KR100281392B1 - How to Eliminate Adjacent Channel Interference in Digital Television Receivers - Google Patents

Abstract

The present invention relates to a technique for canceling adjacent channel interference in a digital terrestrial broadcasting receiver.

The present invention provides a first step of detecting a synchronization signal of an NTSC broadcast by receiving a broadcast of a lower channel adjacent to a channel requested by a user, and setting a lower flag to a first level when a synchronization signal is detected in the first step. If the synchronization signal is not detected, the second step of setting to the second level, the third step of receiving the broadcast of the upper channel adjacent to the channel requested by the user to detect the synchronization signal of the NTSC broadcast, the synchronization signal is detected in the third step If the upper flag is set to the first level, and if the synchronization signal is not detected, the fourth step of setting the second flag; if the upper flag and the lower flag are set to the first level, the filtering operation of the interference elimination filter is turned on. If set to the second level includes a fifth step of turning off the operation of the interference cancellation filter, and a sixth step of receiving a digital television broadcast of the channel requested by the user To remove co-channel interference.

Therefore, according to the present invention, the NTSC cancellation filter of the channel is turned on only when NTSC broadcasting is received by searching for an adjacent channel of a digital television broadcast desired to be watched, thereby preventing the reception signal from being attenuated as a whole. can do.

Description

Method of rejecting neighbor channel interference in a digital TV

The present invention relates to a technique for removing adjacent channel interference in a digital terrestrial television receiver.

In general, a digital terrestrial broadcasting system developed for high quality broadcasting uses a simultaneous broadcasting method in which digital terrestrial TV signals are transmitted using empty channels not currently used in the VHF and UHF frequency bands currently used for analog TV broadcasting. As a result, interference between the same channel or adjacent channels occurs.

FIG. 2 is a conceptual diagram illustrating co-channel interference, showing that digital television broadcasting is broadcasted on channel 20 in region A, and NTSC analog broadcasting is broadcasted on channel 20 in region B. FIG. When digital broadcasting and analog broadcasting are performed on the same channel in different regions as described above, the NTSC broadcasting signal of the neighboring region is received in the digital television receiver 100 located in the A and B neighborhoods to cause co-channel interference. . The co-channel interference cancellation filter is used to remove such co-channel interference.

3A is a conceptual diagram illustrating adjacent channel interference, showing that digital television broadcasting is broadcasted on channel 20 in the same region A, and NTSC analog broadcasting is performed on channels 21 and 19. As described above, when NTSC analog broadcasting is performed on an adjacent channel of a digital broadcasting channel in the same region, the digital television receiver 100 receives an NTSC broadcasting signal of an adjacent channel and causes adjacent channel interference. In order to remove such interference in the adjacent channel, an adjacent channel interference cancellation filter is used. That is, in order to remove adjacent channel interference, NTSC broadcast signals of upper and lower channels through which digital broadcasting is performed are respectively removed through a filter as shown in FIG. 3B.

However, when the interference cancellation filter is used to remove interference of adjacent channels, there is a problem that a digital broadcast signal to be received is also attenuated due to the characteristics of the filter. Therefore, it is more preferable not to use the interference filter when there is no NTSC broadcasting in the adjacent channel.

Accordingly, the present invention has been made to solve the above problems, and detects the presence or absence of the broadcast signal of the upper or lower channel immediately adjacent to the digital television broadcasting channel to receive to remove the adjacent channel interference only when there is NTSC broadcasting It is an object of the present invention to provide a method for canceling adjacent channel interference in a digital television receiver.

In order to achieve the above object, the method of the present invention provides a digital television receiver in which a microprocessor tunes a broadcast channel to a tuner according to user control and detects a synchronization signal received on the channel. Receiving a broadcast of a lower channel adjacent to the requested channel and detecting a synchronization signal of the NTSC broadcast; A second step of setting a lower flag to a first level if a synchronization signal is detected in the first step and a second level if a synchronization signal is not detected; Receiving a broadcast of a higher channel adjacent to a channel requested by a user and detecting a synchronization signal of the NTSC broadcast; A fourth step of setting an upper flag to a first level if a synchronization signal is detected in the third step and a second level if a synchronization signal is not detected; A fifth step of turning on the filtering operation of the interference elimination filter when the upper flag and the lower flag are set to the first level, and turning off the operation of the interference elimination filter when the upper flag and the lower flag are set to the second level; And a sixth step of receiving a digital television broadcast of a channel requested by the user.

1 is a block diagram showing a typical digital television receiver to which the present invention can be applied;

2 is a conceptual diagram illustrating co-channel interference;

3A and 3B are conceptual views illustrating and explaining adjacent channel interference;

4 is a flowchart illustrating a method of canceling adjacent channel interference according to the present invention.

* Explanation of symbols for main parts of the drawings

100: digital TV receiver 102: tuner

104: analog to digital converter 106: VSB demodulator

108: MPEG TS Demux 110: MPEG2 Decoder

112: video memory 114: AC-3 audio decoder

116: audio memory 118: microprocessor

120: system memory

Hereinafter, with reference to the accompanying drawings will be described in detail a specific embodiment of the present invention.

Fig. 1 is a schematic diagram showing a digital television receiver, showing a terrestrial broadcast reception structure of a VSB system. Referring to FIG. 1, a digital television receiver includes an RF tuner 102, an analog-to-digital converter (ADC) 104, a VSB demodulator 106, an MPEG transport stream demux (MPEG TS DeMUX) 108, and an MPEG2 decoder 110. ), A video memory 112, an AC-3 audio decoder 114, an audio memory 116, a microprocessor 118, and a system memory 120. In FIG. 1, the tuner 102 receives a radio broadcast signal of a channel selected according to a tuning signal, outputs an IF signal, and the ADC 104 converts an analog signal into a digital signal. The VSB demodulator 106 receives digital data and outputs an MPEG transport stream, and the MPEG TS Demux 108 decomposes the transport stream in units of 188 bytes and divides the system data, video data, and audio data into outputs. do. At this time, the system data includes program specific information (PSI) for the currently received programs in four tables (PAT, PMT, NIT, CAT). The MPEG decoder 110 processes MPEG decoding to reproduce a video signal YCrCb, and the AC-3 audio decoder 114 receives an audio packet to reproduce a PWM audio signal. In this case, the video memory 112 and the audio memory 116 store corresponding data in each decoding process.

The overall operation of the receiver is controlled by the microprocessor 118, and the microprocessor 118 executes a program included in the system memory 120 and stores various data in the system memory 120. Although not shown in detail in the drawing, video data is converted into an RGB signal by the video processor and displayed on the CRT, and audio data is amplified by the audio processor and output through a speaker, and the microprocessor 118 is connected to a microcom serial communication channel. Can be transferred to the user control.

On the other hand, a filter for removing adjacent channel interference is provided inside the VSB demodulator 106, the structure of this NTSC cancellation filter is as described in the ATV standard. The filter for removing interference of an adjacent channel includes a first interference cancellation filter for removing interference of a lower channel, and a second interference cancellation filter for removing interference of an upper channel, and each interference cancellation filter has its own The filtering operation can be turned on or off according to the register flag value. That is, the first interference elimination filter performs the filtering operation when the lower flag LFLAG is "1", and does not perform the filtering operation when "0". The second interference cancellation filter performs the filtering operation when the upper flag UFLAG is "1", and does not perform the filtering operation when the upper flag UFLAG is "1".

4 is a flowchart illustrating a method of canceling adjacent channel interference according to the present invention. Referring to Fig. 4, in step 401, tuning is requested to channel N on which digital television broadcasting is broadcast under user control. In step 402, the flag operation for turning on and off the filtering operation of the first interference elimination filter and the second interference elimination filter is set to "0" to turn off the filtering operation. In step 403, the microprocessor 118 controls the tuner 102 to tune to the N-1 channel one channel below the desired broadcast channel N. In step 404, it is determined whether a synchronization signal according to the NTSC broadcast standard is detected in the tuned N-1 channel, and if detected, the lower flag LFLAG is set to "1" in step 405.

If the synchronous signal of the N-1 channel is not detected in step 404, in step 406, the microprocessor 118 controls the tuner 102 to tune to the N + 1 channel higher than the desired broadcast channel N. Subsequently, in step 407, it is determined whether a synchronization signal according to the NTSC broadcast standard is detected in the tuned N + 1 channel, and if detected, in step 408, the upper flag UFLAG is set to "1". If the synchronization signal of the N + 1 channel is not detected in step 407, the corresponding interference cancellation filter is operated according to the flag set in step 409, and then in step 410, the tuner 102 is controlled by the microprocessor 118 to broadcast the desired broadcast. Sync to channel N. Subsequently, in step 411, the signal received through the channel N is demodulated, error-corrected, and MPEG-decoded and output.

As described above, according to the present invention, when an NTSC broadcast is received by searching for an adjacent channel of a digital television broadcast to be watched, the NTSC cancellation filter of the corresponding channel is turned on unnecessarily so that the NTSC rejection filter is turned on. There is an effect that can prevent the attenuation.

Claims (1)

A digital television receiver in which a microprocessor tunes a broadcast channel to a tuner and detects a synchronization signal received on the channel according to user control. A first step of detecting a synchronization signal of an NTSC broadcast by receiving a broadcast of a lower channel adjacent to a channel requested by a user; A second step of setting a lower flag to a first level if a synchronization signal is detected in the first step and a second level if a synchronization signal is not detected; Receiving a broadcast of a higher channel adjacent to a channel requested by a user and detecting a synchronization signal of the NTSC broadcast; A fourth step of setting an upper flag to a first level if a synchronization signal is detected in the third step and a second level if a synchronization signal is not detected; A fifth step of turning on the filtering operation of the interference elimination filter when the upper flag and the lower flag are set to the first level, and turning off the operation of the interference elimination filter when the upper flag and the lower flag are set to the second level; And And a sixth step of receiving a digital television broadcast of a channel requested by the user.