Patent Publication Number: US-2006003718-A1

Title: Broadcast receiving apparatus and broadcast receiving method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2004-194310, filed Jun. 30, 2004; No. 2004-229723, filed Aug. 5, 2004; and No. 2004-381560, filed Dec. 28, 2004, the entire contents of all of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a broadcast receiving apparatus and broadcast receiving method for receiving, for example, analog TV broadcasts, and more particularly to a broadcast receiving apparatus and broadcast receiving method compatible with worldwide broadcast programs not limited to any particular country or region.  
      2. Description of the Related Art  
      As is well known, the intermediate frequencies of tuners for analog TV broadcasts are different depending on country and region because of legal restrictions. For example, in Europe, the US and Japan, the frequency is 38.9 MHz and in China and other Asian countries, it is 38.0 MHz.  
      Thus, currently, tuner types handling each of the available intermediate frequencies are prepared, and a method of supplying a machine type compatible with a destination country and a method of selling a machine type corresponding to a user&#39;s region have been adopted.  
      However, these methods have a problem in that the supply system of the tuner to users becomes complicated and users cannot use their purchased tuner if they bring it to a region whose intermediate frequency is different.  
      Jpn. Pat. Appln. KOKAI Publication No. 2000-40977 discloses a frequency converter which converts intermediate frequency TV signals to low frequency using a mixer and Jpn. Pat. Appln. KOKAI Publication No. 9-205593 discloses a circuit which performs digital filtering an intermediate frequency video signal.  
      However, there two publications describe nothing about a method for facilitating supply of the tuner to users to meet the fact that the intermediate frequency of the tuner must differ depending on the country or region.  
     BRIEF SUMMARY OF THE INVENTION  
      According to one aspect of the present invention, there is provided a broadcast receiving apparatus comprising: a receiving section configured to receive a broadcast signal; a tuner section configured to convert a frequency of the broadcast signal received by the receiving section into an intermediate frequency signal having a frequency designated by an intermediate frequency setting signal; a filter section configured to allow the intermediate frequency signal generated in the tuner section to pass through; a demodulating section configured to carry out demodulation of the intermediate frequency signal based on the intermediate frequency setting signal; a memory section configured to store information of the intermediate frequency setting signal corresponding to region where the receiving apparatus practicable; and a control section configured to read the information of the intermediate frequency setting signal corresponding to specific region from the memory section, the specific region is selected by a user, and supply the signal to the tuner section and the demodulating section.  
      According to another aspect of the present invention, there is provided a broadcast receiving method comprising: a first step of receiving a broadcast signal; a second step of generating an intermediate frequency signal having a frequency based on an intermediate frequency setting signal from the received broadcast signal; a third step of allowing the generated intermediate frequency signal to pass through a filter; a fourth step of carrying out demodulation processing based on the intermediate frequency setting signal upon the intermediate frequency signal having passed through the filter; and a fifth step of, after inputting information about a place in which the broadcast signal is received, reading the intermediate frequency setting signal stored in a memory preliminarily corresponding to the place in which the information is input and applying the intermediate frequency setting signal to processing in the second and fourth steps. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       FIG. 1  is a perspective view of the appearance of a broadcast receiving apparatus according to an embodiment of the present invention;  
       FIG. 2  is a block diagram for explaining the signal processing system of the broadcast receiving apparatus of the embodiment;  
       FIG. 3  is a characteristic diagram for explaining the frequency characteristic of a band-pass filter of the broadcast receiving apparatus of the embodiment;  
       FIG. 4  is a block diagram for explaining the details of a tuner section of the broadcast receiving apparatus of the embodiment;  
       FIG. 5  is a block diagram for explaining the details of a demodulating section of the broadcast receiving apparatus of the embodiment;  
       FIG. 6  is a flowchart for explaining an intermediate frequency setting operation of the broadcast receiving apparatus of the embodiment;  
       FIG. 7  is a view for explaining an example of an intermediate frequency setting screen used in the intermediate frequency setting operation of the embodiment;  
       FIG. 8  is a block diagram for explaining a first modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 9  is a block diagram for explaining a second modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 10  is a block diagram for explaining a third modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 11  is a block diagram for explaining a fourth modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 12  is a block diagram for explaining a fifth modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 13  is a block diagram for explaining a sixth modification of the broadcast receiving apparatus of the embodiment;  
       FIG. 14  is a view for explaining a personal computer to which a tuner module of the embodiment is applied; and  
       FIG. 15  is a view for explaining a portable phone to which the tuner module of the embodiment is applied. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.  FIG. 1  shows the appearance of a broadcast receiving apparatus  11  of the embodiment. The broadcast receiving apparatus  11  has a portable thin box-shaped case  12 .  
      The case  12  of the broadcast receiving apparatus  11  has a display section  13  and an operating section  14  on one flat portion  12   a  thereof and a connector  15  for audio output to be connected to a headphone or the like is provided on a side face  12   b.    
       FIG. 2  shows a signal processing system of the broadcast receiving apparatus  11 . That is, a TV broadcast signal received by an antenna  16  incorporated in the case  12  is supplied to a tuner module  17 .  
      The tuner module  17  has a tuner section  18 , a band-pass filter (BPF)  19  and a demodulating section  20 . Then, the tuner section  18  converts an inputted TV broadcasting signal to an intermediate frequency (IF) signal having a predetermined intermediate frequency and outputs to the BPF  19 .  
      The BPF  19  allows modulated wave components satisfying some extent of signal-to-noise ratio of the input IF signal to pass and outputs to the demodulating section  20 . Then, the demodulating section  20  generates a base band video signal and audio signal before demodulation from the input IF signal.  
      In this way, the video signal and the audio signal outputted from the tuner module  17  are supplied to a signal processing section  21 . After converting the input video signal to a format suitable for representation on the display section  13 , the signal processing section  21  outputs to the display section  13  for representation.  
      The signal processing section  21  executes demodulation processing on the inputted audio signal and then, outputs to headphones connected from outside through the connector  15  for audio reproduction.  
      The broadcast receiving apparatus  11  is controlled totally by a control section  23  about its all operations including the above-described receiving operation. The control section  23  incorporates a central processing unit (CPU) or the like, and receives operation information from the operating section  14  in order to control the respective sections so that the content of that operation information is reflected thereon.  
      In this case, the control section  23  uses a memory section  24 . That is, the memory section  24  includes mainly a read only memory storing a control program to be executed by the CPU of the control section  23 , a read-out write memory which provides a work area to that CPU and a nonvolatile memory storing various kinds of setting information including intermediate frequency setting signal described later, control information and the like.  
      Here, as the aforementioned tuner section  18 , for example, a silicon tuner is used. The tuner section  18  is capable of selectively setting the intermediate frequency of the IF signal to 38.9 MHz or 38.0 MHz based on the intermediate frequency setting signal supplied from the control section  23  through, for example, a control bus such as IIC.  
      As the BPF  19 , for example, a digital demodulation surface acoustic wave (SAW) filter is used. The BPF  19  allows the IF signals of two intermediate frequencies, 38.9 MHz and 38.0 MHz, to pass through as shown in  FIG. 3 .  
      Further, the BPF  19  is set so that its frequency characteristic has no Nyquist slope characteristic so as to be able to supply modulated wave components satisfying some extent of signal-to-noise ratio to a demodulating section  20  located on a post stage.  
      In the demodulating section  20 , an internal clock is controlled so that demodulation processing corresponding to the IF signal of the intermediate frequency set by the tuner section  18  can be carried out from the control section  23  based on the intermediate frequency setting signal supplied through a control bus such as IIC.  
      Because the tuner module  17  is capable of meeting the IF signals of two intermediate frequencies, 38.0 MHz and 38.9 MHz, based on the intermediate frequency setting signal output from the control section  23 , the broadcast receiving apparatus  11  can be supplied more easily to users and this is adaptable for practical use.  
       FIG. 4  shows the details of the tuner section  18 . That is, TV broadcast signal received by the antenna  16  is supplied to a frequency mixer  18   c  through an input terminal  18   a  and a gain variable amplifier  18   b.    
      The frequency mixer  18   c  shifts input TV broadcast signal of 50-870 MHz to 1.2 GHz by mixing with local oscillation signal output from a local oscillator  18   d.    
      Then, a high frequency signal outputted from the frequency mixer  18   c  is supplied to a frequency mixer  18   f  through a SAW BPF  18   e.  The frequency mixer  18   f  converts the input high-frequency signal to an IF signal of 38.9 MHz or 38.0 MHz by mixing with a local oscillation signal output from a local oscillator  18   g.    
      Thereafter, the IF signal output from the frequency mixer  18   f  is fetched out from an output terminal  18   k  through an amplifier  18   h , a SAW BPF  18   i  and an amplifier  18   j  and output to the BPF  19 .  
      In the local oscillators  18   d ,  18   g , their oscillation frequencies are controlled by phase-locked loop (PLL) circuits  18   l,    18   m.  Further, an output of a reference oscillator  18   n  is supplied to these PLL circuits  18   l,    18   m  as a reference signal.  
      An intermediate frequency setting signal output from the control section  23  is supplied to the PLL circuit  18   m  through a control terminal  18   o.  In the PLL circuit  18   m , its division ratio is changed based on the intermediate frequency setting signal supplied from the control section  23  and the frequency of a local oscillation signal output from the local oscillator  18   g  is changed based thereon. As a consequence, IF signals of 38.9 and 38.0 MHz can be selectively generated from the frequency mixer  18   f.    
      A gain adjustment signal output from the demodulating section  20  is supplied to the gain variable amplifier  18   b  through a control terminal  18   p.  In the gain variable amplifier  18   b , its gain is changed based on the gain adjustment signal output from the demodulating section  20  and automatic gain adjustment of the tuner module  17  is carried out.  
       FIG. 5  shows the details of the demodulating section  20 . The IF signal of 38.9 or 38.0 MHz outputted from the BPF  19  is supplied to a frequency mixer  20   c  through an input terminal  20   a  and an amplifier  20   b.    
      The frequency mixer  20   c  converts the inputted IF signal to a frequency operable with the digital signal processor (DSP)  20  located at a post stage by mixing with a clock signal output from a clock generating section  20   d.    
      After passing a BPF  20   e , the IF signal output from the frequency mixer  20   c  is digitized by an analog-to-digital converter  20   f  driven based on the clock signal output from the clock generating section  20   d  and supplied to a DSP  20   g.    
      The DSP  20   g  generates a gain adjustment signal to be given to the gain variable amplifier  18   b , video signal of baseband and audio signal prior to demodulation from the input IF signal based on the clock signal output from the clock generating section  20   d.    
      Then, the gain control signal, after being converted to an analog signal by a digital-to-analog converter  20   h,  is supplied to the gain variable amplifier  18   b  through an output terminal  20   i  and the control terminal  18   p  of the tuner section  18 .  
      The video signal, after being converted to an analog signal by a digital-to-analog converter  20   j,  is supplied to the signal processing section  21  through an output terminal  20   k.  Further, the audio signal, after converted to an analog signal by a digital-to-analog converter  20   l,  is supplied to the signal processing section  21  through an output terminal  20   m.    
      The clock generating section  20   d  generates a clock signal based on a reference oscillation signal outputted from a reference oscillator  20   n.  An intermediate frequency setting signal output from the control section  23  is supplied to the clock generating section  20   d  through a control terminal  20   o.    
      The clock generating section  20   d  controls the frequency of the clock signal based on the intermediate frequency setting signal supplied from the control section  23  so that the analog-to-digital converter  20   f  and the DSP  20   g  can execute analog-to-digital conversion processing and demodulation processing upon the IF signal of an intermediate frequency set by the tuner section  18 .  
      Whether the intermediate frequency is set to 38.9 or 38.0 MHz can be set by a user when channel scanning of automatically retrieving a receivable channel by scanning a reception frequency band in succession continuously is demanded.  
       FIG. 6  shows a flowchart summarizing the setting operation of the intermediate frequency. First, if the processing is started (step S 1 ), the control section  23  determines whether or not channel scan is requested in step S 2  and if it is determined that the channel scan is not requested (NO), the processing is terminated (step S 7 ).  
      If it is determined that the channel scan is requested in step S 2  (YES), the control section  23  indicates an intermediate frequency setting screen on the display section  13  in step S 3 . The intermediate frequency setting screen lists regions and countries as shown in  FIG. 7 .  
      Then, a user selects a place where the broadcast receiving apparatus  11  is to be used, that is, a region or country corresponding to the place where the broadcast receiving apparatus  11  is currently installed from the listed regions and countries. The selection is carried out by moving a cursor k on the screen by operating the operating section  14 , and then operating a decision key.  
      Thereafter, the control section  23  waits until a region or a country is selected from the intermediate frequency setting screen by the user in step S 4 , and if it is determined that a region or a country is selected (YES), an intermediate frequency setting signal corresponding to the intermediate frequency of the selected region or country is read out from the memory  24  in step S 5  and output to the tuner section  18  and the demodulating section  20 .  
      Consequently, in the tuner module  17 , an intermediate frequency handled thereby is determined. If the intermediate frequency is determined in this way, the control section  23  executes the channel scan in step S 6  and terminates the processing (step S 7 ).  
      According to the above-described embodiment, since the tuner module  17  is capable of meeting the IF signals of two intermediate frequencies, 38.9 and 38.0 MHz, based on the intermediate frequency setting signal output from the control section  23 , the broadcast receiving apparatus can be supplied to users easily and the apparatus is adaptable for practical use.  
       FIG. 8  shows a first modification of the above embodiment. If  FIG. 8  is explained with the same reference numerals given to the same components, in the tuner module  17 , a BPF  19   a  for 38.9 MHz and a BPF  19   b  for 38.0 MHz are prepared. By using switches  25   a ,  25   b  selectable depending on the intermediate frequency setting signal, a necessary BPF  19   a  or  19   b  is used. Under such a structure, the same operation as the broadcast receiving apparatus  11  shown in  FIG. 2  is carried out and the same effect can be obtained.  
       FIG. 9  shows a second modification of the above embodiment. If  FIG. 19  is explained with the same reference numerals given to the same components, in the tuner module  17 , a single tuned circuit  26  for the IF signal frequency output from the tuner section  18  is connected between the tuner section  18  and the BPF  19 .  
      That is, if a multi-wave signal is inputted to the tuner section  18 , a carrier wave level of a channel adjacent to or second adjacent to a receiving channel is output from the tuner section  18  without being damped because the band of the SAW BPF 18   e  is about 20 MHz, and then input to the demodulating section  20  through the BPF  19 .  
      Although the band characteristic of the IF signal outputted from the tuner section  18  is determined by a fore stage of the analog-to-digital converting section  20   f  in the demodulating section  20  on a post stage, the carrier of the adjacent channel is not damped so much in the preceding BPF  19 . When there exists a difference in signal level between the adjacent channel and the second adjacent channel, if the level of a reception signal is low with respect to a jamming wave, jamming by interference occurs.  
      To solve the problem, by connecting the single tuned circuit  26  for the IF signal frequency between the tuner section  18  and the BPF  19 , the signal levels of the adjacent channel and second adjacent channel can be suppressed, so that a performance resisting interference can be improved.  
       FIG. 10  shows a third modification of the above embodiment. If  FIG. 10  is explained with the same reference numerals given to the same components, in the tuner module  17 , a trap filter  27 , which is a channel upper second adjacent to a receiving channel, is connected between the BFF  19  and the demodulating section  20 .  
      If the multi-wave signal is input to the tuner section  18  as described above, the levels of channels adjacent to and second adjacent to the receiving channel is output from the tuner section  18  without being damped because the band of the SAW BPF  18   e  is about 20 MHz, and then input to the demodulating section  20  through the BPF  19 .  
      Although the band characteristic of the IF signal output from the tuner section  18  is determined on a stage preceding the analog-to-digital converting section  20   f  in the demodulating section  20  on a post stage, the carrier of the adjacent channel is not damped so much in the preceding BPF  19 . If the input IF signal is analog-to-digital converted under such a condition, the performance resisting interference in the vicinity of a channel upper second adjacent to the receiving channel is worsened by sampling distortion in the demodulating section  20 .  
      To solve the problem, by connecting the trap filter  27  between the BPF  19  and the demodulating section  20 , the signal component of the second adjacent channel can be suppressed, so that the performance resisting interference can be improved.  
       FIG. 11  shows a fourth modification of the above embodiment. If  FIG. 11  is explained with the same reference numerals given to the same components, a notch filter  28 , which is a channel upper second adjacent to the receiving channel, is connected between the tuner section  18  and the BPF  19  in the tuner module  17 . With such a structure, the signal component of the channel upper second adjacent to the receiving channel can be suppressed like the third modification, thereby making it possible to improve the performance resisting interference.  
       FIG. 12  shows a fifth modification of the above embodiment. If  FIG. 12  is explained with the same reference numerals given to the same components, a notch filter  29 , which is a channel upper second adjacent to the receiving channel, is connected between the BPF  19  and the demodulating section  20  in the tuner module  17 . With such a structure, the signal component of the channel upper second adjacent to the receiving channel can be suppressed like the third modification, thereby making it possible to improve the performance resisting interference.  
       FIG. 13  shows a sixth modification of the above embodiment. If  FIG. 13  is explained with the same reference numerals given to the same components, notch filters  28 ,  29 , which are a channel upper second adjacent to the receiving channel, are connected between the tuner section  18  and the BPF  19  and between the BPF  19  and the demodulating section  20 , respectively, in the tuner module  17 . With such a structure, the signal component of the channel upper second adjacent to the receiving channel can be suppressed like the third modification, thereby making it possible to improve the performance resisting interference.  
      The above-mentioned tuner module  17  can be applied to a wide application field including the personal computer (PC)  30  shown in  FIG. 14 , the portable phone  31  shown in  FIG. 15  and the like.  
      In the meantime, the present invention is not restricted to the above-described embodiments but upon carrying out the invention, the components of the invention can be modified within a scope not departing from the gist of the invention. Further, by combining plural components disclosed in the above-described embodiments appropriately, various kinds of other inventions can be formed. For example, it is permissible to erase some components from the all components disclosed in the embodiments.