Patent Publication Number: US-2013243067-A1

Title: Broadcast receiving apparatus and method for removing interference signal of analog broadcast signal

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2012-0027074, filed on Mar. 16, 2012 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with the exemplary embodiments relate to a broadcast receiving apparatus and a method for removing an interference signal of an analog broadcast signal. 
     2. Description of the Related Art 
     A broadcast receiving apparatus e.g., a TV or a set-top box which receives a broadcast signal transmitted by a broadcasting station and processes the broadcast signal to display an image on a screen. The broadcast signal which is received by the broadcast receiving apparatus may be largely classified as an analog broadcast signal and a digital broadcast signal, and an aspect of an exemplary embodiment relates to a broadcast receiving apparatus which receives an analog broadcast signal. 
     An analog broadcasting system divides several hundred Mhz of frequency into 6 Mhz to 8 Mhz to transmit a broadcast signal of each channel. There are dozens of or even hundreds of broadcasting channels, the number differing depending on the country or territory in which the channels are broadcasted. 
     If one desires to receive an analog broadcast signal of a specific channel through the broadcast receiving apparatus in the above channel environment, due to adjacent channels, a broadcast signal  10  including a desired signal  11  of the channel added with an interference signal  12  may be received as shown in  FIG. 1 . 
     If such interference signal is received, noise occurs when the signal is processed and displayed on a screen. A conventional broadcast receiving apparatus has no way to correct the noise from the screen which occurs as a result of the interference signal. 
     SUMMARY 
     Accordingly, one or more exemplary embodiments there is provided a broadcast receiving apparatus and a method for removing an interference signal component from an analog broadcast signal received to thereby prevent noise from occurring in a screen. 
     According to an aspect of an exemplary embodiment, there is provided a broadcast receiving apparatus including: a signal receiver which receives an analog broadcast signal in a radio frequency (RF) band; a sync signal detector which detects a sync signal area of the received broadcast signal; an interference signal detector which compares the sync signal area of the broadcast signal with a predetermined reference signal and detects an interference signal component; and an interference signal remover which removes the interference signal component from the broadcast signal based on the interference signal component detected from the sync signal area. 
     The interference signal remover may remove the interference signal component from the broadcast signal according to a pattern of the interference signal. 
     The broadcast receiving apparatus may further include an analog/digital (A/D) converter which converts the analog broadcast signal received by the signal receiver, into a digital signal and outputs the converted broadcast signal to the sync signal detector. 
     The broadcast receiving apparatus may further include a signal demodulator which demodulates a broadcast signal output by the A/D converter, wherein the signal demodulator comprises the sync signal detector. 
     The broadcast receiving apparatus may further include a signal processor which processes a broadcast signal demodulated and output by the signal demodulator, according to a predetermined image processing operation. 
     The interference signal detector may detect the interference signal component of a signal which is output by at least one of the A/D converter, the signal demodulator and the signal processor. 
     The interference signal remover may include a digital comb filter, and may adjust a filter coefficient of the digital comb filter and separates the interference signal component from the broadcast signal. 
     The interference signal remover may include a channel equalizer, and may adjust a filter coefficient of the channel equalizer and adjust a gain of the broadcast signal to remove the interference signal component. 
     The interference signal detector may convert the received broadcast signal into a frequency domain through fast fourier transform (FFT), and compare the frequency domain information with a predetermined reference signal to detect an interference signal component, and the interference signal remover may remove the interference signal component from the frequency domain and output a signal in a time domain through an inverse fast fourier transform. 
     The broadcast receiving apparatus may further include a controller which controls the interference signal detector and the interference signal remover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an interference signal component which is included in a broadcast signal; 
         FIG. 2  is a control block diagram of a broadcast receiving apparatus according to an exemplary embodiment; 
         FIG. 3  illustrates a detection of a sync signal area of a broadcast signal; 
         FIGS. 4A to 4C  illustrate exemplary embodiments for removing an interference signal; and 
         FIGS. 5 and 6  are flowcharts showing a method for removing an interference signal from an analog broadcast signal according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The exemplary embodiments may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout. 
       FIG. 2  is a control block diagram of a broadcast receiving apparatus  100  according to an exemplary embodiment. 
     As shown therein, the broadcast receiving apparatus  100  includes a signal receiver  110 , a sync signal detector  160 , an interference signal detector  170 , and an interference signal remover  180 . The broadcast receiving apparatus  100  may further include an analog/digital (A/D) converter  120 , a signal demodulator  130 , a signal processor  140 , a display unit  150  and a controller  190 . The broadcast receiving apparatus  100  may include a TV or a set-top box but not limited thereto. 
     The signal receiver  110  receives an analog broadcast signal in a radio frequency (RF) band. Broadcast signals of each channel are classified by a predetermined frequency band. The signal receiver  110  receives a broadcast signal of a channel selected by a user, and the received broadcast signal is converted into and output as an intermediate frequency (IF) signal. 
     An image which is displayed in a screen includes a plurality of frames, and each frame includes a plurality of scanning lines. An analog broadcast signal includes image status of each scanning line forming a frame, i.e. brightness and color information. A horizontal sync signal which notifies the beginning of information of a scanning line and a vertical sync signal which notifies the end of information of a last scanning line of a single frame are included in a broadcast signal for transmission. 
     The sync signal detector  160  detects a sync signal, i.e., a vertical sync signal and a horizontal sync signal of a received broadcast signal. As shown in  FIG. 3 , separating a carrier wave from a received broadcast signal and demodulating the broadcast signal generates a signal in a certain format including a sync signal area  20  and a data signal area. As the vertical sync signal and the horizontal sync signal have a certain signal level according to predetermined standards, the sync signal detector  160  may detect the area falling under the signal level of the vertical sync signal and horizontal sync signal by various known methods. 
     The interference signal detector  170  compares the sync signal area  20  with a predetermined reference signal and detects the interference signal component from the sync signal. The analog broadcast signal may include an interference signal component due to an effect of adjacent channels, and such interference signal component has a certain pattern as a result of interference by the adjacent channels, and may appear from a sync signal, too. For example, if a broadcast signal includes an interference signal component in an impulse format due to an effect of adjacent channels in a certain frequency band, an interference signal in a sine waveform may be present in a horizontal sync signal and a vertical sync signal in a time domain in case the broadcast signal is demodulated as it is. 
     The interference signal remover  180  removes an interference signal component from the entire broadcast signal based on the interference signal detected by the interference signal detector  170 . As described above, the interference signal component has a certain pattern and thus may be removed on the basis of the interference signal component detected from the sync signal area. Only principal elements of the broadcast receiving apparatus  100  a have been described. Hereinafter, the overall configuration of the broadcast receiving apparatus  100  including exemplary embodiments will be described. 
     An analog broadcast signal which is received through the signal receiver  110  is converted into an IF signal and output to the A/D converter  120 . The A/D converter  120  converts a received broadcast signal into a digital signal through sampling, quantizing and coding processes, and the converted digital signal is output to the signal demodulator  130 . 
     The signal demodulator  130  includes a demodulator and may perform a demodulation process to separate a carrier wave from a broadcast signal, and perform an automatic gain control to make a level of an output signal uniform. The signal demodulator  130  may detect a sync signal area of a demodulated broadcast signal. That is, the signal demodulator  130  may include the sync signal detector  160 , which means that the signal demodulator  130  may perform the function of the sync signal detector  160 . This does not need to be interpreted that there should be a sync signal detector  160  in the signal demodulator  130 . 
     The signal processor  140  processes a broadcast signal output by the signal demodulator  130 , according to a predetermined image processing operation. The image processing operation of the signal processor  140  may include a decoding operation corresponding to an image format of an image signal, a scaling operation to adjust an image signal into a preset resolution, a noise reduction operation to improve an image quality, a detail enhancement operation, and a frame refresh rate conversion operation, but not limited thereto. The signal processor  140  may be realized as at least one circuit board including various chipsets and memories to perform the aforementioned image processing operations. 
     The broadcast signal which is processed by the signal processor  140  is ultimately displayed on the display unit  150  of the broadcast receiving apparatus  100  or a connected external display apparatus (not shown). The display unit  150  may include a display panel (not shown) such as liquid crystal display (LCD) and plasma display panel (PDP), and a panel driver (not shown) to drive the display panel to display thereon an image, but not limited thereto. 
     As described above, the interference signal detector  170  may compare a sync signal area of a broadcast signal with a predetermined reference signal and detect the interference signal component, in which case it may detect the interference signal component from a signal output by at least one of the A/D converter  120 , the signal demodulator  130  and the signal processor  140 . As an analog broadcast signal is converted into a digital signal through the A/D converter  120 , a reference signal may also include a digital signal corresponding to a vertical sync signal or a horizontal sync signal. 
     If the interference signal component is detected by the interference signal detector  170 , the interference signal remover  180  removes the interference signal component according to the pattern of such interference signal. The interference signal remover  180  may remove the interference signal through various methods, such as a method of using a digital comb filter or a channel equalizer, a method of utilizing a fast fourier transform and a method of processing software through a microprocessor. 
       FIG. 4A  illustrates a digital comb filter  200  implemented as the interference signal remover  180 . 
     According to the present exemplary embodiment, the interference signal remover  180  may include the digital comb filter  200 . A desired signal  11  and the interference signal component  12  may be separated from an input broadcast signal  10  by adjusting a filter coefficient of the digital comb filter  200 . According to analysis of the interference signal in a frequency domain, energy is distributed in a horizontal frequency period according to each image standard (e.g., 15.734 khz in the case of NTSC). If energy in a horizontal frequency period is removed, the interference signal component may be removed from the input broadcast signal by adjusting a filter coefficient of the digital comb filter  200 . 
       FIG. 4  illustrates a channel equalizer implemented as the interference signal remover  180 . 
     As shown therein, an input broadcast signal is input to a line of a buffer  310 , a line of a sync area detection  330  and to an interference signal detection  340 , and the signal of the interference signal detection  340  is removed from the signal output by the buffer  310  to thereby output only the desired signal  11  from the input broadcast signal  10 . 
     A configuration for detecting the sync signal, i.e., the horizontal sync signal and the vertical sync signal is the same as that described above, and noise may be removed from the signal by inserting a low pass filter (LPF)  320  prior to the detection of the sync signal. 
     A configuration for comparing the sync signal with the predetermined reference signal and detecting the interference signal component is the same as that described above. 
     The desired signal may be output by the buffer  310  by removing the detected interference signal component, in which case the interference signal remover  180  may include a channel equalizer. Based on the interference signal detected by the interference signal detector  170 , the channel equalizer may renew the filter coefficient and adjust the gain of the input broadcast signal through the renewed filter coefficient to thereby equalize the broadcast signal. 
       FIG. 4C  illustrates an example of removing an interference signal component in a frequency domain by using a fast fourier transform (FFT). 
     According to the present exemplary embodiment, if the sync signal area is detected from the received broadcast signal ( 430 ), the interference signal detector  170  converts the broadcast signal into a frequency domain by performing the FFT ( 410 ), and may compare the frequency domain information with the predetermined reference signal and detect the interference signal component. 
     The interference signal remover  180  may remove the interference signal component detected by the interference signal detector  170  from the frequency domain, and output a signal in a time domain through an inverse fast fourier transform ( 460 ). 
     The broadcast receiving apparatus  100  may further include a controller  190  to control the interference signal detector  170  and the interference signal remover  180 . The controller  190  may include a microprocessor such as a micom. The broadcast receiving apparatus  100  may perform the detection and removal of the interference signal by performing a software function through the controller  190 . The interference signal information which is detected by the interference signal detector  170  may be transmitted to the controller  190  through an inter-integrated circuit (I2C), and the controller  190  may control the interference signal remover  180  to remove the interference signal from the broadcast signal through a predetermined algorithm. 
     According to the broadcast receiving apparatus  100  which has been described above, the interference signal which is included in the received analog broadcast signal due to the effect of adjacent channels may be removed through a digital device. 
       FIGS. 5 and 6  are flowcharts showing a method for removing the interference signal from the analog broadcast signal according to an exemplary embodiment. 
     The described aspects may be embodied through a broadcast receiving apparatus such as a TV or a set-top box which may receive an analog broadcast signal. The broadcast receiving apparatus receives an analog broadcast signal in an RF band (S 110 ), and converts the received broadcast signal into a digital signal (S 120 ). 
     The broadcast signal which is converted into the digital signal is demodulated by the demodulator (S 130 ). The demodulated broadcast signal is processed according to a predetermined image processing operation (S 140 ), and displayed in the broadcast receiving apparatus or a display unit of a connected display apparatus (S 150 ). 
     The received analog broadcast signal may include the interference signal due to the effect of adjacent channels. The exemplary embodiments include operations (S 210 , S 220  and S 230 ) to remove the interference signal component from the broadcast signal, which may be performed following at least one of the A/D conversion operation (S 120 ), the signal demodulation operation (S 130 ) and the image processing operation (S 140 ). That is, only one of the operations (S 210 , S 220  and S 230 ) for removing the interference signal component shown in  FIG. 5  may be performed. 
     The operations (S 210 , S 220  and S 230 ) for removing the interference signal component are performed as illustrated in  FIG. 6 . 
     First, the sync signal area, i.e., the vertical sync signal and the horizontal sync signal of the broadcast signal is detected (S 201 ). As the vertical sync signal and the horizontal sync signal have a certain signal level according to a predetermined standard, the area falling under the signal level of the vertical sync signal and horizontal sync signal may be detected by various known methods. 
     The detected sync signal area is compared with the predetermined reference signal to detect the interference signal (S 202 ). In this case, the interference signal may be detected from the signal which is output from at least one of the operation of converting the analog signal into a digital signal (S 210 ), the operation of demodulating the signal (S 220 ) and the operation of processing the signal according to the image processing operation (S 230 ). 
     The detected interference signal component is removed according to its pattern by various exemplary embodiments (S 203 ). The interference signal component may be removed (i) by adjusting the filter coefficient through the digital comb filter and separating the interference signal component from the broadcast signal, (ii) by adjusting a gain of the broadcast signal through the channel equalizer and (iii) by detecting the interference signal component from the frequency domain, as described above with reference to  FIGS. 4A ,  4 B and  4 C. However, it is noted that removing of the detected interference signal component is not limited to the methods discussed above, but other methods for removing interference may be utilized. 
     As described above, the interference signal component which is included in the received analog broadcast signal due to the effect of adjacent channels may be removed. 
     As described above, a broadcast receiving apparatus and a method for removing the interference signal of the analog broadcast signal may remove the interference signal component from the received analog broadcast signal through a digital device. 
     Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the inventive concept, the range of which is defined in the appended claims and their equivalents.