JPS5821984B2 - Signal discrimination circuit for automatic channel selection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal discrimination circuit suitable for a television receiver equipped with an automatic channel selection device that automatically performs channel selection operations.

In general, television receivers often select channels by operating the circuit of the channel heirs, but the channel selection operation is cumbersome and troublesome, especially when continuously variable tuning operations are used, such as when selecting UHF channels. .

In addition, in the case of television receivers equipped with touch-type or remote-control type tuning devices, the tuning operation when changing channels is easy, but the preset tuning operation at the time of initial installation is still troublesome and requires inexperienced amateurs. It was difficult.

Therefore, an automatic channel selection device that automatically performs such a tuning operation has been proposed, but the present invention relates to a signal discrimination circuit used in such an automatic channel selection device, and relates to a signal discriminator circuit used in such an automatic channel selection device, and relates to a signal discrimination circuit that is used in such an automatic channel selection device. In order to reliably receive television signals that arrive in confusion, a circuit is provided that determines whether a received signal is a regular television signal or not.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings, but first an automatic channel selection device in which a signal discrimination device according to the present invention is used will be described.

FIG. 1 is a diagram showing an example of a television receiver equipped with an automatic channel selection device, where 1 is an antenna, 2 is a tuner, 3 is an intermediate frequency circuit, 4 is an AFT circuit, and 5 is an antenna. is a video circuit, 6 is a synchronization separation circuit, 7 is a deflection circuit, 8
is a picture tube, and these constitute a normal television receiver.

Here, a start/stop circuit 9, a tuning voltage generating circuit 10, a memory circuit 11, and a signal discriminating circuit 12 are added to these to form an automatic tuning device.

When a search start command (automatic tuning command) is given to the start/stop circuit 9 during preset tuning, a search start pulse is generated from the circuit 9 and supplied to the tuning voltage generation circuit 10.

At this time, the tuning voltage generating circuit 10 generates a sweep voltage or staircase voltage that gradually increases or decreases, and this is supplied as a tuning voltage to the tuning diode of the tuner 2 via the memory circuit 11.

Therefore, at this time, the receiving frequency at the tuner 2 is gradually changed.

When the television radio waves of the current channel are received in this way, a television video signal is derived from the intermediate frequency circuit 3, and in conjunction with this, a synchronization signal is derived from the synchronization separation circuit 6 and supplied to the start/stop circuit 9.

On the other hand, the AFT detection output from the AFT circuit 4 is also supplied to the start/stop circuit 9.

In particular, since the polarity of the AFT detection output voltage changes when the television radio wave is precisely received, this time is detected and the search stop pulse and vertical synchronization signal are generated from the start/stop circuit 9.

Here, the vertical synchronization signal also serves as a search stop pulse.

The search stop pulse is supplied to the tuning voltage generation circuit 10, and accordingly, the sweep wave (or staircase wave) generation operation is stopped in the generation circuit 10. From then on, this instantaneous voltage is held, and this is stored in the memory as the tuning voltage. The signal is supplied to the tuner 2 via the circuit 11.

On the other hand, at this time, the vertical synchronizing signal derived from the start/stop circuit 9 is supplied to a signal discriminating circuit 12, where it is discriminated whether or not the signal is a regular television signal.

The signal discrimination circuit 12 counts the number of synchronization signals as already proposed in, for example, Japanese Patent Application No. 52-51528 or No. 52-51531, and determines whether a predetermined number of synchronization signals are present during a certain period of time. It is determined whether or not it is a regular television signal depending on whether or not the signal is a regular television signal. If it is determined that the signal is a regular television signal, a memory command is derived from the signal discriminating circuit 12, and the command is supplied to the memory circuit 11. As a result, in the memory circuit 11, the tuning voltage generation circuit 10
The tuning voltage supplied by the controller is memorized.

However, when the pseudo synchronization signal is derived from the start/stop circuit 9, it is detected by the signal discrimination circuit 12, and the circuit 12 generates a re-search start pulse.

This pulse is supplied to the start/stop circuit 9, whereby the same operation as when the above-mentioned first search start command was given is repeated again.

In this way, the same operation is repeated until a regular television vertical synchronization signal is derived from the start/stop circuit 9, that is, until correct reception is performed by the tuner 2, and only when the reception state of a certain channel is accurately achieved can signal discrimination be performed. A memory command is issued from the circuit 12, the tuning voltage at this moment is stored in the memory circuit 11, and thereafter this memory voltage is supplied from the memory circuit 11 to the tuner 2.

Once the preset tuning operation for a specific channel as described above is performed, when a tuning command is given to this memory circuit 11 by touch or remote control during normal tuning, the memory circuit 11 The memory voltage is supplied to the tuner 2 as a tuning voltage, and this channel is selectively received.

Although only one memory circuit 11 is shown here, similar memory circuits are actually provided for the number of preset stations, and the tuning voltage stored in each memory circuit is used for preset tuning operation (automatic tuning). The operations) are performed sequentially in the same manner as described above.

By the way, the signal discrimination circuit 12 used in the above-mentioned automatic channel selection device counts the number of synchronization signals and discriminates whether it is a regular television synchronization signal or not. Vertical synchronization signal with a sag as shown in Figure 4a (this occurs due to an abnormality in the transmission system, repeater, etc.)
If this is supplied, there is a risk that one vertical synchronization signal will be miscounted as two.

The present invention was made especially in view of the above points, and in order to prevent such miscounts, a synchronizing signal is added to a one-shot pulse generator, the waveform is shaped into a wide signal, and then the synchronizing signal is This is to determine whether the synchronization signal is a regular synchronization signal or not.

FIG. 2 shows a specific embodiment of the present invention,
Here, 13 is a transistor Q□, a resistor R1゜R2, R8
, and a synchronous signal amplification section consisting of capacitors C1 and C2,
14 is a one-shot pulse generator consisting of OR gates OR1, OR2, resistors R4, R5, and capacitor C3;
5 is transistor Shima, resistor R,, R7, OR gate OR
3 and an inverter IN□.

Now, if a vertical synchronizing signal of negative polarity as shown in FIG. 3a is applied directly from the synchronizing divider circuit 6 in FIG. 1 or via the start/stop circuit 9 to the base of the transistor Q□ of the synchronizing signal amplifier 13. This is amplified and a positive synchronizing signal as shown in FIG. 3 is obtained from the collector and is supplied to the one-shot pulse generator 14.

Here, the synchronization signal is, for example, 4m5 as shown in FIG. 3C.
The waveform is shaped into a wide synchronization pulse of approximately ec and taken out from the OR gate OR2.

This synchronization pulse is then applied to a counter section (not shown), the number of which is counted, and it is determined whether or not it is a regular synchronization signal.

On the other hand, when a synchronizing signal with a sag is supplied to the signal amplifying section 13 as shown in FIG. is applied to the one-shot pulse generator 14, which produces a single synchronizing pulse as shown in FIG. 4C.

Therefore, at this time, the counter section does not miscount the synchronization signal.

In the above embodiment, the noise detection section 15 is provided, but this is supplied with a random noise signal unrelated to the synchronization signal from the synchronization separation circuit 6 or the start/stop circuit 9 as shown in FIG. 5a. As long as a regular synchronizing signal is supplied, transistor Q2 is in the cut-off state, but now as shown in Fig. 5a.
When a noise signal as shown in is supplied, since this noise signal includes a high-level positive polarity component, this positive polarity portion is detected and the transistor Q2 is turned on, and the collector of the transistor Q2 is turned on. A pulse output as shown in FIG. 5d is derived.

This is supplied to the agate OR3 in addition to the output of the pulse generator 14 shown in FIG. 5C, and as a result, a pulse signal as shown in FIG.

This signal is supplied to the start/stop circuit 9 as a re-search start pulse.

Note that even when a synchronization signal with a sag is supplied as shown in FIG. 4a, since this synchronization signal has a positive pulse signal between two negative pulses,
The transistor Q2 is turned on, and a negative pulse as shown in FIG. 4D appears from the collector Q2 of the transistor Q2, but during this period, the output of the one-shot pulse generator 14 is a positive pulse output as shown in FIG. 4C. Therefore, the re-search start pulse is not derived as the output of the noise detection unit 15 as shown in FIG. 4e (G).

Therefore, even when a synchronization signal with this sag is supplied,
The noise detection section 15 is completely unaffected, that is, without erroneously deriving a re-search start pulse, and only the synchronization signal whose waveform has been shaped into a wide width is supplied to the counter section, which counts the number of synchronization signals and calculates the signal. A determination is made.

According to the present invention, in the signal discrimination circuit that counts the number of synchronization signals as described above and determines whether or not the synchronization signal is a regular synchronization signal depending on whether a predetermined number of synchronization signals are present within a certain period of time, Since the synchronization signal is once applied to a one-shot pulse generator and shaped into a wide pulse, the number of synchronization signals is counted by a counter, so a synchronization signal with a sag may arrive due to an abnormality in the transmission system, etc. It is possible to accurately discriminate signals without miscounting.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an automatic channel selection device according to the present invention, FIG. 2 is a circuit configuration diagram of an embodiment of a signal discriminating circuit according to the present invention, and FIGS. 3 to 5 are each part of the embodiment. It is a signal waveform diagram. 1...Antenna, 2...Tuner, 3
......Intermediate frequency circuit, 4...AFT circuit, 5...Video circuit, 6...Period separation circuit, 7...Deflection circuit , 8... picture tube,
9...Start/stop circuit, 10...
... Tuning voltage generation circuit, 11 ... Memory circuit, 12 ... Signal discrimination circuit, 13 ... Synchronization signal amplification section, 14 ... One shot pulse Generating section, 15... Noise detecting section.

Claims (1)

[Claims] 1. In the signal discrimination circuit of the automatic tuning device, which counts the number of synchronization signals and determines whether or not it is a regular television signal based on whether or not a predetermined number of synchronization signals exist within a certain period of time, the synchronization signal is one-shot. 1. A signal discrimination circuit for an automatic channel selection device, characterized in that the number of synchronization signals is counted by a counter after waveform shaping in addition to a pulse generator.