KR930008715B1 - Adaptive automatic fine tuning method and apparatus - Google Patents

Abstract

The fine tuning method is performed by the steps of determining a fine tuning, a first tuning process for incrementing a variable of a frequency to finish the tuning by recognizing the completion of the fine tune when a set variable is one, and a second tuning process for decrementing the frequency value when the variable of the fine tuning determination signal is not one in the first tuning process and the determination signal is of low level during the step of determining the fine tuning to finish the fine tuning by recognizing the completion of the fine tuning when the set variable is one or returning to the first tuning process when the set variable is not one, so that the tuning path differs according to an AFT signal logic and a maximum variable frequency step is tuned to shorten the tuning time and accurately perform the fine tuning.

Description

Fine Tuning Method Using Adaptive Control Method

1 is a fine tuning circuit diagram using an adaptive control method according to the present invention;

2 is an AFT logic conversion diagram in FIG.

3 is a flowchart for implementing a fine tuning method using an adaptive control method according to the present invention;

4 is an AFT search mode diagram in a fine tuning method using an adaptive control method according to the present invention;

5 is an AFT performance mode diagram in a fine tuning method using an adaptive control method according to the present invention.

* Explanation of symbols for main parts of the drawings

10: micom 20: tuner

30: Image demodulation circuit N: Variable of AFT logic transformation

M: fo ± 2 according to AFT logic state. Variable whose logic state changes at 25 MHz

The present invention relates to a video device such as a television and a video recorder. More specifically, the present invention relates to an adaptive control method that enables fine-tuning quickly and precisely by using an adaptive control method when the input broadcast and tuned channel are synthesized. It relates to a fine tuning method used.

In general, the minimum tuning frequency step of fine tuning is 31.25KHZ, and the fine tuning is performed while increasing or decreasing sequentially. Therefore, 4.5 MHZ ÷ 31.25KHZ = 144 steps when searching with the fine tuning mode in the fo ± 2.25MHZ range. In the above, fo is a frequency set by the microcomputer as the frequency of a certain channel. For example, in the case of NTSC-type VHS channel, two channels are 55.25MHZ and three channels are 61.25MHZ. As described above, when the right tuning point is found, the search time is very long and the tuning error is large.

The present invention has been made to solve this problem, and an object of the present invention is to change the tuning frequency to a large frequency range in a sequential control method, and to tune in a small frequency range in an adaptive control method in the vicinity of the forward tuning, so that fine tuning is performed quickly and accurately. The purpose of the present invention is to provide a fine tuning method using an adaptive control method.

The characteristics of the present invention for achieving this purpose is to set the initial value of each variable to transmit the frequency of the channel data set through the microcomputer when the desired channel is tuned, and to perform the mode to find the near tuning in tuning Determining fine tuning by giving a delay time until a fine tuning determination signal is generated; In the process of determining fine tuning, when the fine tuning determination signal is high level, the variable value of the frequency used for tuning is increased and the value of the increased frequency is subtracted from the value of the channel data frequency and the maximum threshold frequency is compared. When the increased frequency is greater than or equal to the judgment, tuning is terminated, and when the frequency of the channel data is greater than the variable value of the frequency, a predetermined delay time is given to determine whether the fine tuning determination signal is low level. A first tuning process that ends the tuning by considering it as fine tuned; When the variable value of the fine tuning determination signal is not 1 in the first tuning process and when the determination signal is low level in the fine tuning process, the frequency is decreased and then the reduced frequency is compared with the frequency of the channel data. The tuning is terminated when the channel frequency is greater than or equal to the channel frequency. When the reduced frequency is greater than the channel frequency, the tuning is terminated, and a predetermined delay time is given to determine whether the fine tuning determination signal is at a high level. In the fine tuning method using an adaptive method consisting of a second tuning process that ends the tuning and returns a first tuning process by changing the variable value at the maximum frequency if it is not 1.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the present invention will be described in detail.

Fig. 1 shows a fine tuning circuit using an adaptive control method according to the present invention. The tuner 20 of the frequency synthesizer (FS) method is applied to a microcomputer 10 that outputs tuning data-specific PLL (Phase Locked Loop) tuning data. Connect it. The tuner 20 is tuned by the tuning data of the microcomputer 10 to output an intermediate frequency (IF) signal. In addition, by connecting the image demodulation circuit 30 to the microcomputer 10 and the tuner 20, the intermediate frequency signal generated by the tuner 20 is converted into a video signal, and the built-in AFT (Auto Fine Tuning) detection circuit. The AFT signal is detected and output to the microcomputer 10 as a determination signal for fine tuning.

3 is a flowchart for implementing a fine tuning method using an adaptive control method according to the present invention. When a user tunes in a desired channel, the frequency of channel data set to the frequency of the channel in the microcomputer 10 is less than or equal to "fo". Perform a first routine L1 which sets an initial value for performing a mode for searching for near tuning and gives a delay time until an AFT signal is detected. .

The routine L1 performs an initial value setting step S2 of each of the variables T1, T2, N, M, and Δf1 used in tuning and gives a delay time (S3). After the delay time has elapsed, a step S4 of checking whether the AFT signal starts to be detected is tw. After the first routine L1 is performed, step S5 of checking the AFT logic state is performed. In the step S5, if the AFT logic is "high", increase the frequency and compare the increased frequency with fo, and if the increased frequency is greater than or equal to the end of the tuning, and if the fo is large, give the delay time after the AFT. If the AFT logic is "low" and the value of the variable of the AFT logic change (hereinafter, referred to as "N") is "1", the logic determines that it is tuned and performs a second routine (L2) to finish tuning. If the AFT logic is "low" in step S5 and if it is not "1" in step S12, the frequency is decreased, and then the tuning is finished if the fo is greater than or equal to fo by comparing the reduced frequency with fo. If the reduced frequency is large, after the delay time, the AFT logic is examined, and if the AFT logic is "high" and the N value is "1", it is determined that the tuning is completed and the third routine (L3) is performed.

This design as described above divides the fine tuning operation into an AFT search mode and an AFT execution mode. Details are as follows.

3 shows the AFT search mode when the fine tuning range is set to fo ± 2.25MHZ. In the initial tuning, the AFT search is performed in 125KHZ steps to shorten the time to fine tuning. Of course, the step range held at 125KHZ is variable and 2.25MHZ, which takes the maximum range of fine tuning in frequency, is also variable. The microcomputer 10 transmits the initial tuning data at the time t = 0 and then checks the logic of the AFT signal output from the image demodulation circuit 30 when the time after the delay time (S3) tw (S4). (S5). At this time, the logic of the AFT signal input to the microcomputer 10 is checked. At this time, if the logic of the signal input to the microcomputer 10 is "high", the microcomputer 10 increases the variable width of the tuning frequency by 125KHZ (S6) and gives a delay time of T2 (S9) Δt (20ms). After the time elapses (S10), check the logic of the AFT signal again.

In this order, increase the frequency to fo + 2.25MHZ while increasing the frequency to fo ± 2.25MHz, but if there is no logic change of the input AFT signal, decrease the frequency to fo-2.25MHZ and then increase to 125KHZ / △ t. If the AFT logic is not changed until the fo is changed to fo, only the AFT search mode is performed and the fine tuning is completed (S14).

That is, in the above case, since there is no broadcast, tuning is completed. On the other hand, if the logic is low when checking the AFT logic at t = tw, check the AFT logic by lowering the frequency to 125KHZ / △ t and if there is no logic change of the input AFT signal even if the frequency is reduced to fo-2.25MHZ, If the frequency is increased to + 2.25KHZ and then reduced to 125KHZ / △ t and changed to fo, if there is no AFT logic change, there is no broadcast, so only the AFT search mode is performed and fine tuning is finished (S14 ').

If the logic of the AFT signal changes from "high" to "low" or "low" to "high" during the AFT search mode, the AFT execution mode is performed and FIG. 5 shows that the AFT logic is "high" → " For example, assume that F1 is a time point at which a broadcast is located. At the time t2, the AFT logic of the microcomputer 10 changes from "high" to "low". In this case, the AFT logic change is shown in FIG. 2. In the case of increasing the tuning frequency in the AFT search mode, the intermediate frequency is generated in the “c” region of FIG.

At the time t2 in FIG. 4, the intermediate frequency is located in the region "b" in FIG. 2, and the AFT logic is in the "L" state (S11).

If the AFT logic is changed once, the microcomputer 10 operates as an AFT performance mode, and from this time, fine tuning is performed while changing the frequency variable step to 31.25KHZ / Δt to fine frequency (S13). From t2 to t1, the AFT logic is "low", so the frequency is lowered to 31.25KHZ / △ t (S6 ') and at the time t1, AFT logic changes from "low" to "high" (S11'), (S12 ' End tuning at). The tuning error generated in this way is always in the range of 31.25 KHZ as F1-2 in FIG.

Unlike the above, when the AFT logic is changed from "low" to "high" at the time of FIG. 5 t2, the intermediate frequency is located in the "b" region of FIG. 2 and the AFT logic is "high" (S11). '). If the AFT logic is changed once, the microcomputer 10 operates as an AFT performance mode. From this time, fine tuning is performed while changing the frequency variable step to 31.25KHZ / Δt to fine frequency (W13 ').

Since the AFT logic becomes high from t2 to t1 in FIG. 4, the frequency is increased to 31.25KHZ / Δt (S6), but at the time when the AFT logic changes from high to low at the time t1 (S11), (S11), ( The tuning ends in S12).

As described above, the present invention is a sequential control method in which the tuning path is changed according to the logic of the AFT signal used as the fine tuning decision signal for correct and accurate fine tuning when the input broadcast and the tuned channel are synthesized. The tuning frequency is changed to a large frequency range, and the adaptive control method reduces the tuning time by tuning the minimum variable frequency step of fine tuning to 31.25KHZ so that the tuning error range is always within 31.25KHZ. This will be improved.

Claims (1)

When tuning the desired channel, the delay time until the fine tuning judgment signal is generated by setting the initial value of each variable to transmit the frequency of the channel data set through the microcomputer and to perform the mode to find the near tuning area during tuning. Judging the subject fine tuning; In the process of determining fine tuning, when the fine tuning determination signal is high level, the variable value of the frequency used for tuning is increased and the value of the increased frequency is subtracted from the value of the channel data frequency and the maximum threshold frequency is compared. Tuning is terminated when the increased frequency is greater than or equal to, and when the frequency of the channel data is greater than the variable value of the frequency, time is given to a predetermined ray to determine whether the fine tuning determination signal is low level. A first tuning process of finishing the tuning by considering it as fine tuned; When the variable value of the fine tuning determination signal is not 1 in the first tuning process and when the determination signal is low level in the fine tuning process, the frequency is decreased and then the reduced frequency is compared with the frequency of the channel data. The tuning is terminated when the channel frequency is greater than or equal to the channel frequency, and a predetermined delay time is given when the reduced frequency is greater than the channel frequency to determine whether the fine tuning determination signal is at a high level. And tuning to the end, and if it is not 1, the fine tuning method using the adaptive control method comprising the second tuning step of changing the variable value at the maximum frequency and returning to the first tuning step.

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