FIG. 1 . In the OFDM demodulating block  7 , MPEG transport stream TS 1  is obtained by OFDM demodulation and supplied to the switching block  8 . 
         [0080]    At this moment, the switching block  8  has been switched to the side of the OFDM demodulating block  7 , so that transport stream TS 1  supplied from the OFDM demodulating block  7  is supplied to the demultiplexer  12  via the switching block  8  to be separated into a video part, an audio part, and a data part for extraction. The video part and the audio part are supplied to the MPEG decoder  13  to be decoded into a video signal and an audio signal that are supplied to the video processing block  14  and the audio processing block  15 , respectively. 
         [0081]    The video signal supplied to the video processing block  14  is image-processed in a predetermined manner to be supplied to the video output apparatus  16 . The audio signal supplied to the audio processing block  15  is audio-processed in a predetermined manner to be supplied to the audio output apparatus  17 . Consequently, the user can view the terrestrial digital television broadcast program being transmitted on channel  27 . 
         [0082]    The data part obtained in the demultiplexer  12  is supplied to the broadcast data processing block  18  to generate a control signal corresponding to the contents of the broadcast data. This control signal is supplied to the video data generating block  19  to generate an image signal corresponding to the contents of the broadcast data. This image data is supplied to the video processing block  14  to be combined with the video signal of the broadcast program. Therefore, the user can view the contents of the data broadcast. 
         [0083]    The following describes an operation of receiving a terrestrial audio broadcast signal. For example, if a terrestrial digital audio broadcast signal being transmitted on channel  7  of VHF is received, the user turns on the terrestrial digital broadcasting button of the remote operation signal transmitter  6  and then presses a service mode button once. 
         [0084]    Remote control signals corresponding to the types of pressed buttons are sequentially transmitted from the remote operation signal transmitter  6  to be received by the remote operation signal receiving block  5  shown in  FIG. 1 . The received remote control signals are converted into the control data corresponding to the types of pressed buttons to be supplied to the control block  4 . 
         [0085]    The control block  4  discriminates the contents of the control data supplied from the remote operation signal receiving block  5 . If the control data is found to be corresponding to the terrestrial digital broadcasting button, then the control block  4  supplies station selection data for enabling the terrestrial digital broadcast tuner circuit  3  to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10 , thereby enabling only the terrestrial digital broadcast tuner circuit  3 . At the same time, the switching block  8  is switched to the side of the OFDM demodulating block  7  by a signal route switching signal supplied from the control block  4 . 
         [0086]    If the control data is found to be corresponding to the button corresponding to terrestrial digital audio broadcasting, then the control block  4  supplies the station selection data for specifying the reception of channel  7  to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10 , upon which channel  7  is received by the terrestrial digital broadcast tuner circuit  3 . 
         [0087]    The following further details the operation of the terrestrial digital broadcast tuner circuit  3 . As shown in  FIG. 2 , when station selection data for specifying the reception of channel  7  is supplied from the control block  4  to the terrestrial digital broadcast tuner circuit  3 , this station selection data is supplied to the station selecting circuit  3   h . Then, the station selecting circuit  3   h  supplies a control voltage for setting a resonance frequency suitable for the reception of channel  7  to the high-frequency amplifying circuit  3   a  and the local oscillating circuit  3   b . Therefore, from the mixing circuit  3   c , an intermediate-frequency signal corresponding to the broadcast contents of channel  7  is outputted. 
         [0088]    The station selection data is supplied from the control block  4  to the terrestrial digital broadcast tuner circuit  3 . Consequently, the intermediate-frequency signal from the mixing circuit  3   c  is supplied to the variable bandwidth filter  3   i . The frequency components of all bands of terrestrial digital television broadcast signals pass the variable bandwidth filter  3   i  without degradation and there is no interference by broadcast signals of adjacent channels because this filter has a passband width of 4 MHz. 
         [0089]    The signal that has passed the variable bandwidth filter  3   i  is amplified by the intermediate-frequency amplifying circuit  3   g  to a desired level to be supplied to the OFDM demodulating block  7  shown in  FIG. 1 . In the OFDM demodulating block  7 , MPEG transport stream TS 1  is obtained by OFDM demodulation and supplied to the switching block  8 . 
         [0090]    At this moment, the switching block  8  has been switched to the side of the OFDM demodulating block  7 , so that transport stream TS 1  supplied from the OFDM demodulating block  7  is supplied to the demultiplexer  12  via the switching block  8 , in which the audio part is separated for extraction. The audio part is supplied to the MPEG decoder  13  to be decoded into an audio signal. The audio signal is supplied to the audio processing block  15  to be audio-processed. The processed audio signal is supplied to the audio output apparatus  17 . Consequently, the user can view the terrestrial digital audio broadcast program being broadcast on channel  7 . 
         [0091]    The following describes an operation of receiving a satellite television broadcast signal. For example, if a BS digital television broadcast signal of service ID 151CH being transmitted on channel  1  (BS 1 ) of SHF is received, the user turns on the BS digital broadcasting button of the remote operation signal transmitter  6 . 
         [0092]    Next, the user presses a channel selection button  5 , namely, a button corresponding to service ID 151CH. From the remote operation signal transmitter  6 , remote control signals corresponding to the types pressed buttons are sequentially transmitted. These remote control signals are received by the remote operation signal receiving block  5  shown in  FIG. 1  to be converted into the control data corresponding to pressed buttons. The control data is then supplied to the control block  4 . 
         [0093]    The control block  4  discriminates the contents of the control data supplied from the remote operation signal receiving block  5 . If the control data is found to be corresponding to the BS digital broadcasting button, then station selection data for enabling the satellite digital broadcast tuner circuit  10  is supplied to the terrestrial digital broadcast tuner circuit  3  and the satellite digital broadcast tuner circuit  10  to enable only the satellite digital broadcast tuner circuit  10 . At the same time, the switching block  8  is switched to the side of the QPSK demodulating block  11  by a signal route switching signal from the control block  4 . 
         [0094]    If the control data is found to be corresponding to channel  1  of SHF, then station selection data for specifying the reception of channel  1  of SHF is supplied from the control block  4  to the terrestrial digital broadcast tuner circuit  3  and satellite digital broadcast tuner circuit  10  to receive channel  1  of SHF by the satellite digital broadcast tuner circuit  10 . An output of the satellite digital broadcast tuner circuit  10  is supplied to the QPSK demodulating block  11  shown in  FIG. 1 . In the QPSK demodulating block  11 , MPEG transport stream TS 2  is obtained by QPSK demodulation to be supplied to the switching block  8 . 
         [0095]    At this moment, the switching block  8  has been switched to the side of the QPSK demodulating block  11 , so that transport stream TS 2  from the QPSK demodulating block  11  is supplied to the demultiplexer  12  via the switching block  8 , in which transport stream TS 2  is separated into a video part, an audio part, and a data part for extraction. The video part and the audio part are supplied to the MPEG decoder  13  to be decoded into a video signal and an audio signal, which are supplied to the video processing block  14  and the video audio processing block  15 , respectively. 
         [0096]    The video signal supplied to the video processing block  14  is image-processed to be supplied to the video output apparatus  16 . The audio signal supplied to the video output apparatus  15  is audio-processed to be supplied to the audio output apparatus  17 . Consequently, the user can view the BS digital television broadcast program of service ID 151CH being broadcast on channel  1  (BS 1 ) of SHF. 
         [0097]    Referring to  FIG. 3 , there is shown a schematic diagram illustrating a tuner circuit and a demodulating circuit of the digital broadcast receiving apparatus of the present embodiment. This digital broadcast receiving apparatus has a terrestrial digital broadcast tuner circuit  21 , a satellite digital broadcast tuner circuit  22 , and a demodulating circuit  23  configured to demodulate IF (Intermediate Frequency) signals  41  and  44 , reception signals of these two schemes. 
         [0098]    These two reception signals IF  41  and  44  are both analog signals, so that these signals are converted into digital signals by an A/D converting circuits  35  and  37  in the preprocessing of the demodulating circuit  23 . The demodulating circuit  23  demodulates these digital signals. The demodulating circuit  23  has a terrestrial digital broadcast tuner circuit control block  24  and a satellite digital broadcast tuner circuit control block  25  for executing control inside the demodulating circuit  23 . 
         [0099]    The terrestrial digital broadcast tuner circuit control block  24  and the satellite digital broadcast tuner circuit control block  25  each have AGCs (Automatic Gain Controls)  36  and  38 . AGC signals from the AGCs  36  and  38  are fed back to the terrestrial digital broadcast tuner circuit  21  and the satellite digital broadcast tuner circuit  22  via terminals  26  and  28 , respectively. The AGC signals are passed to an intermediate-frequency amplifying circuit in the terrestrial digital broadcast tuner circuit  21  and an intermediate-frequency amplifying circuit in the satellite digital broadcast tuner circuit  22 , respectively, to be automatically optimized in amplification. This IF signal amplitude optimizing control provides an effect of widening the dynamic range DR of the A/D converting circuits  35  and  37 . 
         [0100]    Serial communications signals  40  and  43 , such as various setting data, control the selection or passband of the terrestrial digital broadcast tuner circuit  21  and the satellite digital broadcast tuner circuit  22  via a switching circuit B ( 31 ), a terminal B ( 27 ), and a terminal D ( 29 ). 
         [0101]    Also, the serial communications signals  40  and  43  are bidirectionally communicable between the terrestrial digital broadcast tuner circuit  21  and the satellite digital broadcast tuner circuit  22  and the terrestrial digital broadcast tuner circuit control block  24  and the satellite digital broadcast tuner circuit control block  25 . 
         [0102]    Namely, referring to  FIG. 3 , the digital broadcast receiving apparatus of the present embodiment has a host CPU  34  in addition to the demodulating circuit  23  configured to be compatible with two broadcasting schemes, the terrestrial digital broadcasting and the satellite digital broadcasting, the terrestrial digital broadcast tuner circuit  21 , and the satellite digital broadcast tuner circuit  22 . The host CPU  34  has a function of switching between the connection states of a switching circuit A ( 30 ) and a switching circuit B ( 31 ). 
         [0103]    The demodulating circuit  23  has the terrestrial digital broadcast tuner circuit control block  24 , the satellite digital broadcast tuner circuit control block  25 , the switching circuit A ( 30 ) and the switching circuit B ( 31 ). The switching circuit A ( 30 ) and the switching circuit B ( 31 ) are connected to the host CPU  34  via switching signal A ( 32 ) and switching signal B ( 33 ). 
         [0104]    Terminal A ( 26 ) and terminal C ( 28 ) of the demodulating circuit  23  output AGC signals  39  and  42  that are fed back to the terrestrial digital broadcast tuner circuit  21  and the satellite digital broadcast tuner circuit  22 , respectively. 
         [0105]    Terminal B ( 27 ) and terminal D ( 29 ) of the demodulating circuit  23  are terminals for the serial communications signals  40  and  43  that are fed back to the terrestrial digital broadcast tuner circuit  21  and the satellite digital broadcast tuner circuit  22 , respectively. 
         [0106]    The following describes a relation between tuner circuit arrangement and terminal position. As shown in  FIG. 3 , the relation becomes as follows if the terrestrial digital broadcast tuner circuit  21  is arranged near terminal A ( 26 ) and terminal B ( 27 ) and the satellite digital broadcast tuner circuit  22  is arranged near terminal C ( 28 ) and terminal D ( 29 ). 
         [0107]    Referring to  FIG. 13 , there is shown a relation between the control signals switched by a switching signal supplied from the host CPU and the output terminals. In this case, the switching states of switching circuit A ( 30 ) and switching circuit B ( 31 ) are set via switching signal A ( 32 ) and switching signal B ( 33 ) from the host CPU  34 , such as “1” of No. 121 in  FIG. 13 . 
         [0108]    Namely, if switching signal A ( 32 ) is “0” and switching signal B ( 33 ) is also “0,” then terminal A ( 26 ) provides an AGC signal for the terrestrial digital broadcast tuner, terminal B ( 27 ) provides a serial communications signal for the terrestrial digital broadcast tuner, terminal C ( 28 ) provides an AGC signal for the satellite digital broadcast tuner, and terminal D ( 29 ) provides a serial communications signal for the satellite digital broadcast tuner. 
         [0109]    Consequently, the terminal states of terminal A ( 26 ), terminal B ( 27 ), terminal C ( 28 ), and terminal D ( 29 ) can be determined, thereby facilitating the wiring of the AGC signals  39  and  42  and the serial communications signals  40  and  43  for the two tuner circuits. 
         [0110]    The connection state of switching circuit A ( 30 ) and switching circuit B ( 31 ) at that time is shown in  FIG. 4 . As shown in  FIG. 4 , in switching circuit A ( 30 ), the AGC  36  is connected to terminal A ( 26 ) and the AGC  38  is connected to terminal C ( 28 ). In switching circuit B ( 31 ), the terrestrial digital broadcast tuner circuit control block  24  is connected to terminal B ( 27 ) and the satellite digital broadcast tuner circuit control block  25  is connected to terminal D ( 29 ). 
         [0111]    If the satellite digital broadcast tuner circuit  22  is arranged near terminal A ( 26 ) and terminal B ( 27 ) and the terrestrial digital broadcast tuner circuit  21  is arranged near terminal C ( 28 ) and terminal D ( 29 ), the following configuration is obtained. In this case, the switching state of switching terminal A ( 30 ) and switching terminal B ( 31 ) is set via switching signal A ( 32 ) and switching signal B ( 33 ) from the host CPU  34 , such as “4” of No. 121 in  FIG. 13 . 
         [0112]    To be more specific, if switching signal A ( 32 ) is “1” and switching signal B ( 33 ) is also “1,” then terminal A ( 26 ) provides an AGC signal for the satellite digital broadcast tuner, terminal B ( 27 ) provides a serial communications signal for the satellite digital broadcast tuner, terminal C ( 28 ) provides an AGC signal for the terrestrial digital broadcast tuner, and terminal D ( 29 ) provides a serial communications signal for the terrestrial digital broadcast tuner. 
         [0113]    Consequently, the terminal state of terminal A ( 26 ), terminal B ( 27 ), terminal C ( 28 ), and terminal D ( 29 ) can be determined, thereby facilitating the wiring of the AGC signals  39  and  42  and the serial communications signals  40  and  43  for the two tuner circuits. 
         [0114]    A switching connection state of switch circuit A ( 30 ) and switching circuit B ( 31 ) at that time is shown in  FIG. 5 . As shown in  FIG. 5 , in switching circuit A ( 30 ), the AGC  36  is connected to terminal C ( 28 ) and the AGC  38  is connected to terminal A ( 26 ). In switching circuit B ( 31 ), the terrestrial digital broadcast tuner circuit control block  24  is connected to terminal D ( 29 ) and the satellite digital broadcast tuner circuit control block  25  is connected to terminal B ( 27 ). 
         [0115]    The following describes a case in which the satellite digital broadcast tuner circuit  22  and the terrestrial digital broadcast tuner circuit  21  are arranged in a horizontal manner. If the satellite digital broadcast tuner circuit  22  is arranged near terminal A ( 26 ) and terminal D ( 29 ) and the terrestrial digital broadcast tuner circuit  21  is arranged near terminal B ( 27 ) and terminal C ( 28 ), the following configuration is obtained. 
         [0116]    The satellite digital broadcast tuner circuit  22  is arranged to the left of the terrestrial digital broadcast tuner circuit  21 . The terminals of the satellite digital broadcast tuner circuit  22  are positioned at the upper and lower sides thereof and the terminals of the terrestrial digital broadcast tuner circuit  21  are positioned at the right side thereof.  FIG. 6  shows the switching connection state of switching circuit A ( 30 ) and switching circuit B ( 31 ) when the satellite digital broadcast tuner circuit  22  is arranged to the left of the terrestrial digital broadcast tuner circuit  21 . In this case, the switching state of switching circuit A ( 30 ) and switching circuit B ( 30 ) is set via switching signal A ( 32 ) and switching signal B ( 33 ) from the host CPU  34 , as with “2” of No. 121 in  FIG. 13 . 
         [0117]    To be more specific, when switching signal A ( 32 ) is “1” and switching signal B ( 33 ) is “0,” terminal A ( 26 ) provides an AGC signal for the satellite digital broadcast tuner, terminal B ( 27 ) provides a serial communications signal for the terrestrial digital broadcast tuner, terminal C ( 28 ) provides an AGC signal for the terrestrial digital broadcast turner, and terminal D ( 29 ) provides a serial communications signal for the satellite digital broadcast tuner. Consequently, the terminal state of terminal A ( 26 ), terminal B ( 27 ), terminal C ( 28 ), and terminal D ( 29 ) can be determined, thereby facilitating the wiring of the AGC signals  39  and  42  and the serial communications signals  40  and  43  for the two tuner circuits. 
         [0118]    If the satellite digital broadcast tuner circuit  22  is arranged near terminal B ( 27 ) and terminal C ( 28 ) and the terrestrial digital broadcast tuner circuit  21  is arranged near terminal A ( 26 ) and terminal D ( 29 ), the following configuration is obtained. In this configuration, the satellite digital broadcast tuner circuit  22  is arranged to the right of the terrestrial digital broadcast tuner circuit  21 . The terminals of the terrestrial digital broadcast tuner circuit  21  are positioned at the upper and lower ends thereof. The terminals of the satellite digital broadcast tuner circuit  22  are positioned at the right side thereof. In this configuration, the arrangement of the satellite digital broadcast tuner circuit  22  and the terrestrial digital broadcast tuner circuit  21  is reverse to that shown in  FIG. 6 . 
         [0119]    In this case, the switching state of switching circuit A ( 30 ) and switching circuit B ( 31 ) is set via switching signal A ( 32 ) and switching signal B ( 33 ) from the host CPU  34 , such as “3” of No. 121 in  FIG. 13 . To be more specific, when switching signal A ( 32 ) is “0” and switching signal B ( 33 ) is “1,” terminal A ( 26 ) provides an AGC signal for the terrestrial digital broadcast tuner, terminal B ( 27 ) provides a serial communications signal for the satellite digital broadcast tuner, terminal C ( 28 ) provides an AGC signal for the satellite digital broadcast turner, and terminal D ( 29 ) provides a serial communications signal for the terrestrial digital broadcast tuner. 
         [0120]    Consequently, the terminal state of terminal A ( 26 ), terminal B ( 27 ), terminal C ( 28 ), and terminal D ( 29 ) can be determined, thereby facilitating the wiring of the AGC signals  39  and  42  and the serial communications signals  40  and  43  for the two tuner circuits. 
         [0121]    Referring to  FIG. 7 , there is shown a schematic diagram of a tuner circuit and a demodulating circuit of a digital broadcast receiving apparatus practiced as another embodiment of the invention. The digital broadcast receiving apparatus shown in  FIG. 7  has three circuits, a terrestrial digital broadcast tuner circuit  51 , a satellite digital broadcast tuner circuit  52 , and a demodulating circuit  53  configured to demodulate IF signals  72  and  75  that are reception signals of these two schemes. 
         [0122]    These two reception signals IF  72  and  75  are both analog signals, so that these signals are converted into digital signals by an A/D converting circuits  66  and  68  in the preprocessing of the demodulating circuit  53 . The demodulating circuit  53  demodulates these digital signals. The demodulating circuit  53  has a terrestrial digital broadcast tuner circuit control block  54  and a satellite digital broadcast tuner circuit control block  55  for executing control inside the demodulating circuit  53 . 
         [0123]    At this time, the terrestrial digital broadcast tuner circuit control block  54  and the satellite digital broadcast tuner circuit control block  55  each have AGCs (Automatic Gain Controls)  67  and  69 . AGC signals from the AGCs  67  and  69  are fed back to the terrestrial digital broadcast tuner circuit  51  and the satellite digital broadcast tuner circuit  52  via terminals  56  and  58 , respectively. The AGC signals are passed to an intermediate-frequency amplifying circuit in the terrestrial digital broadcast tuner circuit  51  and an intermediate-frequency amplifying circuit in the satellite digital broadcast tuner circuit  52 , respectively, to be automatically optimized in amplification. This IF signal amplitude optimizing control provides an effect of widening the dynamic range DR of the A/D converting circuits  66  and  68 . 
         [0124]    Serial communications signals  71  and  74 , such as various setting data, control the selection or passband of the terrestrial digital broadcast tuner circuit  51  and the satellite digital broadcast tuner circuit  52  via a switching circuit B ( 61 ), a terminal B ( 57 ), and a terminal D ( 59 ). 
         [0125]    Also, the serial communications signals  71  and  74  are bidirectionally communicable between the terrestrial digital broadcast tuner circuit  51  and the satellite digital broadcast tuner circuit  52  and the terrestrial digital broadcast tuner circuit control block  54  and the satellite digital broadcast tuner circuit control block  55 . 
         [0126]    Namely, referring to  FIG. 7 , the digital broadcast receiving apparatus shown has terminals an external circuit configured to give a predetermined voltage to these terminals in addition to the demodulating circuit  53  configured to be compatible with two broadcasting schemes, the terrestrial digital broadcasting and the satellite digital broadcasting, the terrestrial digital broadcast tuner circuit  51 , and the satellite digital broadcast tuner circuit  52 . These terminals and external circuit have a function of switching between the connection states of a switching circuit A ( 60 ) and a switching circuit B ( 61 ). 
         [0127]    The demodulating circuit  53  has the terrestrial digital broadcast tuner circuit control block  54 , the satellite digital broadcast tuner circuit control block  55 , switching circuit A ( 60 ), and switching circuit B ( 61 ). Switching circuit ( 60 ) and switching circuit ( 61 ) are connected to an external circuit via switching signal A ( 62 ) and switching signal B ( 63 ) through terminal E ( 64 ) and terminal F ( 65 ) of the demodulating circuit  53 . The external circuit herein can select logical “High” or “Low” of the potential of switching signal A ( 62 ) and switching signal B ( 63 ). 
         [0128]    For example, by selectively connecting movable contact a, fixed contact b (+ supply), or c (ground) of switch SW 1 , the external circuit gives a predetermined potential to switching signal B ( 63 ). 
         [0129]    Terminal A ( 56 ) and terminal C ( 58 ) of the demodulating circuit  53  output AGC signals  70  and  73  that are fed back to the terrestrial digital broadcast tuner circuit  51  and the satellite digital broadcast tuner circuit  52 , respectively. Terminal B ( 57 ) and terminal D ( 59 ) of the demodulating circuit  53  are for serial communications signals  71  and  74  that are fed back to the terrestrial digital broadcast tuner circuit  51  and the satellite digital broadcast tuner circuit  52 , respectively. 
         [0130]    The following describes a relation between tuner circuit arrangement and terminal position. As shown in  FIG. 7 , the relation becomes as follows if the terrestrial digital broadcast tuner circuit  51  is arranged near terminal A ( 56 ) and terminal B ( 57 ) and the satellite digital broadcast tuner circuit  52  is arranged near terminal C ( 58 ) and terminal D ( 59 ). 
         [0131]    Referring to  FIG. 14 , there is shown a relation between control signals switched by the terminal state set by the switching signal and output terminals. In this case, the switching state of switching circuit A ( 60 ) and switching circuit B ( 61 ) is set via switching signal A ( 62 ) and switching signal B ( 63 ) to terminal E ( 64 ) and terminal F ( 65 ) from the external circuit. 
         [0132]    Namely, when switching signal A ( 62 ) is “Low” and switching signal B ( 63 ) is also “Low,” terminal A ( 56 ) provides an AGC signal for terrestrial digital broadcast tuner, terminal B ( 57 ) provides a serial communications signal for terrestrial digital broadcast tuner, terminal C ( 58 ) provides an AGC signal for satellite digital broadcast tuner, and terminal D ( 59 ) provides a serial communications signal for satellite digital broadcast tuner. 
         [0133]    Consequently, the terminal state of terminal A ( 56 ), terminal B ( 57 ), terminal C ( 58 ), and terminal D ( 59 ) can be determined, thereby facilitating the wiring of the AGC signals  70  and  73  and the serial communications signals  71  and  74  for the two tuner circuits. 
         [0134]    A connection state of switching circuit A ( 60 ) and switching circuit B ( 61 ) at that time is shown in  FIG. 8 . As shown in  FIG. 8 , in switching circuit A ( 60 ), the AGC  67  is connected to terminal A ( 56 ) and the AGC  69  is connected to terminal C ( 58 ). In switching circuit B ( 61 ), the terrestrial digital broadcast tuner circuit control block  54  is connected to terminal B ( 57 ) and the satellite digital broadcast tuner circuit control block  55  is connected to terminal D ( 59 ). 
         [0135]    If the satellite digital broadcast tuner circuit  51  is arranged near terminal A ( 56 ) and terminal B ( 57 ) and the terrestrial digital broadcast tuner circuit  52  is arranged near terminal C ( 58 ) and terminal D ( 59 ), the following configuration is obtained. In this configuration, the switching state of switching circuit A ( 60 ) and switching circuit B ( 61 ) is set via switching signal A ( 62 ) and switching signal B ( 63 ) to terminal E ( 64 ) and terminal F ( 65 ) from the external circuit, such as “4” of No. 131 in  FIG. 14 . 
         [0136]    Namely, when switching signal A ( 62 ) is “High” and switching signal B ( 63 ) is also “High,” terminal A ( 56 ) provides an AGC signal for satellite digital broadcast tuner, terminal B ( 57 ) provides a serial communications signal for satellite digital broadcast tuner, terminal C ( 58 ) provides an AGC signal for terrestrial digital broadcast tuner, and terminal D ( 59 ) provides a serial communications signal for terrestrial digital broadcast tuner. 
         [0137]    Consequently, the terminal state of terminal A ( 56 ), terminal B ( 57 ), terminal C ( 58 ), and terminal D ( 59 ) can be determined, thereby facilitating the wiring of the AGC signals  70  and  73  and the serial communications signals  71  and  74  for the two tuner circuits. 
         [0138]    A connection state of switching circuit A ( 60 ) and switching circuit B ( 61 ) at that time is shown in  FIG. 9 . As shown in  FIG. 9 , in switching circuit A ( 60 ), the AGC  67  is connected to terminal C ( 58 ) and the AGC  69  is connected to terminal A ( 56 ). In switching circuit B ( 61 ), the terrestrial digital broadcast tuner circuit control block  54  is connected to terminal D ( 59 ) and the satellite digital broadcast tuner circuit control block  55  is connected to terminal B ( 57 ). 
         [0139]    Consequently, by setting the switching state of switching circuit A ( 60 ) and switching circuit B ( 61 ) via switching signal A ( 62 ) and switching signal B ( 63 ) to terminal E ( 64 ) and terminal F ( 65 ) from the external circuit, the terminal state of terminal A ( 56 ), terminal B ( 57 ), terminal C ( 58 ), and terminal D ( 59 ) can be determined, thereby facilitating the wiring of the AGC signals  70  and  73  and the serial communications signals  71  and  74  for the two tuner circuits. 
         [0140]    The following describes a configuration in which the satellite digital broadcast tuner circuit  52  and the terrestrial digital broadcast tuner circuit  51  are arranged in a horizontal manner. If the satellite digital broadcast tuner circuit  52  is arranged near terminal A ( 56 ) and terminal D ( 59 ) and the terrestrial digital broadcast tuner circuit  51  is arranged near terminal B ( 57 ) and terminal C ( 58 ), the following configuration is obtained. In this configuration the satellite digital broadcast tuner circuit  52  is arranged to the left of the terrestrial digital broadcast tuner circuit  51 . Also, in this configuration, the terminals of the satellite digital broadcast tuner circuit  52  are positioned at the upper and lower sides thereof and the terminals of the terrestrial digital broadcast tuner circuit  51  are positioned at the right side thereof. This switching connection state is substantially the same as that of switching circuit A ( 30 ) and switching circuit B ( 31 ) in which satellite digital broadcast tuner circuit  22  is arranged to the left of the terrestrial digital broadcast tuner circuit  21  as shown in  FIG. 6 . 
         [0141]    In this configuration, the switching state of switching circuit A ( 60 ) and switching circuit B ( 61 ) is set via switching signal A ( 62 ) and switching signal B ( 63 ) to terminal E ( 64 ) and terminal F ( 65 ) from the external circuit, such as “2” of No. 131 in  FIG. 14 . 
         [0142]    Namely, when switching signal A ( 62 ) is “High” and switching signal B ( 63 ) is also “Low,” terminal A ( 56 ) provides an AGC signal for satellite digital broadcast tuner, terminal B ( 57 ) provides a serial communications signal for terrestrial digital broadcast tuner, terminal C ( 58 ) provides an AGC signal for terrestrial digital broadcast tuner, and terminal D ( 59 ) provides a serial communications signal for satellite digital broadcast tuner. 
         [0143]    Consequently, the terminal state of terminal A ( 56 ), terminal B ( 57 ), terminal C ( 58 ), and terminal D ( 59 ) can be determined, thereby facilitating the wiring of the AGC signals  70  and  73  and the serial communications signals  71  and  74  for the two tuner circuits. 
         [0144]    If the satellite digital broadcast tuner circuit  52  is arranged near terminal B ( 57 ) and terminal C ( 58 ) and the terrestrial digital broadcast tuner circuit  51  is arranged near terminal A ( 56 ) and terminal D ( 59 ), the following configuration is obtained. In this configuration, the satellite digital broadcast tuner circuit  52  is arranged to the right of the terrestrial digital broadcast tuner circuit  51 . Also, in this configuration, the terminals of the terrestrial digital broadcast tuner circuit  51  are positioned at the upper and lower sides thereof and the terminals of the satellite digital broadcast tuner circuit  52  are positioned at the right side thereof. This switching connection state is reverse to the arrangement of the satellite digital broadcast tuner circuit  22  and the terrestrial digital broadcast tuner circuit  21  shown in  FIG. 6 . 
         [0145]    In this case, the switching state of switching circuit A ( 60 ) and switching circuit B ( 61 ) is set via switching signal A ( 62 ) and switching signal B ( 63 ) to terminal E ( 64 ) and terminal F ( 65 ) from the external circuit. 
         [0146]    Namely, when switching signal A ( 62 ) is “Low” and switching signal B ( 63 ) is also “High,” terminal A ( 56 ) provides an AGC signal for terrestrial digital broadcast tuner, terminal B ( 57 ) provides a serial communications signal for satellite digital broadcast tuner, terminal C ( 58 ) provides an AGC signal for satellite digital broadcast tuner, and terminal D ( 59 ) provides a serial communications signal for terrestrial digital broadcast tuner. 
         [0147]    Consequently, the terminal state of terminal A ( 56 ), terminal B ( 57 ), terminal C ( 58 ), and terminal D ( 59 ) can be determined, thereby facilitating the wiring of the AGC signals  70  and  73  and the serial communications signals  71  and  74  for the two tuner circuits. 
         [0148]    Referring to  FIG. 10 , there is shown a schematic diagram of a tuner circuit and a demodulating circuit of a digital broadcast receiving apparatus practiced as still another embodiment of the invention. The digital broadcast receiving apparatus shown in  FIG. 10  has three circuits, a terrestrial digital broadcast tuner circuit  81 , a satellite digital broadcast tuner circuit  82 , and a demodulating circuit  83  configured to demodulate IF signals  103  and  106  that are reception signals of these two schemes. 
         [0149]    These two reception signals IF  103  and  106  are both analog signals, so that these signals are converted into digital signals by an A/D converting circuits  97  and  99  in the preprocessing of the demodulating circuit  53 . The demodulating circuit  83  demodulates these digital signals. The demodulating circuit  83  has a terrestrial digital broadcast tuner circuit control block  84  and a satellite digital broadcast tuner circuit control block  85  for executing control inside the circuit. 
         [0150]    At this time, the terrestrial digital broadcast tuner circuit control block  84  and the satellite digital broadcast tuner circuit control block  85  each have AGCs (Automatic Gain Controls)  98  and  100 . AGC signals from the AGCs  98  and  100  are fed back to the terrestrial digital broadcast tuner circuit  81  and the satellite digital broadcast tuner circuit  82  via terminals  86  and  88 , respectively. The AGC signals are passed to an intermediate-frequency amplifying circuit in the terrestrial digital broadcast tuner circuit  81  and an intermediate-frequency amplifying circuit in the satellite digital broadcast tuner circuit  82 , respectively, to be automatically optimized in amplification. This IF signal amplitude optimizing control provides an effect of widening the dynamic range DR of the A/D converting circuits  97  and  99 . 
         [0151]    Serial communications signals  102  and  105 , such as various setting data, control the selection or passband of the terrestrial digital broadcast tuner circuit  81  and the satellite digital broadcast tuner circuit  82  via a switching circuit B ( 91 ), a terminal B ( 87 ), and a terminal D ( 89 ). 
         [0152]    Also, the serial communications signals  102  and  105  are bidirectionally communicable between the terrestrial digital broadcast tuner circuit  81  and the satellite digital broadcast tuner circuit  82  and the terrestrial digital broadcast tuner circuit control block  84  and the satellite digital broadcast tuner circuit control block  85 . 
         [0153]    The digital broadcast receiving apparatus shown in  FIG. 10  has an I 2 C I/F block  94  and a host CPU  96  in addition to the demodulating circuit  83  capable of the reception signals of two schemes, terrestrial digital broadcasting and satellite digital broadcasting, the terrestrial digital broadcast tuner circuit  81 , and the satellite digital broadcast tuner circuit  82 . The I 2 C I/F block  94  and the host CPU  96  each have a function of switching the connection states of switching circuit A ( 90 ) and switching circuit B ( 91 ). 
         [0154]    The demodulating circuit  83  has the terrestrial digital broadcast tuner circuit control block  84 , the satellite digital tuner circuit control block  85 , switching circuit A ( 90 ), switching circuit B ( 91 ), and the I 2 C I/F block  94 . Switching circuit A ( 90 ) and switching circuit B ( 91 ) are connected to switching signal A ( 92 ), switching signal B ( 93 ), and the I 2 C I/F block  94 . The I 2 C I/F block  94  is connected to the host CPU  96  via I 2 C communication  95 . 
         [0155]    Terminal A ( 86 ) and terminal C ( 88 ) of the demodulating circuit  83  output AGC signals  101  and  104  that are fed back to the terrestrial digital broadcast tuner circuit  81  and the satellite digital broadcast tuner circuit  82 , respectively. 
         [0156]    Terminal B ( 87 ) and terminal D ( 89 ) of the demodulating circuit  83  are for serial communications signals  102  and  105  that are fed back to the terrestrial digital broadcast tuner circuit  81  and the satellite digital broadcast tuner circuit  82 , respectively. 
         [0157]    The following describes a relation between tuner circuit arrangement and terminal position. As shown in  FIG. 10 , the relation becomes as follows if the terrestrial digital broadcast tuner circuit  81  is arranged near terminal A ( 86 ) and terminal B ( 87 ) and the satellite digital broadcast tuner circuit  82  is arranged near terminal C ( 88 ) and terminal D ( 89 ). 
         [0158]    Referring to  FIG. 15 , there is shown a relation between control signals switched by the switching signal from the I 2 C I/F block and output terminals by the setting from the host CPU. In this case, the terminal states of terminal A ( 86 ), terminal B ( 87 ), terminal C ( 88 ), and terminal D ( 89 ) can be determined via switching signal A ( 92 ) and switching signal B ( 93 ) set to the I 2 C I/F block  94  by the I 2 C communication  95  from the host CPU  96 , such as “1” of No. 141 in  FIG. 15 , thereby facilitating the wiring of the AGC signals  101  and  104  and the serial communications signal  102  and  105  for the two tuner circuits. 
         [0159]      FIG. 11  shows a connection state of switching circuit A ( 90 ) and switching circuit B ( 91 ) at that time. As shown in  FIG. 11 , in switching circuit A ( 90 ), an AGC  98  is connected to terminal A ( 86 ) and an AGC  100  is connected to the terminal C ( 88 ). In switching circuit B ( 91 ), the terrestrial digital broadcast tuner circuit control block  84  is connected to terminal B ( 87 ) and the satellite digital broadcast tuner circuit control block  85  is connected to terminal D ( 99 ). 
         [0160]    If the terrestrial digital broadcast tuner circuit  81  is arranged near terminal A ( 86 ) and terminal B ( 87 ) and the satellite digital broadcast tuner circuit  82  is arranged near terminal C ( 88 ) and terminal D ( 89 ), the following configuration is obtained. 
         [0161]    In this case, the switching state of switching circuit A ( 90 ) and switching circuit B ( 91 ) is set via switching signal A ( 92 ) and switching signal B ( 93 ) set to the I 2 C I/F block  94  by I 2 C communication  95  from the host CPU  96 , such as “4” of No. 141 in  FIG. 15 . 
         [0162]    Namely, if switching signal A ( 92 ) is “1” and switching signal B ( 93 ) is also “1,” terminal A ( 86 ) provides an AGC signal for satellite digital broadcast tuner, terminal B ( 87 ) provides a serial communications signal for satellite digital broadcast tuner, terminal C ( 88 ) provides an AGC signal for terrestrial digital broadcast tuner, and terminal D ( 89 ) provides a serial communications signal for terrestrial digital broadcast tuner. 
         [0163]    Consequently, the terminal state of terminal A ( 86 ), terminal B ( 87 ), terminal C ( 88 ), and terminal D ( 89 ) can be determined, thereby facilitating the wiring of the AGC signals  101  and  104  and the serial communications signals  102  and  105  for the two tuner circuits. 
         [0164]    A switching connection state of switch circuit A ( 90 ) and switching circuit B ( 91 ) at that time is shown in  FIG. 12 . As shown in  FIG. 12 , in switching circuit A ( 90 ), the AGC  98  is connected to terminal C ( 88 ) and the AGC  100  is connected to terminal A ( 86 ). In switching circuit B ( 91 ), the terrestrial digital broadcast tuner circuit control block  84  is connected to terminal D ( 89 ) and the satellite digital broadcast tuner circuit control block  85  is connected to terminal B ( 87 ). 
         [0165]    Consequently, by setting the switching state of switching circuit A ( 90 ) and switching circuit B ( 91 ) via switching signal A ( 92 ) and switching signal B ( 93 ) set to the I 2 C I/F block  94  by I 2 C communication  95  from the host CPU  96 , the terminal states of terminal A ( 86 ), terminal B ( 87 ), terminal C ( 88 ), and terminal D ( 89 ) can be determined, thereby facilitating the wiring of the AGC signals  101  and  104  and serial communications signals  102  and  105  for the two tuner circuits. 
         [0166]    The following describes a configuration in which the satellite digital broadcast tuner circuit  82  and the terrestrial digital broadcast tuner circuit  81  are arranged in a horizontal manner. If the satellite digital broadcast tuner circuit  82  is arranged near terminal A ( 86 ) and terminal D ( 89 ) and the terrestrial digital broadcast tuner circuit  81  is arranged near terminal B ( 87 ) and terminal C ( 88 ), the following configuration is obtained. In this configuration, the satellite digital broadcast tuner circuit  82  is arranged to the left of the terrestrial digital broadcast tuner circuit  81 . Also, in this configuration, the terminals of the satellite digital broadcast tuner circuit  82  are positioned at the upper and lower sides thereof, and the terminals of the satellite digital broadcast tuner circuit  81  are positioned at the right side thereof. This switching connection state is substantially the same as the switching connection state of circuit A ( 30 ) and switching circuit B ( 31 ) when the satellite digital broadcast tuner circuit  22  is arranged to the left of the terrestrial digital broadcast tuner circuit  21  as shown in  FIG. 6 . 
         [0167]    In this case, the switching state of switching circuit A ( 90 ) and switching circuit B ( 91 ) is set via switching signal A ( 92 ) and switching signal B ( 93 ) set to the I 2 C I/F block  94  by I 2 C communication  95  from the host CPU  96 , such as “2” of No 141 in  FIG. 15 . 
         [0168]    Namely, if switching signal A ( 92 ) is “1” and switching signal B ( 93 ) is “0,” then terminal A ( 86 ) provides an AGC signal for satellite digital broadcast tuner, terminal B ( 87 ) provides a serial communications signal for terrestrial digital broadcast tuner, terminal C ( 88 ) provides an AGC signal for terrestrial digital broadcast tuner, and terminal D ( 89 ) provides a serial communications signal for satellite digital broadcast tuner. 
         [0169]    Consequently, the terminal states of terminal A ( 86 ), terminal B ( 87 ), terminal C ( 88 ), and terminal D ( 89 ) can be determined, thereby facilitating the wiring of the AGC signals  101  and  104  and the serial communications signals  102  and  105 . 
         [0170]    If the satellite digital broadcast tuner circuit  82  is arranged near terminal B ( 87 ) and terminal C ( 88 ) and the terrestrial digital broadcast tuner circuit  81  is arranged near terminal A ( 86 ) and terminal D ( 89 ), the following configuration is obtained. In this configuration, the satellite digital broadcast tuner circuit  82  is arranged to the right of the terrestrial digital broadcast tuner circuit  81 . Also, in this configuration, the terminals of the terrestrial digital broadcast tuner circuit  81  are positioned at the upper and lower sides thereof and the terminals of the satellite digital broadcast tuner circuit  82  are positioned at the right side thereof. This switching connection state is reverse to the arrangement of the satellite digital broadcast tuner circuit  22  and the terrestrial digital broadcast tuner circuit  21  shown in  FIG. 6 . 
         [0171]    In this case, the switching state of switching circuit A ( 90 ) and switching circuit B ( 91 ) is set via switching signal A ( 92 ) and switching signal B ( 93 ) set to the I 2 C I/F block  94  by I 2 C communication  95  from the host CPU  96 , such as “3” of No 141 in  FIG. 15 . 
         [0172]    Namely, if switching signal A ( 92 ) is “0” and switching signal B ( 93 ) is “1,” then terminal A ( 86 ) provides an AGC signal for terrestrial digital broadcast tuner, terminal B ( 87 ) provides a serial communications signal for satellite digital broadcast tuner, terminal C ( 88 ) provides an AGC signal for satellite digital broadcast tuner, and terminal D ( 89 ) provides a serial communications signal for terrestrial digital broadcast tuner. 
         [0173]    Consequently, the terminal states of terminal A ( 86 ), terminal B ( 87 ), terminal C ( 88 ), and terminal D ( 89 ) can be determined, thereby facilitating the wiring of the AGC signals  101  and  104  and the serial communications signals  102  and  105 . 
         [0174]    According to the above-mentioned embodiments of the invention, a terrestrial digital broadcast tuner circuit, a satellite digital broadcast tuner circuit, and a demodulating circuit can be arranged without restraint. Consequently, if the terminals of each of these circuits are different in orientation due to changed arrangements of these circuits, the control signals that are transferred between the three circuits can be wired without restraint. 
         [0175]    In addition, the above-mentioned embodiments of the invention significantly enhance the selectivity in wiring, thereby contributing to the reduced size and cost of an entire system. 
         [0176]    While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purpose only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.