JPH02260984A - Video intermediate frequency signal processor - Google Patents

Abstract

PURPOSE:To simplify a circuit configuration and to reduce costs by switching a switching means according to the type of a broadcasting system, multiplying a lock signal from a video signal processing side by a second filter output by a multiplier, and outputting a first sound signal. CONSTITUTION:For example, a broadcast signal in a PAL B/G system received by an antenna 1 is converted into a video intermediate frequency signal having a video and audio carrier frequencies fP1 and fS1 by a tuner 2, and applied to a video SAW filter 3 and audio SAW filters 4a and 4b. An AMP 21 amplifies the filter output of the filter 3, and applys it to a PLL video detector 23. The PLL video detector 23 demodulates the filter output to the video signal with the use of the oscillating output of a VCO 23d. A multiplier 25 multiplies the VCO output of the PLL video detector 23 by the output of an AMP 22, and outputs the difference between the frequency fP1 and fSP1, namely a PAL inter- carrier. Since the inter-carrier in the PAL B/G system and a sound signal in a SECAM L system are obtained without using a picture trap circuit, the circuit configuration is simplified, and the costs can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for processing a video intermediate frequency signal,
In particular, the present invention relates to a video intermediate frequency signal processing device that can support different broadcasting systems.

[Conventional technology]

In Europe, the Middle East, and the like, there are regions where it is possible to receive television broadcasts from neighboring countries, and television sets that can support multiple broadcasting systems are manufactured for these regions. Figure 6 shows France's S E CA
M (s6quentlcel couleura
m6molre color TV system)
L system (audio signals are transmitted with FM modulation) and PAL (Phase^Iternation) in neighboring countries.
by Line) A conventional video intermediate frequency signal processing device built into a television set that can receive broadcast signals of two broadcast systems: B/G system (audio signals are transmitted after being AM modulated). FIG. 2 is a block diagram showing the circuit configuration of FIG.

The broadcast signal received by antenna 1 is sent to tuner 2,
Depending on the type of broadcast signal, the video carrier frequency f and the audio carrier frequency f f' API
st' s or converted into a video intermediate frequency signal having a video carrier frequency 'P2 and an audio carrier frequency f8□, and this video intermediate frequency signal is converted into a video intermediate frequency signal having a video carrier frequency 'P2 and an audio carrier frequency f8
A W (acoustic 5ur-faee w
aves) filter 3 and audio SAW filter 4. The video SAW filter 3 has a well-known bandpass characteristic necessary for demodulating a video intermediate frequency signal into a normal video signal, and the bandpass characteristic is as shown in FIG. The video intermediate frequency signal filtered by the video SAW filter 3 is applied to a video intermediate frequency (IF) signal processing unit C5. A video IF signal processing IC (hereinafter referred to as VIP IC) 5 includes an amplifier (hereinafter referred to as AMP) 6 and a video intermediate frequency LLD (Low Level
l De-tector) (hereinafter referred to as VIF LLD)
VIF LLD7 consists of VIF LLD7.
LLD: Ill 7a is connected.

The audio SAW filter 4 has a frequency f f'81'
31'' Bandpass characteristic A and frequency f such that P2 is filtered
, f is filtered such that the bandpass characteristic BPI
S2 (see Figure 8). The video intermediate frequency signal that has passed through the audio SAW filter 4 is applied to a picture trap circuit 8.9 and a switch SWI. The picture trap circuits 8 and 9 are each for removing the component of frequency fpt''P2. The switch SW1 switches the picture trap circuits 8 and 9 according to the signal from the switch switching terminal 10.
Alternatively, the output of the audio SAW filter 4 is selectively transmitted. An audio intermediate frequency signal processing IC (hereinafter abbreviated as QIF IC) 11 is connected to the output side of the switch SWI. QIF ICII is AMPl 2. It consists of an audio intermediate frequency LLD (hereinafter abbreviated as QIF LLD) 13, and the QIF LLD 13 includes a QIF LLD coil 1.
3a is connected. The resonant frequencies of the VIF LLD coil 7a and the QIF'LLD coil 13g change according to the signal from the switch switching terminal 10.

First, a case will be described in which a PAL B/G broadcast signal is received. At this time, the switch sw1 is switched to X by a signal from the switch switching terminal 10, and the resonance frequencies of the VIF LLD coil 7a and the QIF LLD coil 13a are set to the frequency f, 1. A PAL B/G broadcast signal received by the antenna 1 is converted by the tuner 2 into a video intermediate frequency signal having a video carrier frequency f,1 and an audio carrier frequency f81, and is applied to the video SAW filter 3 and the audio filter 4. It will be done. The video intermediate frequency signal is filtered by the bandpass characteristics of these filters, and the filtered outputs are respectively VIF I
C5, QIF ICIII: Given.

The filtered output of the video SAW filter 3 is amplified by the AMP 6 and then demodulated into a video signal by detection by the VIF LLD 7, that is, by removing a frequency component equal to the resonant frequency 'PI of the VIF LLD coil 7a. On the other hand, the filtered output from the audio SAW filter 4 is AMP
After being amplified by QIF LLD 12, the signal is subjected to frequency conversion by QIF LLD 13 to determine the difference between the resonance frequency f of QIF LLD coil 13a and audio carrier frequency f8□, and a 5.5 MHz PAL intercarrier is output. The PAL intercarrier is then audio detected and demodulated into a PAL audio signal.

Next, the case of receiving a SECAM L broadcast signal will be explained. The case of VHF High channel, UHF, and VHF Low channel will be explained separately. In the former case, the switch SWI is switched to Y by the signal from the switch switching terminal 10, and
VIF LLD coil 7a.

The resonance layer and wave number of the QIF LLD coil 13a are set to frequencies f and f'8□, respectively. The broadcasting signal of the SECAM L system has the above-mentioned frequencies f and f'8 in tuner 2.
．． is converted into a video intermediate frequency signal having a video SAW filter 3 and an audio SAW filter 4.
given to. The filtered output of the video SAW filter 3 is demodulated into a video signal by the same operation as described above. On the other hand, since the switch SWI is switched to Y, the filtered output of the audio SAW filter 4 is applied to the QIF IC 11 via the picture trap circuit 8. Since the picture trap circuit 8 removes the frequency fP1 component from the filtered output of the audio SAW filter 4, only the signal (audio signal) having the frequency f'8 is input to the QIF C11. This signal is amplified by AMP 12 and QIF
It is given to LLD13. In general, SECAM L
Since the audio modulation method in the system is AM modulation, the QI
AM detection is performed by the FLLD 13 and demodulated into a SECAM audio signal.

In the latter case, that is, in the case of VHF Low channel, the switch SW is switched by the signal from the switch switching terminal 10.
At the same time as switching I to Z, VIFLLD: Fill 7
a The resonance frequencies of the QIF LLD coil 13a are set to frequencies f and f, respectively.2S2. In the case of VHF Low channel, changing the resonant frequency of the coils 7a and lla in this way is done when the video carrier frequency is changed from f to fP2 and the audio carrier frequency is changed to fP2.
This is because it changes from f32 to f32. In addition, the frequency fP
The magnitude relationship between 2 and f8° is as shown in Figures 7 and 8.
This is the reverse of the VHF H1gh channel or UHF in the PAL B/G system or SECAM L system. The broadcast signal of the VHF Low channel is converted into a video intermediate frequency signal P2 S2 having the above-mentioned frequencies f and f'b by the tuner 2, and then passed through the video SAW filter 3 and the audio SAW filter 4.
given to. The filtered output of the video SAW filter 3 is demodulated into a video signal by the same operation as described above. On the other hand, the filter output of the audio SAW filter 4 is SW;
is switched to Z, so the picture trap circuit 9
QIF IC11 via QIF IC11. The picture trap circuit 9 removes the frequency fP2 component from the filtered output of the audio SAW filter 4, so the QIF ICI
Only a signal (audio signal) having a frequency f8□ is input to I. Then, as in the case of the VHF High channel, the QIF LLD13 performs AM detection and the S
It is demodulated into an ECAM audio signal.

[Problems to be Solved by the Invention] The conventional video intermediate frequency signal processing device is configured as described above, and includes parts and switches for changing the resonance frequencies of the two picture trap circuits 8 and 9, and the coils 7a and 13a. Since SW1 is required, the number of parts increases and Q
There have been problems in that the configuration of the peripheral circuits of the IF ICII is complicated and the cost is high.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a video intermediate frequency signal processing device with a small number of parts.

[Means to solve the problem]

A video intermediate frequency processing device according to the present invention includes an input means for inputting a video intermediate frequency signal having a video signal component and an audio signal component of a predetermined video carrier frequency determined for each broadcasting system, and an audio carrier frequency; a video filter connected to the means for filtering the video intermediate frequency signal with a bandpass characteristic necessary for demodulating the video intermediate frequency signal into a normal video signal and outputting a first filtered output; and a voltage control an oscillator, connected to the video filter;
a phase-locked loop circuit that outputs a lock signal phase-locked to the video carrier frequency from the voltage-controlled oscillator; and a phase-locked loop circuit that is connected to the video filter and the phase-locked loop circuit, and that outputs the first filtered output using the lock signal. a video detector that detects and outputs the video signal; and a plurality of audio filters each having a bandpass characteristic centered on a different audio carrier frequency, which are connected to the input means and filter the video intermediate frequency signal. an audio filter group that outputs a plurality of second filtered outputs; switching means connected to said voltage controlled oscillator and said switching means for selectively delivering one of said first a multiplier for outputting an audio signal; and an oscillator for generating a signal synchronized with a signal component of the audio carrier frequency; an audio detector that detects the output signal of the oscillator using the output signal of the oscillator and outputs an audio signal; and oscillation frequency changing means for changing the oscillation frequency.

[Effect]

In this invention, the phase-locked loop circuit including the voltage-controlled oscillator provided on the video signal processing side outputs a lock signal phase-locked to the video carrier frequency from the voltage-controlled oscillator, and the phase-locked loop circuit includes the voltage-controlled oscillator provided on the audio signal processing side. the given multiplier. The audio filter group filters the video intermediate frequency signal with bandpass characteristics centered around different audio carrier frequencies, and outputs a plurality of second filtered outputs. The switching means switches according to the type of broadcasting system, and selectively outputs any one of the plurality of second filtered outputs. The multiplier is provided with one of the plurality of second filtered outputs via switching means. The multiplier multiplies the lock signal from the video signal processing side and the second filtered output, and outputs the first audio signal, for example, a PAL intercarrier.

〔Example〕

FIG. 1 is a block diagram showing an example of the configuration of a video intermediate frequency signal processing device according to the present invention. As before, the broadcast signal received by the antenna 1 is converted into a video carrier frequency f and an audio carrier frequency f f' apt by the tuner 2 according to the type of the broadcast signal.
st's or converted into a video intermediate frequency signal having a video carrier frequency 'P2 and an audio carrier frequency f3□, and then passed through a video SAW filter 3. Audio SAW filter 4a
.

4b. The optical 11s AW filter 3 has bandpass characteristics similar to the conventional one (see FIG. 7). Video S
The filtered output of the AW filter 3 is processed by an intermediate frequency processing IC (hereinafter referred to as I).
(abbreviated as FIC) 20.

As shown in FIG. 2, the bandpass characteristic of the audio filter 4a is such that the audio carrier frequency ff' of both the PAL B/G system and the SECAML system is filtered by S1° St. The filtered output of the audio filter 4a is given to the switch SW2.

As shown in FIG. 3, the audio SAW filter 4b has a symmetrical band-pass characteristic centered on the frequency f8°, and its filtered output is given to the switch SW2. switch S
W2 is switched by a signal from the switch switching terminal 10. IF IC20 is a PLL including AMP21, 22 and a phase locked loop (hereinafter referred to as PLL) circuit.
PLL AM that includes a video detector 23 and a PLL circuit
It consists of a detector 24° and a multiplier 25. AMP21 is video S
Amplify the filtered output of AW filter 3 and display PLL video@! It is given to the detector 23. The PLL video detector 23 includes a voltage controlled oscillator (hereinafter referred to as vCO) as described later, and the oscillation frequency of the vCO changes in accordance with the signal from the switch switching terminal 10. AMP 22 is connected to switch SW2, amplifies the filtered output provided via switch SW2, and provides the amplified filtered output to PLLAM detector 24 and multiplier 25. The PLLAM detector 24 includes a vCO as described later, and the oscillation frequency of this vCO also changes in accordance with the signal from the switch switching terminal 10.

The multiplier 25 receives the VCO output of the PLL video detector 23,
This is for multiplying the output of the AMP 22.

Figures 4 and 5 each show a PLL video detector 23° PLL.
It is a block diagram showing an example of the configuration of an AM detector 24,
These configurations are compatible with the commonly available PLL VI
It is similar to FIC.

In FIG. 4, the video intermediate frequency signal given from the AMP 21 is transmitted to an automatic phase comparator (hereinafter abbreviated as APC) 23a.
, is applied to the video detector 23b.

The video detector 23b detects the video intermediate frequency signal, and the detected output is amplified by the video AMP 23c and output as a video signal. On the other hand, the APC 23a compares the frequency and phase of the video intermediate frequency signal with the oscillation frequency and phase of the VCO 23d, and generates an average DC voltage proportional to the error.

This error voltage is passed through the low-pass filter 23e to the VCO
23d, and the video intermediate frequency signal and VC
The oscillation frequency of the VCO 23d is changed in a direction that reduces the oscillation frequency difference and phase difference of the O 23d, and finally the oscillation frequency is locked to the video carrier frequency. The oscillation frequency (VCO output) of the locked VCO 23d is
given to 5.

The configuration of the PLL AM detector 24 shown in FIG. 5 is as follows.
3b to AM detector 24b, video AMP23C to audio A
It is equivalent to the one replaced with MP24c. The AM detector 24b performs AM detection on the audio intermediate frequency signal from the AMP 22, and the AM detection output is amplified by the audio AMP 24c and output as an audio signal. Other configurations and operations are similar to those of the PLL video detector 23. In addition, VC02
The 4d oscillation frequency is ultimately locked to the audio carrier frequency.

As described above, a method in which a video intermediate frequency signal and an audio intermediate frequency signal are input separately and each signal is processed using a PLL circuit is generally called a PLL split method.

Regarding the operation of the circuit shown in FIG. 1, first, the case where a PALB/G broadcast signal is received will be described. At this time, the switch SW is switched by the signal from the switch switching terminal 1o.
2 to Xl. In response to this, VCO23d,2
4d free oscillation frequency is set, PLL video detector 2
3. Each PLL loop in the PLLAM detector 24 has a PA
The video carrier wave frequency f and the audio carrier wave t of the LB/G system are locked to the frequency fSl. A 'PAL B/G broadcast signal received by the antenna 1 is converted by the tuner 2 into a video intermediate frequency signal having a video carrier frequency f,1 and an audio carrier frequency f3□, and is then passed through a video SAW filter 3 and an audio SAW filter 4a. .

4b. AMP21 is video SAW filter 3
The filtered output of P is amplified and given to the PLL video detector 23.
LL video detector 23 demodulates the filtered output into a video signal using the oscillation output of VCO 23d.

Since the switch SW2 is switched to Xl, the filtered output of the audio SAW filter 4a is applied to the AMP 22, amplified, and applied to the multiplier 25. The multiplier 25 multiplies the VCO output of the PLL video detector 23 and the output of the AMP 22, and calculates the difference between the frequencies fpt and fSl (5,
5MHz), outputs exactly PAL intercarrier.

Next, a case will be described in which a SECAM L broadcast signal is received. The case of VHF High channel and UHF, and the case of VHF Low channel will be explained separately. In the former case, PAL G/B
Switch sw2 is switched to Xl as in the case of the method. In response to this, VCO23d.

The free oscillation frequency of 24d is set, and the PLL loops in the PLL video detector 23 and PLL AM detector 24 are respectively locked to the video carrier frequency f and the audio carrier t frequency "st" of the SECAM L system V HF I11gh channel.Antenna The broadcast signal received by 1 is converted into a video intermediate frequency signal having a video carrier frequency 'PI' and an audio carrier frequency f'3□ by a tuner 2, as in the case of the PAL B/G system, and the video S
The signal is applied to the AW filter 3 and the audio SAW filters 4a and 4b. Then, the video intermediate frequency signal is demodulated into a video signal in the same manner as in the case of the PAL G/B system. Further, the filtered output of the audio SAW filter 4a is applied to the AMP 22 via the switch SW2. Generally SECAM
Since the audio modulation method of L method is AM modulation, PLL
The AM detector 24 demodulates the output of the AMP 22 into a SECAM audio signal using the oscillation output of the VCO 24d(7).

In the latter case, that is, in the case of VHF Lov channel, the switch S is switched by the signal from the switch changeover terminal 10.
Switch W2 to Yl. In response to this, VCO23d
, 24d are set, and the PLL loops in the PLL video detector 23 and PLL AM detector 24 are respectively locked to the video carrier frequency f and the audio carrier frequency '82 of the SECAML VHF Low channel. The broadcast signal received by the antenna 1 is converted by the tuner 2 into a video intermediate frequency signal P2 S2 having frequencies f , f , and is passed through the video S A W filter 3 and the audio SA
It is applied to W filters 4a and 4b. Then, the video intermediate frequency signal is demodulated into a video signal by the PLL video detector 23 through the same operation as described above. switch SW2
is switched to Yl, the AMP 22 is given a filtered output obtained by filtering the video intermediate frequency signal by the audio SAM filter 4b with a band-pass characteristic centered on the frequency fS2, and the AMP 22 amplifies the filtered output and outputs it to the PLL. A.M.
It is given to the detector 24. The PLL AM detector 24 is ■
The output of the AMP 22 is detected using the oscillation output of the CO 24d, and a SECAM audio signal is output.

According to the above embodiment, the audio SAW filter 4a.

4b, the audio carrier frequency f(f') and St
Audio signals of SL and f8° are extracted individually, and PAL B/G
In the case of the PAL method, the output of the VCO 23d in the PLL video detector 23, which is locked to the video carrier frequency f, the phase and frequency of one component in the video intermediate frequency signal, is used to detect the PAL signal.
Since intercarriers are obtained, there is no need to use the conventionally used picture trap circuit, and the number of components is reduced. Therefore, the circuit configuration becomes simple and costs can be reduced. Furthermore, since the PLL split method is used, the audio sensitivity and buzz characteristics are improved.

In the above embodiment, a case has been described in which broadcast signals of two broadcast systems are received, but the present invention can also be applied to a case where broadcast signals of three or more broadcast systems are received.

〔Effect of the invention〕

As described above, according to the present invention, the phase-locked loop circuit includes a voltage-controlled oscillator, is connected to a video filter, and outputs a lock signal phase-locked to a video carrier frequency from the voltage-controlled oscillator, and the video filter and a phase-locked loop circuit, the first signal from the video filter
a video detector that detects the filtered output of the filter using a lock signal and outputs a video signal, and a plurality of audio filters each having a bandpass characteristic centered on a different audio carrier frequency. An audio filter group that filters an intermediate frequency signal and outputs a second filtered output; and an audio filter group that is connected to the video filter group and outputs one of the plurality of second filtered outputs of the audio filter group depending on the type of broadcasting system. a switching means for selectively transmitting one audio signal; and a switching means connected to the voltage controlled oscillator and the switching means, and outputting a first audio signal by multiplying the phase lock signal by a second filtered output provided via the switching means. Since intercarriers are obtained without using a picture trap circuit, the circuit configuration is simplified and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a video intermediate frequency signal processing device according to the present invention, FIGS. 2 and 3 are diagrams showing bandpass characteristics of an audio SAW filter applied to the present invention, FIG. 4 is a block diagram showing an example of the configuration of a PLL video detector, FIG. 5 is a block diagram showing an example of the configuration of a PLL AM detector, and FIG. 6 is a block diagram showing the configuration of a conventional video intermediate frequency signal processing device. A block diagram, FIG. 7 is a diagram showing the bandpass characteristics of the video SAW filter included in the device shown in FIG. 6, and FIG. 8 is a diagram showing the audio SAW filter included in the device shown in FIG. 6.
FIG. 3 is a diagram showing bandpass characteristics of an AW filter. In the figure, 1 is an antenna, 2 is a tuner, 3 is a video S
AW filter, 4a and 4b are audio SAW filters, 1
0 is a switch switching terminal, 23 is a PLL video detector, 24
is a PLL AM detector, 25 is a multiplier, and SW2 is a switch. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) input means for inputting a video signal component and an audio signal component of a predetermined video carrier frequency determined for each broadcasting system, and a video intermediate frequency signal having the audio carrier frequency; a video filter that filters the video intermediate frequency signal with a bandpass characteristic necessary for demodulating the frequency signal into a normal video signal and outputs a first filtered output; and a voltage controlled oscillator; a phase-locked loop circuit connected to output a lock signal phase-locked to the video carrier frequency from the voltage controlled oscillator; and a phase-locked loop circuit connected to the video filter and the phase-locked loop circuit to output a lock signal phase-locked to the video carrier frequency; a video detector that detects a lock signal using a lock signal and outputs the video signal; and a plurality of audio filters each having a band-pass characteristic centered on a different audio carrier frequency, which is connected to the input means and is connected to the video intermediate an audio filter group that filters a frequency signal and outputs a plurality of second filter outputs; and a plurality of second filter outputs of the audio filter group that are connected to the audio filter group and that are configured to output a plurality of second filter outputs according to the type of the broadcasting system. switching means for selectively transmitting one of the outputs, connected to the voltage controlled oscillator and the switching means, multiplying the phase lock signal by the second filtered output provided via the switching means; and a multiplier configured to perform a first audio signal and output a first audio signal; and an oscillator that generates a signal synchronized with a signal component of the audio carrier frequency, and connected to the switching means;
an audio detector configured to detect the second filtered output provided via the switching means using an output signal of the oscillator and output an audio signal; A video intermediate frequency signal processing device comprising: the voltage controlled oscillator; and oscillation frequency changing means for changing the oscillation frequency of the oscillator.