JPH03261283A - Television set - Google Patents

Abstract

PURPOSE:To reduce the cost of the TV set, to simplify and miniaturize the TV set by devising the TV set such that an audio intermediate frequency signal is separated by a band pass filter from a video signal resulting from a video intermediate frequency signal subject to synchronization detection or the like at a PLL circuit and AM-detecting the resulting signal. CONSTITUTION:A video intermediate frequency signal VIF is subject to synchronization detection by a PLL circuit 5, and a signal resulting from integrating an output signal of the PLL circuit 5 and the video intermediate frequency signal VIF is inputted to an AM detection circuit 11 via a band pass filter 9. An SIF signal inputted to the AM detection circuit 11 is obtained from a video signal generated synchronously with the PLL circuit 5, then an excellent audio signal with less effect of the video signal is outputted. Thus, an AM detection IC used for the AM detection circuit 11 has a band characteristic to a degree of used for a conventional AM radio receiver and an SAW filter is not required for each frequency band. Thus, the cost of the TV set is reduced and the TV set is simplified and miniaturization is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television device suitable for receiving television signals transmitted by system L.

[Summary of the invention]

The present invention relates to a television device suitable for receiving a television signal transmitted as a system, in which a video signal obtained by synchronously detecting a video intermediate frequency signal in a PLL circuit, etc.
The audio intermediate frequency signal is separated by a bandpass filter and A
The configuration that performs M detection makes it possible to reduce the cost of the IC for AM detection, thereby reducing the cost of the device, as well as simplifying and downsizing the device.

[Conventional technology]

Currently, in the Republic of France, the standard television broadcasting system is
System L is adopted, and both the video signal and the audio signal are AM modulated and transmitted.

In this case, as understood from Fig. 2, the amplifier (10
From the IF multiplied signal (intermediate frequency signal) amplified by 0), the video intermediate frequency signal (VIP) is passed through the SAW filter (S
surface Acoustic Wave filter;
The audio intermediate frequency signal (SIF) is separated by the SAW filter (110), (13) provided separately for each frequency band.
0) directly separated (split carrier method),
The SIF signal is detected by an AM detection circuit (120) and converted into an audio signal.

Additionally, due to geographical conditions, it is also possible to receive TV broadcasts from System B and System G (for example, in West Germany).
Dual type television devices that can also receive television broadcasts from these systems are becoming popular.

Problems to be solved by the invention C] However, the SIF signal is not processed by the SAW filter (110
), (130), the split carrier method requires an expensive detection IC with a wide detection band to be used in the AM detection circuit (120), etc., making it difficult to reduce the cost of television equipment. It becomes a hindrance.

In addition, a SAW filter (110
), (130) (value 39.2 for CMtIzE and value 32.4 for [MHz:]), and especially in dual type television equipment, SIF Signal (FM)
Since an additional SAW filter is required to separate the two, there is a problem in that it hinders the simplification and downsizing of the device.

On the other hand, an intercarrier method using pseudo-synchronous detection is also considered, but since the audio signal is AM modulated in system L, the influence of the video signal is large and there is a problem that it cannot be put to practical use.

The present invention was made in view of the problems of the prior art, and its purpose is to reduce the cost of the device by using an inexpensive detection IC, and to
It is an object of the present invention to provide a television device which can be simplified and downsized by eliminating the need for a SAW filter for signal separation.

[Means to solve the problem]

In order to achieve the above object, the television device according to the present invention includes a PLL circuit in which a television signal transmitted by system L of the television broadcasting standard system is converted into a video intermediate frequency signal (VIP) and inputted. (5) and the above PLL circuit (5)
) and the video intermediate frequency signal (VIP>) are integrated and a video signal is output. It is characterized by comprising: a band-pass filter (9) to which the band-pass filter (9) is input; and an AM detection circuit (11) to which the output signal of the band-pass filter (9) is input and an audio signal is output.

[Effect]

In the television device according to the present invention, the video intermediate frequency signal is synchronously detected by the PLL circuit, and the signal obtained by integrating the output signal of the PLL circuit and the video intermediate frequency signal is input to the AM detection circuit via the bandpass filter. be done.

〔Example〕

Hereinafter, preferred embodiments of the television device according to the present invention will be described based on the drawings.

FIG. 1 shows the main electrical configuration of a television device to which the present invention is applied, in which an IF multiplied signal is amplified by a preamplifier (1), a video intermediate frequency signal ( VIP) and PLL circuit (5)
is input.

In the PLL circuit (5), the VIP signal taken in from the SAW filter (3) to the phase detector (5a) is passed through a low-pass filter (LPF>(5b)) to V CO (5c).
The output signal of the VCO (5c) is fed back to the phase detector (5a), and the integrator (7)
is input.

The integrator (7) receives the output signal V of the SAW filter (3).
IP is also input, and the video signal generated by integrating the output signal of these V CO (5c) and the VIP signal is input to a band pass filter (BPF) (9), and this B P F (9 ) has a band characteristic corresponding to the difference in video and audio carrier frequencies.

That is, in system L, the difference between the video frequency and the audio frequency is 6.5 CMHz, so the integrator (7 CMHz)
) from the output signal (video signal) of B P F (9)
Therefore, an AM signal (SIF) with a value of 6.5 [MHz]
is separated and input to the AM detection circuit (11) (intercarrier method), and the SIF signal is input to the PLL circuit (5).
Since the audio signal is obtained from a video signal generated in synchronization with the video signal, a good audio signal with little influence from the video signal is output.

Therefore, the AM detection IC used in the AM detection circuit <11) has a value of 10 [MH2
] It is sufficient if the band characteristics are approximately the same.

As explained above, in this embodiment, the VIF signal is
The signal synchronously detected by the L circuit and the VIP signal are sent to the integrator (
From the video signal accumulated and generated in step 7), B P F
The SIF signal is separated by (9), and the SIF signal is subjected to AM detection.

Therefore, since an inexpensive AM detection IC can be used in the AM detection circuit (11), it is possible to reduce the cost of the television device.

Further, since there is no need to provide a SAW filter for each frequency band as in the conventional case, it is possible to simplify and downsize the device.

Therefore, it is suitable for receiving television broadcasts from a plurality of systems, especially when using a hand-held television device.

〔Effect of the invention〕

As can be understood from the above description, in the television device according to the present invention, the output signal of the PLL circuit and the video intermediate frequency signal are integrated and input to the band pass filter, and the 8-power signal of the band pass filter is AM detection is performed.

Therefore, the band characteristics of the AM detection IC can be equivalent to that of an IC used in a general AM radio, and the cost of the device can be reduced.

Furthermore, since there is no need to separately provide a SAW filter for obtaining an audio intermediate frequency signal, it is possible to simplify and downsize the device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main electrical configuration of a preferred embodiment of the television apparatus according to the present invention, and FIG. 2 is an explanatory diagram of the configuration of a conventional system L receiving circuit. (3) is the SA'vV filter, (5) is the PLL circuit, (
7) is an integrator, (9) is a band pass filter, and 11) is an AM detection circuit.

Claims (1)

[Claims] A PLL circuit into which a television signal transmitted by system L of the standard television broadcasting system is converted into a video intermediate frequency signal and input; an output signal of the PLL circuit; and a video intermediate frequency signal an integrator that integrates the signals and outputs a video signal; a bandpass filter that has a band characteristic corresponding to the video/audio carrier frequency difference and that receives the video signal; and an output signal of the bandpass filter that outputs the video signal. A television device comprising: an AM detection circuit into which an audio signal is input and an audio signal is output.