KR19980041342A - Synchronization signal detection method for channel tuning of video equipment - Google Patents

Abstract

The present invention relates to a channel tuning method of a video device that detects a broadcast channel as an AFT voltage and whether there is a synchronization signal in the channel tuning mode. When the automatic channel tuning mode is set, the channel of the lowest frequency band among all receivable channels ( First steps 21, 22 and 23 for setting CH = 1); A second step (24, 25, 26) of changing the intermediate frequency signal f0 of the set channel after performing the first step, and detecting the intermediate frequency signal at which the synchronization signal is detected; A third step (28, 29) of determining whether a synchronization signal is detected at f0-1.5 MHz with respect to the intermediate frequency signal f0 from which the synchronization signal is detected as a result of performing the second step; A fourth step (30,31) for determining whether a synchronization signal is detected at f0 + 0,5NHz with respect to the intermediate frequency f0 as a result of performing the third step; As a result of the determination in the fourth step, when a synchronous signal is detected at f0 + 0,5NHz with respect to the intermediate frequency f0, the intermediate frequency of the corresponding reception channel according to the AFT voltage within a predetermined window range with respect to the detected intermediate frequency f0 a fifth step (32, 33) of resetting to f0); And a sixth step 34,35 in which steps 2, 3, 4, and 5 are sequentially performed on all receivable channels after the fifth step is performed.

That is, according to the present invention, it is possible to accurately detect a channel in which a synchronization signal is detected at the time of channel tuning, thereby reducing the time required for channel tuning and storing only a broadcast channel accurately in the video device.

Description

Synchronization signal detection method for channel tuning of video equipment

The present invention relates to a channel tuning method in an image processing apparatus, and more particularly, to a method of detecting a channel having a synchronization signal in channel channel selection.

In general, the channel auto-tuning function determines whether a broadcast signal is input among all broadcast channels as the presence or absence of a synchronization signal and stores the channel to which the broadcast signal is input in a memory, so that when a user switches a channel, that is, a channel up / down It is a function to facilitate channel switching by only up / down channels where broadcast is performed at a time.

On the other hand, in order to receive signals in these frequency bands in a television or cable broadcasting system in which various frequency bands, that is, broadcasts of a plurality of channels, are tuned to the carrier frequency of the channel to be received.

NTSC (National Television System Committe) FS (Frequency Synchronizing) method adopts AFT (Automatic Fine Tunning) voltage to tune the tuner of the receiver to the carrier frequency of each channel. . That is, when the PLL data for tuning the frequency of each channel is stored in the memory of the microcomputer of the receiver and the user selects a predetermined channel by dial or the like, the microcomputer applies the PLL data of the selected channel to the tuner.

On the other hand, a phase lock loop is formed in the tuner to control the oscillation frequency of the voltage controlled oscillator according to the PLL data to receive the frequency signal of the channel selected by the user.

However, since the carrier frequency of the signal transmitted from the broadcasting station varies slightly depending on the region or environment, it is necessary to change the oscillation frequency of the voltage controlled oscillator in order to synchronize the carrier frequency with the tuner.

To this end, in the FS scheme, the AFT voltage is output according to the frequency of the intermediate frequency (IF) signal output from the tuner, and the microcomputer is configured to finely change the PLL data according to the AFT voltage.

That is, an intermediate frequency (IF) signal outputted from the tuner by finely changing the PLL data in predetermined step units so that the applied AFT voltage becomes an intermediate voltage within a predetermined window range (for example, 2.8-3.8 V). The frequency is 45.75 MHz (in case of NTSC), and the PLL data at this time is stored as the reception channel data.

The detection of a broadcast channel for channel auto-tuning in the video device employing the AFT method performs the following steps.

That is, the microcomputer in the video device determines whether a broadcast channel is present by applying PLL data corresponding to the intermediate frequency f0 of a receivable channel to the tuner and detecting a synchronization signal. In this case, the intermediate frequency f0 is an intermediate frequency in the video device and may not be an intermediate frequency of a broadcast channel. The video device may set the intermediate frequency in the order of f0-1 MHz, f0-2 MHz, f0 + 1 MHz, and f0 + 2 MHz. Change the PLL data, detect a frequency within which the AFT voltage is optimal when a synchronization signal is detected, and store the detected frequency in the internal memory as the intermediate frequency f0 of the corresponding channel. Done.

At this time, the synchronization signal transmitted from the broadcasting station should exist between f0 + 0.6MHz and f0-1.5MHz of the intermediate frequency signal f0 of the corresponding channel. However, in the channel auto-tuning process described above, the intermediate frequency f0 is changed in the order of f0, f0-1 MHz, f0-2 MHz, f0 + 1 MHz, f0 + 2 MHz, and when the synchronization signal is detected, the AFT voltage within the window range is changed. There is a problem that the broadcast channel cannot be detected correctly by searching.

That is, since a lot of noise is generated by the surrounding environment during transmission, the broadcast signal may misjudge the noise as a synchronization signal during channel tuning. In this case, an accurate intermediate frequency f0 is detected within a predetermined window range. The process FS may take a considerable time, and there is also a problem that this channel may not be broadcasting.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for detecting a synchronization signal for channel tuning, which makes it possible to accurately detect a synchronization signal during channel tuning.

The present invention relates to a channel tuning method of a video device that detects a broadcast channel as an AFT voltage and whether there is a synchronization signal in the channel tuning mode, and when the automatic channel tuning mode is set, the channel of the lowest frequency band among all channels that can be received. Setting a first step; A second step of changing the intermediate frequency signal of the set channel after performing the first step, and detecting the intermediate frequency signal from which the synchronization signal is detected; A third step of determining whether a synchronization signal is detected at f0-1.5 MHz with respect to the intermediate frequency signal at which the synchronization signal is detected as a result of performing the second step; A fourth step of determining whether a synchronization signal is detected at f0 + 0,5 NHz with respect to the intermediate frequency f0 as a result of performing the third step; As a result of the determination in the fourth step, when a synchronous signal is detected at f0 + 0,5NHz with respect to the intermediate frequency f0, the intermediate frequency of the corresponding reception channel according to the AFT voltage within a predetermined window range with respect to the detected intermediate frequency f0 a fifth step of resetting to f0); And a sixth step of sequentially performing the second, third, fourth, and fifth steps on all receivable channels after the fifth step.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a video device for performing a synchronization signal detection method for channel tuning according to the present invention.

2 is a flowchart of a method of detecting a synchronization signal for channel tuning of a video device according to the present invention;

* Description of the symbols for the main parts of the drawings *

1: key input 2: microcomputer

3: tuner 4: synchronization detector

5: signal processing unit 6: OSD unit

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

FIG. 2 is a block diagram of a video device for performing a synchronization signal detection method for channel selection according to the present invention. As shown, a key input unit 1, a microcomputer 2, a tuner 3, and a synchronization detection unit 4 are shown. ) And a signal processing unit 5 and an OSD unit 6.

In such a configuration, the key input unit 1 is provided with a plurality of keys including a tuning key for channel automatic tuning, and applies a key signal corresponding to the user's key operation to the microcomputer 2, and the input is normally If possible, the remote controller detects a key signal on the infrared carrier and applies it to the microcomputer 2.

The microcomputer 2 is a means for controlling the overall operation of the video apparatus based on the key signal from the key input unit 1, and the tuning key input through the key input unit 1 as can be seen from the description below. The PLL data for tuning is output to the tuner 3 based on the signal, and channel selection is controlled based on the presence or absence of a synchronization signal from the synchronization detector 4 and the AFT voltage from the tuner 3.

Further, the tuner 3 is configured to receive a broadcast signal of a channel corresponding to PLL data, which is a tune signal of the microcomputer 2, among a plurality of broadcast frequency signals transmitted from the broadcast system, and the tuner 3 is in a tuned state. The AFT voltage according to this is applied to the microcomputer (2).

In addition, the tuner 3 is connected to the sync detector 4, and the sync detector 4 detects the sync signal separately from the broadcast signal received from the tuner 3 and applies it to the microcomputer 2.

On the other hand, the signal processor 5 separates the video signal and the audio signal from the broadcast signal from the tuner 3 under the control of the microcomputer 2, and applies the video signal to the OSD unit 6 and to the speaker, respectively. do. At this time, the OSD unit 6 is configured to display a monitor or the like by mixing a predetermined text signal with the video signal of the signal processing unit 5 under the control of the microcomputer 2.

2 shows a flowchart of a program for a microcomputer to carry out the present invention in a video device having the above-described configuration.

As shown, the microcomputer 2 of the present invention determines whether the tuning key signal is applied from the key input unit 1, and sets the automatic channel tuning mode when the tuning key signal is applied (steps 21 and 22).

When the automatic channel tuning mode is set, the channel (CH = 1) of the lowest frequency band among all the receivable channels of the microcomputer 2 is set, and the PLL data of the intermediate frequency signal f0 of this channel is applied to the tuner 3. (Steps 23, 24). Therefore, the tuner 3 receives a broadcast channel of a frequency corresponding to the PLL data, and the signal received by the tuner 3 is applied to the synchronization detector 4 and the signal processor 5.

Since the synchronization detector 4 detects the synchronization signal from the received signal of the tuner 3 and applies it to the microcomputer 2, the microcomputer 2 determines whether the synchronization signal is applied in step 25 and there is no synchronization signal. Proceed to step 26. In steps 26 and 27, the microcomputer 2 sequentially changes the intermediate frequency signal f0 in the order of f0-1 MHz, f0-2 MHz, f0 + 1 MHz and f0 + 2 MHz as described above. It is determined whether or not a synchronization signal is applied.

When the synchronization signal is detected by the synchronization detector 4 as a result of performing steps 25 and 26, the microcomputer 2 determines whether there is a synchronization signal at f0-1.5 MHz with respect to the intermediate frequency signal f0 where the synchronization signal is detected. (Steps 28, 29). At this time, if the intermediate frequency signal f0 of step 25 is an intermediate frequency signal of the corresponding broadcast channel, the synchronization signal will be detected in the f0-1.5 MHz band as described above, but if the synchronization signal is not detected, step 25 In step 26, the synchronous signal can be determined as noise.

As a result of performing step 29, when the synchronization signal is detected, the microcomputer 2 determines whether there is a synchronization signal at f0 + 0.5 MHz with respect to the intermediate frequency signal f0 where the synchronization signal is detected (steps 30 and 31). At this time, if the intermediate frequency signal f0 of step 25 is an intermediate frequency signal of the corresponding broadcast channel, the synchronization signal will be detected in the f0 + 0.5 MHz band as described above, but if the synchronization signal is not detected, step 25 In step 26, the synchronization signal at may be determined as noise.

When the synchronization signal is simultaneously detected in the bands f0-1.5 MHz and f0 + 0,5 NHz with respect to the intermediate frequency f0 in which the synchronization signal is detected, this intermediate frequency f0 can be determined by the intermediate frequency signal of the broadcast channel. The microcomputer 2 resets the frequency at which the AFT voltage within the above-described window range is optimal for the detected intermediate frequency f0 to the intermediate frequency f0 of the corresponding reception channel (steps 32 and 33).

Then, the microcomputer 2 performs the above-described process on all receivable channels (steps 34 and 35), whereby the channel on which the broadcast is being performed and the optimum intermediate frequency f0 for each channel can be set. will be.

That is, in the present invention, when the synchronization signal is detected in the channel selection process, it is determined whether the synchronization signal is detected in the frequency band within a predetermined range with respect to the frequency where the synchronization signal is detected, and thus, the presence of the synchronization signal is determined. You can judge exactly.

As described above, according to the present invention, it is possible to accurately detect a channel in which a synchronization signal is detected at the time of channel tuning, thereby reducing the time required for channel tuning and storing only a broadcast channel accurately in the video device.

Claims (1)

A channel tuning method of a video device that detects a broadcast channel as a presence or absence of a synchronization signal and an AFT voltage in a channel tuning mode, A first step (21, 22, 23) of setting a channel (CH = 1) of the lowest frequency band among all receivable channels when the automatic channel tuning mode is set; A second step (24, 25, 26, 27) of changing the intermediate frequency signal (f0) of the set channel after performing the first step, and detecting the intermediate frequency signal at which the synchronization signal is detected; As a result of performing the second step, when the synchronization signal is detected, determining whether the synchronization signal is detected at f0-1.5 MHz with respect to the intermediate frequency signal f0 where the synchronization signal is detected (28,29) Wow; A fourth step (30,31) of determining whether a synchronization signal is detected at f0 + 0,5 NHz with respect to the intermediate frequency f0 as a result of performing the third step; remind As a result of the determination in the fourth step, when a synchronous signal is detected at f0 + 0,5 NHz with respect to the intermediate frequency f0, the intermediate of the corresponding reception channel is determined according to the AFT voltage within a predetermined window range with respect to the detected intermediate frequency f0. A fifth step (32, 33) of resetting to frequency f0; And a sixth step (34,35) of sequentially performing the second, third, fourth, and fifth steps on all receivable channels after performing the fifth step.