KR920010321B1 - Tunning method of catv - Google Patents

Abstract

The number of key operation to select channels in cable television is reduced using the method. The method comprises: (A) checking that the selected channel is special channel; (B) setting search reference frequency according to checked result of step (A); and (C) seaching frequency band determined by the search reference frequency and fixing frequency containing video signal. The search reference frequency is set by a mean frequency of center frequency of channel determined by incremently related carrier broadcasting type and standard broadcasting type.

Description

Cable TV Broadcasting Synchronization Method

1 is a frequency array contrast diagram between cable television broadcasting.

2 is a flow chart of an embodiment according to the present invention.

3 is a circuit diagram for performing the flowchart shown in FIG.

4 is a tuning characteristic diagram according to the present invention.

* Explanation of symbols for the main parts of the drawings

30: micom 31: key input means

32: tuner 33: demodulation circuit

ANT: Aerial

The present invention relates to a tuning technique for an image receiving apparatus, and more particularly, to a method for allowing a viewer to easily select a desired broadcasting frequency band when receiving a television broadcast transmitted through a cable.

In general, cable television broadcasting refers to providing diversified and congested information in the form of a television broadcasting signal to a desired subscriber through a cable according to the diversification and specialization of the occupation, and the CATV broadcasting frequency is The frequency band assigned to each channel is slightly different according to the broadcasting company and region, and the CATV broadcasting method according to the arrangement difference of the frequency band allocated per channel is standard. STANDARD (hereinafter referred to as STD) broadcasting method and homogeneous regulation It is classified into three broadcasting systems, such as a broadcast method called a HOMOGENEOUSLY REGULATED CARRIER (hereinafter referred to as HRC) and an Incrementally Related Carrier (ICR).

Differences in the frequency arrangement between the three CATV broadcasting schemes will be described with reference to the contrast shown in FIG. In the IRC broadcasting method, in the remaining channels except for the fifth and sixth channels, the center frequency assigned to each channel coincides with the center frequency assigned to each channel of the STD broadcasting method as shown in FIG. In the method, the center frequency applied to each channel except for the fifth and sixth channels is about 1.25MHZ lower than the center frequency applied to each channel of the STD method as shown in FIG. In the IRC broadcasting method, the center frequencies assigned to the fifth and sixth channels are arranged to be 2 MHZ higher than the center frequencies assigned to the fifth and sixth channels of the STD broadcasting method as shown in FIG. The center frequencies assigned to the fifth and sixth channels of are arranged as high as 0.75MHZ higher than the center frequencies applied to the fifth and sixth channels of the STD broadcasting system as shown in FIG.

In addition, a television receiver for receiving a general television broadcast using CATV broadcasting and standby as a transmission medium has a TV broadcasting mode selection switch for selecting one of the CATV broadcasting and the general TV broadcasting, and one of the three CATV broadcasting methods when the CATV broadcasting mode is selected. And a broadcast method selection switch for selecting a channel, and a channel selection switch for channel selection. Therefore, it was necessary to select the CATV broadcasting mode, select the broadcasting method corresponding to the CATV broadcasting method transmitted through the cable by using the broadcasting method selection switch, and then select the desired CATV broadcasting frequency band by using the channel selection switch.

As such, the conventional video receiver has a burden for subscribers to operate a plurality of switches when receiving a CATV broadcast, and has a cause of cost increase by adding unnecessary selection switches.

Accordingly, an object of the present invention is to provide a cable television broadcast tuning method that enables the user to easily select a desired CATV broadcasting band and remove unnecessary components in the CATV broadcasting tuning method.

In order to achieve the above object, the present invention provides a method for tuning an image receiving apparatus, the method comprising: a specific channel searching process for checking whether a selected channel is a specific channel when selecting a CATV broadcasting mode, and specifying the search result after performing the specific channel searching process; Searching reference frequency setting process for setting the search reference frequency of the channel and non-specific channels differently, and the search and reference frequency set after performing the search reference frequency and the frequency of the image information within a certain range of the fixed frequency band based on It is characterized by including a broadcast frequency search process.

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

2 is a flowchart of an embodiment according to the present invention, wherein a specific channel search process is performed in steps 20 to 24, the search reference frequency setting process is performed in steps 25 and 26, and the broadcast frequency search process is performed in FIG. Corresponds to the steps.

3 is a circuit diagram for performing the flowchart shown in FIG. 2.

A microcomputer (hereinafter referred to as a microcomputer) 30 controls the painting of various circuits in the image receiving apparatus.

The key input unit 31 transmits a command designated by the user to the micom 30 in the form of key data, including a keyboard and remote receiving. The tuner 32 tunes a high frequency signal corresponding to a frequency band designated by the microcomputer 30 among a high frequency signal for general TV or a high frequency signal for CATV received through the aerial ANT.

The demodulation circuit 33 demodulates the high frequency signal tuned by the tuner 32 and transmits it through the output terminal OP. The automatic frequency has a logic state in which the frequency of the tuned high frequency signal varies depending on the size of the broadcast frequency. An AUTO FREQUENCY TUNNING (hereinafter referred to as AFT) signal is supplied to the microcomputer 30.

4 is a tuning characteristic diagram according to the present invention, 40 is a tuning characteristic diagram in a non-specific channel, and 41 is a tuning characteristic diagram in a specific channel.

Next, the flowchart shown in FIG. 2 will be described in detail with reference to the circuit diagram shown in FIG. 3 and the tuning characteristic diagram shown in FIG.

The flowchart shown in FIG. 2 is performed by the microcomputer 30 of the circuit diagram shown in FIG. 3, and the microcomputer 30 checks whether key data is drawn from the key input means 31 at predetermined intervals and enters the imported key. If there is data, the flowchart shown in FIG. 2 is performed.

The microcomputer 30 determines whether the CATV broadcast mode designation key is determined by examining the logical value of the inserted key data when there is key data drawn in from the key input means 31. (Step 20).

If the key data input in step 20 is key data for CATV broadcasting mode designation, the microcomputer 30 sets the CATV broadcasting mode by setting the CATV broadcasting mode flag assigned to one of its own registers to "1". (Step 21)

If the key data input in step 20 is not the CATV broadcast mode designation key, the microcomputer 30 checks whether the CATV broadcast mode flag assigned to one of the registers built in the device is set to "1", and then the current CATV. It is determined whether the program is being broadcast. (Step 22)

When the CATV broadcasting mode flag is set to "1" in step 22, that is, during the CATV broadcasting mode, the microcomputer 30 checks the logical value of the incoming key data and determines whether the channel selection key is present. )

If the key data input in step 23 is channel selection key data, the microcomputer 30 moves the channel to the number designated by the channel selection key, and then the currently selected channel is a specific channel (i.e. 6 channels) (Step 24).

In the case of a specific channel (i.e., fifth or sixth channel) in step 24, the microcomputer 30 sets the search reference frequency fo to a center frequency corresponding to the fifth or sixth channel of the STD broadcasting method as shown in FIG. Set the frequency as high as 1MHZ (step 25).

In the case of the non-specific channel (ie, a channel other than the fifth or sixth channel) in step 24, the microcomputer 30 sets the search reference frequency fO as the center frequency corresponding to the channel of the STD broadcasting method as shown in FIG. The second predetermined frequency (ie, 0.625MHZ) is set lower than that (step 26).

After performing step 25 or step 26, the microcomputer 30 changes the logic state of the ATF signal applied from the demodulation circuit 33 from a low logic state to a high logic state or from a high logic state to a low logic state. The strobe signal of the low logic state until the tuning control frequency information is increased or decreased by the third predetermined frequency (0.25MHZ) so as to change up to 2MHZ based on the search reference frequency fO set in step 25 or 26 until The CATV broadcast frequency is searched by applying to the tuner 32 in accordance with the clock pulse train during the period (step 27).

At this time, the tuner 32 selects a high frequency signal of a frequency corresponding to the tuning control frequency information introduced from the microcomputer 30 among the CATV broadcasting high frequency signals introduced through the aerial line ANT and supplies it to the demodulation circuit 33. The demodulation circuit 33 for inputting the high frequency signal tuned from the tuner 32 is used when the signal-to-noise ratio of the tuned high frequency signal is large (that is, when image information is loaded in the tuned high frequency signal). The logic state is changed and applied to the microcomputer 30.

As described above, according to the present invention, when the CATV broadcast is received, the center frequency assigned to each channel of the STD broadcasting method and the frequency having the center frequency and the intermediate value assigned to each channel of the HRC and IRC broadcasting methods are set as search reference frequencies. By selecting the broadcasting frequency by searching the frequency range automatically, the selection switch of CATV broadcasting method can be removed, and the switch operation procedure can be reduced so that it does not bother viewers.

Claims (1)

In the tuning industry of an image receiving apparatus, a particular channel inspection process for checking whether a selected channel is a specific channel or a non-specific channel when the CATV broadcasting mode is selected, and a specific channel and an unspecific channel according to the search result after performing the specific channel inspection process. A search reference frequency setting process for differently setting a search reference frequency and a broadcast frequency search process for finding and fixing a frequency with image information within a predetermined range of frequency bands based on the search reference frequency set after performing the search reference frequency setting. Cable television broadcast tuning method characterized in that it comprises a.

Images