KR19980068547U - Tuner for TV signal reception - Google Patents

Abstract

The present invention improves the sound quality of the FM-detected audio signal by reducing the amplitude modulation received by the audio intermediate frequency signal by the video signal.

To this end, a frequency converter 5 comprising a mixer 3 and a local oscillator 4, and a frequency converter 2 having the frequency converter 5, which are tuned in a television signal of UHF band or VHF band. Converts the television signal into an intermediate frequency signal by the frequency converter 5 of the frequency converter 2, detects the intermediate frequency signal with an image detector 8, outputs a video signal, and simultaneously outputs the image signal. From the audio intermediate frequency filter 9 to output the audio intermediate frequency signal.

Description

Tuner for TV signal reception

The present invention relates to a tuner for receiving a television signal, for example, to a tuner for receiving a television signal, which can be incorporated into a car navigation system or a car audio system and can listen to voice with excellent sound quality equivalent to that of an FM radio broadcast.

A conventional television signal reception tuner will be described with reference to Figs. First, the television signal received by the antenna 31 or the like in FIG. After the intermediate frequency signal is amplified by the intermediate frequency amplifier 34, a predetermined selectivity characteristic (frequency response characteristic) is given by the SAW filter 35, which is an intermediate frequency filter, and is input to the integrated circuit detector 36. .

The detector 36 has an image detector circuit 37, a 4.5 MHz detector circuit 38, an FM detector circuit 39, and the like. The image intermediate frequency signal is detected by the image detector circuit 37 to detect the image signal V. ) Is withdrawn. On the other hand, the audio intermediate frequency signal is input to the 4.5MHz detection circuit 38 together with the video intermediate frequency signal, where the first audio intermediate frequency signal of 4.5MHz is extracted, and is detected by the FM detection circuit 39 to generate an audio signal ( A) is to be withdrawn.

6 is an example of the frequency response characteristic at the point R which is the output point of the frequency converter 33. This frequency response characteristic is imparted by a not shown tuning circuit provided in the frequency converter 33 at the rear end of the frequency converter 32. As is clear from the frequency response characteristic of FIG. 6, the level of the image intermediate frequency signal P (58.75 MHz in Japanese specification) and the color subcarrier signal C (55.17 MHz in Japanese specification) is set to be approximately 1.5 dB from the peak. In addition, the level of the audio intermediate frequency signal S (54.25 MHz in Japanese specification) is set so that the attenuation is approximately 4 dB from the peak.

7 is an example of the frequency response characteristic at the point T which is the output point of the SAW filter 35, and the frequency response characteristic of the SAW filter 35 is shown as it is. The level of the video intermediate frequency signal P and the color subcarrier signal C is attenuated by approximately 6 dB and 2.5 dB from the peak, respectively, and the audio intermediate frequency signal S is attenuated by approximately 18 dB from the peak. In particular, the attenuation of the speech intermediate frequency signal S is greatly attenuated so that a bit due to interference between the color subcarrier signal C and the speech intermediate frequency signal S does not appear on the screen.

In the television signal receiving tuner, the frequency response characteristic (see Fig. 7) of the intermediate frequency band at the point T, which is the input terminal of the detector 36, is the level of the audio intermediate frequency signal S in order to suppress the bit generation during image detection as much as possible. Is attenuating. On the other hand, the audio signal A obtained from the FM detection circuit 39 is obtained by the detection by the FM detection circuit 39, but before the FM detection is performed by the video intermediate frequency signal P and the audio intermediate frequency signal S 4.5. A bit signal of MHz, that is, a first voice intermediate frequency signal, is generated. Therefore, the audio signal is subjected to amplitude modulation by the video signal in addition to the noise, and since the level of the audio intermediate frequency signal S is low, the degree of amplitude modulation received by the audio signal is relatively large. As a result, the sound quality of the FM signal detected was deteriorated, and the sound quality of the FM signal was not satisfied.

Therefore, the TV tuner of the present invention can improve the sound quality of the FM detected audio signal by reducing the amplitude modulation received by the audio intermediate frequency signal by the video signal.

1 is a diagram illustrating the configuration of a tuner for receiving a television signal of the present invention;

2 and 3 are frequency response characteristics of the intermediate frequency band in the television tuner of the present invention,

4 is a frequency response characteristic diagram of an audio intermediate frequency filter in a television tuner of the present invention;

5 is a diagram for explaining the configuration of a conventional TV signal receiving tuner;

6 and 7 are frequency response characteristics of the intermediate frequency band in the conventional television tuner.

※ Explanation of symbols for main parts of drawing

1 antenna 2 frequency converter

3: mixer 4: local oscillator

5: frequency converter 6: intermediate frequency amplifier

7: SAW filter 8: Image detection circuit

9: voice intermediate frequency filter 10, 12: condenser

11: inductance element 13: voice intermediate frequency amplifier

14 second SAW filter 15 second mixer

16: second local oscillator 17: second frequency converter

18: FM detection circuit

In order to solve the above problems, a television signal reception tuner of the present invention comprises a frequency converter consisting of a mixer and a local oscillator, and a frequency converter having the frequency converter, and a television signal of a channel selected from among UHF or VHF band television signals. The frequency converter converts the frequency into an intermediate frequency signal by the frequency converter, detects the intermediate frequency signal and outputs an image signal, and outputs an audio intermediate frequency signal from the intermediate frequency signal.

In addition, the tuner for receiving a television signal of the present invention outputs the audio intermediate frequency signal through an audio intermediate frequency filter passing through the frequency of the audio intermediate frequency signal.

In addition, the tuner for receiving a television signal of the present invention prevents passage of local oscillation signals output by the local oscillator and the harmonics of the local oscillation signals to the voice intermediate frequency filter.

Also, the tuner for receiving a television signal of the present invention is provided with an FM detection circuit for FM detection of the audio intermediate frequency signal, and the audio signal is extracted from the FM detection circuit.

In addition, the tuner for receiving a television signal according to the present invention is to perform FM detection after frequency converting the frequency of the voice intermediate frequency signal to 10.7MHz.

(Example)

Hereinafter, a tuner for receiving a television signal of the present invention will be described with reference to FIGS. 1 to 4. First, Fig. 1 is an explanatory view of the configuration of a tuner for receiving a television signal of the present invention. The television signal of the UHF band or the VHF band is received by the antenna 1 and then input to the frequency converter 2. The frequency converter 2 has a frequency converter 5 composed of a mixer 3 and a local oscillator 4. The frequency converter 2 selects a television signal received from the UHF band or the VHF band television signal inputted by a tuning circuit (not shown) in the frequency converter 2, and converts the selected television signal into a frequency converter (5). ) Is converted into an intermediate frequency signal and outputted.

Here, the frequency response characteristic (selectivity characteristic) at the point X which is the output point of the frequency converter 2 is as shown in Fig. 2, and the video intermediate frequency signal P (58.75 MHz in Japanese specification) and the color subcarrier are shown. The level of the signal C (55.17 MHz in Japanese specification) is set to attenuation within approximately 1.5 dB from the peak, and the level of the audio intermediate frequency signal S (54.25 MHz in Japanese specification) is approximately 4 dB from the peak. It is set to attenuation. This frequency response characteristic is imparted by a not shown tuning circuit provided at the rear end of the frequency converter 5 in the frequency converter 2.

The intermediate frequency signal output from the frequency converter 2 is amplified by the intermediate frequency amplifier 6 and then input to the SAW filter 7, which is an intermediate frequency filter, and is provided with a predetermined frequency response characteristic, thereby receiving an image detection circuit. It is input in (8). The frequency response characteristic at the point Y which is the output point of the SAW filter 7 is determined by the frequency response characteristic of this SAW filter 7 and, as shown in FIG. 3, the image intermediate frequency signal P and the color subcarrier signal. The level of (C) is set to attenuate approximately 6 dB and 2.5 dB from the peak, respectively, and the level of the voice intermediate frequency signal S is set to attenuate about 18 dB.

The intermediate frequency signal from the SAW filter 7 is input to an image detection circuit 8 composed of a synchronous detection circuit or the like, where the image intermediate frequency signal P is image detected so that the image signal V is extracted.

On the other hand, the intermediate frequency signal output from the frequency converter 2 is also input to the voice intermediate frequency filter 9. The voice intermediate frequency filter 9 is constituted by, for example, a capacitor 10 and an inductance element 11 connected in series with each other, and a capacitor 12 connected between one end and a gland of the inductance element 11. have. Then, the series resonance frequency of the capacitor 10 and the inductance element 11 approximately matches the frequency of the audio intermediate frequency signal S, and at a frequency higher than the frequency of the audio intermediate frequency signal S, the inductance element 11 and The capacitor 12 constitutes a low pass filter having a cut-off frequency at 103 MHz, for example.

By configuring the audio intermediate frequency filter 9 in this manner, the frequency response characteristic at the point Z, which is the output point thereof, shows that the audio intermediate frequency signal S is attenuated in the state where the video intermediate frequency signal P is attenuated as shown in FIG. Withdrawn. In addition, the local oscillation signal of the local oscillator 4 of the frequency converter 5 of the frequency converter 5 and its harmonics are generated by the low pass filter of the inductance element 11 and the condenser 12. 9) entry to the rear end is blocked.

The voice intermediate frequency signal S output from the voice intermediate filter 9 is amplified by the voice intermediate frequency amplifier 13 and then input to the second SAW filter 14 which is a second voice intermediate frequency filter. In particular, the second SAW filter 14 is configured to attenuate the video intermediate frequency signal P. The frequency response characteristic at the point Q, which is the output point of the second SAW filter 14, is shown in FIG. It has a steeper frequency response characteristic than the frequency response characteristic of 9) (not shown).

And the voice intermediate frequency signal S from the 2nd SAW filter 14 is 10.7MHz of 2nd voice intermediate | middle by the 2nd frequency converter 17 which consists of the 2nd mixer 15 and the 2nd local oscillator 16. The frequency signal is converted into a frequency signal, and the audio signal A is extracted by the FM detection circuit 18.

As described above, the tuner for receiving a television signal of the present invention extracts the audio intermediate frequency signal from the intermediate frequency signal output from the frequency converter 2 so as to detect the FM signal. By using a low frequency amplifier as it is, it is possible to simplify listening with excellent sound quality. Since the frequency of the second audio intermediate frequency signal is 10.7 MHz, the FM detector 18 can use a general-purpose detector used for the FM radio as it is.

As the tuner for receiving a television signal of the present invention, the audio intermediate frequency amplifier 13 to the FM detection circuit 18 may not be provided, but the audio intermediate frequency filter 9 may be provided. In this case, a slight change is made to the configuration of the FM radio in the car audio device or the like, and the FM radio side detects the audio intermediate frequency signal from the audio intermediate frequency filter 9, so that the audio of the television can be heard with excellent sound quality.

As described above, the tuner for receiving a television signal of the present invention comprises a frequency converter consisting of a mixer and a local oscillator, and a frequency converter having the frequency converter, and frequency converting a television signal of a channel selected from among UHF or VHF television signals. A negative frequency converter converts the frequency into an intermediate frequency signal, detects the intermediate frequency signal, outputs the video signal, and outputs the audio intermediate frequency signal from the intermediate frequency signal. In the case of assembling and the like, it is possible to listen to the television sound with excellent sound quality by detecting the voice intermediate frequency signal by using the FM radio of the car audio device or the like.

In addition, the tuner for receiving a television signal of the present invention outputs an audio intermediate frequency signal through an audio intermediate frequency filter that passes through the frequency of the audio intermediate frequency signal, thereby reducing the influence of the video intermediate frequency signal, thereby obtaining high quality audio. Lose.

In addition, since the tuner for receiving a television signal of the present invention prevents passage of local oscillation signals output by the local oscillator and the harmonics of the local oscillation signal to the voice intermediate frequency filter, a local oscillation signal or its harmonics are input to the FM detector. This prevents unnecessary bit obstruction signals from occurring and thus obtains sound signals with good sound quality.

In addition, the tuner for receiving a television signal of the present invention is provided with an FM detection circuit for FM detection of the audio intermediate frequency signal, and a voice signal is extracted from the FM detection circuit, so that a low frequency amplifier such as a car audio device can be used as it is. You can hear the voice of a TV.

Also, since the tuner for receiving a television signal of the present invention converts the frequency of the voice intermediate frequency signal to 10.7 MHz and then detects FM, a general purpose FM detector used in an FM radio can be used as an FM detection circuit. It becomes easy to design a tuner for signal reception.

Claims (5)

A frequency converter which converts a television signal of a channel selected from a UHF band or a VHF band television signal with a local oscillation signal and converts the frequency into an intermediate frequency signal, and an image detection circuit for detecting the intermediate frequency signal and outputting a video signal. A video signal output terminal connected to an output terminal of the video detection circuit, an audio intermediate frequency signal extracting means for extracting an audio intermediate frequency signal from the intermediate frequency signal, and an audio intermediate connected to an output terminal of the audio intermediate frequency signal extracting means A tuner for receiving a television signal, comprising a frequency signal output terminal. The method of claim 1, And said voice intermediate frequency signal extracting means is a voice intermediate frequency filter which passes said voice intermediate frequency signal and blocks said harmonics of said local oscillation signal and said local oscillation signal. A frequency converter which converts a television signal of a channel selected from a UHF band or a VHF band television signal with a local oscillation signal and converts the frequency into an intermediate frequency signal, and an image detection circuit for detecting the intermediate frequency signal and outputting a video signal. And a video signal output terminal connected to an output terminal of the video detection circuit, an audio intermediate frequency signal extracting means for extracting an audio intermediate frequency signal from the intermediate frequency signal, and FM detecting the audio intermediate frequency signal to output an audio signal. And an FM signal detection circuit and an audio signal output terminal connected to an output terminal of the FM detection circuit. The method of claim 3, And said voice intermediate frequency signal extracting means is a voice intermediate frequency filter which passes said voice intermediate frequency signal and blocks said harmonics of said local oscillation signal and said local oscillation signal. The method of claim 3, And a FM signal is detected after frequency conversion of the frequency of the voice intermediate frequency signal to 10.7 MHz.