KR890003611Y1 - Tuner circuit for vtr - Google Patents

Abstract

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Description

110-Channel VTR Tuner Circuit Using Vertical Synchronization Signal and Controller

1 is a circuit diagram of the present invention.

2 is an output waveform diagram of the microcomputer of FIG.

3 is a diagram showing a relationship between a local oscillation frequency and a tuning voltage.

4 is an AFT curve output from an intermediate width portion of the video signal of FIG.

* Explanation of symbols for main parts of the drawings

A: channel selector MC: microcomputer

B: Display part C: Video signal middle width part

D: Vertical sync signal separator F: Phase detector

E: Monostable multivibrator G: Tuner stage

R1-R8: Resistor C1-C4: Capacitor

DE: diode OP1, OP2: comparator

The present invention relates to a VTR tuner circuit using a vertical synchronization signal and a controller, and in particular, to cope with an increase in the number of channels due to an increase in cable broadcasting (CATV) and the opening of a domestic broadcasting system, a frequency synthesis method is used in a TV and a VTR. Not only is it possible to tune channels, it is also a circuit that can achieve the best picture by automatic fine tuning (AFT).

In general, it is essential to increase the number of TV channels as the number of TV channels increases due to the increase in cable broadcasting (CATV) and scheduled to open domestic broadcasts. By the way, the number of existing VTR channels cannot be used effectively with TVs with increasing channel numbers as described above.

Therefore, by devising the present invention to solve the above drawbacks, as the number of TV channels increases, not only can 110 channels be tuned using the frequency synthesis method of the VTR, but also the automatic fine adjustment can obtain an optimal screen. The aim is to provide a tuner system using a vertical synchronous signal and a 1-chip controller.

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

The 110 channel used in the present invention is composed of 28 channels in 82-channel cable television (CATV) mode in the TV mode as shown in (Table 1). Among the 82 channels, TV mode consists of 5 channels (channel numbers 2-6) in the VHF LOW band, 7 channels (channel numbers 7-13) in the VHF HIGH band, and 70 channels (channel numbers 14-83) in the UHF band. The CATV mode consists of 12 channels (channels 95-97 and 14-22) in the VHF LOW band and 14 channels (channels 23-36) in the VHF HIGH band, respectively.

TABLE 1

1 is a tuner circuit diagram of the present invention, and outputs serial PLL data consisting of system clock signal data and an enable signal to a phase detector F according to a channel up / down key input of a remote controller or a channel selector A. FIG. And a channel selector for determining an AFT input to the high state signal application terminal (AFT) to the sync port SYS, and a 1-chip controller that controls the AFT, that is, a microcomputer MC and the microcomputer MC. The analog signal is compared by comparing the AFT signal output from the display section B displaying the channel recognized by the video signal intermediate amplifier C with the reference voltage set by the voltage 12V and the resistors R1-R3. Comparator operational amplifiers (OP1, OP2) for converting to digital data, and a vertical synchronous signal separation unit (D) for separating the vertical synchronous signal from the composite video signal output from the video signal intermediate amplifier (C), and Trigger a separate vertical sync signal If there is a vertical synchronization signal, the output becomes "high" and if not, the output becomes "low". The monostable multivibrator E, the clock pulses CK, data DA, The phase detection unit F and the tuner stage G which receive the enable signal EN and select the channel by the output signals b1 and b2, and detect the phase by outputting the tuning voltage to select the channel. The circuit of the present invention is constructed.

The circuit operation of the present invention having the above configuration will be described in detail.

First, a method of tuning 110 channels is described. When a user selects a channel according to a channel up / down key input through a remote controller or a channel selector A, a scan pulse generated from the microcomputer MC is used. The channel number recognized by the channel selector A is recognized and applied to the display unit B to display the channel number.

In addition, the microcomputer MC includes a second diagram including data DA, a clock pulse CK, and an enable signal EN corresponding to a channel number input to a phase locked loop (PLL) that is a phase detector F. Pass PLL data, which is the same serial data.

At this time, it is used to select the upper 4 bits of 18-bit PLL data, the next 9 bits are used to tune the channel by generating the main frequency, and the last 5 bits are used for automatic fine tuning.

First, in the band selecting operation, transistors TR1 of the tuner stage G are turned on when both of b1 and b2, which are outputs of the phase detector F, are 0 according to the upper 4 bits of the PLL data. The LOW band is selected to activate the VHF RF amplifier inside the tuner.

If b1 and b2 are 1 and 0, the VHF HIGH band is selected. If 0 and 1, the UHF band is selected.

Secondly, the tuning of the channel of the selected band is performed by the local oscillation frequency of the OSC fed back to the phase detector F so that the local oscillation frequency of the local oscillator and the 9-bit data of the PLL are selected. After the frequencies are compared in the phase detector F, the phase difference is applied to the low pass filter LPF, where the DC voltage is applied to the local oscillator so that the local oscillation frequency is changed to tune the channel.

That is, as shown in FIG. 3 showing the relationship between the tuning voltage and the frequency, the channel is tuned by changing according to the frequency-voltage oscillator of the tuner.

Third, the operation of performing AFT so that the screen of the tuned channel is optimized is determined by the upper four bits of the PLL data input to the phase detector F as described above, and then by the next nine bits. When the channel of the selected band is tuned, the video signal intermediate amplifier C outputs a composite video signal and an AFT signal having a curve as shown in FIG.

The output composite video signal is removed from the color components by the resistors R6 and R7 and the capacitors C2 and C3 and then applied to the vertical synchronous signal separator D so that only the vertical synchronous signal is separated. It is used as trigger input signal of (E).

At this time, the output Q of the monostable multi-vibration 9E having the vertical synchronization signal as the trigger input is " high " if there is a composite video signal, and " low "

After the channel is tuned, the microcomputer MC checks the synchronization signal input of the port SYS to which the output Q of the monostable multivibrator E is input and performs AFT when it is "high".

Therefore, the image signal is output from the intermediate amplification unit C. The AFT signals having the curve as shown in FIG. 4 (a) are applied to the comparators OP1 and OP2 and are analog-digital converted as shown in FIG. 4 (b).

The microcomputer MC determines the input signal of the AFT terminal to which the AD conversion is applied and changes the lower 5 bits so that when found in the AFT window as shown in FIG. 4 (b), the frequency of the position is fixed and the phase detection is performed. The frequency transmission, which is the serial PLL data input to the negative portion F, is stopped to end the tuning operation.

In an AFT window where the output of the comparator is converted from "high" to "low" or "low" to "high", the picture is optimal.

At this time, the port (SYS) of the microcomputer (MC) should always be "high" when performing the AFT in order to find the AFT window in the entire AFT area, so that the output is higher than the trigger input of the monostable multivibrator. The period of the pulse should be large.

That is, the period of the output pulse of the monostable multivibrator determined by the resistor R8 and the capacitor C4 should be set to be larger than the period of the vertical synchronization signal.

Therefore, the period of the output pulse is larger than the period of the vertical synchronization signal so that the synchronization port SYS of the microcomputer MC becomes "high" so that the AFT can be adjusted.

As described above, according to the present invention, it is possible to provide a VTR tuner system capable of tuning a frequency band and 110 channels using a vertical synchronization signal and a 1-chip controller as well as automatically performing an automatic fine tuning function. There is an advantage to provide a VTR tuner system.

Claims (1)

The AFT signal output from the image signal amplifier C is compared with the reference voltage determined by the power supply voltage 12V and the resistors R1-R3, converted into a digital signal, and applied to the microcomputer M for automatic fine adjustment. Comparator (OP1, OP2) to perform, the vertical synchronization signal separation unit (D) for separating only the vertical synchronization signal from the composite video signal output from the video signal intermediate amplifier (C), and the vertical synchronization signal separation unit ( Monostable multi-stage that applies an output pulse having a pulse width determined by the resistor R8 and the capacitor C4 to the input terminal SYS of the microcomputer MC using the vertical synchronization signal separated in D) as a trigger voltage. Depending on the vibrator E and the channel up / down key input of the channel selector A, the clock CK, data, and enable power of the phase detector F are adjusted so that the frequency band, channel tuning, and AFT are adjusted. This includes one-chip microcomputer (MC) controlling 110-channel VTR circuit using a vertical synchronizing signal and a controller, characterized in that.