JP2718461B2 - AFT device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AFT (automatic fine tuning) apparatus used for a radio receiver or a television receiver (VTR, television receiver).

[0002]

2. Description of the Related Art In a channel preset type tuner, a deviation occurs between a correct tuning point and a preset frequency due to drift due to temperature or the like. An AFT device is provided to correct this.

[0003] A in a conventional television signal receiver
As shown in FIG. 5, the FT device determines the presence or absence of a synchronization signal in the received video signal, and outputs a high-level voltage (FIG. 6B) when a synchronization signal is present, 58.75MHz IF signal carrier for signal
AF that outputs the amount of deviation from (in the case of Japan) by voltage
A tuning circuit includes a T voltage generating circuit 2 and a control unit 3 for digitally processing the detection signal and the AFT voltage to form a tuning correction voltage. The voltage is combined with the voltage by the adder 5 and supplied to the tuner 6. Reference numeral 7 denotes a digital processing unit of the AFT, and the digital processing unit 7 is provided with a control unit 3. Control unit 3
In the operation (1), when tuning is performed, first, the tuner 6 waits until it is stabilized, and then checks the synchronization determination output of the synchronization signal detecting circuit 1. The synchronization determination output goes high when a synchronization signal is obtained. When the synchronization determination is at the high level, the output voltage of the AFT voltage generation circuit 2 (FIG. 6)
Using (a)), it is determined whether the tuning voltage Vt (FIG. 6 (c)) is higher or lower than the optimum tuning point, and the tuning voltage Vt is corrected by several volts / step.

[0004]

However, in an AFT apparatus including such digital processing, the current tuning
From the point to the optimum tuning point, several volts / step in steps
Night both can be only in the beauty to change the tuning voltage
To, because the correction voltage becomes rough, the best by a change in each step the same
In many cases , the tuning point is skipped , resulting in a problem that the tuner cannot be adjusted to the optimum tuning point. In view of the foregoing, an object of the present invention is to provide an AFT apparatus that can adjust a tuner to an optimum tuning point.

[0005]

Means for Solving the Problems] To achieve the above object AFT apparatus of the present invention, the AFT voltage generating circuit, the A
The AFT voltage obtained from the FT voltage generation circuit is the desired tuning point
To show how much the AFT voltage is
Means having a membership function for a plurality of AFT voltages provided to the tuner provided to the tuner from the tuner.
A membership function relating to a correction amount for correcting a tuning voltage to be applied , wherein each membership function of the first means is provided.
A second means having a plurality of membership functions corresponding to the first and second means, and a member of a tuning voltage correction amount for an AFT voltage value output from the AFT voltage generation circuit based on the membership functions of the first and second means. a fuzzy controller to derive a correction amount of the tuning voltage from the center of gravity of the fuzzy set indicated by the membership functions determine the membership functions, and means for applying a voltage correction amount derived by the fuzzy controller to the tuning voltage, consist ing.

In the present invention, the AFT device is used for a television receiver. In this case, the control unit operates when a detection signal is output from the synchronization signal detection circuit.

[0007]

According to such a construction, the center of gravity of the fuzzy set indicates a desired correction amount, so that the tuner can be accurately tuned to the tuning point by adding the correction amount to the tuning voltage. Can be.

In FIG. 1 embodying the present invention, the same parts as those of the prior art shown in FIG. In this embodiment, the digital processing unit 7 is provided with a memory 8 that stores a membership function.
The memory 8 stores a plurality of membership functions 9 relating to the AFT voltage as shown in FIG. 2 and a plurality of memberships relating to the tuning voltage correction amount as shown in FIG.
Function (corresponds to the membership function for AFT voltage)
) Is stored. Figure 2
2.5V is the AFT voltage value at the optimum tuning point.
Is the AFT voltage waveform shown in FIG.
Above) and above the optimum tuning point of the frequency shown in the lower part of FIG.
It corresponds to the voltage at the intersection with the extended line. FIG.
5V is a high flat portion of the AFT voltage waveform in FIG.
Voltage. The low flat portion of the AFT voltage waveform is 0
It is a voltage close to V. The digital processing unit 7 is further provided with a fuzzy control unit 11, which operates when the synchronization determination signal from the synchronization signal detection circuit 1 is at a high level, and generates an AFT voltage. The tuning voltage correction amount at the time of the AFT voltage value given from the circuit 2 is subjected to a fuzzy operation using the respective membership functions stored in the two portions 9 and 10 of the memory 8, and the tuning voltage correction amount is output. I do. The tuning voltage correction amount is combined with the tuning voltage from the tuning device 4 in the adder 5 and then supplied to the tuner 6.

The fuzzy operation is performed as follows. First, FIG. 4 shows a process when the AFT voltage given from the AFT voltage generation circuit 2 is 3 V,
Among them, (A) to (E) show the membership functions related to the AFT voltage of 3 V, and (a) to (f) process the membership functions related to the tuning voltage correction amount based on the membership functions. 2 shows a method for calculating the correction amount of the tuning voltage.

First, when the membership function is very low with respect to the AFT voltage of 3 V as shown in FIG. 4A, the corresponding membership function of the tuning voltage correction amount (the tuning function) shown in FIG. The membership function of greatly reducing the voltage is not adopted. Similarly, in the case of a slightly lower membership function as in (B), the corresponding membership function of the tuning voltage correction amount (the membership function of slightly lowering the tuning voltage) in FIG. Adopted.

However, the membership function shown in (C) (a membership function with an optimum grade of 2.5 V) includes an AFT voltage of 3 V as an optimum point of 50%. As shown in the figure, the upper part 12 of the membership function relating to the tuning voltage correction amount corresponding to this is cut off, and the lower part 13 is adopted as the remaining form.
Similarly, since the membership function of (D) includes an AFT voltage of 3 V as an optimum point of 20%, as shown in (d), the corresponding upper part 14 of the membership function relating to the tuning voltage correction amount is changed. It is cut off and adopted while leaving the lower part 15. The membership function shown in FIG.
This is a very high membership function with respect to the AFT voltage of V, and the corresponding membership function of (e) (a membership function of increasing it greatly) is not adopted.

[0012] Out of the above, it has been adopted (c)
The membership function of (d) is overlapped with the membership function of (d) to form a membership function as shown in (f). Then, the barycenter (line bisecting the area) 16 of the fuzzy set in the membership function of (f) is obtained. In this case, 3V AF
The T voltage point is 0 V, and the voltage XV up to the center of gravity 16 based on the T voltage point is the tuning voltage correction amount to be obtained. The XV obtained in this manner changes according to the AFT voltage value, and always becomes the optimum correction voltage value.

[0013]

As described above, according to the present invention, there is an effect that the tuning deviation of the tuner can be corrected by the AFT device and adjusted to the optimum tuning point, which is extremely useful. Even if the tuner or the AFT circuit is changed, the AFT
The development period can be shortened because it can be dealt with only by changing the data of the membership function relating to the voltage and the membership function relating to the correction amount of the tuning voltage.

[Brief description of the drawings]

FIG. 1 is an AF in which the present invention is applied to a television receiver
Block diagram of T device

FIG. 2 is a diagram illustrating a membership function regarding an AFT voltage according to the present embodiment.

FIG. 3 illustrates members related to a tuning voltage correction amount according to the present embodiment.
Diagram showing ship function

FIG. 4 is a diagram for explaining the operation of a fuzzy control unit according to the embodiment;

FIG. 5 is a block diagram of a conventional AFT device.

FIG. 6 is a diagram illustrating digital processing of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Synchronous signal detection circuit 2 AFT voltage generation circuit 4 Tuning device 5 Adder 6 Tuner 7 Digital processing unit 8 Memory 11 Fuzzy control unit

Claims (2)

(57) [Claims] An AFT voltage generating circuit and an AFT voltage obtained from the AFT voltage generating circuit are desired.
It shows how much the AFT voltage is at the tuning point.
Means having a membership function for a plurality of AFT voltages provided for correcting the tuning voltage supplied to the tuner from the tuning device.
A membership function for the correction amount for the previous
A second means having a plurality of membership functions corresponding to each membership function of the first means, and an output from the AFT voltage generation circuit based on the membership functions of the first and second means. A fuzzy control unit for obtaining a membership function of a tuning voltage correction amount with respect to the obtained AFT voltage value and deriving a tuning voltage correction amount from the center of gravity of a fuzzy set indicated by the membership function; and a correction amount voltage derived by the fuzzy control unit. and means for applying to said <br/> tuning voltage, AFT apparatus consisting of. 2. A synchronous signal detecting circuit for detecting a synchronous signal in a received video signal and outputting the detected signal, and a synchronizing signal when a carrier of an IF signal related to the received video signal deviates from a regular value. the AFT voltage generating circuit for generating an AFT voltage representative, AFT voltage obtained from said AFT voltage generating circuit is desired
It shows how much the AFT voltage is at the tuning point.
Means having a membership function for a plurality of AFT voltages provided for correcting the tuning voltage supplied to the tuner from the tuning device.
A membership function for the correction amount for the previous
A second means having a plurality of membership functions corresponding to the respective membership functions of the first means, and operating when the synchronization signal detection circuit outputs a detection signal; A membership function of a tuning voltage correction amount with respect to the AFT voltage value output from the AFT voltage generation circuit is obtained based on the membership function of the two means, and a tuning voltage correction amount is derived from the center of gravity of the fuzzy set indicated by the membership function. and means for applying a fuzzy controller, the voltage of the correction amount derived by the fuzzy controller to the <br/> tuning voltage, AFT unit in the television signal receiver comprising a.