JPH03127586A - Multi-system television signal reception tuner device - Google Patents

Abstract

PURPOSE:To facilitate IF detection circuit processing by setting an oscillating frequency of a local oscillator circuit to under heterodyne at the reception of a VHF low band signal of the L-SECAM system. CONSTITUTION:A switching means 52 setting an oscillating frequency of a local oscillation circuit 51 to under heterodyne at the reception of L-SECAM system VHF low band signal to a multi-system television signal reception tuner 50 is provided. Then the local oscillating frequency of the local oscillation circuit 51 is decreased by using a transistor(TR) or a diode to switch L' or C' of LC elements determining the local oscillation frequency only at the L- SECAM system reception and is changed into the lower heterodyne frequency. Thus, the same intermediate frequency is outputted from a tuner section and the multi-system television signal reception tuner 50 is realized simply.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention provides a television that can selectively receive both the L-SECAM system and other television broadcasting systems, such as the PAL (B/G) system. The present invention relates to tuner devices such as television receivers and video tape recorders.

(b) Conventional technology A variety of television systems are used in various countries, and as is well known (PAL (B/G) system television broadcast waves are The carrier frequency (f,) is 5.5 MHz higher over the entire band.

On the other hand, the L-5ECAM system uses VHF high band and U
Similarly, the audio carrier frequency is 6.0 for the video carrier frequency in the HF band. sMH has a high frequency, but only in the VHF low band, the audio carrier frequency is 6.5 MHz lower than the video carrier frequency. (Hereinafter, this VHF low band method will be referred to as L'
-5ECAM method. ) Regarding the television systems of each country, please refer to Japanese Patent Application Laid-Open No. 63-4.
It is described in Publication No. 5987 (HO4N 9100).

These PAL (B/G), L-5ECAM-L'-SE
There is a tuner/IF device shown in FIG. 3 for receiving each CAM system.

In FIG. 3, by key operation on the keyboard (1), a serial data signal from a tuning microcomputer (2) is distributed through a data decoder (3) into band data and programmable divider data, and the former is divided into band data and programmable divider data.
VHF low band signal (V L), V
HF high band signal (■□), U HF band signal (V
u), ANT coil, RF coil,
Set the local oscillator coil etc. to the desired reception band. On the other hand, the programmable divider data is input to a PLL circuit (5) consisting of a reference oscillation circuit, a phase comparison circuit, etc., and is compared in phase with the local oscillation frequency from the local oscillation circuit (6).
The tuning voltage (V, ) is fed back to the local oscillation circuit (6) via the PF (7) to control the phase of the local oscillation frequency (fo). The signal received by the antenna (A N T ) is R
It is amplified by the F amplifier (8) and mixed with the local oscillator frequency (fo) of the local oscillator circuit (6) in the next mixing circuit (9) to obtain an IF (intermediate frequency) signal. The tuner section (1o) is preferably one in which the above-mentioned data decoder (3) to mixing circuit (9) are assembled into a shield case. The IF multiplied signal from the tuner section (10) is processed by the IF/detection section (20) to obtain video output and audio output according to each system.

The configuration of the 1F detection section (20) includes a first I for IF signal amplification.
A desired VIF signal is obtained via an F amplifier (21) and a video intermediate frequency (VrF) broadband filter (22). The filter (22) is a PAL (B/G) system,
L-5ECAM system VHF high band and UHF/<
When receiving :/, VTF 38,9 MIIJ' is obtained, and when receiving L-5ECAM system VHF low band (L'-5ECAM mentioned above), VTF 34.5M I(z
is obtained. The VIF signal of each method is amplified by the 21st F amplifier (23) and given to the AFT circuit (24) and the video detection circuit (25).

A method switching circuit (26) selects a predetermined method (P A L (B/G
), L-5ECAM method, or L'-5ECAM method) is selected, and the next stage switching circuit (27) switches to AFT coils (two) corresponding to a predetermined band to perform AFT control of the VIF signal. . Switching circuit (2
8) switches to a detection coil (30) corresponding to a predetermined band, performs tuned detection on the VIP signal, and outputs PAL (B/
G), L-5ECAM.

Obtain the video signal output of any of the L'-SECAM systems. On the other hand, the IF multiplied signal from the tuner section (10) is amplified as a sound intermediate frequency (SIF) by the IF amplifier (31), and is set to a predetermined value by the method switching circuit (32) according to the signal from the aforementioned tuning microcomputer (2). The system is selected and switched to a predetermined band by the next stage switching circuit (33). The amplified SIF signal is passed through a switching circuit (33) to bandpass filters (34) (35) (
36) to a predetermined audio intermediate frequency (33, 4
MHz, 32.4 MHz, or 41 MHz) is obtained, is amplified by the IF amplifier (37) in the next stage, and is output to the switching circuit (34) by the signal from the switching circuit (32) in the audio detection circuit (38) in the next stage. ) selects a predetermined detection coil (35), the audio intermediate frequency signal is tuned-detected, and a PAL (B/G) audio signal or an L-5ECAM or L'-5ECAM audio signal is output. .

Further, FIG. 4 shows another processing circuit block diagram for the IF multiplied signal obtained by the tuner section (10).

In the figure, the IF output from the tuner section (10)
, only when receiving an L'-SECAM signal, the second local oscillator circuit (42) is operated via the switching circuit (41) by the signal from the tuning microcomputer (2), and the oscillation frequency is 71.3 MH. is oscillated, inputted to the double balanced mixer circuit (43), and mixed with the IF+ signal to obtain a second IF signal (IFf). PAL(B
/G) and L-5ECAM system VHF high band, U
When receiving an HF band signal, the double balanced mixer circuit (43) is turned on. The IF signal is amplified by an IF amplifier (21), and is amplified by a bandpass filter (44).
Obtaining an F signal of 38.91VfH, the video detection circuit (25
) to get the video output. On the other hand, the audio intermediate frequency signal is S
Amplified by IF amplifier (31) and passed through bandpass filter (47)
The SIF signal 32.4 MHz is obtained through the IF amplifier (37) in the next stage, and is further amplified, provided to the audio detection circuit (48), and then harmonically detected by the detection coil (49) to generate the audio signal. is output.

In the circuit shown in Fig. 4, in the case of the PAL (B/G) system, the signal after video detection is further synchronously detected via the audio detection circuit (45) using the pseudo synchronous detection method to obtain the audio signal. , L-5ECAM system, and L'-SECAM system use a split detection system for signal demodulation.

In addition, as a prior art similar to FIG.
6386 (HO4N 9/64).

(c) Problem to be solved by the invention In the split detection method shown in FIG.
When the oscillation frequency of the local oscillator circuit 0) is of the upper heterodyne system, the intermediate frequency IF is as follows.

(a) PAL (B/G) and L SECAM (V
When receiving HF high band, U HF band) method, VIF = 38.9M) 12. 5IF=33.4M1l
z(B/G) or 1iSIF-32,4MHz(L) When receiving L'-SECAM method, VIF=34.5M) It, 5IF=41.0MH
It becomes 2.

(b) The disadvantage of this method is ■ When receiving (a) and (b), the same I
Symmetry in filters and tuning circuits is required to obtain F-characteristics, making component selection difficult.

■ It is necessary to switch SIF, SAW filters and LC tank circuits, making the circuit configuration complex and requiring adjustment work.

On the other hand, in the case of the pseudo synchronous detection and split detection hybrid method shown in Fig. 4, the IF when receiving PAL (B/G), L-5ECAM method (VHF high band and UHF band) is: VIP+=38.9Mfh , SIF+=33.4M)
It(PAL(B/G))SIF= 32.4Mtb(
L-5ECAM).

■ IF when receiving L'-5ECAM method is VIP+
= 32.4MHz, SIF+ = 38.9Mfhte.

Next, the second local oscillation frequency is 71.3MH! When the wave is detected using the upper heterodyne method using the balanced mixer circuit (43), V I Fm = 71.3-32.4 = 3 s, c + MH
zSI Fm=71.3-38.9=32.4MHz
get. That is, PAL (B/G) system, L-SECAM
The IF is the same as when receiving the method, but there are the following problems.

■ Circuit configuration for operating the second local oscillator circuit only when receiving L'-SECAM system (balanced mixer circuit,
(switching circuit, etc.) is required.

(2) The L'-5ECAM method is a double superheterodyne detection method, and requires precision of the second local oscillation frequency.

■ Since the input and output signals of the balanced mixer circuit are placed in the same way, the signal is separated only a few times, making it difficult to obtain good characteristics.

(2) The L'-5ECAM system has poor spurious interference characteristics due to its double super.

(d) Means for Solving the Problems The present invention provides a switching means for setting the oscillation frequency of the local oscillator circuit to underheterodyne when receiving an L-5ECAM VHF low band signal in a tuner for receiving multi-system television signals. It was composed of

Moreover, one output of a band decoder that controls the tuner section as HIi is applied to the local oscillator circuit as the switching signal to switch the oscillation circuit constant of the local oscillator circuit.

(e) Operation only when receiving L-SECAM system VHF low band signal.
The oscillation frequency of the local oscillator circuit in the tuner section is switched to under-heterodyne, and when receiving signals other than the L-5ECAM VHF low band, the oscillation frequency of the local oscillator circuit is set to upper heterodyne, and the oscillation frequency from the tuner section is set to upper heterodyne. The same intermediate frequency is output.

(f) Embodiment FIG. 1 is a circuit block diagram showing an embodiment of the present invention. Components that are the same as those in the conventional example are given the same reference numerals and their explanations will be omitted. The embodiment of the present invention has a tuner section (5
L'-5ECAM lower heterodan switching circuit (52) operated by the signal (S, ) from the band decoder (4) of 0) and the switching circuit (52)
The difference is that the oscillation frequency of the local oscillator circuit (51) is switched to the lower heterodyne in response to the signal, and the IF detection stage (60) has a switching circuit ( 41), second local oscillator circuit (4
2), the only difference is that the double balanced mixer (43>) has been deleted.

In Figure 1, press the keyboard (1) to select '-SECA'.
M system, that is, L-SECAM system V. When you select an HF low band channel, the L
'-SECAM lower heterodyne switch 7
A signal (S, ) is supplied to path 7 to switch the oscillation frequency of the local oscillator circuit (51) to the lower heterodyne detection method.

That is, in the multi-system television signal receiving tuner device of the present invention, the video intermediate frequency (VIF) and the audio intermediate frequency (SIF) are set as follows.

VIF=38.9MH2 (PAL (B/G), L/L
'-SECAM).

5IF=33.4M+1□(PAL(B/G)).

5IF = 32.4MHz (L/L'-5ECAM) Also, the heterodyne detection method of the tuner section (50) is PAL
(B/G) or L-SECAM system When receiving the VHF high band or UHF band, the upper heterodyne detection method is used, and only when receiving the L'-5ECAM VFH low band, the lower heterodyne detection method is used, so that the local frequency is lower than the video frequency. lower it and invert it.

When receiving by the above method, the relationship between the local frequency (fo) and intermediate frequency (IF) of each receiving channel is as follows.

The following margins are PAL (B/G), L/L'-SECAM as described above.
Set the intermediate frequency to the same value regardless of the system or channel. In the embodiment of the present invention, the IF
- The detection unit uses a pseudo-synchronous detection method for PAL (B/G) vX modulation, and a split detection method for L/L'-SECAM demodulation.

Regarding the local oscillator circuit of the tuner section (50) of the present invention, L
'-Determine local frequency only when receiving SECAM method L
By switching L'' or Co in the C element with a transistor or diode, the local frequency is lowered and changed to the lower heterodyne frequency.

Figure 2 shows the local oscillator circuit (51) and switching circuit (52).
), PAL (B/G) or L-
5ECAM, VHFHF pie band 1H1L' Since the input part is Hi, the Tr is in the ON state, and the capacitor C
Since 0 is a low impedance, C' and L' have oscillation frequencies determined by the constants of ground ftC1 and Cat Ll.

When receiving L''-SECAM method, L input becomes Lo r)T
Since r is turned off, L' and C' are added and the local oscillation frequency is switched to the lower heterodyne.

The configuration of the present invention uses one output (Sl) of the band decoder (4) as a signal source for operating the switching circuit (52) when receiving the L'-5ECAM system.

In addition, although the frequency synthesizer tuning method was explained in the embodiment, even if the voltage synthesizer tuning method is used, the VL
, Vfl, and vu, connect each band voltage application terminal to L″-5E.
This can be realized by simply providing the tuner (50) with a terminal that is applied as a switching voltage only during CAM.

However, if the frequency synthesizer tuning method as in the embodiment of the present invention is used, tuning information for each band of PAL (B/G) and L-5ECAM methods can be transmitted with just a tuning microcomputer and two to three wires. It can easily realize a tuner for multi-system television signal reception.

Although this embodiment only mentions PAL (B/G), I, and -5ECAM multi-tuners, the L-5ECAM (L-5ECAM)
L'-5ECAM) method and P A L (B/G), I,
It is also easy to develop a multi-system tuner that receives a broadcast system that combines M and Dt.

(G) Effects of the Invention The present invention has a configuration in which the local oscillation frequency is switched to the underheterodyne detection method only when receiving the L-5ECAM system VI (F low band), so the IF/detection section has a fixed frequency, and the general IF detection It is circuit processing, and the tuner can be completed as an I-back with an extremely simple circuit configuration.Therefore, it greatly contributes to miniaturization, low cost, and high performance.Also, L-5 of the tuner section
The switching circuit required only when receiving the ECAM VHF low band can be realized with the simple switching circuit used for the band switch of the tuner, so it has the characteristic that it can be completed without making any major changes to the tuner.

[Brief explanation of the drawing]

FIG. 1 is a specific circuit block diagram of the present invention, FIG. 2 is a diagram showing a circuit embodiment of the main part of the present invention, and FIGS. 3 and 4 are circuit block diagrams of conventional examples, respectively. 50... Tuner section, 51... Local oscillator circuit, 52...
・Switching circuit. 4゜

Claims (4)

[Claims] (1) In tuners for receiving television signals such as PAL (B/G) and L-SECAM systems, L-SECA
1. A tuner device for receiving a multi-system television signal, comprising means for setting the oscillation frequency of a local oscillator circuit to underheterodyne when receiving an M-system VHF low band signal. (2) L-SECAM system VHF high band, UHF
2. The tuner device for receiving a multi-system television signal according to claim 1, wherein the oscillation frequency of the local oscillator circuit is set to upper heterodyne when receiving a band or other television system signal. (3) The means for setting the oscillation frequency of the local oscillator circuit to underheterodyne is a switching circuit operated by the output of a band decoder circuit constituting a frequency synthesizer tuning device. Tuner device for receiving multi-system television signals. (4) The means for setting the oscillation frequency of the local oscillator circuit to underheterodyne is a switching circuit operated by the output of a band decoder circuit constituting a voltage synthesizer tuning device.
A tuner device for receiving multi-system television signals as described in .