KR19980040698A - AFT automatic adjustment device and method - Google Patents

Abstract

The present invention provides an RF amplifier 110 for amplifying an RF signal received through an antenna ANT, a PLL 120 for detecting a phase difference by receiving a tuning voltage VT transmitted from a microcomputer 300, and a PLL. Local oscillator 130 for oscillating the local oscillation frequency of different frequencies by the phase difference detected by 120, and the RF signal amplified by the RF amplifier 110 and the local oscillation frequency oscillated by the local oscillator 130 A tuner unit 100 comprising a mixer 140 to mix, an IF amplifier 210 for amplifying the IF signal output from the mixer 140, and a demodulator for demodulating the IF signal amplified by the IF amplifier 210 ( 220) and an AFT regulator having an IF amplification unit 200 composed of a phase comparator 230 for comparing an IF signal amplified by the IF amplifier 210 with a phase of 45.75 MHz to transmit an AFT voltage to the microcomputer 300. In the present invention, the 45.75MHz oscillator 500 for supplying the oscillation frequency of 45.75MHz to the IF amplifier 210, and the The AFT adjustment frequency oscillator 700 for oscillating the AFT adjustment frequency supplied to the phase comparator 230 by receiving the AFT adjustment signal output from the 300, and the microcomputer 300 compares the AFT voltage with the reference voltage. When the AFT voltage is fixed to the preset voltage, the AFT adjustment can be performed automatically.

Description

AFT automatic control device and method thereof.

The present invention relates to an AFT adjusting device and method, and more particularly, to an AFT automatic adjusting device and a method for performing an AFT adjusting operation using a varactor (VCD) without using an existing AFT coil. It is about.

Referring to FIG. 1, a conventional tuner and a peripheral configuration thereof are broadly divided into a tuner unit 100 that tunes a multi-channel RF signal received through an antenna ANT and converts it into an IF signal, and a tuner unit 100. It consists of an IF amplification unit 200 for amplifying the tuned IF signal in the). In more detail, the tuner unit 100 receives an RF amplifier 110 for amplifying a radio frequency (RF) signal received from an antenna ANT, and a preset voltage VT3 transmitted from the microcomputer 200. A PLL (Phase Lock Loop) 120 for detecting a signal, a local oscillator 130 for oscillating a local oscillation frequency corresponding to a phase difference detected in the PLL 120, and an RF signal and a local oscillator amplified by the RF amplifier 110. Composed of a mixer 140 for mixing the local oscillation frequency converted in 130, IF amplifier 200 is an IF amplifier 210 for amplifying the IF signal output from the mixer 140, and the IF amplifier ( A demodulation unit 220 for demodulating the IF signal amplified by 210, a synchronization signal separation unit 600 for separating the synchronization signal from the demodulated signal and transmitting it to the microcomputer 300, and amplifying the IF amplifier 210; 45.75 MHz supplied from a 45.75 MHz oscillator 400 consisting of an IF signal and an AFT coil L1 and a capacitor C1 Obtaining the phase difference is configured it to the phase comparator (230) for transmission to the microcomputer 300.

Referring to the AFT operation of the tuner configured as described above, when a tuning voltage VT3 for tuning a specific channel output from the microcomputer 300 is output to the PLL 120 of the tuner unit 100, the PLL 120 receives the PLL 120. By controlling the oscillation frequency of the local oscillator 130. The RF signal received through the antenna ANT is amplified and applied to the mixer 140 supplied with the local oscillation frequency oscillated by the local oscillator 130, so that the mixer 140 mixes them. Converts it to an IF signal of 55.75 MHz and supplies it to an input of an IF amplifier 230.

Subsequently, the demodulator 220 receiving the IF signal amplified by the IF amplifier 210 of the IF amplifier 200 demodulates the video signal from the IF signal and uses the synchronization signal separator 600 therefrom. Since the horizontal synchronization signal is separated and supplied to the microcomputer 300, the microcomputer 300 recognizes that a specific channel is tuned. The tuning state is determined by the AFT voltage supplied from the phase comparator 230, and a tuning voltage VT3 for adjusting the tuning state is generated and supplied to the PLL 120 of the tuner unit 100. That is, the microcomputer 300 adjusts the oscillation frequency of the local oscillator 130 by changing the tuning voltage VT3 (generally composed of 12 steps of 6 steps each with respect to the tuning voltage of a specific channel) by 1 step. The tuning state is determined by the AFT voltage level generated by the phase comparator 230. Here, the phase comparator 230 contrasts the phase difference between the IF signal applied from the IF amplifier 210 and the frequency of 45.75 MHz and transmits the AFT voltage according to the result to the microcomputer 300.

In the process of producing such a tuner, the tuner 100 is tuned to the preset voltage stored in the microcomputer 300 or the input terminal of the phase comparator 230 so that the tuner 100 can tune a specific channel by the tuner voltage output from the microcomputer. This will set the frequency for the AFT adjustment. However, because the operation is set manually, the preset voltage or the frequency for AFT adjustment may not be set correctly. That is, in order to adjust the AFT adjustment frequency, the reactance and capacitance of the coil L1 or the capacitor C1 are adjusted, and the preset voltage is set according to the AFT voltage output from the phase comparator 230. The error is that the correct setting is not made.

The present invention for solving the above-mentioned shortcomings includes a first step of checking the setting state of the AFT adjustment mode, a second step of supplying an oscillation frequency of 45.75 MHz to the input terminal of the IF amplification means, and the AFT adjustment signal and the reference. A third step of outputting a reference voltage while outputting a voltage, a fourth step of checking a tuning state by comparing an AFT voltage and a reference voltage while increasing or decreasing an AFT adjustment signal, and selecting an AFT voltage when the AFT voltage and the reference voltage are the same. Characterized in that the fifth step of setting to perform.

That is, according to the present invention, an RF amplification means configured to amplify an RF signal received through an antenna, a PLL configured to detect a phase difference by receiving a preset voltage transmitted from a control means, and a phase difference detected by the PLL, A tuning means comprising a local oscillation means adapted to oscillate a local oscillation frequency of another frequency, a mixing means configured to mix an RF signal amplified by the RF amplification means and a local oscillation frequency oscillated by the local oscillation means, and a mixing means. IF amplification means for amplifying the IF signal output from An AFT adjusting device having an IF amplifying amplifying means consisting of a phase comparing means adapted to transmit a signal to a control means, said IF amplifying means. A 45.75 MHz oscillation means adapted to supply an oscillation frequency of 45.75 MHz, an AFT adjustment frequency oscillation means adapted to oscillate an AFT adjustment frequency supplied to a phase comparison means by receiving an AFT adjustment signal output from the control means, and the control The means is characterized in that it is arranged to fix the AFT voltage to the preset voltage when the AFT voltage and the reference voltage are the same.

1 is a block diagram illustrating a conventional AFT adjustment;

2 is a block diagram of the present invention for automatically performing the AFT adjustment work,

3 is a flowchart illustrating a process of performing an AFT adjustment operation according to the present invention.

Explanation of symbols on the main parts of the drawings

100: tuner unit 110: RF amplifier

120: PLL 130: local oscillator

140: mixer 200: IF amplifier

210: RF amplifier 220: demodulator

230: phase comparator 300: microcomputer

500: 45.75MHz oscillator 600: Sync signal separator

700: frequency oscillator for AFT adjustment L: coil

C: Capacitor VCD: Varactor

R1, R2: resistance

As shown in FIG. 2, the present invention detects a phase difference by receiving an RF amplifier 110 for amplifying an RF signal received through an antenna ANT and a preset voltage VT transmitted from the microcomputer 300. Local oscillator 130 oscillating the local oscillation frequency of different frequencies by the PLL 120, the phase difference detected by the PLL 120, and the RF signal and the local oscillator 130 amplified by the RF amplifier 110 A tuner unit 100 composed of a mixer 140 for mixing the local oscillation frequency oscillated at; IF amplifier 210 for amplifying the IF signal output from the mixer 140, a demodulator 220 for demodulating the IF signal amplified by the IF amplifier 210, and the IF signal amplified by the IF amplifier 210 and In the AFT regulator having an IF amplification unit 200 composed of a phase comparator 230 for comparing the phase of 45.75MHz to transmit the AFT voltage to the microcomputer 300, the oscillation frequency of 45.75MHz to the IF amplifier 210 AFT adjustment frequency oscillator 700 for oscillating the AFT adjustment frequency supplied to the phase comparator 230 by receiving the 45.75 MHz oscillator 500 and the AFT adjustment signal output from the microcomputer 300, and the microcomputer ( 300 is configured to fix the AFT voltage to the preset voltage when the AFT voltage and the reference voltage are the same.

Here, the AFT adjustment frequency oscillator 700 includes a capacitor (C) connected to the input terminal of the phase comparator 230, a coil (L) connected in series with the capacitor (C), and parallel with the coil (L). It is connected and is composed of a varactor (VCD; this is a device that the capacitance is converted by the AFT adjustment signal output from the microcomputer 300) to vary the capacitance for varying the AFT adjustment frequency, the varactor (VCD) is a microcomputer The capacitance is adjusted by the AFT adjustment signal output from 300.

3 is a flow chart for explaining the present invention, a first step of checking the setting state of the AFT adjustment mode, a second step of supplying an oscillation frequency of 45.75MHz to the input terminal of the IF amplifier 210, and AFT adjustment A third step of outputting a reference voltage while outputting a signal and a reference voltage;

While the AFT adjustment signal is increased or decreased, the fourth step of checking the tuning state in comparison with the AFT voltage and the reference voltage and the fifth step of setting the AFT voltage as the tuning voltage when the AFT voltage and the reference voltage are the same are shown.

In particular, if the AFT voltage is lower than the reference voltage, reduce the AFT adjustment signal by one step, and then prepare for the relationship between the AFT voltage and the reference voltage.If the AFT voltage is higher than the reference voltage, increase the AFT adjustment signal by one step and then It is made to prepare the magnitude relationship of the reference voltage.

According to the present invention configured as described above, when the operation mode is determined and set to the AFT automatic adjustment mode, the microcomputer 300 generates an AFT adjustment signal having a specific level and supplies it to one end of the varactor VCD and simultaneously generates a reference voltage. do. Then, the oscillation frequency of 45.75 MHz oscillated (S2) in the 45.75 MHz oscillator 500 connected to the input terminal of the IF amplifier 210 is amplified by the IF amplifier 210 and applied to the input terminal of the phase comparator 230. . In addition, the oscillation frequency f _o oscillated by the AFT adjustment frequency oscillator 700 for oscillating different frequencies by receiving the AFT adjustment signal output from the microcomputer 300 is applied to the input terminal of the phase comparator 230.

Here, as shown in Equation 1, the oscillation frequency f _{o of} the AFT adjustment frequency is adjusted by receiving an AFT adjustment signal output from the microcomputer 300.

[Equation 1]

Where f _o is the oscillation frequency of the adjustable frequency oscillator 700 for AFT,

L is the reactance of the coil,

C is the capacitance of the coil C and the varactor VCD.

A phase comparator 230 to which an oscillation frequency of 45.75 MHz arbitrarily oscillated and an AFT adjustment oscillation frequency oscillated by the AFT adjustment frequency oscillator 700 is applied, contrasts the phases of the two signals and generates the AFT voltage. 300). Then, the microcomputer 300 determines whether the AFT voltage is detected higher than the reference voltage by comparing the AFT voltage transmitted from the phase comparator 230 with the reference voltage (S4). As the AFT voltage is higher or lower than the reference voltage, the AFT voltage is detected by stepping the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 step by step. In addition to setting the AFT voltage tuning voltage, the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 is set.

In more detail, when the AFT voltage is compared with the reference voltage as a result of comparing the AFT voltage transmitted from the phase comparator 230 with the reference voltage, the AFT adjustment signal currently applied to the AFT adjustment frequency oscillator 700 is One step lower (S5) is supplied to the AFT adjustment frequency oscillator 700 to vary the oscillation frequency is supplied to the input terminal of the phase comparator 230. Next, as described above, it is determined whether the AFT voltage output from the phase comparator 230 and the reference voltage are the same (S6). If the AFT voltage and the reference voltage are different from each other, the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 is lowered by one step to change the oscillation frequency of the AFT adjustment frequency oscillator 700 and then change the oscillation frequency of the phase comparator 230. Repeat the operation to supply the input. Due to this operation, when the AFT voltage output from the phase comparator 230 is the same as the reference voltage, the AFT voltage detected at this time is set as the tuning voltage and the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 is set ( S7).

In addition, if it is determined that the AFT voltage is higher than the reference voltage as a result of comparing the AFT voltage transmitted from the phase comparator 230 with the reference voltage, the AFT adjustment signal currently applied to the AFT adjustment frequency oscillator 700 is increased by one step. (S8) It is supplied to the AFT adjustment frequency oscillator 700 to vary the oscillation frequency is supplied to the input terminal of the phase comparator 230. Next, as described above, it is determined whether the AFT voltage output from the phase comparator 230 and the reference voltage are the same (S9). When the AFT voltage and the reference voltage are different, the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 is increased by one step to change the oscillation frequency of the AFT adjustment frequency oscillator 700 and then change the oscillation frequency of the phase comparator 230 again. Repeat the operation to supply the input. Due to this operation, when the AFT voltage output from the phase comparator 230 is the same as the reference voltage, the AFT voltage detected at this time is set as the tuning voltage and the AFT adjustment signal applied to the AFT adjustment frequency oscillator 700 is set ( S10).

Accordingly, the tuner's AFT adjustment process can be performed more accurately in the production stage, so that the TV signal of a specific channel can be viewed more clearly.

The present invention amplifies a frequency of 45.75MHz arbitrarily oscillated in place of an IF signal of a specific channel by inputting it to an input terminal of a phase comparator by amplifying an IF amplifier of an IF amplifier and generating an arbitrary AFT adjustment signal. The tuning voltage can be set more accurately by setting the tuning voltage against the AFT voltage and the reference voltage while varying the oscillation frequency of the frequency oscillator.

Claims (5)

An RF amplifier 110 for amplifying the RF signal received through the antenna ANT, a PLL 120 for detecting a phase difference by receiving a tuning voltage VT transmitted from the microcomputer 300, and a PLL 120. Local oscillator 130 for oscillating the local oscillation frequency of different frequencies by the phase difference detected in the mixer, and a mixer for mixing the local oscillation frequency oscillated in the local oscillator 130 and the RF signal amplified by the RF amplifier 110 A tuner unit 100 composed of 140; IF amplifier 210 for amplifying the IF signal output from the mixer 140, a demodulator 220 for demodulating the IF signal amplified by the IF amplifier 210, and the IF signal amplified by the IF amplifier 210 and In the AFT regulator having an IF amplification unit 200 composed of a phase comparator 230 for comparing the phase of 45.75MHz and transmits the AFT voltage to the microcomputer 300, A 45.75 MHz oscillator 500 for supplying an oscillation frequency of 45.75 MHz to the IF amplifier 210; An AFT adjustment frequency oscillator 700 for receiving the AFT adjustment signal output from the microcomputer 300 and oscillating the AFT adjustment frequency supplied to the phase comparator 230; The microcomputer 300 is AFT automatic adjustment device, characterized in that configured to set the fixed AFT voltage to the preset voltage when the same compared to the AFT voltage and the reference voltage. The frequency oscillator 700 for adjusting the AFT has a capacitor C connected to an input terminal of the phase comparator 230, a coil L connected in series with the capacitor C, and the coil. (L) is connected in parallel with the AFT automatic adjustment device, characterized in that it consists of a varactor (VCD) for varying the frequency for AFT adjustment while the capacitance is variable. The apparatus of claim 2, wherein the varactor (VCD) is characterized in that the capacitance is adjusted by the AFT adjustment signal output from the microcomputer (300). Checking a setting state of the AFT adjustment mode; Supplying an oscillation frequency of 45.75 MHz to an input terminal of the IF amplifier 210; A third step of outputting a reference voltage while outputting an AFT adjustment signal and a reference voltage; A fourth step of checking a tuning state by comparing the AFT voltage and the reference voltage while increasing or decreasing the AFT adjustment signal; And performing a fifth step of setting the AFT voltage to the preset voltage when the AFT voltage and the reference voltage are the same. 5. The method of claim 4, wherein if the AFT voltage is lower than the reference voltage, the AFT adjustment signal is decreased by one step, and then the contrast between the AFT voltage and the reference voltage is prepared. If the AFT voltage is higher than the reference voltage, the AFT adjustment signal is increased by one step. AFT automatic adjustment method characterized in that to be made to prepare the magnitude relationship between the AFT voltage and the reference voltage.