JP3010904U - Receiving channel switching circuit device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide a receiving channel switching circuit device that does not disturb the screen disorder during channel switching by performing channel switching in a short time. [Structure] Frequency deviation amount detecting means 7 for detecting a difference between a reception channel frequency at the time of previous channel reception and a reception channel frequency at the time of receiving the previous channel in a standard channel plan, and the frequency deviation amount. Based on the frequency deviation amount storage means 8 for storing the difference in the reception channel frequency detected by the detection means, and the difference in the reception channel frequency stored in the frequency deviation amount storage means,
The receiving channel switching circuit device includes a tuning operation information correction unit 7 that corrects tuning operation information used to select a new channel.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a receiving channel switching circuit device suitable for use in switching a receiving channel of a broadcasting channel by a cable television broadcasting system.

[0002]

[Prior art]

 Cable television broadcasting systems (hereinafter referred to as CATV) are widely spread nationwide in foreign countries, particularly in the United States. There are a plurality of channel plans for the CATV that is prevalent in the United States and the like, and there are three types of channel plans, STD, IRC, and HRC. Therefore, the video signal frequency of the channel of CATV may differ for each channel plan of STD, IRC, and HRC. For example, in channel 2, the video signal frequency in channel plan STD is 55.25 MHz, and in channel plan IRC. The video signal frequency is 55.25 MHz, and the video signal frequency in the channel plan HRC is 54.0 MHz. When switching the normal channel, first, the video signal frequency of the switching channel in the channel plan STD is received, the automatic fine tuning tuning operation is performed, and the channel selection switching is performed.

[0003]

[Problems to be solved by the device]

 In the conventional receiving channel switching circuit device, channel selection switching is performed as described above. Therefore, when receiving a channel having only the channel plan HRC, for example, as shown in FIG. The case of switching from 2 to channel 4 will be described. At the time of channel switching, the channel plan STD is first switched to channel 4, the channel 4 video signal frequency is selected, and then the automatic fine adjustment tuning operation is performed. Since the video signal frequency of the channel 4 of the channel plan HRC is shifted by 1.25 MHz with respect to the channel 4 of the channel plan STD, the shift of the 1.25 MHz is canceled by pulling in the automatic fine adjustment tuning operation, and the channel plan HRC is eliminated. However, there is a problem that it takes time to eliminate this 1.25 MHz shift, and the image during this time is disturbed and annoying.

The present invention has been made in order to solve the above-mentioned problems, and a receiving channel switching circuit device is provided in which a screen disorder at the time of channel switching is not annoying by switching channels in a short time. The purpose is to provide.

[0005]

[Means for Solving the Problems]

 A receiving channel switching circuit device according to the present invention is a receiving channel switching circuit device for switching a receiving channel when receiving a video of a desired channel from a broadcasting channel by a cable television broadcasting system having a plurality of different channel plans. , The frequency deviation for detecting the difference between the reception channel frequency at the time of the previous channel reception and the reception channel frequency at the time of receiving the previous channel in the standard channel plan among the plurality of different channel plans. Based on the frequency deviation amount storage means and the difference between the reception channel frequencies stored in the frequency deviation amount storage means. , Correction for tuning operation information used to select a new channel Those having a Usenkyoku operation information correction means.

Further, the reception channel switching circuit device according to the present invention corrects the oscillation frequency of the local oscillation circuit for selecting a new channel based on the difference between the reception channel frequencies stored in the frequency deviation amount storage means. It is equipped with a tuning operation information correction means for

[0007]

[Action]

 The receiving channel switching circuit device according to the present invention detects the difference between the previously received channel frequency and the channel frequency when the previous channel is received in the standard channel plan, and detects the detected channel frequency. The difference between the stored channel frequencies is stored, and based on the stored difference in channel frequency, the channel selection operation information used to select a new channel is corrected, and the new Directly obtain the tuning operation information used to select a different channel, shorten the time required to switch to the new channel, shorten the time when the screen is disturbed when switching channels, and Avoid screen disturbances that can be annoying.

Further, the receiving channel switching circuit device according to the present invention detects the difference between the previously received channel frequency and the channel frequency at the time of receiving the previous channel in the standard channel plan, The detected channel frequency difference is stored, and based on the stored channel frequency difference, the oscillation frequency of the local oscillation circuit for selecting a new channel is corrected, and the new channel is selected. To directly control the oscillation frequency of the local oscillator circuit to shorten the time required to switch to the new channel, shorten the time when the screen is disturbed when switching channels, and cause obstruction when switching channels. Avoid screen distortion.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a receiving channel switching circuit device of the present invention. In the figure, reference numeral 1 is a tuner section for selecting a broadcasting channel by CATV, and a local oscillation frequency generated in a high frequency amplification section 1a for amplifying a reception output received from a transmission cable (not shown) and a local oscillation circuit 1c. It has a mixing circuit 1b for mixing with a signal. Reference numeral 2 is a video intermediate frequency amplification circuit for amplifying the video intermediate frequency, and 3 is a video detection circuit for detecting and extracting a video signal from the video intermediate frequency amplified by the video intermediate frequency amplification circuit 2. Reference numeral 4 denotes an automatic fine adjustment tuning unit (hereinafter referred to as an AFT unit) which automatically performs fine adjustment with respect to the fluctuation of the local oscillation frequency. The AFT unit 4 includes a video carrier amplification circuit 4a that extracts and amplifies a video carrier from the output of the video intermediate frequency amplification circuit 2, a limiter 4b that eliminates the amplitude modulation of the output of the video carrier amplification circuit 4a, and a video carrier frequency. It has an FM detection section 4c for extracting the change of the above as a change of the DC voltage by the FM detection, and a DC amplification section 4d for DC amplifying the output of the FM detection section 4c. Reference numeral 5 is a low-pass filter that stabilizes the DC voltage output from the DC amplifier 4d. Reference numeral 7 denotes a system control unit that outputs a control signal for the local oscillation circuit 1c to generate a local oscillation frequency signal according to the channel to be selected, and is composed of a microcomputer. Reference numeral 8 denotes a memory, a register for storing channel selection information 11 before channel switching shown in FIG. 2 and frequency deviation information 12 corresponding to the channel selection information, each channel selection information shown in FIG. 3 and each channel selection information thereof. A table in which local oscillation frequency control information in the channel plan STD is stored, and a program for channel switching processing shown in the flowchart of FIG. 4 are stored.

Channel selection information 11 before channel switching shown in FIG. 2 is information indicating a channel selected before channel switching. The frequency deviation information 12 is deviation information indicating a deviation between the channel frequency before the channel switching in the channel plan by the channel plan STD and the channel frequency at the time of receiving the channel before the channel switching. The frequency deviation information 12 has a value close to "0" MHz when the channel reception before switching is performed for the channel plan STD, and the frequency deviation information 12 is "-1" when it is performed for the channel plan HRC. The value is close to 0.25 MHz.

Further, the tuning information shown in FIG. 3 is information input for tuning each channel, and the local oscillation frequency control information corresponds to each channel selected by the tuning information. Control information for generating a control signal for controlling the frequency of the local oscillation signal in the channel plan STD of the local oscillation circuit 1c.

Next, the operation of the channel switching process will be described based on the flowchart of FIG. Note that this flowchart will be described on the premise that channel reception is performed only for the channel plan HRC. Before executing the channel switching process shown in this flow chart, the microcomputer 7 stores the channel selection information (chN) of the previously received channel and the frequency deviation information fn in the register shown in FIG. There is. When the tuning information for selecting a new channel is input in this state, the process proceeds to channel switching processing, and the tuning information (chN) before switching is first read from the register shown in FIG. 2 (step S1). Further, the frequency deviation information fn for the case of receiving the channel N according to the channel plan STD is read (step S2). The micro computer 7 stores the tuning information for tuning the new channel, and switches the channel based on the new tuning information and the frequency deviation information stored in the register. A control signal for setting the subsequent local oscillation frequency is generated and output to the local oscillation circuit 1c (step S3).

That is, when the new tuning information indicates that the channel 101 is different from the channel N, for example, channel 101 is conventionally selected to the channel plan STD, and the channel plan STD and the channel plan are further selected. In the HRCs, the deviation between the channel frequencies of the channels 101 of −1.25 MHz is pulled in by the AFT operation to complete the channel 101 tuning (see FIG. 5A). When the tuning information indicates the channel 101, the local oscillation frequency control information V101 corresponding to the channel 101 is read from the table shown in FIG. 3, and the frequency deviation information shown in FIG. 2 with respect to the read local oscillation frequency control information V101. The local oscillation frequency control information V101 is corrected by fn. A control signal corresponding to the channel plan HRC is generated and output to the local oscillator circuit 1c (see FIG. 5B).

Then, the microcomputer 7 terminates the channel switching process if the output voltage value of the low pass filter 5 thus fetched is within the specified range (step S4).

As described above, according to this embodiment, the deviation between the channel frequencies of the channel plan STD and the channel plan HRC of −1.25 MHz is not adjusted by pulling in the AFT operation, but the channel frequency of the previously received channel frequency is adjusted. The difference from the previously received channel frequency in the channel plan STD is stored, and tuning operation information or local oscillation frequency control information when receiving a new channel due to the stored difference in the channel frequency is stored. Since the channel is corrected and the new channel is selected and received, the time required for channel switching and the time when the screen is disturbed during channel switching can be shortened.

[0016]

[Effect of device]

 As described above, according to the present invention, a new channel frequency is selected according to the standard channel plan, and then a new channel frequency is tuned in by the AFT operation to correct the new channel frequency without switching and selecting the new channel. Since the channel frequency is selected directly, the time required for channel switching and the time when the screen is disturbed during channel switching can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a receiving channel switching circuit device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a register that stores tuning information before channel switching and frequency deviation information corresponding to the tuning information in the receiving channel switching circuit device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a table storing channel selection information and local oscillation frequency control information in a channel plan STD for each channel selection information in the receiving channel switching circuit device according to an embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of a receiving channel switching circuit device according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram when the channel plan HRC is switched from ch2 to ch4.

[Explanation of symbols]

7 Microcomputer (frequency deviation amount detection means,
Correction means) 8 memory (frequency deviation amount storage means) V101 Local oscillation frequency control information (tuning operation information)

Claims (2)

[Scope of utility model registration request] 1. A receiving channel switching circuit device for switching a receiving channel when receiving a video of a desired channel from a broadcasting channel by a cable television broadcasting system having a plurality of different channel plans,
Frequency deviation amount detecting means for detecting a difference between a reception channel frequency at the time of the previous channel reception and a reception channel frequency at the time of receiving the previous channel in a standard channel plan of the plurality of different channel plans. And frequency deviation amount storage means for storing a difference about the reception channel frequency detected by the frequency deviation amount detection means,
Receiving provided with tuning operation information correction means for correcting the tuning operation information used for selecting a new channel based on the difference between the reception channel frequencies stored in the frequency deviation amount storage means. Channel switching circuit device. 2. The tuning operation information correction means determines an oscillation frequency of a local oscillation circuit for selecting a new channel based on the difference between the reception channel frequencies stored in the frequency deviation amount storage means. The reception channel switching circuit device according to claim 1, wherein the reception channel switching circuit device is corrected.