KR19980067954A - Unnecessary channel memory protection circuit during automatic search - Google Patents

Abstract

The present invention relates to an unnecessary channel memory prevention circuit during automatic search for preventing unnecessary weak electric field broadcasting channels having poor reception status when performing the automatic broadcasting memory function of a TV broadcasting channel using a TV or a tuner of a television.

The present invention provides a tuner circuit for converting a television RF broadcast signal input through an antenna into an intermediate frequency signal, and generates a large AGC signal when a weak field signal is input according to the tuning output level of the tuner circuit. An AGC generation circuit for generating a small AGC signal at the time of input, an AGC level comparison circuit for outputting the AGC signal level to a reference value, and an intermediate frequency output signal of the tuner circuit to output audio and video signals. A synchronous detection circuit for detecting a synchronous signal by inputting an IF circuit, a video output of the IF circuit, and outputting a broadcasting channel tuning signal to a tuner circuit through a PLL circuit, and outputting and synchronizing a detection circuit of the AGC level comparison circuit. Unnecessary channel memory prevention circuit including a microcomputer that accepts the output of the channel and selectively stores broadcasting channels above a certain field strength level in a memory. It is.

The circuit of the present invention has an effect of preventing unnecessary storage of the weak field broadcast signal during automatic channel search.

Description

Unnecessary channel memory protection circuit during automatic search

The present invention relates to an unnecessary channel memory prevention circuit during automatic search for preventing unnecessary weak electric field broadcasting channels having poor reception status when performing the automatic broadcasting memory function of a TV broadcasting channel using a TV or a tuner of a television.

In order to receive a broadcast program using VSI or to make a reservation recording using it, a tuner is installed inside VSI.

The tuner mounted on the VSI, like the tuner mounted on the television, selects the desired broadcasting channel from the TV broadcasting RF signal in the 54MHz to 890MHz range received through the antenna and transmits the broadcasting signal to a constant frequency (45.75MHz for video and audio). Is converted into an intermediate frequency signal of 41.25 MHz).

This tuner has a high frequency input circuit for selectively filtering only the RF signal of the television band among the airwaves, and a high frequency amplification circuit for amplifying the weak signal forces through the high frequency input circuit to a certain level.

A high frequency signal output from the high frequency amplification circuit is mixed with a local oscillation signal, and has a mixing circuit for converting a broadcast signal of a desired channel into an image intermediate frequency signal of 45.75 MHz.

And an intermediate frequency amplifying circuit for amplifying the image intermediate frequency signal output from the mixing circuit and a local oscillating circuit for supplying the oscillation signal to be mixed with the input high frequency signal to the mixing circuit.

Here, the magnitude of the oscillation frequency of the local oscillation circuit to be input for mixing the high frequency input signal into the mixing circuit is varied depending on the high frequency frequency band of the desired tuning channel. In other words, in the recently mainstream fully tuned tuner, the broadcasting channel input by the user is tuned by changing the oscillation frequency output from the local oscillation circuit.

Therefore, the local oscillator circuit is designed as a voltage controlled oscillator circuit capable of outputting various oscillation frequencies determined for each broadcast reception channel.

The local oscillation circuit of the voltage control method is controlled by a microcomputer that receives an external channel selection key input signal and generates a variable voltage corresponding to the frequency of the corresponding channel.

The microcomputer performs the tuner channel tuning by monitoring whether the intermediate frequency of the image is accurately converted while increasing or decreasing the control voltage applied to the voltage controlled oscillator in order to accurately tune the channel desired by the user during channel tuning. do.

The intermediate frequency signal of the television broadcast signal tuned by the tuner is processed by the intermediate frequency signal processing circuit inside VSI and output to the TV or monitor through the video and audio circuits, and the operation of V's Decal mechanism is performed. Is sometimes recorded on a videotape.

The tuner of the electronic tuning method is provided with automatic channel search and automatic memo function of the search channel.

The broadcast channel search in the tuner is determined by judging whether there is a synchronization signal level over all channels selected through the PLL (phase lock loop) method in accordance with the control of the microcomputer.

However, because the electric field strength of each channel is different according to the local conditions and surrounding conditions, when setting up VSI or TV for the first time, the channel is automatically tuned in the tuner under the control of the microcomputer when the automatic channel tuning and memory functions are performed. Will be saved.

In such a channel, when the field strength is weak, the AGC circuit automatically increases the AGC level to increase the reception level of the corresponding channel. On the contrary, when the field strength of the selected channel is strong, the AGC level is relatively low. Lowering the level always maintains a constant reception level.

The problem here is that when the adjacent channel jamming frequency signal or unnecessary noise signal is searched, the microcomputer judges it as a regular broadcasting channel signal and raises the AGC level to the maximum so that the channel is tuned and stored in memory. It is tuned and stored.

An object of the present invention relates to a circuit for preventing unnecessary channel memory during automatic search, which can prevent unnecessary memory areas from being consumed by selecting and storing unnecessary channels in the conventional automatic channel search as described above.

The present invention provides a tuner circuit for converting a television RF broadcast signal input through an antenna into an intermediate frequency signal, and generates a large AGC signal when a weak field signal is input according to the tuning output level of the tuner circuit. An AGC generation circuit for generating a small AGC signal at the time of input, an AGC level comparison circuit for outputting the AGC signal level to a reference value, and an intermediate frequency output signal of the tuner circuit to output audio and video signals. A synchronous detection circuit for detecting a synchronous signal by inputting an IF circuit, a video output of the IF circuit, and outputting a broadcasting channel tuning signal to a tuner circuit through a PLL circuit, and outputting and synchronizing a detection circuit of the AGC level comparison circuit. Unnecessary channels are automatically tuned using a microcomputer that accepts the output of the channel and selectively stores broadcasting channels above a certain field strength level in memory. Can I prevent that memory.

1 is a circuit configuration diagram of the present invention.

2 is a flow chart illustrating the practice of the present invention.

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

10: tuner circuit 11: AGC generating circuit

12: AGC level comparison circuit 13: microcomputer

14: IF circuit 15: synchronous detection circuit

16: PLL circuit 17: memory

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

1 is a circuit diagram of the present invention. As referred to herein, the television RF broadcast signal received through the antenna is connected to the tuner circuit 10 which converts and outputs the broadcast signal of the channel tuned through the auto tuning into an intermediate frequency signal, and the tuner described above. The circuit 10 is connected such that the output of the PLL circuit 16 is applied so that autotuning takes place therein.

The intermediate frequency signal output from the tuner circuit 10 is connected to the IF circuit 14 which receives the intermediate frequency signal and processes the video signal and the audio signal. In addition, the video output of the IF circuit 14 is inputted to the synchronous detection circuit 15 to be synchronously detected and then connected to the microcomputer 13 to provide a synchronous detection signal.

The synchronization signal detected and output by the synchronization detection circuit may be applied to the microcomputer through a filter circuit for band-passing only the horizontal synchronization frequency signal component of 15.7 KHz.

The tuner circuit 10 is connected to the broadcast channel by the microcomputer 13 through the PLL circuit 16 in a self-tuning manner, and the tuning output level of the tuner circuit 10 is connected to the AGC generation circuit 11. Through this, the AGC level is determined to be connected, and the AGC signal level determined here is connected to the microcomputer 13 through the AGC level comparison circuit 12 through which the reference value is input.

The operation process of the present invention configured as described above will be described with reference to the flowchart of FIG. 2.

First, when the RF signal received through the antenna is input to the tuner circuit 10, the automatic channel search mode is executed by the channel search command from the microcomputer 13 through the PLL circuit 16 in the tuner circuit.

In detail, the tuner circuit 10 converts a television broadcast RF signal in a 54 MHz to 890 MHz range received through an antenna into an intermediate frequency signal having a constant frequency (45.75 MHz for video and 41.25 MHz for audio). .

The tuner circuit is provided with a high frequency input circuit for selectively filtering only the RF signal of the television band among the airwaves, and a high frequency amplification circuit for amplifying the weak signal forces through the high frequency input circuit to a certain level.

The high frequency signal output from the high frequency amplification circuit is mixed with the oscillation frequency signal of the local oscillation circuit in the mixing circuit to convert the RF signal of a desired broadcast channel into an image intermediate frequency signal of 45.75 MHz.

Here, the magnitude of the oscillation frequency of the local oscillation circuit to be input for mixing the high frequency input signal into the mixing circuit varies depending on the high frequency frequency band of the channel to be tuned. In order to change the oscillation frequency output from the local oscillation circuit, the PLL method under the control of the microcomputer 13 is adopted.

To this end, the local oscillator circuit is designed as a voltage controlled oscillator circuit capable of outputting various oscillation frequencies determined for each broadcast reception channel.

The microcomputer 13 sequentially tunes or decreases the control voltage applied to the voltage controlled oscillator in order to precisely tune the channel desired by the user during channel tuning, and monitors whether the intermediate frequency of the image is correctly converted. Will be performed.

Meanwhile, the tuning output level of the tuner circuit is input to the AGC generation circuit 11. At this time, if the strong electric field signal input condition, the tuning output level will be large, so the AGC signal level is adjusted to a small value, and the tuning level is lowered to a certain level. However, if the tuning output level is a very low weak field signal input condition, the AGC level is determined to be large.

Since such a large AGC level value is very likely that the current tuning channel is an unnecessary channel or an unreceivable broadcast channel signal, it is necessary to determine whether the AGC level at this time exceeds the reference value. This comparison occurs in the AGC level comparison circuit and the result is input to the microcomputer 130.

On the other hand, the video output of the IF circuit 14 is input to the synchronous detection circuit 15 to detect a synchronous signal which appears when there is a broadcast, and the result is input to the microcomputer 13.

Accordingly, the microcomputer 13 receives the outputs of the AGC level comparator 12 and the synchronization detection circuit 15, and if the currently searched channel does not exceed the maximum AGC level, the synchronization signal is present. If the search channel memory condition is not satisfied, the search channel is skipped and the next channel is searched.

Therefore, as shown in FIG. 2, only the broadcast channel for which a good reception state is guaranteed is selectively searched for.

As described above, in the present invention, a weak electric field input signal or an unnecessary adjacent channel signal according to the installation region and surrounding conditions of VSI is memorized unnecessarily during channel search using an autotuning tuner, thereby unnecessary unnecessary channels for subsequent channel selection. The selection can be prevented and the problem of unnecessary channel memory areas can be solved.

Claims (1)

A television broadcast channel search and search channel information memo device using a built-in tuner, comprising: a tuner circuit (10) for converting a television RF broadcast signal input through an antenna into an intermediate frequency signal, and a tuner output level of the tuner circuit. Accordingly, the AGC generation circuit 11 generates a large AGC signal when the weak electric field signal is input, and generates a small AGC signal when the strong electric field signal is input, and an AGC level comparison circuit that outputs the AGC signal level to a reference value. (12), an IF circuit 14 for processing the intermediate frequency output signal of the tuner circuit and outputting audio and video signals, and a synchronous detection circuit 15 for detecting a synchronization signal by inputting the video output of the IF circuit. And the PLL circuit 16 outputting the broadcast channel tuning signal to the tuner circuit, and receiving the output of the AGC level comparison circuit and the output of the synchronous detection circuit so as to have a constant field strength level. And a microcomputer (13) for selectively storing the broadcasting channel on the memory (17).