KR950009600B1 - Dynamic auto fine tuming form use micom - Google Patents

Abstract

inputting an AFT signal outputted from a PIF circuit to a microcomputer; checking whether the input AFT signal is in a constant level or not; outputting a corresponding local oscillation frequency data, if the input AFT signal is in the constant level; increasing the frequency of the AFT signal by 1 step, if the AFT signal is in a reference level; reducing the frequency thereof by 1 step, if the level is below the reference level; compensating the local oscillation frequency data; checking whether the AFT signal is in a constant frequency or not; returning to the AFT signal level checking step, if the AFT signal frequency is constant; and outputting the oscillation frequency data to a phase loop IC according to the microcomputer, if the AFT signa frequency is not constant.

Description

Dynamic Auto Fine Tuning using Microcomputer

1 is a block diagram showing a channel tuning apparatus using a frequency synthesis method according to an embodiment of the present invention.

2 is a flow chart for explaining the operation of the microcomputer shown in FIG.

3 is a waveform diagram of an AFT voltage output from the PIF circuit shown in FIG.

* Explanation of symbols for main parts of the drawings

A10 Tuner A11 Local Oscillation Circuit

A12: phase locked loop IC A13: PIF circuit

A14: Channel Up / Down Switch A100: Microcomputer

A, B: the maximum AFT signal level at which the broadcast can be viewed in good condition

AFT: Auto Tuning Fine Tuning Signal

The present invention relates to a dynamic auto-fine tuning method using a microcomputer, and in particular, to prevent broadcast noise generated when a frequency of a broadcast signal is not input to an intermediate frequency corresponding to a selected channel when channel tuning by a frequency synthesis method. The present invention relates to a dynamic auto fine tuning method using a microcomputer that can receive a stable broadcast by correcting and outputting an intermediate frequency signal as an accurate intermediate frequency.

In general, a high frequency broadcast signal transmitted from a broadcasting station and received by an antenna is fixed in phase by predetermined control data output from a microcomputer according to a channel selected by a user through a tuner section comprising a local oscillation circuit and a phase locked loop IC. After synthesized with the local oscillation frequency generated from the loop IC and demodulated to the intermediate frequency and output to the intermediate frequency amplifier, it was possible to watch the desired channel by separating the video and audio signals from each device.

However, in the conventional channel tuning method using the conventional frequency synthesis method, when the local oscillation frequency is generated from the phase locked loop IC to demodulate the received broadcast signal to the intermediate frequency, the microcomputer is unique to the channel, that is, the tuned station. Local oscillation frequency data for the channel frequency is fixedly output. When the frequency of the broadcasting signal transmitted from the broadcasting station is distorted by disturbance or noise and applied to the tuner unit, the fixed local oscillation frequency is output from the microcomputer. Since the broadcast signal output by being synthesized with the data cannot be demodulated at the correct intermediate frequency, the broadcast signal includes a lot of high-frequency noise, and thus a video signal mixed with the noise is output on the CRT.

The present invention has been made in view of the above circumstances, and by correcting the intermediate frequency by dynamically outputting an AFT (Automatic Fine Tunning) signal output from a PIF circuit to a phase locked loop IC, thereby correcting an accurate intermediate frequency. The purpose is to provide a dynamic auto-fine tuning method using a microcomputer that allows you to watch a clear screen by using the microcomputer.

A dynamic auto fine tuning method using a microcomputer according to the present invention for realizing the above object includes an AFT signal input step of applying an AFT signal output from a PIF circuit to the microcomputer and an AFT input to the microcomputer through the AFT signal input step. AFT signal level determination step of judging whether a signal exists within a predetermined reference level (B-A) and outputting the corresponding local oscillation frequency data when it exists within a predetermined reference level (B-A), and AFT signal in this AFT signal level determination step. If is equal to or greater than the upper limit A of the reference level, the frequency of the AFT signal is increased by one step, and if it is less than or equal to the lower limit B of the reference level, the local oscillation frequency data is corrected by decreasing the frequency of the AFT signal by one step. The AFT signal output from the PIF circuit is corrected by the oscillation frequency data correction step and the local oscillation frequency data correction step. The AFT signal frequency determination step returns to the AFT signal level determination step if the AFT signal exists within a predetermined frequency range and the AFT signal is within a predetermined frequency. If not present, it characterized in that it comprises a fixed local oscillation frequency output step of outputting the local oscillation frequency data for the corresponding channel that is fixedly set according to each channel in the microcomputer to the phase-locked loop IC.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram illustrating a channel tuning apparatus using a frequency synthesis method according to an embodiment of the present invention, in which reference numeral A100 denotes a specific operation selected by a user in addition to performing a control operation for the entire apparatus. A microcomputer serving as a control unit for outputting local oscillation frequency data corresponding to a channel, and A10 receives a broadcast signal transmitted from a broadcasting station, and is based on a local oscillation frequency signal oscillated by local oscillation frequency data output from the microcomputer A100. Tuner section for outputting intermediate frequencies.

On the other hand, the tuner unit A10 transmits a phase locked loop IC A12 for outputting a synchronized signal fed back based on the local oscillation frequency data output from the microcomputer A100 and a high frequency broadcast transmitted from a broadcasting station. Local oscillation circuit A11 for outputting the local oscillation frequency signal based on the feedback-synchronized signal outputted from the phase locked loop IC A12, and the local oscillation frequency and the input broadcast signal (RF signal) It consists of an IF circuit (not shown) which outputs a frequency signal.

Also, reference numeral A13 denotes a PIF circuit that detects an AFT (Automatic Fine Tunning) signal from an intermediate frequency output from the IF circuit (not shown) and outputs it to the microcomputer A100. Channel up / down switch.

FIG. 2 is a flowchart illustrating the operation of the microcomputer A100 shown in FIG. 1. Referring to the drawings, the operation of the apparatus according to the present invention will be described below.

When the AFT signal output from the PIF circuit 13 is input to the microcomputer A100 based on the intermediate frequency signal output from the IF circuit (ST1), as shown in FIG. 3, the AFT signal is Typically, each broadcast channel does not affect the signals between the channels, i.e., it is within the level range of the minimum (B) and maximum (A) AFT signals where good viewing is possible (B≤AFT (V) ≤A) It is determined (ST2).

At this time, if the AFT signal is within the allowable level range B to A, the local oscillation frequency F data is outputted to the phase locked loop IC A12, and feedback oscillated from this phase locked loop IC A12. The control signal is output (ST3).

On the other hand, if the AFT signal does not exist within the allowable level range (B to A), it is determined whether the AFT signal is larger than the upper limit value (A) (AFT (V)> A) (ST4), and if AFT (V)> A, the local Local oscillation frequency data corrected by increasing the oscillation frequency data by one step is outputted to the phase-locked loop IC A12 (ST5), and if the AFT signal is not AFT (V)> A, that is, the AFT signal is the lower limit value (B). (ATF (V) < B), the local oscillation frequency data is reduced by one step and corrected, and the local oscillation frequency data is outputted to the phase-locked loop IC A12 (ST6). For example, the frequency between steps is 32.5 [KHz].

Subsequently, the AFT signal [AFT (f)] output from the PIF circuit 13 is input again by the corrected local oscillation frequency data (ST7), and the frequency [AFT (f)] of this AFT signal is assigned to the corresponding channel. It is judged whether or not it is within ± 2 [MHz], which is the normal frequency range of the intermediate frequency that can be corrected (ST8). If the frequency of this AFT signal is within the range of -2 [MHz] ≤ ATF (f) ≤ +2 [MHz], ST2 Returning to the step, the above process is repeated until the AFT signal is within the maximum level range (B to A).

On the other hand, if the frequency of the AFT signal input from ST7 is not within the range of -2 [MHz] ≤ AFT (f) ≤ +2 [MHz], the local oscillation frequency data fixed for the channel selected by the user is phased. Output to the fixed loop IC A12 (ST9).

3 is a waveform diagram of the AFT voltage output from the PIF circuit A13, and in the case of a normal broadcast signal, it falls within ± 2 [MHz], which is a typical frequency range available for each channel centered on an intermediate frequency. , B is the upper / lower limit of the AFT signal level at which the broadcast can be viewed in good condition.

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

In general, a high frequency broadcast signal transmitted from a broadcasting station is synthesized and transmitted with a video signal and an audio signal, and each channel is allocated at a frequency interval of 6 MHz.

Therefore, when a channel is selected by a user, the frequency of the high frequency signal input through the broadcast signal input terminal is generally constant. In this state, when the user operates the channel up / down switch A14 to select a channel, a pulse corresponding to the selected channel is generated and input to the channel selection terminals C and D of the microcomputer A100. Lose.

At this time, the microcomputer A100 automatically tunes the channel by a voltage tuning method or a counter method according to channel channel switching. First, the phase locked loop IC A12 is tuned through the phase locked loop clock terminal PLL CLK. Next, the local oscillation frequency data is output to the phase locked loop IC A12 through the data signal terminal PLL DATA in synchronization with the data valid signal terminal PLL STB. The oscillation frequency data from A100 is received and the synchronized oscillation control signal is output based on the oscillation frequency data.

The local oscillation frequency signal oscillated by the local oscillation circuit A11 is synthesized with the input broadcast signal (RF signal) and then demodulated and output at an intermediate frequency and applied to the PIF circuit A13 and the intermediate frequency amplifier (not shown).

At this time, the microcomputer A100 checks the AFT signal generated from the PIF circuit A13 and corrects the local oscillation frequency data. Such a process has been described above with reference to FIG.

First, the microcomputer A100 checks whether the AFT signal is within the channel allocation range B-A. The waveform of the AFT signal output from the PIF circuit A13 is as shown in FIG. 3, and in the case of a normal broadcast signal, it is within a predetermined range B-A up and down about the center frequency, and the range B If the AFT signal is present within -A), since the broadcast can be viewed in a good state, the oscillation frequency data is output without correction.

On the other hand, if the AFT signal does not fall within the normal range (B to A) as described above, it is checked which part of the upper / lower part of the predetermined range (B to A) is greater than the upper limit, so that the local oscillation frequency data Increases by one step and decreases the local oscillation frequency data by one step when it is smaller than the lower limit.

Subsequently, it is checked whether the AFT signal according to the oscillation frequency corrected as described above is within the channel frequency band (± 2 MHz) allocated centered on the intermediate frequency, and if it does not fall within the frequency band, it is determined that the broadcast signal is impossible to correct. The fixed local oscillation frequency data corresponding to the output is outputted, and if the band enters the band, the above-described steps are repeated to continuously correct the oscillation frequency until the AFT signal is in the normal range (B to A).

As described above, the dynamic auto fine tuning method using the microcomputer according to the present invention is a normal state when the frequency of the channel selected by the user becomes abnormal due to some factors such as a broadcast station or disturbance. By correcting the frequency of the city to an appropriate range of intermediate frequencies to avoid frequency interference of adjacent channels, it not only ensures a clear picture at all times, but also solves local problems in areas with weak electric fields such as blind spots. There is an effect to overcome.

In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the technical spirit of the present invention.

Claims (1)

The AFT signal input step of applying the AFT signal output from the PIF circuit to the microcomputer and the AFT signal input to the microcomputer through the AFT signal input step determine whether the AFT signal is within a predetermined reference level (B to A) and then the predetermined reference level (B). AFT signal level determination step for outputting the corresponding local oscillation frequency data when present within ˜A), and when the AFT signal is higher than the upper limit value A of the reference level in this AFT signal level determination step, increase the frequency of the AFT signal by one step. In the case of below the lower limit value B of the reference level, the local oscillation frequency data correction step of correcting the local oscillation frequency data by reducing the frequency of the AFT signal by one step, and the PIF by the correction by the local oscillation frequency data correction step Receives the AFT signal output from the circuit and determines whether the corresponding AFT signal is within a certain frequency range. If present in the AFT signal frequency determination step to return to the AFT signal level determination step, and if the AFT signal is not present within a predetermined frequency in this AFT signal frequency determination step for the corresponding channel that is fixedly set according to each channel in the microcomputer A dynamic auto fine tuning method using a microcomputer, comprising a fixed local oscillation frequency output step of outputting local oscillation frequency data to a phase locked loop IC.