KR100262649B1 - Method and device of searching channel of digital tv - Google Patents

Abstract

PURPOSE: An apparatus and method for searching a channel of a digital TV is provided to reduce the time for searching a channel of a digital broadcasting receiver in case that a digital broadcasting and an analog broadcasting are mixed. CONSTITUTION: A tuner unit(100) includes an antenna(110), a digital tuner(120) and an intermediate frequency generator(130). A digital demodulation unit(200) includes an AD converter(210), an I and Q demodulator(220), an automatic gain detector(230), an FFT(240), a frequency synchronizer(250) and a TPS demodulator(260). The second AD converter(400) converts an electric field proportion gain voltage into a digital signal. An analog searching unit(600) searches an analog broadcasting signal. A frequency analyzer(300) detects a spectrum waveform.

Description

Digital TV Channel Search Device and Method

The present invention relates to digital TV, and more particularly, to a channel searching method and structure of digital broadcasting and analog broadcasting.

The operation of the channel search unit for receiving the conventional analog broadcast signal is as shown in FIG. First, tuning data is input to a tuner 10. Then, the video intermediate frequency generator (VIF) 11 outputs a video signal, and the synchronization signal detector 12 detects the synchronization signal of the video signal. If the signal received from the antenna includes a synchronization signal, the signal is an analog broadcast signal. If there is no synchronization signal, the signal is not an analog broadcast signal. The analog broadcast receiver determines whether the broadcast signal is based on the detected sync signal, and stores the channel number where the broadcast signal is located in the memory. Therefore, the analog broadcast receiver provided with the channel search section of the analog broadcast signal has a very short channel search time.

However, a digital broadcast receiver is different from an analog broadcast receiver. The analog broadcast signal includes a horizontal sync signal and a vertical sync signal in the video signal, so that the broadcast channel can be easily searched, but the digital broadcast signal cannot easily detect such a horizontal sync signal and the vertical sync signal. Therefore, the channel search method of the digital broadcast signal has a slightly complicated configuration. 2 is a block diagram illustrating a channel searching method of such a digital broadcast signal.

First, information corresponding to a predetermined channel number is input to the tuner 20 from the processor. When the broadcast signal is received from the antenna 21, the received broadcast signal is input to the tuner. The broadcast signal input to the tuner is sent to the intermediate wave generator (IF) 22, modulated into a low frequency intermediate wave, and then transmitted to a converter (ADC) 23 to be converted into a digital signal. The intermediate wave generator adjusts the signal received from the digital tuner by applying the AGC_IF signal to the digital tuner.

The digital signal is applied to the I & Q demodulator 24 to demodulate the I and Q signals, and the FFT 25, an Auto Gain Controller detect (AGC) 26, and a frequency sync 27 ) And time sync 28. The time synchronizer adjusts the timing synchronization of the signal, and is applied to the VCXO 29 to generate a clock signal and then to the AD converter 23. The frequency tuner 27 generates an AFC signal and applies it to the intermediate wave generator 22 to adjust the frequency of the signal. The automatic gain detector 26 applies an AGC signal to the intermediate wave generator 22.

The FFT 25 is an essential component of the COFDM demodulation method. The FFT 25 receives I and Q signals and converts them into frequency components. The signal converted into frequency components in this FFT is applied to a TPS decoder 30 and a channel estimation & correction 31.

The channel compensator is a kind of equalizer, and compensates for the distortion of the frequency response signal generated in the transmission channel. The output of the channel compensator is sent to a MPEG multiplexer (not shown) through a deinterleaver 32 and a Forward Error Correction (FEC) 33 for proper processing.

The TPS decoder 30 receives a frequency component output from the FFT, analyzes a modulation method of the signal, and applies the result to a processor. In the TPS decoder, several parameters are sequentially input until the signal modulation method is correctly analyzed. Thus, when the modulation scheme of the signal is correctly analyzed, the processor stores the channel of the signal analyzed by the TPS decoder in the built-in memory. If the TPS decoder cannot determine the modulation scheme of the signal, the digital tuner is updated with new channel number information and repeats the above-described operation. This TPS decoder outputs correct results only when the entire COFDM demodulator of the digital broadcast receiver operates normally.

However, the channel search unit of the conventional digital broadcast receiver has the following problems. As described with reference to FIG. 2, the channel search unit of the digital broadcast receiver not only inputs the tuning data to the tuner 20, but also the automatic gain detector 26, the frequency tuner 27, the intermediate wave generator 22, , COFDM demodulators (23, 24, 25, 28, 29, 31, 32) must be properly engaged with the entire operation to output the correct results to the TPS decoder. Therefore, since the COFDM demodulator is operated repeatedly until the correct operation is performed, it takes a lot of time to search the channel.

In addition, in order for the COFDM to operate normally, a parameter corresponding to a modulation scheme for transmitting a signal received to the antenna must be input to the TPS decoder. By the way, the transmission method of the signal varies greatly depending on the region. For example, in the case of European terrestrial broadcasting, there are about 24 such transmission methods. Therefore, in the conventional digital broadcasting receiver, 24 parameters must be sequentially applied to the digital demodulator in order to search for channels, and the same demodulation operation is repeated every time the parameters are applied. have.

And even if digital broadcasting is performed, analog broadcasting cannot be ignored. Accordingly, there is a need for a receiver capable of receiving both an analog broadcast signal and a digital broadcast signal to perform channel search.

The present invention has been made to solve such a problem, and an object thereof is to reduce a channel search time of a digital broadcast receiver in a mixed state of digital broadcasting and analog broadcasting.

1 is a block diagram showing a channel search circuit of a conventional analog broadcast receiver.

2 is a block diagram showing a channel search circuit of a conventional digital broadcast receiver.

Figure 3 is a block diagram showing a channel search circuit of the digital broadcast receiver of the present invention.

4 is a graph showing the frequency components detected by the frequency analyzer.

5 is a graph showing electric field proportional gain voltage detected by AGC_IF.

6 is a flowchart illustrating an example of a channel search algorithm of a digital TV of the present invention.

7 is a flowchart illustrating a channel search algorithm of the STB of the present invention.

Explanation of symbols for main parts of the drawings

100: tuner unit 110: antenna

120: digital tuner 130: intermediate wave generator

200: digital demodulator 210: AD converter

220: I & Q demodulator 230: automatic gain detector

240: FFT 250: Frequency Tuner

260: TPS decoder 300: frequency analyzer

400: AD converter 500: processor unit

600: analog broadcast searcher 610: analog tuner

620: image intermediate frequency generator 630: tuning signal detector

The present invention is characterized by reducing the search time of the channel by using an AGC voltage meter for measuring the electric field strength, a synchronous signal detector for checking the transmission of the analog broadcast, and a frequency analyzer for analyzing the spectral waveform of the digital signal. As shown in FIG. 3, the channel finder of the present invention includes a tuner unit 100, a digital demodulator 200, a frequency analyzer 300, an AD converter 400, and a processor unit 500. As shown in FIG. In addition, the channel detector according to the present invention further includes an analog search unit 600 including an analog tuner 610, an image intermediate wave generator 620, and a tuning signal detector 630 to process an analog broadcast signal together. Consists of.

The tuner unit 100 includes an antenna 110, a digital tuner 120, and an intermediate wave generator 130. The antenna receives a broadcast signal transmitted through free space. This broadcast signal is a high frequency signal modulated by a predetermined modulation method. It depends on the region of this modulation. For example, there are about 24 modulations for terrestrial broadcasting in Europe.

The digital tuner 120 continuously receives the broadcast signal received by the antenna, and receives the electric field proportional gain voltage AGC_IF from the intermediate wave generator. The intermediate wave generator 130 lowers the frequency of the broadcast signal, which is a high frequency signal, modulates the intermediate wave IF, receives the automatic gain signal AGC from the automatic gain detector 230, and automatically supplies the automatic frequency from the frequency tuner 250. The correction signal AFC is applied, and the electric field proportional gain voltage AGC_IF is generated and applied to the digital tuner 120. Therefore, the tuner receives the broadcast signal, the automatic gain signal AGC, and the automatic frequency correction signal AFC, and outputs the intermediate wave and the electric field proportional gain voltage AGC_IF.

The digital demodulator 200 includes an AD converter 210, an I & Q demodulator 220, an automatic gain detector (AGC) 230 and an FFT 240, a frequency tuner 250, and a TPS decoder 260. It is composed. The AD converter converts the intermediate wave modulated by the intermediate wave generator into a digital signal. The I & Q demodulator then demodulates the digital signal. At this time, the automatic gain detector AGC detects the voltage gain value of the demodulated digital signal and returns it to the intermediate wave generator of the tuner unit. The frequency tuner detects this frequency correction signal (AFC) of the I and Q signals and returns them to the intermediate wave generator. The intermediate wave generator receives the voltage gain value AGC and the automatic frequency correction signal AFC and outputs the electric field proportional gain voltage AGC_IF.

The FFT converts the demodulated digital signal into I and Q signals into frequency components. The FFT, I & Q demodulator, time synchronizer and frequency tuner are the same as in the prior art. In addition, the TPS decoder receives the frequency component converted from the FFT and continuously updates and analyzes a predetermined parameter to detect a modulation method of the broadcast signal originally received by the antenna. That is, the digital demodulator 200 receives the intermediate wave from the tuner 100 and continuously updates predetermined parameters to output information on the voltage gain value, the automatic frequency compensation signal, and the modulation method of the broadcast signal.

The present invention is different from the conventional digital channel detector in that the frequency analyzer 300 and the second AD converter 400 for converting the electric field proportional gain voltage AGC_IF into a digital signal are installed. It is also a feature of the present invention that an analog search unit 600 is further provided for searching for an analog broadcast signal. The frequency analyzer 300 detects a spectral waveform by receiving a frequency component which is the same signal as that of the TPS decoder 260.

Therefore, if the spectrum waveform is flat as shown in Fig. 4, the output signal of the TPS is read. If the spectrum waveform is not flat, the output signal of the TPS is not read. This is because the current broadcast signal is a digital broadcast signal when the spectral waveform is flat, and an analog broadcast signal when the spectral waveform is not flat. In the analog video signal, as shown in Fig. 4, the spectral waveform of the frequency at which the carrier is present is very strong, but the peripheral part thereof is very weak. Therefore, the digital broadcast signal and the analog broadcast signal can be distinguished by spectral waveforms. The analog broadcast signal is processed by a separate analog broadcast processor. The second AD converter converts the electric field proportional gain voltage AGC_IF applied from the intermediate wave generator to the digital tuner into a digital signal and applies it to the processor 500.

The processor unit analyzes the digital signal applied from the second AD converter 400 and ignores the broadcast signal currently received by the antenna when the electric field strength of the signal is less than a predetermined minimum value that the system can process, as shown in FIG. The new channel number is input to the digital tuner 120 so that the antenna 110 receives a broadcast signal of a different frequency band. When the signal value is determined to be greater than or equal to the minimum value, the frequency analyzer 300 reads the spectral waveform of the signal output from the FFT. When the signal is determined to be a digital broadcast signal (COFDM spectrum), the output of the TPS decoder 260 is applied. If the signal is determined to be an analog broadcast signal (PAL spectrum), whether the channel currently input to the digital tuner 120 is the last channel. Determine. If the current channel is the last channel, the operation is terminated. If there are more channels to search, the new channel number is input again to the digital tuner to receive more broadcast signals from the antenna.

In addition, when the TPS decoder 260 correctly analyzes the modulation method of the broadcast signal, the processor 500 receives the output signal and stores the frequency band and channel number of the currently received broadcast signal in an internal memory (not shown). If the TPS decoder fails to analyze, the new channel number is input again to the digital tuner so that the broadcast signal of another frequency band is further received by the antenna 110.

That is, the processor 500 first reads the electric field proportional gain voltage AGC_IF generated by the intermediate wave generator 130 and reads the spectral waveform of the frequency analyzer 300 when the predetermined value is more than a predetermined minimum value, and the spectral waveform is digitally broadcast. In the case of spectrum (COFDM spectrum), the output signal of the TPS decoder 260 is read, and when the TPS decoder correctly analyzes the modulation method of the broadcast signal, it stores the currently received broadcast signal and channel number. If all of the above conditions are not met, the processor retrieves the broadcast signal of another channel by updating and inputting information on the channel number input to the digital tuner.

The channel detector of the present invention may also be equipped with a conventional analog broadcast detector 600. The structure of the analog broadcast searcher may be the same as that installed in a conventional analog broadcast receiver.

The channel finder of the present invention can be installed in a digital TV. The channel search algorithm of the processor unit installed in the channel searcher of the present invention installed in the digital TV is as shown in FIG.

First, a signal corresponding to a certain channel N is received. Then, parameters corresponding to the channel N are input to the analog tuner and the digital tuner. In addition, predetermined parameters corresponding to this channel N are also input to the digital demodulator. Thereafter, when the electric field proportional gain voltage is detected and smaller than the predetermined comparison value, the current broadcast signal is ignored and the channel is updated.

If the electric field proportional gain voltage is detected to be equal to or greater than a predetermined comparison value, the output signal of the synchronous signal detector is detected. If it is found that the synchronization signal is included in the output signal of the synchronization signal detector (high), since the currently received signal is an analog broadcast signal, the broadcast signal is ignored and the channel is updated. If the synchronization signal is not included in the output signal, since the signal currently received is likely to be a digital broadcast signal, the TPS decoder detects the TPS signal. If the TPS signal is detected correctly, the current channel is stored in memory, the channel N value is updated, and the parameters of the analog tuner and the digital tuner are changed and searched. At this time, if the current channel value is the last channel, the channel search algorithm is finished.

If the TPS signal has not been detected correctly, the parameters of the digital demodulator are updated to continue detecting the TPS signal. If the TPS signal cannot be detected even if all parameters of the digital demodulator are changed, the channel N value is updated, and the parameters are searched by changing the parameters in the analog tuner and the digital tuner.

The channel search algorithm when the channel searcher of the present invention is installed in a STB (Set-Top Box) is as shown in FIG.

Unlike the digital TV, the STB checks the spectral waveform of the frequency component detected by the frequency analyzer when the electric field proportional gain voltage is larger than a predetermined comparison value. Thus, if the spectral waveform is an analog broadcast spectrum (PAL spectrum), the last number of the channel number input to the tuner section is checked. If the number of the channel currently input to the tuner is the end number, the channel search is completed, and if there is a channel to be searched further, the channel of the tuner is updated to receive another broadcast signal. If the spectrum waveform is a digital broadcast spectrum (COFDM spectrum), the modulation method of the broadcast signal analyzed by the TPS decoder is examined. The subsequent procedure is the same as the algorithm of FIG. 6 described above.

The channel detector of the present invention first checks the electric field proportional gain voltage of the broadcast signal received on the current channel in the AD converter, and ignores the unnecessary broadcast signal first, and secondly, the frequency component of the broadcast signal received on the current channel in the frequency analyzer. It filters the analog broadcast signal, and stores only the channel of the broadcast signal that can be demodulated by examining the modulation method of the broadcast signal received on the current channel in the third TPS decoder. Therefore, the channel searching time can be shortened compared to the conventional one, so that the channel searching time is shortened.

In addition, since the broadcast signal that has passed three searches is stored, there is an effect of increasing the reliability of the operation compared with the conventional method.

Claims (4)

A tuner unit receiving a broadcast signal and outputting an intermediate frequency and an electric field proportional gain voltage AGC_IF; The tuner unit receives an intermediate frequency and applies an automatic gain signal and an automatic frequency correction signal to the tuner unit, generates a frequency component while updating a predetermined parameter, and analyzes the frequency component to modulate the broadcast signal. A digital demodulator for detecting; A frequency analyzer for receiving the frequency components and examining their spectral waveforms; And, When the electric field proportional gain voltage is greater than or equal to a predetermined value, the spectrum waveform is a digital broadcast spectrum (COFDM spectrum), and the digital demodulator detects a modulation method of the broadcast signal, the current received broadcast signal is input to the tuner. Channel searcher of the digital broadcast receiver comprising a processor for storing a channel number. The digital demodulator of claim 1, wherein the digital demodulator comprises: an AD converter for converting the intermediate wave into a digital signal; An I & Q demodulator for demodulating the digital signal into an I signal and a Q signal; An AGC detector which receives the signal of the I & Q demodulator and detects a voltage gain value and returns it to an intermediate wave generator; An FFT for converting the I signal and the Q signal into the frequency component; A frequency tuner receiving the I and Q signals and applying the automatic frequency correction signal to the intermediate wave generator; And a TPS decoder which receives the frequency component and continuously updates the parameter until the modulation method of the broadcast signal is analyzed. The apparatus of claim 1, wherein the channel searcher comprises: an analog tuner configured to receive a channel number from the processor and receive a broadcast signal from the antenna; An image intermediate wave generator for receiving a broadcast signal from the analog tuner and outputting an image signal and a voltage gain (AGC) signal; And, And a sync detector for detecting a sync signal of the video signal and applying the sync signal to the processor. Comparing the proportional gain voltage with a predetermined minimum value and updating the channel to receive another proportional gain voltage when the field gain voltage is smaller than the minimum value, and reading the waveform of the frequency component when the field proportional gain voltage is greater than the minimum value. ; Determining the shape of the spectrum waveform of the frequency component to read a modulation signal of a broadcast signal when the waveform spectrum is a digital broadcast spectrum (COFDM spectrum) and to determine whether the channel number is the last when the analog broadcast spectrum is an analog broadcast spectrum; ; If the modulation scheme signal is correct, storing the currently received broadcast signal and channel, and if not corrected, updating the channel to receive another electric field proportional gain voltage; And, If the channel number is not last, updating the channel to receive another electric field proportional gain voltage, and if the channel number is last, ending the operation.