Abstract:
A tuner for receiving a digital broadcast is disclosed which prevents application of an unexpected excessively high voltage to a power supply pin or the like upon inspection or adjustment or after it is assembled into a set. The digital broadcast receiving tuner includes a channel selection section, a demodulation section, and a plurality of terminal pins electrically connected to the channel selection section and the demodulation section and including a power supply pin. The terminal pins further include a grounding pin disposed on at least one side of the power supply pin.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a tuner for receiving a digital broadcast.  
         [0002]     Conventionally, various tuners for receiving a BS digital broadcast have been proposed, and one of such tuners is shown in  FIGS. 4 and 5 .  FIG. 5  shows an appearance of the BS digital broadcast receiving tuner. Referring to  FIG. 5 , the BS digital broadcast receiving tuner shown includes a shield case  1  in which, for example, such a tuner circuit as shown in  FIG. 4  is provided.  
         [0003]     Referring to  FIG. 4 , the tuner circuit shown includes an input terminal  2  to which a BS digital broadcast signal received by a BS antenna or the like is supplied. The BS digital broadcast signal obtained at the input terminal  2  is supplied to a variable attenuator  4  through an amplification circuit  3 . For example, a dc power supply of 5 V supplied to a power supply pin  1   a  is supplied as a power supply to the amplification circuit  3 .  
         [0004]     The variable attenuator  4  is controlled in accordance with the signal level obtained at a QPSK/8PSK demodulation circuit  5  hereinafter described so that the signal level obtained at the output side of the variable attenuator  4  may be fixed.  
         [0005]     An output signal of the variable attenuator  4  is supplied to a variable gain amplification circuit  6   b,  which forms an automatic gain control circuit, through an amplification circuit  6   a  of a Zero-IF QPSK/8PSK down converter  6  which forms channel selection-means. The variable gain amplification circuit  6   b  is controlled in gain in accordance with a gain control signal from a gain control signal production circuit  6   c,  which produces a gain control signal in response to the signal level obtained at the QPSK/8PSK demodulation circuit  5 .  
         [0006]     An output signal of the variable gain amplification circuit  6   b  is supplied to one of input terminals of each of multiplication circuits  6   d  and  6   e.    
         [0007]     The tuner circuit further includes a local oscillation circuit  7  formed from a PLL circuit and including a variable frequency oscillation circuit  7   a  for controlling the capacitance of a variable capacitor to vary the oscillation frequency of the local oscillation circuit  7 . An oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to one of input terminals of a comparison circuit  7   b  while a channel selection signal obtained at a terminal pin  1   f  is supplied to the other input terminal of the comparison circuit  7   b.    
         [0008]     An error signal obtained by the comparison circuit  7   b  is supplied to a low-pass filter  7   c.  The low-pass filter  7   c  adds a dc voltage of the error signal and a dc voltage of, for example, 32 V supplied to a power supply pin  1   c  to obtain a tuning voltage and supplies the tuning voltage to the variable capacitor of the variable frequency oscillation circuit  7   a.    
         [0009]     The oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to the other input terminal of the multiplication circuit  6   d.  Further, the oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to the other input terminal of the multiplication circuit  6   e  through a 90° phase-shift circuit  6   f.    
         [0010]     An I signal obtained on the output side of the multiplication circuit  6   d  is supplied to the QPSK/ 8 PSK demodulation circuit  5  formed from a semiconductor integrated circuit through a series circuit of the low-pass filter  6   g  and an amplification circuit  6   h.  Further, a Q signal obtained on the output side of the multiplication circuit  6   e  is supplied to the QPSK/8PSK demodulation circuit  5  through another series circuit of a low-pass filter  6   i  and an amplification circuit  6   j.  A transport stream packet obtained on the output side of the QPSK/8PSK demodulation circuit  5  is supplied to a back end circuit from eight output terminal pins  1   g.    
         [0011]     Further, a stable dc power supply of, for example, 5 V obtained at the power supply pin  1   b  is supplied as a power supply to the Zero-IF QPSK/8PSK down converter  6  and the local oscillation circuit  7 .  
         [0012]     To the QPSK/8PSK demodulation circuit  5  formed from a semiconductor integrated circuit, dc power supplies of, for example, 1.5 V and 3.3 V obtained at the power supply pins  1   d  and  1   e,  respectively, are supplied as power supplies.  
         [0013]     The power supply pins  1   a,    1   b,  . . . ,  1   e  of the conventional BS digital broadcast receiving tuner are arranged in a mutually adjacent juxtaposed relationship as seen in  FIG. 5 .  
         [0014]     The BS digital broadcast receiving tuner further includes, in addition to the terminal pins mentioned hereinabove, terminal pins for synchronizing signals, terminal pins for clock signals, terminal pins for an error indicator and so forth. Thus, the BS digital broadcast receiving tuner includes totally approximately 30 terminal pins.  
         [0015]     Incidentally, miniaturization is demanded also for a BS digital broadcast receiving tuner. However, miniaturization of the conventional BS digital broadcast receiving tuner is difficult because a distance of 2.54 mm is required between adjacent ones of the approximately 30 terminal pins.  
         [0016]     Thus, it is a possible idea to set the distance between adjacent ones of such approximately 30 terminal pins to a comparatively small distance such as, for example, to 2 mm to achieve miniaturization of the BS digital broadcast receiving tuner while the power supply pins  1   a,    1   b,  . . . ,  1   e  are arranged in a juxtaposed relationship as in the conventional BS digital broadcast receiving tuner.  
         [0017]     In this instance, since the distance between adjacent ones of the power supply pins  1   a,    1   b,  . . . ,  1   e  is comparatively small such as, for example, 2 mm, there is the possibility that, upon inspection or adjustment in manufacture of the BS digital broadcast receiving tuner, for example, a check pin for supplying a dc power supply of 32 V or a like pin may contact not only with the power supply pin  1   c  but also with the adjacent power supply pin  1   b  or  1   d.  If the check pin contacts with the power supply pin  1   b  or  1   d  in error, then an unexpected excessively high voltage is supplied to the power supply pin  1   b  or  1   d.  The BS digital broadcast receiving tuner cannot take a sufficient countermeasure for protection against the inrush of the excessively high voltage, and disadvantageously there is the possibility that the BS digital broadcast receiving tuner may suffer from breakdown of an internal part thereof.  
         [0018]     Further, when such a BS digital broadcast receiving tuner as described above is assembled into a set, the terminal pins are inserted into, a main board of the set and soldered to the main board using a solder tank. Thereupon, since the distance between adjacent ones of the power supply pins  1   a,    1   b,  . . . ,  1   e  is comparatively small, a solder bridge is likely to appear. If a solder bridge is produced between, for example, the power supply pin  1   c  for supplying a dc power supply of 32 V and the power supply pin  1   b  or  1   d,  then even if the BS digital broadcast receiving tuner is normal before it is assembled, disadvantageously there is the possibility that an unexpected excessively high voltage may rush into the BS digital broadcast receiving tuner to give rise to a breakdown of an internal part of the BS digital broadcast receiving tuner or to a breakdown of the set in which the BS digital broadcast receiving tuner is assembled.  
         [0019]     In this instance, since the BS digital broadcast receiving tuner before the incorporation is normal, disadvantageously it is comparatively difficult to find out a cause of the failure.  
       SUMMARY OF THE INVENTION  
       [0020]     It is an object of the present invention to provide a tuner for receiving a digital broadcast which prevents application of an unexpected excessively high voltage to a power supply pin or the like thereof upon inspection or adjustment or after it is assembled into a set.  
         [0021]     In order to attain the object described above, according to an aspect of the present invention, there is provided a tuner for receiving a digital broadcast, comprising channel selection means, demodulation means, and a plurality of terminal pins electrically connected to the channel selection means and the demodulation means and including a power supply pin and a grounding pin disposed on at least one side of the power supply pin.  
         [0022]     With the tuner for receiving a digital broadcast, since the grounding pin is disposed on at least one side of the power supply pin, an adjacent pin to the power supply pin is the grounding pin, and a pin with or to which a check pin or the like to which a power supply of, for example, 32 V is supplied is contacted in error or bridged by solder upon inspection or adjustment or after the digital broadcast receiving tuner is assembled into a set is the grounding pin. Consequently, the possibility that an unexpected voltage may be applied to the other pins can be eliminated. In this instance, even if a high voltage of, for example, 32 V is applied to the grounding pin in error, there is no possibility that it may break down a part of the digital broadcast receiving tuner or an apparatus connected to the tuner.  
         [0023]     According to another aspect of the present invention, there is provided a tuner for receiving a digital broadcast, comprising channel selection means, demodulation means, and a plurality of terminal pins electrically connected to the channel selection means and the demodulation means and including a plurality of power supply pins for supplying a plurality of powers of voltages different from each other and a pair of grounding pins disposed on the opposite sides of that one of the power supply pins which is for the power supply of the highest one of the different voltages.  
         [0024]     With the tuner for receiving a digital broadcast, the grounding pins are disposed on the opposite sides of the power supply pin to which the highest power supply voltage is applied. Consequently, similar advantages to those described above are achieved.  
         [0025]     The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a block diagram showing a tuner for receiving a digital broadcast to which the present invention is applied;  
         [0027]      FIG. 2  is a side elevational view showing an appearance of the digital broadcast receiving tuner of  FIG. 1 ;  
         [0028]      FIG. 3  is a top plan view showing an appearance of the digital broadcast receiving tuner of  FIG. 1 ;  
         [0029]      FIG. 4  is a block diagram showing an example of conventional tuner for receiving a digital broadcast; and  
         [0030]      FIG. 5  is a plan view showing an appearance of the conventional digital broadcast tuner of  FIG. 4 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]      FIGS. 1, 2  and  3  show a tuner for receiving a digital broadcast to which the present invention is applied. Of the reference characters in  FIGS. 1, 2  and  3 , those already used in  FIGS. 4 and 5  designate like or corresponding parts.  FIGS. 2 and 3  show side and top appearances of the BS digital broadcast receiving tuner and show a shield case  1  in which a tuner circuit for receiving a BS digital broadcast similar to that of  FIG. 4  is provided.  
         [0032]     Referring to  FIG. 1 , a BS digital broadcast signal received by a BS antenna or the like is supplied to an input terminal  2 . The BS digital broadcast signal obtained at the input terminal  2  is supplied to a variable attenuator  4  through an amplification circuit  3 . For example, a dc power supply of 5 V supplied to a power supply pin  1   a  is supplied as a power supply to the amplification circuit  3 .  
         [0033]     The variable attenuator  4  is controlled in accordance with the signal level obtained at a QPSK/8PSK demodulation circuit  5  hereinafter described so that the signal level obtained at the output side of the variable attenuator  4  may be fixed.  
         [0034]     An output signal of the variable attenuator  4  is supplied to a variable gain amplification circuit  6   b,  which forms an automatic gain control circuit, through an amplification circuit  6   a  of a Zero-IF QPSK/8PSK down converter  6  which forms channel selection means. The variable gain amplification circuit  6   b  is controlled in gain in accordance with a gain control signal from a gain control signal production circuit  6   c,  which produces a gain control signal in response to the signal level obtained at the QPSK/8PSK demodulation circuit  5 .  
         [0035]     An output signal of the variable gain amplification circuit  6   b  is supplied to one of input terminals of each of multiplication circuits  6   d  and  6   e.    
         [0036]     The tuner circuit further includes a local oscillation circuit  7  formed from a PLL circuit and including a variable frequency oscillation circuit  7   a  for controlling the capacitance of a variable capacitor to vary the oscillation frequency of the local oscillation circuit  7 . An oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to one of input terminals of a comparison circuit  7   b  while a channel selection signal obtained at a terminal pin  1   f  is supplied to the other input terminal of the comparison circuit  7   b.    
         [0037]     An error signal obtained by the comparison circuit  7   b  is supplied to a low-pass filter  7   c.  The low-pass filter  7   c  adds a dc voltage of the error signal and a dc voltage of, for example, 32 V supplied to a power supply pin  1   c  to obtain a tuning voltage and supplies the tuning voltage to the variable capacitor of the variable frequency oscillation circuit  7   a.    
         [0038]     The oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to the other input terminal of the multiplication circuit  6   d.  Further, the oscillation signal of the variable frequency oscillation circuit  7   a  is supplied to the other input terminal of the multiplication circuit  6   e  through a 90° phase-shift circuit  6   f.    
         [0039]     An I signal obtained on the output side of the multiplication circuit  6   d  is supplied to the QPSK/8PSK demodulation circuit  5  formed from a semiconductor integrated circuit through a series circuit of the low-pass filter  6   g  and an amplification circuit  6   h.  Further, a Q signal obtained on the output side of the multiplication circuit  6   e  is supplied to the QPSK/8PSK demodulation circuit  5  through another series circuit of a low-pass filter  6   i  and an amplification circuit  6   j.  A transport stream packet obtained on the output side of the QPSK/8PSK demodulation circuit  5  is supplied to a back end circuit from eight output terminal pins  1   g.    
         [0040]     Further, a stable dc power supply of, for example, 5 V obtained at the power supply pin  1   b  is supplied as a power supply to the Zero-IF QPSK/8PSK down converter  6  and the local oscillation circuit  7 .  
         [0041]     To the QPSK/8PSK demodulation circuit  5  formed from a semiconductor integrated circuit, dc power supplies of, for example, 1.5 V and 3.3 V obtained at the power supply pins  1   d  and  1   e,  respectively, are supplied as power supplies.  
         [0042]     In the present embodiment, a predetermined number of, for example,  30 , terminal pins including the power supply pins  1   a,    1   b,  . . . ,  1   e,  output terminal pins  1   g  and terminal pin  1   f  of the BS digital broadcast receiving tuner are provided at equal distances as shown in  FIG. 2 .  
         [0043]     In the present embodiment, grounding pins  10   a  and  10   b  connected to the ground of the BS digital broadcast receiving tuner are disposed between the power supply pin  1   b  and the power supply pin  1   c  and between the power supply pin  1   c  and the terminal pin  1   f,  respectively.  
         [0044]     Incidentally, from among the  30  terminal pins of the BS digital broadcast receiving tuner shown in  FIG. 2  according to the present embodiment, the first terminal pin from the left side in  FIG. 2  is a free pin connected to no circuit element.  
         [0045]     The second terminal pin is the power supply pin  1   a  to which a dc power supply of, for example, 5 V is supplied. The third terminal pin is a low noise blocking power supply pin. The fourth terminal pin is the power supply pin  1   b  to which a stable dc power supply of, for example, 5 V is supplied. The fifth terminal pin is the grounding pin  10   a  connected to the ground. The sixth terminal is the power supply pin  1   c  to which a maximum dc voltage of, for example, 32 V is supplied. The seventh terminal pin is the grounding pin  10   b  connected to the ground.  
         [0046]     The eighth terminal pin is the terminal pin  1   f  to which a channel selection signal is supplied. The ninth terminal pin is a terminal pin to which an address selection signal for a demodulation IC is supplied. The tenth terminal pin is a terminal pin to which a hard reset signal is supplied. The eleventh and twelfth terminal pins are terminal pins to which an interface is connected. The thirteenth terminal pin is a terminal pin to which an activation control signal in a TMCC signal is outputted.  
         [0047]     The fourteenth terminal pin is a terminal pin from which a change instruction signal in the TMCC signal is outputted. The fifteenth terminal pin is a terminal pin from which a frame synchronizing signal is outputted. The sixteenth terminal pin is the power supply pin  1   e  to which a dc voltage of, for example, 3.3 V is supplied. The seventeenth to twenty-fourth terminals are the output terminal pins  1   g  for a transport stream packet.  
         [0048]     The twenty-fifth terminal pin is the power supply pin  1   d  to which a dc voltage of, for example, 1.5 V is supplied. The twenty-sixth terminal pin is a terminal pin from which a transport stream clock is outputted. The twenty-seventh terminal pin is a terminal pin for a synchronizing signal for transport stream data. The twenty-eighth terminal pin is an enable terminal pin for transport stream data. The twenty-ninth terminal pin is a terminal for a synchronizing signal for a transport stream data super frame. The thirtieth terminal pin is a terminal pin for connection of an error indicator.  
         [0049]     In the present embodiment, since the grounding pins  10   a  and  10   b  connected to the ground are disposed between the power supply pins  1   b  and  1   c  and between the power supply pin  1   c  and the next terminal pin  1   f,  respectively, for example, adjacent pins to the power supply pin  1   c  to which the power supply of 32 V is supplied are the grounding pins  10   a  and  10   b.  Thus, a pin with which a check pin or the like to which, for example, a power supply of 32 V is supplied upon inspection or adjustment may contact in error is the grounding pin  10   a  or  10   b.  Further, a pin to which the power supply pin  1   c  is bridged by solder when the BS digital broadcast receiving tuner is assembled into a set is the grounding pin  10   a  or  10   b.  Thus, an unexpected excessively high voltage is not applied to the other power supply pins  1   b  and  1   d  at all.  
         [0050]     In this instance, even if a high voltage of, for example, 32 V is applied in error to the grounding pin  10   a  or  10   b,  there is no possibility that the high voltage may break down a part in the BS digital broadcast receiving tuner or the set in which the BS digital broadcast receiving tuner is assembled.  
         [0051]     Accordingly, with the embodiment described above, the distance between adjacent ones of the terminal pins can be reduced and the BS digital broadcast receiving tuner can be miniaturized with safety.  
         [0052]     While a preferred embodiment of the present invention has been described using specific terms, such description is for illustrative purposes 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.