JPH07176992A - Channel selection device - Google Patents

Abstract

PURPOSE:To provide the channel selection device in which the effect of detuning such as drift due to a secular change or a temperature or a moisture on a tuning voltage stored in advance in a memory is prevented. CONSTITUTION:Tuning voltage data corresponding to each channel are stored in advance in a nonvolatile memory 8, and when the operator selects a channel, data are read from the nonvolatile memory 8 and a tuning voltage is outputted from a tuning voltage control circuit 7. On the other hand, an AFT signal is outputted from an AFT circuit 5, which corrects detuning. Simultaneously a drift arithmetic operation circuit 9 detects an upper limit and a lower limit or a voltage at a predetermined interval by using the tuning voltage after the detuning correction as a drift and the maximum value is stored in the nonvolatile memory 8. When a channel is selected again, the tuning voltage stored in the nonvolatile memory 8 is averaged with the upper limit voltage and the lower limit voltage and the result is outputted as the tuning voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection device for storing a broadcast signal of television broadcast, radio broadcast or the like in a memory for each position in advance so that a desired channel can be directly selected. It is a thing.

[0002]

2. Description of the Related Art Conventionally, for example, as a method of selecting a television broadcast, an operator stores tuning voltage data in a predetermined position of a non-volatile memory for each reception channel of a broadcast signal, and the position is stored. If you select
There is a so-called voltage synthesizer system in which a desired channel is selected (for example, such a technique is disclosed in Japanese Patent Publication No. 53-12321 (H03J).
It is a known technique as shown in 5/04)).

Needless to say, such a point is a technique which is naturally used not only for television broadcasting but also for radio broadcasting.

By the way, in the tuning system by this voltage synthesizer system, the data of the tuning voltage stored in the non-volatile memory is read out, added to the tuner as the tuning voltage, and then drawn into the tuning point of the receiving channel by the AFT circuit. It keeps that state as well.

The AFT circuit detects the video carrier frequency, creates a DC voltage having an S-shaped curve centered on the tuning point, and superimposes this DC voltage on the tuning voltage to obtain the tuning point of the receiving channel. It is pulled in and kept in that state (this AFT circuit is edited by the Japan Broadcasting Corporation, published on April 1, 1983, "NH
K-Color Television Textbook (above), pp. 99-102
It is a known technique as described on the page).

However, the performance of this AFT circuit is about ± 1 MHz with respect to the deviation of the tuning point due to the drift of the tuning voltage. On the other hand, with respect to the deviation of the tuning point, the tuning voltage, the AFT circuit, the local oscillation circuit of the tuner, etc., drift depending on the environment such as temperature / humidity.

Further, when the broadcast signal is searched and the reception channel is stored, if it is not searched automatically but an attempt is made to search and store manually, it is not always stored at the tuning point.

In such a situation, even if the broadcast signal is searched once and the reception channel is stored, when viewed in units of one year / two years, the width of the deviation of the tuning point becomes large and exceeds the pull-in range of the AFT. There is a risk that In this case, it is necessary to search the broadcast signal again and store the reception channel. On the other hand, some users may misunderstand that it is a failure.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned drawbacks, the present invention provides a voltage which prevents a tuning voltage stored in a memory from being affected by a tuning deviation such as a change with time or a drift due to temperature and humidity. It is an object of the present invention to provide a synthesizer type tuning device.

[0010]

According to the present invention, tuning voltage data for each receiving channel is stored in advance for each position of a non-volatile memory, and when an operator selects a position corresponding to a desired channel, the above memory is stored. In the tuning device that reads the tuning voltage data stored in, and outputs the tuning voltage to the tuner to receive the desired channel, discriminate the frequency of the received signal of the selected receiving channel, and then from the tuning point. Fine tuning (AFT) means for compensating for the deviation of the frequency, and means for storing the corrected tuning voltage corrected by the automatic fine tuning means in the memory as the corrected tuning data with respect to the tuning voltage data stored in the memory. Then, when the operator again specifies the channel, the average value of the tuning voltage data and the corrected tuning voltage data stored in the memory is output. And voltage data, a channel selection apparatus comprising a means for supplying a tuning voltage based on the data to the tuner.

[0011]

According to the present invention, with the above configuration, the tuning voltage tuned by the AFT due to the deviation of tuning due to drift or the like is stored in the nonvolatile memory as the corrected tuning voltage data, and then the same channel is stored in the memory when the channel is selected. An average value of the tuning voltage data and the corrected tuning voltage data stored in advance is output as tuning voltage data.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which 1 is a high frequency amplifier, 2 is a mixing circuit, 3 is a local oscillation circuit, and 4 is a circuit.
Is an image intermediate frequency circuit, 5 is an AFT circuit, 6 is an operation unit, 7
Is a tuning voltage control circuit, 8 is a non-volatile memory, 9 is a drift amount calculation circuit, and 10 is a synchronization signal presence / absence determination circuit.

First, the operator adjusts the tuning voltage corresponding to each reception channel in advance while watching the screen on the operation unit 6,
The tuning voltage control circuit 7 writes the tuning voltage as data to a desired position of the nonvolatile memory 8.

The memory map structure of the non-volatile memory 8 is as follows.
As shown in FIG. 2, tuning voltage data is stored at a determined position, that is, a memory address. For example, addresses 00 and 01 are position 1, address 0
6, 07 is position 2, and addresses 0C, 0D are position 3. The number of positions is determined by the capacity of the memory, and tuning voltage data is stored in each position. The address areas of 00 and 01 have 14 bits of tuning voltage data, but the address area has only 8 bits, so that the data is separated into upper and lower data.

As described above, the operator can write tuning voltage data of an arbitrary channel in each position in the nonvolatile memory 8. For example, tuning voltage data is written such that position 1 has 2 channels, position 2 has 4 channels, and position 3 has 5 channels.

In the above, the operator adjusts the tuning voltage data and writes it in the non-volatile memory 8. For example, Japanese Patent Publication No. 56-49493 (H03J5 / 0).
As described in 2), the tuning point may be automatically detected and the tuning voltage data may be stored in the nonvolatile memory 8. In this case, the method of detecting the tuning point is, for example, Japanese Patent Publication No. 59-22407 (H04J7 / 0).
As known in 2), the AFT circuit 5 and the sync signal presence / absence determining circuit 10 detect the tuning point.

When the tuning voltage data is stored in the non-volatile memory 8, the upper limit value and the lower limit value of the drift amount, which is the correction tuning voltage data due to the drift change, are stored in each position of the non-volatile memory 8. For example, as shown in FIG. 2, the upper limit value is stored in 02, 03 and the lower limit value is stored in 04, 05 at the position of 00, 01. The reason why two addresses are allocated is for the same reason as described above.

However, since there is no drift at the stage of storing the tuning voltage in the non-volatile memory 8, the same data as the tuning voltage data is stored in the upper and lower limits of the drift of the non-volatile memory 8 at this time. (See FIG. 5).

Since the tuning voltage data is written in the nonvolatile memory 8 in advance in this way, when the operator designates the position corresponding to the desired channel, the tuning voltage control circuit 7 causes the tuning voltage data to be read from the nonvolatile memory 8. Is read and a tuning voltage is supplied to the local oscillator circuit 3 to change the oscillation frequency. Then, the high frequency signal obtained from the antenna is amplified by the amplifier circuit 1 and mixed by the mixing circuit 2 to obtain a television signal.

As for the television signal, the IF signal of the television signal is output by the video intermediate frequency circuit 4. This I
The AFT signal is taken out from the F signal by the AFT circuit 5 and is supplied as a DC voltage to the tuning voltage control circuit 7 to change the tuning voltage to the local oscillation circuit 3 to lead it to the regular tuning point.

If the tuning point by the AFT circuit 5 deviates from the tuning voltage, the drift data as the corrected tuning voltage data is stored in the memory 8 at that position. The flow chart of the storage is shown in FIG.

First, when the channel is selected, the drift amount is checked once every 160 ms while the channel is being received. That is, if 160 ms has elapsed (S
1), the 160 ms timer is reset (S2), the presence / absence of synchronization is determined, and if synchronization is present, the process proceeds to the drift amount determination process. If there is no synchronization signal, the determination process is not performed (S3). .

For example, when there is no synchronization signal, it means that the tuning point is not in the vicinity, and the drift amount with respect to the tuning point cannot be determined. However, when there is a synchronization signal, the AFT voltage is judged, and when it is, for example, 3.5 V or more, the reception frequency is largely drifted to the lower side of the tuning point (S4), and the tuning voltage control is performed. The circuit 7 raises the tuning voltage data by one step (S8).

Next, when the AFT voltage is 2.5 V or less, it means that the receiving frequency has largely drifted to the higher point with respect to the tuning point (S5), and the tuning voltage is lowered by one step (S9).

The AFT voltage is 2.5V to 3.5V.
When it is within the range, the drift amount calculation circuit 9 operates as follows. That is, the drift upper limit value data (for example, 5 V) corresponding to the corrected tuning voltage data stored in the non-volatile memory 8 and the tuning voltage data (for example, 5.1 V) that is set to the tuning point when drifting. The values are compared (S6), and if the voltage is higher than the upper limit value, the value (5.1 V) is set as the upper limit value and stored again (S1).
0).

If it is lower than the upper limit value (5.0V), the lower limit value (4.9) stored in the non-volatile memory 8 is used.
V) (S7), and if lower than the lower limit value (4.8).
V), the value is set as the lower limit and is newly stored (S1).
1). However, if it is within the lower limit value to the upper limit value, the contents of the nonvolatile memory 8 are not changed.

In this way, the tuning voltage data corresponding to the upper and lower limits of the drift are stored in the non-volatile memory 8, and when the same channel is newly selected, the tuning voltage control circuit 7 shows in FIG. Tuning voltage data stored in the non-volatile memory 8 corresponding to the selected position,
The drift upper limit value and lower limit value are read out, the average value is calculated and output as tuning voltage data, and the channel is received.

[0028]

According to the present invention, when a broadcasting channel is first selected and a drift occurs with respect to the tuning point due to changes in various conditions from the stored state, re-tuning is performed.
The AFT can be operated at a tuning voltage closer to the actual tuning point than the initially stored tuning voltage, and the AFT can be brought into the pull-in range.

This reduces the need to select the broadcast channel signal again and store the reception channel in the memory again. Also, depending on the user, it is possible to prevent misunderstanding.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a map of a nonvolatile memory of the present invention.

FIG. 3 is a diagram showing a flowchart of the present invention.

FIG. 4 is a diagram showing a flowchart for outputting a tuning voltage at the time of channel selection according to the present invention.

FIG. 5 is a diagram showing a flowchart of a storage operation in the memory at the time of initial setting of the present invention.

[Explanation of symbols]

 1 High Frequency Amplifier 2 Mixing Circuit 3 Local Oscillation Circuit 4 Video Intermediate Frequency Circuit 5 AFT Circuit 6 Operation Unit 7 Tuning Voltage Control Circuit 8 Nonvolatile Memory 9 Drift Amount Calculation Circuit 10 Synchronous Signal Presence / Absence Discrimination Circuit

Claims (3)

[Claims] 1. Tuning voltage data for each reception channel is stored in advance for each position of a non-volatile memory, and when the operator selects a position corresponding to a desired channel, the tuning voltage data stored in the memory is stored. A tuning device that reads out and outputs the tuning voltage to the tuner to receive the desired channel, discriminates the frequency of the received signal of the selected reception channel, and corrects the deviation from the tuning point. (AF
T) means, means for storing the corrected tuning voltage corrected by the automatic fine tuning means in the memory as the corrected tuning data for the tuning voltage data stored in the memory, and the operator re-specified the channel. At this time, a tuning device comprising: an average value of the tuning voltage data and the corrected tuning voltage data stored in the memory as output tuning voltage data, and means for supplying the tuning voltage to the tuner based on the data. 2. The tuning device according to claim 1, wherein an upper limit value and a lower limit value of the corrected tuning voltage data for the regular tuning point are stored in the memory. 3. The tuning device according to claim 1, wherein when the channel designated by the operator is received, the corrected tuning voltage data is updated every predetermined time.