JPS6281886A - Television receiver - Google Patents

Abstract

PURPOSE:To stably receive a television signal of different system by applying a frequency conversion on a video and a sound intermediate frequency signals so that the frequencies of them are set in a reverse state with each other when a specified band of specified system is received. CONSTITUTION:First of all, in a receiving time of a SECAM-L broadcasting, a VL detection on the upper side of a VH band and a heterodyne detection on the lower side of an U band are applied, and from a tuner 1, a video intermediate frequency of 32.7mHz and a sound intermediate frequency of 39.2mHz are outputted. They pass a mixer 2 receiving no process within it, and are band-limited with a trap circuit 3 and a SAW filter 4. At such a time,when the VL band of a PAL-B broadcasting is received, signals of a video intermediate frequency of 38.2mHz and a sound intermediate frequency of 32.7mHz, on the upper side of which the heterodyne detection is applied, are outputted from the tuner 1, being supplied to the mixer circuit 2. The mixer circuit 2 converts reversely them to a video of 32.7mHz and a sound of 38.2mHz, continuing the same processes.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a television receiver capable of receiving television signals of different systems.

(b) Conventional technology There are a wide variety of television systems currently in use, and neighboring countries, especially in Europe and the Middle East, sometimes use different systems. In such neighboring areas, it is desirable to have a color television receiver that can receive not only the television system of the home country (but also the television system of neighboring countries with different systems. This is a so-called dual-type receiver for Spain and Switzerland (both PAL-B systems) that can receive PAL-B systems.

By the way, in the above PAL-B system, as shown in FIG.
High band) and U (UHF band), both the audio carrier frequency (f
s) is higher, and the intercarrier frequency is 5.5MH
z, and in normal television receivers VL,
For each VH1U band, the tuner's local generation frequency fO is set at the frequency position shown by the broken line, and the video intermediate frequency is frequency-converted to 38.9 MHz and the audio intermediate frequency to 33.4 MHz by upper heterodyne detection.

On the other hand, in the SECAM-L system, as shown in FIGS. 5(B) and 5(C), fp and fs are also high in the VL band, and fs is higher than ip in the V■ and U bands. In a normal receiver, fO is set at the position indicated by the dotted line, and upper heterodyne detection is performed for the VL band, and lower heterodyne detection is performed for the Vm%U band, thereby increasing the video intermediate frequency to 52. 7MHz, audio intermediate frequency 39.2M
Hz, and the intercarrier frequency is 6.5 MHz.

Therefore, in order to receive both of the above two methods, each IF (
It would be sufficient to install a dedicated VIP" (video intermediate frequency) filter and VIP signal processing circuit in parallel for each No. 7j, but with this method, the switching circuit etc. between the two processing circuits would also be required. Since it is necessary, the cost is high and it is not a good idea.

Therefore, as an alternative method, a single VIP signal processing circuit designed for the SECAM-L system and having fractional band characteristics is used to perform VIF processing for PAL-B television signals.
Possible methods include width amplification and detection.

First, the SECAM-L system can receive all bands due to its band characteristics (see Figure 4).

Next, lower heterodyne detection is used for the VH and U bands of the PAL-B system, and as shown in Figure 4 (b), the video intermediate frequency (1 f o - f p I - b 2,7 MHz, f voice intermediate frequency) f o-f s l-31-3l3-2
If fo is selected so that Reception is possible by switching the color signal circuit.

Furthermore, regarding the Vx and band of the PAL-B system, first consider the case where upper hetero gain detection is performed.

In this case, since the video intermediate frequency is higher than the audio intermediate frequency, if the video intermediate frequency is set to 32.7 MHz, the band cannot be limited, but for example, as shown in FIG. 4(c), the video intermediate frequency is set to 57.13 MHz.

If the audio intermediate frequency is 3163 MHz, the band can be limited by adding the trap and switching circuit described above. Such a method has been proposed, for example, in Japanese Unexamined Utility Model Publication A60-505788◇ By the way, when using an IC configured with a synchronous detection circuit for VIP detection, the tuning frequency should be set to 32.7 si.
It is necessary to switch the frequency from 1 to 37.13 MHz, but if this frequency is different, the detection efficiency will be different, leading to deterioration of image quality.

When using primary and lower hetero gain detection, the audio intermediate frequency can be selected higher than the video intermediate frequency, but PAL-B
The image of the armpit side channel has a carrier frequency of 4 B, 2
5 LVIHZ, so the tuner fo for this channel is fO = 48.25-62.7 = 15.
55Mf(z), which is considerably low. This means that the relative changes in Vr and fo in the band become large.

Therefore, it is difficult to always obtain a constant oscillation output for each channel within this band, and there has been a problem in that a sufficient oscillation output cannot be obtained particularly at low frequencies such as those mentioned above.

In FIG. 4, Ap is the video intermediate frequency of the first channel, and A8 is the audio intermediate frequency of the adjacent channel.

(c) Problems to be solved by the invention The present invention has been made in view of the above-mentioned points, and is based on simple 4 problems.
The present invention provides a television receiver that can stably receive television signals of different formats such as PAL-B format and SECAM-[2] format.

2) Means for Solving the Problem The present invention normally uses the tuner to transmit the frequency fN% of the video and audio intermediate frequency jI+, but when receiving a specific band of a specific system, the video and audio intermediate station e, the signal is deleted. Furthermore, these frequencies are converted into opposite frequencies and then input to a single video intermediate frequency signal processing circuit.

(e) Effect: In addition to the above-mentioned means, ninthly, a single video intermediate frequency signal processing circuit is used, which allows the same video and audio intermediate frequency signals to be obtained when receiving a specific band using a specific method as when receiving other receptions. I can do it.

(f) Implementation example DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be fully described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a television receiver in this embodiment. In the same figure, (1) is SECAM-
A tuner for L system reception, (2) is a mixer circuit,
All bands of SECAM-L system and V of PAL-B system
When receiving H and U bands, the signal is passed through as is,
Vr of PAL-B system.

During band reception, the intermediate frequency output from the tuner (1) is frequency converted to make the video intermediate frequency 32.7 MHz.

The grooves are arranged so that the audio intermediate frequency is 3B and 2MHz.

(3) is a trap circuit, which uses a built-in switching circuit (not shown) to trap audio only when receiving PAL-B format.
38.2 MHz) and an adjacent channel video intermediate frequency trap (39.7 MHz).

Incidentally, the above trap can be used without the above switching circuit.
A configuration may also be adopted in which the trap is allowed to pass even when receiving the -L method. (4) is a SAW filter with a predetermined passband specification, (5JVIP' signal processing [IC.

(6) is the 18th IF' used when receiving PAL-B broadcasting.
Signal processing IC1 (71 is the 28th IF' signal processing rc used when receiving SECAM-L broadcasting, cat is for matching the polarity of the video signal of positive modulation SECAM-L broadcasting and negative modulation PAL-B broadcasting. For example, when receiving SECAM-L broadcasting, a video inversion switching circuit (9) inverts the polarity of the signal.
) is an audio switching circuit that selectively switches the outputs of the first and second SIFIg processing ICs and supplies them to a temporary vocal circuit.

Next, referring to FIG. 2, a miasma circuit, which is a feature of this embodiment, will be explained. In the figure, (SW) is a changeover switch that is connected to the a terminal when receiving all bands of SECAM-L broadcasting and the Va%U band of PAL-B broadcasting, and connected to the b terminal when receiving the VL band of PAL-B broadcasting, 121 is a t-first mixer connected to the b terminal of this changeover switch;
Oscillation frequency f 1 (frtJtJ(100~150M
A first local oscillator UIJ (set to Hz) is connected. The α force is a bandpass filter, the skewer is a second mixer, and a second local oscillator @ of excavation frequency f2 is connected.

In addition, +2 is set to fz-fl-7Q, 9MHz, and 70. ．． 9MHz is the sum of the video intermediate open mantissa and audio intermediate frequency in PAL-B broadcasting, which is 2t! It is direct.

The operation of the circuit of this embodiment will now be explained.

1. When receiving SECAM-L broadcasts, it is the same as before! ! ! I
! -Image intermediate frequency! A signal with a 12.7 MHz 2% audio intermediate frequency of 39.2 MHz is output, and the mixer circuit (2)
The circle passes through without any processing, and the trap circuit (3)
The SAW filter (4) limits the band according to the custom order shown in Figure 4.

Then, this SAW filter output is processed by the VIP signal 4j processing ICl 5), and is output as a video output via the video inversion switching circuit (8).

Part of the output of the SAW filter (4) is supplied to the 28th IF signal processing IC (71) so that the SECAM-L signal is
72J& is supplied to the transcription voice switching circuit.

In addition, V I P'i + I C + 5) Color OA F
Tlt17J is supplied to tuner (1).

For a long time, when receiving PAL-B broadcast Vu and K-bands, the tuner (lower heterodyne configuration from IJ,
A signal with a video intermediate frequency of 32.7 Mf(z) and an audio intermediate frequency of 38.2 MHz is output, passes through the mixer circuit (2) without any processing, and is sent to the trap circuit (3) and S.
The AW filter (4) is limited to a healthy band 1tiIl by the characteristic shown in the fourth section (b). At this time, in the trap circuit (3), the audio trap (38.2 MHz) and the adjacent channel video transmission intermediate frequency trap (697 MHz) are operated. The output of this SAW filter is sent to the VIP signal processing IC (51), and outputted as a video output via the video inversion circuit (8).

- 10,000#'lJki VI I Pl'j WFHI C+5
) Medium (7) vI Part of the Fq width circuit output is the 18th I
The PAL and -B signals are supplied to the F1 η processing IC (61) and converted into F'M signals, which are then selected by the audio switching circuit (9) and output as audio output.

Finally, when receiving VL band of PAL-B broadcast, tuner (
From 1), the upper heterodyne detected video intermediate frequency is 38.2M) IZ1 Jin vocal intermediate frequency') -7MH
The signal z is output and supplied to the mixer circuit (2). At this time, since the changeover switch (SW) in the mixer circuit is connected to the b terminal, the signal is sent to the first mixer (to), the video intermediate frequency signal is fx-38°2 MHz K, and the audio intermediate frequency signal is fl-32.7 MHz, only the intermediate frequency component of the band C is selected by the band pass filter 0 and supplied to the second mixer Z3. Furthermore, in this second mirror Φ, the video intermediate frequency signal is (f 1
-s 8. zMHz ) - (f 1 - 70.9MHz
)=52.7MHz.

The audio intermediate frequency signal is (fl-52,78・IHz)
-(f1-70.9MHz)=38.2MHzK
Husband A is converted. Therefore, even though the tuner (IJ) was heterodyned on the upper side, the VH of PAL-B number one.

An intermediate frequency signal having exactly the same frequency as that during U-band reception is obtained, and subsequent processing is performed in exactly the same manner as described above.

In addition, in the mixer circuit mentioned above, the intermediate frequency is raised once at the 7th point where the input and output frequencies are the same and this prevents beat interference. If the oscillation frequency of the second local oscillator C is set to 70.9 MHz, the first local oscillator C!V and the bandpass filter become unnecessary.

Nine, in the above embodiment, the receiver circuit such as the tuner is
Although the configuration is such that it can also receive the PAL-B system based on the ECAM-L system, the nine circuits designed for the PAL-B system may also be configured so that it can also receive the SECAM-L system.

(G) Effects of the Invention As mentioned above, according to the present invention, the tuner, intermediate frequency band! Without changing the characteristics of the II limiter circuit and the detector circuit,
With a simple circuit configuration, PAL-B system and SECAM-
It is possible to receive the entire range of television signals of two different systems, such as the L system.

-27yAF'T output corrects the tuner's local oscillation frequency 1M, and the frequency difference of the first and second local oscillators in the mixer circuit is also corrected at the same time. There is little performance deterioration due to frequency fluctuations.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a television receiver according to an embodiment of the present invention, FIG. 2 is a block diagram of a mixer circuit,
Figure 6 B), (B), and (C) are PAL-B system and SE system, respectively.
A diagram showing the frequency relationship of the VLbyF band of the CAM-L system and the VH%U band of the SECAM-IJ system, FIG.

Claims (1)

[Claims] (1) In a television receiver that receives multiple different television signals, the frequency-converted video and audio intermediate frequency signals are normally received by the tuner, and when receiving a specific band of a specific method, the video and audio intermediate frequency signals are further received. A television receiver characterized in that the frequencies are converted so that these frequencies are opposite to each other and then input to a single video intermediate frequency signal processing circuit.