JP2002369098A - PAL and SECAM-L compatible TV receivers - Google Patents

Abstract

(57) [Problem] To provide a television receiver compatible with the PAL and SECAM-L system in which buzz noise is unlikely to be generated even in a vehicle, where reception conditions vary greatly. SOLUTION: In a television receiver compatible with the PAL and SECAM-L system, an SIF tuning amplifier 6 is provided between a tuner 2 and a SIF SAW filter 3, and this SI
A signal obtained by amplifying only the SIF signal by the F tuning circuit 6 is input to the SIF SAW filter 3. For this reason, SI
Since the video signal component that cannot be removed only by the F-SAW filter 3 can be amplified / detected in a sufficiently reduced state, it is possible to prevent the buzz sound from being generated due to the video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PAL and SECAM-L television receiver capable of receiving television signals of the PAL system adopted in Europe and Australia and the SECAM-L system adopted in France. It is about the machine.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of a receiving circuit up to video and audio detection in a conventional television receiver capable of receiving the SECAM-L system. 8, 1 is an antenna, 2 is a tuner, 3 is an audio intermediate frequency (hereinafter, SI)
F), a SAW filter for image intermediate frequency (hereinafter referred to as PIF), 5
Is an IF amplification / detection circuit.

[0003] In FIG. 8, R
The F-TV signal is selected / frequency-converted by the tuner 2 and then output at point a as an intermediate frequency (hereinafter referred to as IF) signal having frequency characteristics as shown in FIG. In FIG. 9, “P” indicates PIF (38.9 MHz).
z), “C” is the color carrier frequency (about 34.5 MH)
z) and "S" are SIF (32.4 MHz), which have characteristics such that a video signal band for one channel is extracted.

Referring again to FIG. 8, the IF signal output from the tuner 2 includes an SIF SAW filter 3 for eliminating an adjacent channel television signal and a PIF SW filter.
It is supplied to the AW filter 4. Examples of the characteristics of the SAW filter are as shown in FIGS. 10A and 10B, and the PIF SAW filter 4 has such characteristics as to extract only the video signal as shown in FIG. 10A. And unnecessary S
The IF signal is dropped. On the other hand, SIF
As shown in FIG. 10B, the SAW filter 3 for S
The characteristic is such that only the IF signal is extracted, and unnecessary PIF signal components are reduced as much as possible.

[0005] Therefore, by passing through the SAW filter, only the audio signal component is obtained at point c in FIG.
At point d, only the video signal component is obtained, and IF
In the amplification / detection circuit 5, as a result of the amplification / detection under the optimum conditions by the dedicated circuits, the voice detection output and the f
A video detection output is obtained at the point. Thereafter, the video detection output is chroma-demodulated, and the video is reproduced on the display element by the synchronization signal processing, while the audio detection output is amplified and output from the speaker. Here, since the configuration of the chroma demodulation circuit, the audio circuit, and the like is well known, detailed description is omitted.

By the way, in such a receiving circuit, the video signal and the audio signal are separately amplified / detected under the optimum conditions. Therefore, in principle, the audio detection output should not be affected by the video signal at all. Actually, since the rejection performance of the SAW filter is limited, it is difficult to completely eliminate the influence of the video signal.

Further, since the sound signal of the SECAM-L system television signal is amplitude modulated (AM) like the video signal, it is destined to be more susceptible to the video signal than the frequency modulation (FM). In order to cope with such a fate of the broadcasting system, the transmission power ratio of the video signal and the audio signal of the broadcast wave is set to be larger than that of the NTSC or PAL television signal of the FM sound, and FIG. As shown, the spectrum of the received television signal also has a so-called P
The -S ratio is about 6 to 10 dB in the NTSC / PAL system, whereas the SECAM-L system is about 10 to 20 dB.
B is bigger.

[0008] When the television receiver is used in a vehicle,
Multipath deteriorates the reception condition, and adds an element in which the PS ratio fluctuates, which deteriorates the reception condition as compared with the reception by the stationary television receiver.

When the audio signal is affected by the video signal, the S / N of the audio detection output deteriorates, but the biggest deterioration phenomenon is the occurrence of video buzz. If the frequency components that are adversely affected by the video signal are high,
Although the sound quality can be reduced by the pass filter (LPF) without significantly impairing the sound quality, in the case of a buzz including a vertical synchronous component of 50 Hz, it is difficult to remove the buzz after detection output.

[0010]

As described above, the SEC
In AM-L television broadcasting, since both video and audio are AM, the audio signal is easily affected by the video signal in principle, and the PS ratio of the broadcast signal is large. It has a fate that buzz is likely to occur due to video signals.

An object of the present invention is to provide a television receiver compatible with the PAL and SECAM-L system in which a buzzing sound is less likely to occur even in a vehicular vehicle in which the receiving conditions vary greatly under such disadvantageous conditions. It is in.

[0012]

According to the present invention, there is provided a tuner for outputting an intermediate frequency signal of a desired channel band, and an audio intermediate frequency signal extraction for extracting an audio intermediate frequency signal from the intermediate frequency signal. For SA
In a PAL and SECAM-L system compatible television receiver having a W filter and a video intermediate frequency signal extraction SAW filter for extracting a video intermediate frequency signal from the intermediate frequency signal, the tuner and the audio intermediate frequency signal extraction An audio intermediate frequency tuning amplifier tuned to the audio intermediate frequency is provided between the audio intermediate frequency and the SAW filter.

In the present invention, since the audio intermediate frequency tuning amplifier circuit is provided between the tuner and the audio intermediate frequency signal extraction SAW filter, a signal obtained by amplifying only the audio intermediate frequency signal by the audio intermediate frequency tuning amplifier circuit. To the audio intermediate frequency signal extraction SAW filter. Therefore, it is possible to amplify / detect the video signal components which cannot be removed only by the audio intermediate frequency signal extraction SAW filter, in a sufficiently reduced state. Therefore, when receiving a TV signal of the SECAM-L system in which the audio signal is amplitude-modulated similarly to the video signal, it is possible to effectively improve the audio reception sensitivity and effectively reduce the buzz sound caused by the video signal. be able to. This is particularly effective when the PS ratio of the transmission signal is large or when the PS ratio is increased due to multipath during mobile reception. In addition, SECAM-
Even when receiving FM television audio other than L, it is possible to improve reception sensitivity and further improve audio quality.

In the present invention, it is preferable that the audio intermediate frequency tuning amplification circuit has a larger amplification degree at the audio intermediate frequency than that at the video intermediate frequency.

In the present invention, the audio intermediate frequency tuning amplifying circuit includes a tuning tank circuit in which a capacitance of a tuning capacitor is set to be larger than an input capacitance of the audio intermediate frequency signal extracting SAW filter. Is preferred. With this configuration, it is possible to prevent the input capacitance of the audio intermediate frequency signal extraction SAW filter from affecting the tuning frequency.

In the present invention, the audio intermediate frequency tuning amplifying circuit has, for example, a difference between the video intermediate frequency and the video intermediate frequency.
Three types of audio intermediate frequencies of 5 MHz, 6.0 MHz, and 6.5 MHz are used as amplification bands.

In the present invention, it is preferable that the audio intermediate frequency tuning amplifying circuit is configured to be capable of switching a tuning frequency in accordance with an audio intermediate frequency of a received television signal.

In the present invention, it is preferable that a video intermediate frequency trap circuit for attenuating the video intermediate frequency with respect to the output signal from the audio intermediate frequency signal extraction SAW filter is further provided. With this configuration, since the video signal component can be sufficiently removed and amplified / detected, when receiving a TV signal of the SECAM-L system in which the audio signal is amplitude-modulated similarly to the video signal, Generation of buzz sound due to the influence of the video signal can be further effectively reduced. Therefore, in particular, the P-
If the S ratio is large or if multipath during mobile reception
This is effective when the -S ratio increases.

In the present invention, the video intermediate frequency trap circuit is composed of, for example, a SAW filter element.

In the present invention, it is preferable that an impedance element is interposed between the audio intermediate frequency signal extracting SAW filter and the video intermediate frequency trap circuit. With this configuration, even when the audio intermediate frequency signal extraction SAW filter and the video intermediate frequency trap circuit are both configured by SAW filters,
Since these SAW filters are connected via an impedance element, it is possible to eliminate an influence on characteristics due to mutual interference between the SAW filters.

In the present invention, the video intermediate frequency trap circuit may be constituted by, for example, a series resonance circuit including an inductor and a capacitor.

According to the present invention, the attenuation band of the video intermediate frequency trap circuit includes a video intermediate frequency signal band excluding an audio intermediate frequency, or the attenuation band of the video intermediate frequency trap circuit is an image excluding an audio intermediate frequency. A configuration in which the Q of the video intermediate frequency trap circuit is set so as to include the intermediate frequency signal band can be adopted.

In the present invention, a plurality of trap circuits including at least the video intermediate frequency trap circuit may be provided so that an attenuation band of the video intermediate frequency trap circuit includes a video intermediate frequency signal band excluding an audio intermediate frequency. Good.

In this case, it is preferable to use a trap element in which the plurality of trap circuits are integrated.

[0025]

Embodiments of the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram relating to a receiving circuit of a television receiver to which the present invention is applied.
Note that the basic configuration of a receiving circuit of a television receiver to which the present invention is applied is the same as that of a conventional television receiver, and thus, portions having common functions are denoted by the same reference numerals.

In FIG. 1, the television receiver of the present embodiment has
An antenna 1, a tuner 2 for outputting an intermediate frequency (hereinafter, referred to as IF) signal of a desired channel band, and an audio intermediate frequency (hereinafter, referred to as SIF) signal from an IF signal. SIF SAW filter (SAW filter for extracting SIF signal) 3, which extracts the video intermediate frequency (hereinafter referred to as PIF
PIF SAW filter (PI
SAW filter for F signal extraction) 4 and IF amplification / detection circuit 5.

In the television receiver of the present embodiment, as in the prior art, the RF television signal received by the antenna 1 is tuned / frequency-converted by the tuner 2 and the frequency characteristic described with reference to FIG. Is output. In FIG. 9, "P" is PIF (38.9 MHz).
z), “C” is the color carrier frequency (about 34.5 MH)
z) and "S" are SIF (32.4 MHz), which have characteristics such that a video signal band for one channel is extracted.

Referring again to FIG. 1, the IF signal output from the tuner 2 includes an SIF SAW filter 3 for eliminating a television signal of an adjacent channel and a PIF SW filter.
It is supplied to the AW filter 4.

Here, the characteristics of the SAW filter are shown in FIG.
As described with reference to (a) and (b), the PIF S
As shown in FIG. 10A, the AW filter 4 has such a characteristic that only the video signal is extracted, and the unnecessary SI
The F signal is dropped. On the other hand, as shown in FIG. 10B, the SIF SAW filter 3 has such a characteristic that only the SIF signal is extracted, and unnecessary PIF signal components are reduced as much as possible.

By passing through such a SAW filter, an audio signal component is obtained at the point c in FIG. 1, while a video signal component is obtained at the point d. In the IF amplification / detection circuit 5, As a result of the amplification / detection under the optimum conditions by the dedicated circuits, an audio detection output is obtained at point e and a video detection output is obtained at point f. Thereafter, although not shown, the video detection output is chroma-demodulated and the video is reproduced on the display element by the synchronization signal processing, while the audio detection output is amplified and output as audio from the speaker.

The television receiver of this embodiment is different from the conventional one in that an SIF tuning amplifier 6 (audio intermediate frequency tuning amplifying circuit) for tuning to the SIF is provided between the tuner 2 and the input of the SIF SAW filter 3. That is the provision.

With such a circuit configuration, S
Since the level difference between the necessary SIF signal and the unnecessary PIF signal at the time of input to the IF SAW filter 3 has increased,
High-level video signal components that cannot be completely removed by the IF SAW filter 3 alone can be further reduced.
Therefore, the generation of the buzz sound due to the video signal component in the audio detection output can be reduced.

(Specific Example 1 of SIF Tuning Amplifier 6) FIG.
(A) and (b) are a circuit diagram showing a specific example of the SIF tuning amplifier 6 shown in FIG. 1 and an explanatory diagram showing an amplifier characteristic of the SIF tuning amplifier 6 in a television receiver to which the present invention is applied. is there.

In FIG. 2A, the SIF tuning amplifier 6
Comprises a bias resistor R1, R2, an emitter resistor R4, a transistor Q, and an SIF tank circuit 61 tuned to the SIF. The SIF tank circuit 61 includes a capacitor C2, an inductor L, and a damping resistor R of the tank circuit.
3 is comprised. The input of the SIF tuning amplifier 6 is connected to the IF output terminal (point a) of the tuner 2 via the capacitor C1, and the collector output of the transistor Q is connected to the SIF SAW filter 3 via the coupling capacitor C3.
Are connected to the unbalanced input terminal b.

Further, connected to the SIF differential input terminals c _c and c _d of IF amplifier / detector circuit 5 through a respective balanced output terminal c _a and c _b a SIF SAW filter 3 coupling capacitors C4 and C5 ing.

In the SIF tuning amplifier 6 having this circuit configuration,
At the tuning frequency, the collector impedance becomes maximum, and the gain determined by the ratio of the impedance Z to the emitter resistance R4 also becomes maximum at the tuning frequency. Therefore, SIF
As shown in FIG. 2B, the tuning amplifier 6 can be an amplifier having a peak-shaped frequency characteristic that has a maximum gain at the audio intermediate frequency S (S1, S2, S3).
Therefore, since the video intermediate frequency P can be dropped outside the band of the amplifier, its level B is equal to the audio intermediate frequency S.
Can be sufficiently reduced with respect to the level A (A1, A2, A3).

Therefore, in this embodiment, the SIF tuning amplifier 6
The SIF SAW filter 3 is used in combination with the SIF SIF S3 as described with reference to FIG.
Since the level of the video signal component (P) which cannot be completely removed by the AW filter 3 can be further reduced, the amplification of the audio signal and the AM
Detection can be performed. Therefore, in the SECAM-L system compatible television receiver, it is possible to suppress the occurrence of the buzz sound caused by the video signal, and to improve the sound receiving sensitivity.

In FIG. 2 (a), the tuning capacitor C2 is used to increase the Q of the tuning circuit and reduce the influence of the input capacitance of the SIF SAW filter 3 on the tuning frequency. It is desirable to set as large as possible.

FIG. 2B shows three waves S1, S2, and S3 as audio intermediate frequencies. This is because the television receiver can receive a PAL and SECAM-L television signal. Because it is configured to support
5. The PS frequency difference is 6.5 MHz (S1: 32.4 MHz) as well as 32.4 MHz in the ECAM-L system.
0 MHz (S2: 32.9 MHz), 5.5 MHz (S
3: 33.4MHz) PAL or SECAM F
This shows a case where M voice reception is also supported. That is, even in the case of FM audio, if the influence of the video signal causes buzz sound mixing, it is desirable that the number be small. By adopting the SIF tuning amplifier 6 as described above, it is possible to improve reception sensitivity and demodulate audio. Needless to say, this is effective in improving the quality of the product.

(Specific Example 2 of SIF Tuning Amplifier 6) FIG.
(A) and (b) are circuit diagrams showing another specific example of the SIF tuning amplifier 6 shown in FIG. 1 and a description showing the amplifier characteristics of the SIF tuning amplifier 6 in a television receiver to which the present invention is applied. FIG. FIG. 4 is an explanatory diagram showing the voltage-capacity characteristics of the variable capacitance diode used in the audio intermediate frequency tuning amplifier shown in FIG.

The configuration of the SIF tuning amplifier 6 of this embodiment is basically the same as that described with reference to FIG. 2A, except that the tuning frequency of the SIF tank circuit 61 is variable. Is different. That is, FIGS. 2 (a) and 2 (b)
In the embodiment described with reference to FIG. 3, the tuning point is fixed and used at any one of S1 to S3. In the embodiment, as shown in FIG. Since the tuning point of the circuit 61 is variable, the tuning frequency can be switched in accordance with the SIF signal of the receiving channel.

Specifically, in the SIF tank circuit 61,
A series circuit including a capacitor C6 and a variable capacitance diode VD is connected in parallel to a parallel resonance circuit including a capacitor C2 and an inductor L, and a DC voltage is applied to one end of the variable capacitance diode VD via a resistor R5 and a switching SW. It is. Here, C6 is a capacitor for the purpose of blocking direct current, and is set to a sufficiently large capacitance value compared to the maximum capacitance of the variable capacitance diode VD, and the equivalent capacitance of the series circuit composed of the capacitor C6 and the variable capacitance diode VD is reduced. , Is determined substantially only by the capacitance of the variable capacitance diode VD.

The other configuration is the same as that described with reference to FIG. 2A, so that the description thereof is omitted.

In the SIF tuning amplifier 6 configured as described above, when the voltage V1 is applied to the anode of the variable capacitance diode VD by, for example, the switch SW, the voltage-capacity characteristic of the variable capacitance diode VD is shown in FIG. The capacitance between the variable capacitance diode VD terminals is C _V1 . Accordingly, since the synthesized tuning capacitance becomes (C2 + C _V1 ), the SIF
The tuning frequency of the tank circuit 61 is equal to S1 shown in FIG.
Becomes

On the other hand, the variable capacitance diode VD
When the voltage V2 is applied, the capacitance of the variable capacitance diode VD
The quantity is C_V2Becomes Therefore, the combined tuning capacitance is (C2
+ C _V2), The tuning frequency of the SIF tank circuit 61
The number is S2 shown in FIG.

The voltage V3 is applied to the variable capacitance diode VD.
Is applied, the capacitance of the variable capacitance diode VD becomes C _V3
Becomes Therefore, the synthesized tuning capacitance is (C2 + C _V3 )
Therefore, the tuning frequency of the SIF tank circuit 61 is S3 shown in FIG.

Therefore, in the SIF tuning amplifier 6, FIG.
As shown in (b), switching of the switch SW causes SI
Since the tuning frequency of the F tuning amplifier 6 can be always adjusted to the frequency of the received signal, the effect of the present invention can be maximized.

The switching of the voltage applied to the variable capacitance diode VD can be relatively easily performed using the same microcomputer as long as the system controls the setting of the receiving area of the broadcast wave and the channel selection operation. It goes without saying that it can be controlled.

[Second Embodiment] FIG. 5 is a block diagram of a receiving circuit for another television receiver to which the present invention is applied.

The television receiver of this embodiment also has an antenna 1, a tuner 2 for outputting an IF signal of a desired channel band, and a SIF from the IF signal, as described with reference to FIG.
It has a SIF SAW filter 3 for extracting a signal, a PIF SAW filter 4 for extracting a PIF signal from an IF signal, and an IF amplification / detection circuit 5. Also in this embodiment, the tuner 2 is similar to that described with reference to FIG.
An SIF tuning amplifier 6 is provided between the SIF SAW filter 3 and the input of the SIF SAW filter 3. Therefore, SAW for SIF
Unnecessary SIF signal and unnecessary PI at input of filter 3
Since the level difference of the F signal increases, the high-level video signal component that could not be removed by the SIF SAW filter alone can be further reduced. As a result, the buzz sound due to the video signal component in the audio detection output can be reduced. The generation can be reduced.

Further, in this embodiment, a PIF trap circuit 7 is provided between the output of the SIF SAW filter 3 and the IF amplification / detection circuit 5. Here, the trap circuit resonates a signal of a predetermined frequency to remove or sufficiently reduce the signal.
Attenuates the video frequency signal from the SIF output output from the SIF SAW filter 3.

The other configuration is the same as that described with reference to FIG. 1, and the description thereof will be omitted.

In the television receiver of this embodiment configured as described above, the high-level video signal components that cannot be removed by the SIF tuning amplifier 6 and the SIF SAW filter 3 are converted to P
This can be further reduced by the IF trap circuit 7. For this reason, as a result, it is possible to reduce the detection of the video signal component being superimposed on the audio detection output, and thus it is possible to reduce the occurrence of the buzz sound due to the video signal component. That is, SE
In the CAM-L system, both the video signal and the audio signal are likely to interfere with each other by amplitude modulation (AM), and the transmission power ratio (P-
(S ratio) is originally large, so that it is more susceptible to the video signal than FM, so that no matter how much the video signal component is reduced relative to the audio signal component, it is not too much. Therefore, the circuit configuration as shown in FIG. 5 can improve the quality of the demodulated voice more than that described with reference to FIG.

(Specific Example 1 of PIF Trap Circuit 7) FIG.
(A) and (b) are a circuit diagram showing a specific example of the PIF trap circuit 7 (video intermediate frequency trap circuit) shown in FIG. 5 and the PIF, respectively, in the television receiver according to Embodiment 2 of the present invention. FIG. 4 is an explanatory diagram showing trap characteristics of a trap circuit 7;

As shown in FIG. 6A, in this embodiment, P
SAW filter element 71 as IF trap circuit 7
(SAW trap). Where SIF
Input terminal (point b) of the SAW filter 3 for
The signal output from the IF tuning amplifier 6 is input, and the balanced output terminals c _a and c _b are respectively provided with a resistor R11 and a capacitor C11, a resistor R12 and a capacitor C12.
There are connected in series, are input to the SIF differential input terminal of the IF amplifier / detector 5 c _c and c _d.

[0057] The connection point c _e of the resistor R11 and capacitor C11, and between the resistor R12 and the connection point c _f of the capacitor C12, SA as PIF trap circuit 7
A W filter element 71 is connected, and the PIF trap circuit 7 has a trap characteristic as shown in FIG.

For this reason, in the television receiver of the present embodiment, the SIF tuning amplifier 6 as illustrated in FIG.
The level of the video signal component (P) that cannot be completely removed by the SIF SAW filter 3 as exemplified in FIG. 0 (b) can be further reduced. Therefore, the amplification and AM detection of the audio signal can be performed in a state where the influence of the video signal is further eliminated, so that the occurrence of the buzz sound caused by the video signal can be suppressed.

In this embodiment, both the SIF SAW filter 3 and the PIF trap circuit 7 are composed of SAW filters.
1 and R12, it is possible to eliminate the influence of the mutual interference between the SAW filters on the characteristics.

In order to eliminate the influence of the mutual interference between the SAW filters on the characteristics, the impedance is not limited to the resistance and may be replaced with another impedance element.

(Specific Example 2 of PIF Trap Circuit 7) FIG.
(A) and (b) are circuit diagrams each showing a specific example of the PIF trap circuit 7 shown in FIG. 5 and a trap characteristic of the PIF trap circuit 7 in the television receiver according to Embodiment 2 of the present invention. FIG.

In this embodiment, as shown in FIG.
The unbalanced input terminal of the IF SAW filter 3 (point b), the input signal output from the SIF tuning amplifier 6, the balanced output terminal c _a and c _b, capacitors C11 and C12 are connected in series, respectively are input to the SIF differential input terminal of the IF amplifier / detector 5 c _c and c _d.

In this embodiment, the PIF trap circuit 7
A series resonance circuit 72 including an inductor Lp and a capacitor Cp is used. In the series resonant circuit 72 having such an LC configuration, as shown in FIG. 7B, it is difficult to obtain a steeper trap characteristic as the SAW trap described with reference to FIGS. 6A and 6B. But,
Since an arbitrary Q trap can be configured depending on the setting of the LC constant, it is possible to relatively easily achieve the purpose with general-purpose components.

Further, even if the absolute attenuation at the trap frequency is small, the modulated video signal components before and after the carrier frequency can be effectively removed at the same time, so that the influence of the video signal on the audio detection output can be reduced. As a result, the occurrence of buzz can be prevented.

(Another Example of PIF Trap Circuit 7)
Since the PIF band may be widened, the PIF trap circuit 7 includes the PIF signal band excluding the SIF.
Or the P band excluding SIF
A configuration in which the Q of the PIF trap circuit 7 is set so as to cover the IF signal band may be adopted.

Further, a plurality of trap circuits including at least the PIF trap circuit 7 may be provided so that the attenuation band of the PIF trap circuit 7 includes the PIF signal band excluding the SIF. It is preferable to use an integrated trap element.

[0067]

As described above, in the PAL and SECAM-L system compatible television receiver to which the present invention is applied, the SEC in which the audio signal is amplitude-modulated similarly to the video signal.
When receiving an AM-L television signal, it is possible to improve the sound receiving sensitivity and effectively reduce the occurrence of buzz sound due to the influence of a video signal. This is particularly effective when the PS ratio of the transmission signal is large or when the PS ratio is increased due to multipath during mobile reception. Also, when receiving FM television audio other than SECAM-L such as the PAL system, it is possible to improve reception sensitivity and further improve audio quality.

[Brief description of the drawings]

FIG. 1 is a block diagram related to a receiving circuit of a television receiver according to Embodiment 1 of the present invention.

FIGS. 2A and 2B are a circuit diagram showing a specific example of an audio intermediate frequency tuning amplifier of the television receiver shown in FIG. 1 and an explanatory diagram showing amplifier characteristics of the audio intermediate frequency tuning amplifier, respectively. is there.

3 (a) and 3 (b) are circuit diagrams showing another specific example of the audio intermediate frequency tuning amplifier of the television receiver shown in FIG. 1 and amplifier characteristics of the audio intermediate frequency tuning amplifier, respectively. FIG.

FIG. 4 is an explanatory diagram showing voltage-capacity characteristics of a variable capacitance diode used in the audio intermediate frequency tuning amplifier shown in FIG.

FIG. 5 is a block diagram related to a receiving circuit of the television receiver according to Embodiment 2 of the present invention.

6A and 6B are a circuit diagram showing a specific example of a video intermediate frequency trap circuit of the television receiver shown in FIG. 5 and an explanatory diagram showing trap characteristics of the video intermediate frequency trap circuit, respectively. is there.

FIGS. 7A and 7B are circuit diagrams showing another specific example of the video intermediate frequency trap circuit of the television receiver shown in FIG. 5 and trap characteristics of the video intermediate frequency trap circuit, respectively. FIG.

FIG. 8 is a block diagram related to a receiving circuit of a conventional television receiver.

FIG. 9 is an explanatory diagram illustrating an example of a frequency characteristic of a tuner output.

FIGS. 10A and 10B are explanatory diagrams illustrating an example of characteristics of a video intermediate frequency SAW filter and an audio intermediate frequency SAW filter, respectively.

FIG. 11 is an explanatory diagram illustrating an example of a spectrum of a television signal.

[Explanation of symbols]

Reference Signs List 1 antenna 2 tuner 3 SIF SAW filter (audio intermediate frequency SAW
4) SAW filter for PIF (SAW for video intermediate frequency)
5 IF amplification / detection circuit 6 SIF tuning amplifier (audio intermediate frequency tuning amplification circuit) 61 SIF tank circuit 7 PIF trap circuit (video intermediate frequency trap circuit) 71 SAW filter element constituting PIF trap circuit 72 PIF trap circuit Constituting series resonance circuit

Claims (13)

[Claims] 1. A tuner for outputting an intermediate frequency signal of a desired channel band, and an audio intermediate frequency signal extracting SAW for extracting an audio intermediate frequency signal from the intermediate frequency signal.
A PAL and SECAM-L compatible television receiver having a filter and a video intermediate frequency signal extraction SAW filter for extracting a video intermediate frequency signal from the intermediate frequency signal, wherein the tuner and the audio intermediate frequency signal extraction SAW A PAL comprising an audio intermediate frequency tuning amplifier tuned to the audio intermediate frequency between the filter and a filter.
And SECAM-L system compatible television receivers. 2. The PAL and SECAM circuit according to claim 1, wherein said audio intermediate frequency tuning amplifier circuit has an amplification degree at said audio intermediate frequency larger than an amplification degree at said video intermediate frequency. TV receiver compatible with L system. 3. The audio intermediate frequency tuning amplifier circuit includes a tuning tank circuit in which a capacitance of a tuning capacitor is set to be larger than an input capacitance of the audio intermediate frequency signal extraction SAW filter. Claim 1
The described PAL and SECAM-L system compatible television receiver. 4. The audio intermediate frequency tuning amplifier circuit has a difference from the video intermediate frequency of 5.5 MHz and 6.0 MHz.
The PAL and SECAM-L system compatible television receiver according to claim 1, wherein three kinds of audio intermediate frequencies of z and 6.5 MHz are used as amplification bands. 5. The PAL and SECAM-L according to claim 1, wherein said audio intermediate frequency tuning amplifier circuit is configured to be capable of switching a tuning frequency in accordance with an audio intermediate frequency of a received television signal. TV receiver compatible with the system. 6. The video intermediate frequency trap circuit according to claim 1, further comprising a video intermediate frequency trap circuit for attenuating a video intermediate frequency from an output signal of the audio intermediate frequency signal extraction SAW filter. PAL and SECAM-L compatible TV receivers. 7. The video intermediate frequency trapping circuit according to claim
7. The television receiver according to claim 6, wherein the television receiver comprises a W filter element. 8. An impedance element is interposed between the audio intermediate frequency signal extraction SAW filter and the video intermediate frequency trap circuit.
The described PAL and SECAM-L system compatible television receiver. 9. The PAL and SECAM according to claim 6, wherein said video intermediate frequency trap circuit is constituted by a series resonance circuit comprising an inductor and a capacitor.
-An L-type compatible television receiver. 10. The PAL and SECAM-L system according to claim 6, wherein the attenuation band of the video intermediate frequency trap circuit includes a video intermediate frequency signal band excluding an audio intermediate frequency. Compatible TV receiver. 11. The Q of the video intermediate frequency trapping circuit so that an attenuation band of the video intermediate frequency trapping circuit includes a video intermediate frequency signal band excluding an audio intermediate frequency.
10. The PAL and SECAM-L compatible television receiver according to claim 9, wherein: 12. A plurality of trap circuits including at least the video intermediate frequency trap circuit so that an attenuation band of the video intermediate frequency trap circuit includes a video intermediate frequency signal band excluding an audio intermediate frequency. The PAL and SECAM-L system compatible television receiver according to claim 11. 13. The PAL and SECAM-L system compatible television receiver according to claim 12, wherein a trap element in which said plurality of trap circuits are integrated is used.