JP3123622B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terrestrial television broadcast signal (hereinafter sometimes referred to as a TV signal), a satellite broadcast signal (hereinafter sometimes referred to as a BS signal), and a CATV broadcast signal (hereinafter referred to as a CATV signal). The present invention relates to a receiving device that receives a video signal and an audio signal after signal processing.

[0002]

2. Description of the Related Art Conventionally, TV signals, BS signals, and CAT
To collectively receive V signals, it is necessary to combine devices that receive the respective broadcast signals, or prepare a receiving device that individually includes a circuit that receives the respective broadcast signals.

[0003] In addition, the current satellite broadcasting is broadcast in two systems, that is, a broadcasting according to the NTSC system and a high-vision broadcasting according to the MUSE system. Therefore MUSE system and NTSC
Means for discriminating the method is required, and a receiver having the method discrimination means is described in Japanese Patent Application Laid-Open No. 3-204287.

[0004]

However, conventional TV signals, BS signals (MUSE system, NTSC system),
In a receiving apparatus that receives a CATV signal, a TV signal, a BS signal,
Since the signals are received by the respective tuner circuits, it is necessary to select the TV signal and the BS signal, respectively, which complicates the operation and makes it difficult to reduce the circuit scale of the receiving device.

[0005] In the above-mentioned prior art, the signal transmission system of CATV broadcasting is NTS based on the AM modulation system.
Since the transmission of C signal is mainly considered, the NTSC signal
In case of transmission by M modulation method or FTV by CATV broadcasting
M modulation method or MUS transmitted by AM modulation method
Receiving and processing the E signal is not considered.

A sync signal of an NTSC system television signal has a negative polarity, and a method of performing AGC (automatic gain control) by a voltage proportional to a peak value of the sync signal is generally used. Since the signal employs a positive polarity synchronization signal having no transmission loss, the peak value AG
When C is applied, it is considered that waveform distortion is caused.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a receiving apparatus which can receive a TV signal, a BS signal, and a CATV signal, has a simple circuit configuration and is excellent in operability. It is in.

Another object of the present invention is to provide a BS signal
It is an object of the present invention to provide a receiving device capable of receiving a television signal belonging to either the NTSC system or the MUSE system.

Further, another object of the present invention is to selectively process a signal through an AM demodulation system or an FM demodulation system regardless of whether the signal transmission system of a CATV signal is an AM modulation system or an FM modulation system. To be able to receive NTSC and MUSE television signals,
An object of the present invention is to provide a receiving device and to obtain good receiving performance.

[0010] In addition, the above-mentioned prior art does not sufficiently consider the case where two or more front ends are used for reception, and the video and audio signal processing circuit system becomes complicated and the circuit scale becomes large. , BS signal, and CATV signal are received and the signal is distributed,
Circuit connection becomes complicated.

[0011] Therefore, still another object of the present invention is to provide a TV signal, a BS signal, and a CATV signal, which can be received simultaneously using two or more front ends.
It is an object of the present invention to provide an easy-to-use receiving apparatus that can easily input, distribute, and output signals, BS signals, and CATV signals, and has a simple circuit configuration.

[0012]

In order to achieve the above object, according to the present invention, a TV signal and a CATV signal band are converted to a B signal.
BS / TV / CA with variable continuous tuning up to S signal band
A TV shared tuner was provided, and the tuning circuit was shared between receiving a BS signal, receiving a TV signal, and receiving a CATV signal.

Further, in order to receive two types of BS signals,
MUSE / NTSC system determination means for determining whether the BS signal is of the NTSC system or the MUSE system is provided.
The receiving apparatus includes a BS signal demodulation circuit, a TV / CATV signal demodulation circuit equipped with an NTSC demodulation circuit and a MUSE demodulation circuit, a BS signal processing circuit, a TV signal processing circuit, and a MUSE.
MUSE decoder (or MUSE-
(NTSC converter).

Further, an AM / FM method discriminating means for discriminating the signal transmission method of the CATV signal is provided.
AM demodulation processing based on the discrimination result of the M / FM
Local oscillation frequency switching control means for selecting M demodulation processing is provided. Further, the above MUSE / NTSC system discriminating means can perform signal processing regardless of whether the CATV signal is based on the NTSC system or the MUSE system. Even when the MUSE signal is based on the AM modulation system, excellent reception characteristics can be obtained. A to perform AGC system switching to obtain
A GC control circuit and a demodulation circuit switching control means are provided.

Further, a TV signal processing circuit for receiving a TV / CATV demodulated signal and performing signal processing, a BS signal processing circuit for receiving a BS demodulated signal and performing signal processing, and a MUSE decoder (or a MUSE decoder for processing a MUSE signal). MUSE-N
TSC converters are provided in two or more systems, respectively, and the above-mentioned channel selection circuit is shared by the BS signal reception, the TV signal reception and the CATV signal reception.
Shared tuner and its BS signal demodulation circuit and TV / CAT
Using two or more V signal demodulation circuits,

The TV / CATV demodulated signal or the BS demodulated signal output from these is switched and input to a TV signal processing circuit, a BS signal processing circuit, a MUSE decoder (or a MUSE-NTSC converter), and a TV signal is output. ,
CATV signals and BS signals can be received simultaneously or individually,

Each of the TV signal processing circuit, BS signal processing circuit, and MUSE decoder (or MUSE-NTSC converter) outputs video signals and audio signals from two or more output terminals. C
A common signal input terminal for inputting an ATV signal and a BS signal from the same terminal is connected to each of the BS / TV / CATV shared tubes.
And the TV signal, the CATV signal, and the BS signal are distributed to the respective tuners.

[0018]

According to the present invention, at least the channel selecting circuit is used commonly for receiving the BS signal, for receiving the TV signal, and for receiving the CATV signal. A receiving device capable of receiving a TV signal and a CATV signal can be obtained.

Further, by providing the MUSE / NTSC system discriminating means, the NT currently used in satellite broadcasting is provided.
It is possible to obtain a receiving apparatus compatible with two systems, that is, the SC system broadcasting and the MUSE system high-vision broadcasting.

Further, an AM / FM type discriminating means, MUS
By using the E / NTSC method discriminating means, the local oscillation frequency switching control means, the AGC method switching circuit, and the demodulation circuit switching control means, whether the CATV signal transmission method is the AM modulation method or the FM modulation method. ,
Even if the television signal system is the NTSC system, the MUS
Even with the E method, signal processing can be performed selectively,
Good reception performance can be obtained.

In addition, a TV signal processing circuit, a BS signal processing circuit, a MUSE decoder (or a MUSE-NT) using two or more tuner shared by BS, TV and CATV.
SC converters) are provided separately and switched to two or more systems, so that BS signals, TV signals,
A receiving device capable of receiving a CATV signal can be obtained.

Furthermore, a common signal input terminal for inputting a BS signal, a TV signal and a CATV signal from the same terminal is provided in each tuner, and the BS signal, the TV signal and the CATV signal are multiplexed and distributed to the respective tuners. Accordingly, the BS signal, the TV signal, and the CATV signal can be easily connected by one cable instead of using separate cables, so that an input connection is easy and an easy-to-use receiver can be obtained.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 show that when joining along the line AA,
FIG. 1 is a block diagram illustrating a receiving apparatus according to a first embodiment of the present invention.

In the figure, 1 is a first front end, 2 is a second front end, 100 is a signal distributor,
Reference numeral 101 denotes a signal input terminal for inputting a TV signal, a BS signal, and a CATV signal; 102, a first tuner circuit common to BS, TV, and CATV; 103, a first BS signal demodulation circuit;
04 is a first AM demodulation circuit for NTSC signal, 105 is a first AM demodulation circuit for MUSE signal, and 106 is a first BS
A signal processing circuit; 107, a first MUSE decoder (or MUSE-NTSC converter); 108, a first TV signal processing circuit; 130, a first AGC control circuit;
Reference numeral 12 denotes a first BS / TV / CATV shared channel selection means.

Reference numeral 202 denotes a second BS / TV / CATV.
A shared tuner circuit; 203, a second BS signal demodulation circuit;
204 is a second NTSC signal AM demodulation circuit, 205 is a second MUSE signal AM demodulation circuit, and 206 is a second B
S signal processing circuit, 207 is a second MUSE decoder (or MUSE-NTSC converter), 208 is a second MUSE decoder
TV signal processing circuit, 230 is a second AGC control circuit,
212 is a second BS / TV / CATV shared channel selection means, 1
13 is a keyed pulse output control circuit, 114 is a demodulation signal switching circuit, and 115 is a video and audio signal switching circuit.

Reference numeral 24 denotes a first video signal output terminal;
Is a first audio signal output terminal, 26 is a second video signal output terminal, 27 is a second audio signal output terminal, 28 is a third video signal output terminal, 29 is a third audio signal output terminal, 48
Denotes a fourth video signal output terminal, 49 denotes a fourth audio signal output terminal, 70 denotes a channel selection keyboard, and 71 denotes a reception control circuit.

The 12 GHz BS signal is down-converted.
The data is converted into a BS first intermediate frequency band (hereinafter, referred to as a BS-IF band) of about 1 to 2 GHz by a TV (not shown),
The signal is input to the common input terminal 101 together with the CATV signal. The signal is supplied to the first BS / TV by the distributor 100.
· CATV shared tuner circuit 102 and second BS · T
The signal is input to the V / CATV shared tuner circuit 202.

In the first front end 1, the first common tuner circuit 102 responds to a control signal output from the reception control circuit 71 in response to an input signal from the tuning keyboard 70, 1 if the signal selected by the BS / TV / CATV shared channel selecting means 112 is a BS signal, the BS-IF signal is referred to as an intermediate frequency signal (hereinafter, referred to as an IF signal. 78MH
z. ), And when the TV / CATV signal is selected by the shared channel selection means 112, the TV / CATV signal is
F signal (in Japan, the video carrier frequency is 58.7)
5 MHz. ).

Thereafter, each IF signal is supplied to the BS signal demodulation circuit 103 and the first NTSC signal AM demodulation circuit 1
04 or the first MUSE signal AM demodulation circuit 10
5 and demodulated. The video and audio signals are collectively FM-modulated in the BS signal, and the first BS signal demodulation circuit 103 performs an FM demodulation operation and performs the NTSC demodulation signal.
And a base band signal of the MUSE system to the demodulation signal switching circuit 114.

The TV signal is transmitted after the video signal is AM-modulated and the audio signal is FM-modulated.
The C signal AM demodulation circuit 104 performs the video signal AM demodulation operation and the audio signal FM demodulation operation, and outputs the video demodulation signal and the audio demodulation signal to the demodulation signal switching circuit 114.

Next, when the CATV signal is selected,
If the CATV signal is the same transmission system as the TV signal, the same signal processing as when the TV signal is selected is performed, and the description is omitted.

Next, if the selected CATV signal is an AM-modulated MUSE signal, the first MUSE signal AM
The demodulation circuit 105 outputs a MUSE baseband signal to the demodulation signal switching circuit 114. In the AM-modulated MUSE signal, the video and audio signals are collectively AM-modulated, and the occupied bandwidth becomes about 12 MHz by adding a residual sideband to the base band bandwidth of 8.1 MHz. AM transmission channel (6 MH)
A bandwidth twice that of z) is required.

Further, the polarity of the MUSE signal is different from that of the NTSC signal in the synchronizing signal, and it is not suitable to use the AGC circuit using the horizontal synchronizing signal of the NTSC signal conventionally used in the NTSC signal AM demodulator. Therefore, the first M
The AM demodulation circuit 105 for USE signal uses a PLL synchronous detection method having a wideband demodulation characteristic,
A keyed AGC circuit using a keyed pulse output from the MUSE decoder 107 and selectively input through the keyed pulse output control circuit 113 is provided.

Next, if the selected CATV signal is the FM transmission system of the NTSC system or the MUSE system, the demodulation circuit is switched to the first BS signal demodulation circuit 103,
The baseband signal of the SC system or the MUSE system is output to the demodulation signal switching circuit 114. The AGC control circuit 130 switches the AGC voltage input from the first BS signal demodulation circuit 103, the first NTSC signal AM demodulation circuit 104, and the first MUSE signal AM demodulation circuit 105 to switch the first common channel. To the AGC circuit in the

As simple means, a first BS signal demodulation circuit 103, a first NTSC signal AM demodulation circuit 104,
In the first MUSE signal AM demodulation circuit 105, if a normal AGC voltage is input from a demodulation circuit performing a demodulation operation and a zero potential is input from other demodulation circuits, AGC control is performed. The circuit 130 can be constituted by a simple addition circuit.

The same channel selection operation is performed in the second front end 2. The demodulated signal switching circuit 114 to which the demodulated signals from the first and second front ends 1 and 2 are input corresponds to the control signal output from the reception control circuit 71 in response to the input signal from the tuning keyboard 70. Then, the first TV signal processing circuit 108, the second TV signal processing circuit 208, the first BS signal processing circuit 106, the second BS signal processing circuit 206, the first MUSE decoder 10
7. Output to the second MUSE decoder 207 as appropriate.

The first TV signal processing circuit 108 performs signal processing such as amplitude adjustment and audio signal carrier removal on the video signal of the TV demodulated signal (NTSC-AM), and performs audio multiplexing on the audio signal. Signal processing such as stereo demodulation of the signal is performed, and the TV video and audio signals are output to the video and audio signal switching circuit 115.

Similarly, the second TV signal processing circuit 208 also outputs TV video and audio signals to the video and audio signal switching circuit 115. On the other hand, the first BS signal processing circuit 10
In step 6, the video signal of the BS demodulated signal (NTSC-FM) is subjected to signal processing such as removal of an energy spread signal, de-emphasis of an FM modulation signal, reproduction of a synchronizing signal, and amplitude amplification. Is a QPS that extracts a digital audio signal in a certain frequency band from the demodulated BS signal.
K (quadrature phase shift keying)
After demodulation, the digital signal subjected to QPSK demodulation is subjected to PCM (pulse code modulation) decoding and is converted to an analog audio signal.

The processed BS video and audio signals are
Output to the video and audio signal switching circuit 115. Similarly,
The second BS signal processing circuit 206 also outputs the video and audio signals to the video and audio signal switching circuit 115.

In the first MUSE decoder 107, the video signal is subjected to waveform equalization, synchronous reproduction, decode, de-emphasis, still image, and MUSE signals (AM and FM) of the CATV demodulated signal and the BS demodulated signal. Performs signal processing such as interpolation of video, inverse matrix, gamma processing, etc., performs audio signal processing such as waveform equalization, signal separation, time expansion, decoding, etc., and outputs the video signal to a third video signal output terminal 2.
8, the audio signal is output to the third audio signal output terminal 29.

Similarly, the second MUSE decoder 207 performs the above signal processing, and outputs the video signal to the fourth video signal output terminal 48 and the audio signal to the fourth audio signal output terminal 49.

The video and audio signal switching circuit 115 responds to the control signal output from the reception control circuit 71 in response to the input signal from the channel selection keyboard 70, and
V and BS video and audio signals are selected and switched, and the first video output terminal 24 and the first audio output terminal 25 and the second
From the video output terminal 26 and the second audio output terminal 27.

As described above, the receiving apparatus of this embodiment not only can receive the BS signal, the TV signal, and the CATV signal, but also can receive the tuner circuit 102 (at the time of receiving the BS / TV / CATV signal). And 202), channel selection means 112
Since (and 212) are shared, a receiver having a simple circuit configuration and excellent operability can be obtained.

The BS signal demodulation circuit 103 (and 2)
03), the NTSC signal AM demodulation circuit 104 (and 2
04), the MUSE signal AM demodulation circuit 105 (and 2
05), the transmission system of the CATV signal becomes
Reception is possible regardless of whether it is the AM modulation method, the FM modulation method, or the television signal method is the NTSC method or the MUSE method.

The first front end 1 and the second front end 2 can perform separate simultaneous channel selection operations of a TV signal, a CATV signal, and a BS signal, and each has two signal processing circuits. , Two systems of TV signal simultaneous reception, two systems of BS signal simultaneous reception, two systems of CAT
Various reception modes such as simultaneous reception of V signals, simultaneous reception of TV and BS signals, simultaneous reception of CATV and BS, and simultaneous reception of TV and CATV are possible.

In the signal format, NTSC-AM, N
From TSC-FM, MUSE-AM, and MUSE-FM, simultaneous reception is possible in any combination of two signal formats including the same format.

FIGS. 3 and 4 are block diagrams showing a receiving apparatus according to a second embodiment of the present invention when coupled along the line BB. In this figure, parts performing the same operations as those in FIGS. 1 and 2 are denoted by the same reference numerals as in FIGS. 1 and 2, and description thereof is omitted.

3 and 4, 117 is NTSC.
TV with demodulation circuit for MUSE and demodulation circuit for MUSE
CATV signal demodulation circuit, 116 is the first MUSE · N
TSC determination means, 118 is a first demodulation circuit switching control means, 130 is a first AGC control circuit, and 119 is a first local oscillation frequency switching control means.

217 is a second TV / CATV signal demodulation circuit, 216 is second MUSE / NTSC discriminating means,
218 is a second demodulation circuit switching control means, 230 is a second AGC control circuit, 219 is a second local oscillation frequency switching control means, 80 is a first changeover switch, 190 is a second changeover switch, 81, 82, 83, 191, 19
2, 193 are switch terminals.

In the present embodiment, in the first front end 1, the first shared tuner circuit 102 is connected to the first BS.
If the signal selected by the TV / CATV shared channel selecting means 112 is a BS signal, the BS-IF signal is converted into an intermediate frequency signal, and the TV / CATV signal is selected by the shared channel selecting means 112. If the TV / CATV signal is
Convert to a signal.

Thereafter, each IF signal is converted to the first B signal.
S signal demodulation circuit 103 or first TV / CATV
The signal is input to the signal demodulation circuit 117 and demodulated. First BS
The signal demodulation circuit 103 performs an FM demodulation operation and outputs a demodulated base band signal such as an NTSC system or a MUSE system. The switch terminal 8 is connected to the first changeover switch 80.
1, 83 are connected and the output BS demodulated signal is
The MUSE / NTSC discriminating means 116 outputs the signal to the demodulation signal switching circuit 114. If the signal is an NTSC signal, the signal is processed by a first BS signal processing circuit 106. If the signal is a MUSE signal, the signal is processed by a first MUSE decoder 107.

The TV signal is transmitted after the video signal is AM-modulated and the audio signal is FM-modulated.
The V signal demodulation circuit 117 performs a video signal AM demodulation operation and an audio signal FM demodulation operation, and outputs a video demodulation signal and an audio demodulation signal. The output TV demodulated signal is the first M
The signal is input to the demodulated signal switching circuit 114 through the USE / NTSC discriminating means 116, and the first TV signal processing circuit 10
The signal is processed at 8.

Next, when the CATV signal is selected,
If the CATV signal is the same transmission system as the TV signal, the same signal processing as when the TV signal is selected is performed, and the description is omitted.

Next, if the selected CATV signal is a MUSE type AM transmission system, the demodulation circuit (for NTSC / MUSE) and A
It is necessary to switch the GC system, and the first TV / CAT
The signal demodulated by the V signal demodulation circuit 117 is transmitted to the first MUS
The demodulation signal is discriminated by the E / NTSC discrimination means 116, the demodulation circuit is switched by the first demodulation circuit switching control means 118, and the AGC method is switched and controlled by the first AGC control circuit 130.
14 and the signal is processed by the first MUSE decoder 107.

Next, if the selected CATV signal is the FM transmission system of the NTSC system or the MUSE system, the first
It is necessary to switch from the TV / CATV signal demodulation circuit 117 to the first BS signal demodulation circuit 103, and the first TV
The signal demodulated by the CATV signal demodulation circuit 117 is the first
And the local oscillation frequency is switched and controlled by the first local oscillation frequency switching control means 119, and the CATV signal of the FM transmission system is used as the IF signal.

Subsequent processing is the same signal processing as when the BS signal is selected, and thus the description is omitted. The first
The MUSE / NTSC discriminating means 116 uses the separation of a specific signal such as a keyed pulse or a synchronization signal output from the first MUSE decoder 107 for discriminating the television system.

The same channel selection operation is performed in the second front end 2. The demodulated signals output from the first and second front ends 1 and 2 are input to a demodulated signal switching circuit 114. In the demodulation signal switching circuit 114, the first TV signal processing circuit 10
8, the second TV signal processing circuit 208, the first BS signal processing circuit 106, the second BS signal processing circuit 206, the first MUSE decoder 107, the second MUSE decoder 20
7 as appropriate.

The video and audio signal switching circuit 115 selects and switches the input TV and BS video and audio signals, and outputs the first video output terminal 24 and the first audio output terminal 2.
5 and a second video output terminal 26 and a second audio output terminal 27.

As described above, the receiving apparatus of the present embodiment has the MU in addition to the effects described in the embodiments of FIGS.
SE / NTSC determination means, demodulation circuit switching control means,
By using an AGC system switching circuit (AGC control circuit) and a local oscillation frequency switching control means, a demodulation circuit suitable for a signal format can be automatically selected.
Regardless of whether the signal transmission method is the AM modulation method, the FM modulation method, or the television signal method is the NTSC method or the MUSE method, reception is possible.

In addition, the first front end 1 and the second front end 2 can perform separate simultaneous channel selection operations of a TV signal, a CATV signal, and a BS signal, and each has two signal processing circuits. , Two systems of TV signal simultaneous reception, two systems of BS signal simultaneous reception, two systems of CAT
V signal simultaneous reception, TV signal and BS signal simultaneous reception, CAT
Various reception modes such as simultaneous reception of a V signal and a BS signal and simultaneous reception of a TV signal and a CATV signal are possible. In signal format, NTSC-AM, NTSC-FM, MUS
From E-AM and MUSE-FM, simultaneous reception is possible in any combination of two signal formats including the same format.

FIGS. 5 and 6 are block diagrams showing a receiving apparatus according to a third embodiment of the present invention when coupled along the line CC. In the same figure, FIG.
The same operations as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted. 5 and 6, reference numeral 109 denotes a first AM / FM determination unit, and reference numeral 209 denotes a second AM / FM determination unit.

The receiving apparatus of the third embodiment shown in FIGS. 5 and 6 takes into account that the signal processing of the receiving channel is performed at a higher speed than that of the second embodiment shown in FIGS. ing. That is, in the first front end 1, the first B
When the CATV broadcast is selected by the S / TV / CATV common channel selecting means 112, in the second embodiment shown in FIGS. 3 and 4, the received signal is transmitted to the first BS / TV / CATV shared channel. After receiving the signal processing by the analog circuit 102 and the first TV / CATV signal demodulation circuit 117, the control signal of the first local oscillation frequency switching control means 119 is output. When the television system is determined based on separation of a key pulse or a specific signal (for example, a synchronization signal) output from the first MUSE decoder 107, it takes a long time to perform the processing.

Therefore, in the present embodiment, the first BS / TV /
CAT output from CATV shared tuner circuit 102
Before the V signal is demodulated by the first TV / CATV signal demodulation circuit 117, the first AM / FM discriminating means 109
To determine the AM / FM system, and if the FM system is determined, the first local oscillation frequency switching control means 1
19, and outputs a signal for controlling the FM modulation before performing the signal processing in the first TV / CATV signal demodulation circuit 117 and the first MUSE / NTSC discriminating means 116, unlike the second embodiment. It is possible to determine the type of CATV signal.

The same signal processing is performed in the second front end 2. As described above, in addition to the effects described in the first and second embodiments, the receiving apparatus according to the present embodiment is different from the second embodiment in that a CATV signal is received when a CATV signal is received.
A indicates whether the V signal transmission method is the AM modulation method or the FM modulation method.
By performing the discrimination by the M / FM discriminating means, the signal processing of the receiving channel can be performed at high speed.

FIGS. 7 and 8 are block diagrams showing a receiving apparatus according to a fourth embodiment of the present invention when coupled along the line DD. In the same figure, FIG.
4, 5, and 6 are denoted by the same reference numerals, and description thereof is omitted.

The receiving apparatus according to the fourth embodiment shown in FIGS. 7 and 8 has a simpler configuration of the receiving apparatus and performs signal processing at a higher speed than the second and third embodiments described above. Is considered. That is, in the first front end 1, in the second and third embodiments described above, the first demodulation circuit switching control means 118 and the first AGC control circuit 13
0, the control of the first local oscillation frequency switching control means 119 is controlled by the output from the first MUSE / NTSC discriminating means 116 and the first AM / FM discriminating means 109.

On the other hand, in the fourth embodiment shown in FIGS. 7 and 8, the first BS / TV / CATV shared channel selecting means 1
12, the first switch 80, the first switch 80,
Demodulation circuit switching control means 118, first AGC control circuit 130, first local oscillation frequency switching control means 1
19 is controlled.

The BS signal of the NTSC system (NTSC-F
M) and a MUSE-type BS signal (MUSE-FM), a control signal is output from the first BS / TV / CATV shared channel selecting means 112 and the first switch 80 is output.
Connects the terminals 81 and 83 and inputs the BS demodulated signal to the demodulated signal switching circuit 114.

In the demodulation signal switching circuit 114, in the case of the BS signal of the NTSC system, the first BS signal processing circuit 106
Alternatively, the signal is output to the second BS signal processing circuit 206 and the MU
In the case of the BS signal of the SE system, the signal is output to the first MUSE decoder 107 or the second MUSE decoder 207 to perform signal processing.

When a TV signal (NTSC-AM) is selected, a control signal is output from the first BS / TV / CATV shared channel selection means 112 and input to the first demodulation circuit switching control means 118. The first TV / CATV demodulation circuit 117 is a circuit for demodulating an NTSC signal, and the switch 80 connects the terminals 82 and 83 to input the TV demodulated signal to the demodulated signal switching circuit 114.

When the AM modulation type CATV signal is selected, the first BS / TV / CATV shared channel selecting means 11 is used.
2 outputs a control signal and the television signal is NTSC
In the case of the system (NTSC-AM), the same processing as that in the case of receiving the TV signal is performed, so the description is omitted. However, in the case of the MUSE system (MUSE-AM), the first BS / TV / CATV shared channel selecting means 112 is used. , A control signal is output to the first demodulation circuit switching control means 118, and the first TV · C
The ATV demodulation circuit 117 is a circuit for demodulating a MUSE signal, and controls the first AGC control circuit.
The first switch 80 connects the terminals 82 and 83 and inputs to the demodulation signal switching circuit 114.

In demodulated signal switching circuit 114, NTSC-
The input signal of the AM system is output to the first TV signal processing circuit 108 or the second TV signal processing circuit 208, and the input signal of the MUSE-AM system is output to the first M
The signal is output to the USE decoder 107 or the second MUSE decoder 207 and subjected to signal processing.

The CATV signal of the FM system (NTSC-FM
And MUSE-FM) are selected, the first BS
A control signal is output from the TV / CATV shared channel selection means 112 and input to the first local oscillation frequency switching control means 119. Hereinafter, the description is omitted because it is the same as the case where the BS signal is selected. The same signal processing is performed in the second front end 2 as well.

As described above, in the receiving apparatus of this embodiment, since the signal processing path is determined at the same time as channel selection, in addition to the effects described in the first, second, and third embodiments, the receiving apparatus of the second, third, and fourth embodiments will be described. BS, TV, CAT
By using the output from the V common channel selecting means, the configuration of the receiving apparatus is simple and the signal processing can be performed at high speed.

FIG. 9 shows N in FIGS. 3, 5, and 7.
First equipped with a demodulation circuit for TSC and a demodulation circuit for MUSE
And second TV / CATV signal demodulation circuits 117 and 2
17 is a circuit diagram showing a specific example in which the circuit configuration of FIG. 17 is simplified. The TV / CATV signal demodulation circuit described above uses the NTSC
The demodulation circuit for MUSE and the demodulation circuit for MUSE,
Since the video signal of the TSC signal and the MUSE signal are the same AM modulation, the detection circuit can be used in common.

In FIG. 9, reference numerals 75, 76, 77, 78 denote changeover switches, 120 denotes an IF signal input terminal, 121
Is an AM detection output terminal, 122 is an audio detection output terminal, 12
3 is a control signal input terminal, 140, 141, 142, 14
3, 144, 145 are switch terminals, 180 is a wide band surface acoustic wave (hereinafter, referred to as SAW) filter, 181 is a narrow band SAW filter, 182 is an IF amplifier circuit,
3 is an AM detection circuit, 184 is an audio detection circuit, 185 is a peaking adjustment circuit, and 186 is a 4.5 MHz trap.

The TV / CATV signal demodulation circuit 117 shown in FIG.
a indicates that the IF signal input from the input terminal 120 is NTS
In the case of the C system, the switch 75 is connected to the terminal 142 and the switch 7 by a control signal from the demodulation circuit switching control means 109.
6 is connected to the terminal 145 and the narrow band SAW filter 18
1 is selected, the switch 77 is connected, the voice detection (FM demodulation) circuit 184 is operated, and the switch 78 is connected, the 4.5 MHz trap circuit 186 is operated, and the peaking adjustment circuit 185 is controlled. I do. as a result,
An AM detection signal is output from a terminal 121 and an audio detection signal is output from a terminal 122.

Next, in the case of the MUSE system, the switch 75 is connected to the terminal 140 and the switch 76 is connected to the terminal 1 by a control signal from the demodulation circuit switching control means 118 or 218.
43, a wide-band SAW filter 180 is selected, the switch 77 is disconnected, and the audio detection circuit 184 is connected.
Does not operate, and furthermore, the switch 78 is disconnected and 4.5M
The Hz trap circuit 186 also does not operate, and controls the peaking adjustment circuit 185 so as to compensate for the high-frequency side of the output from the AM detection circuit 183. As a result, the MU is
The baseband signal of the SE system is output.

As described above, the circuit of FIG.
Wideband and narrowband SAW filters that share a detection circuit,
By controlling the audio detection circuit, the peaking adjustment circuit, and the 4.5 MHz trap, signal processing can be performed regardless of whether the AM transmission type CATV signal is the NTSC type or the MUSE type.

In the embodiment of the present invention, the case where the television signal is the NTSC system and the MUSE system has been described. However, even if the NTSC system is replaced with the PAL system or the SECAM system, the HDTV signal is not a MUSE system but a U.S. digital system. HDTV system or European HD-MAC
Even in the case of the system, the same effect can be obtained by changing the bandwidth, the frequency of the IF signal and the local oscillation signal, the type of the decoder, and the like.

Next, FIG. 10 shows a specific example of the AGC voltage generator for the AM-modulated MUSE signal in the AGC control circuit of the embodiment shown in FIGS. 3, 5, and 7. FIG.
, 50 is a demodulated signal input terminal, 51 is a keyed pulse input terminal, 52 is a noise removal filter for the demodulated signal, 53
Is a gate circuit using a keyed pulse, 54 is an AGC voltage generation detection circuit, 55 is a low-pass filter for smoothing, 56,
57 is an AGC voltage amplifier circuit.

After the demodulated MUSE signal is input from the demodulated signal input terminal 50 and the noise is removed by the noise elimination filter 52, the signal is passed through a gate circuit 53 that passes the demodulated signal during the keyed pulse period input from the keyed pulse input terminal 51. The signal is input to the AGC detection circuit 54.

In the AGC detection circuit 54, since the keyed pulse corresponds to the clamp period of the MUSE signal, detection is performed at a clamp level independent of the image content, and a detection voltage is output. This detected voltage is smoothed by the low-pass filter 55. Since the cycle of the keyed pulse is 60 Hz,
The time constant of the low-pass filter 55 needs to be set to several tens of seconds.

In this case, high-speed level fluctuation such as flutter caused by an airplane or the like, which is observed in the terrestrial broadcasting of NTSC signals, cannot be followed. Level fluctuation is small and there is no practical problem. The AGC voltage smoothed by the low-pass filter 55 is amplified by an AGC voltage amplifying circuit 56 and then output as a gain control voltage of an IF amplifying circuit in a demodulating circuit. Further, the AGC voltage amplification circuit 57 performs amplification and voltage shift, and outputs it as a gain control voltage for an RF amplification circuit or the like in the tuner unit.

According to this specific example, the AM-modulated MUS
Since the AGC voltage generator for the E signal is configured to detect the demodulated signal during the keyed pulse period, the AGC voltage is generated during the clamp period that does not depend on the image content. Therefore, a stable AGC voltage is obtained even when the APL fluctuates. Demodulation characteristics are obtained.

FIG. 11 shows another specific example of the AGC voltage generator. In the figure, parts performing the same operations as those in FIG. 10 are denoted by the same reference numerals, and description thereof is omitted. FIG.
Medium, 58 is a low-pass filter with switchable time constant, 59
Is a MUSE, NTSC switching signal input terminal.

This specific example aims to simplify the circuit by sharing the AGC voltage generator for the AM-modulated NTSC signal and the MUSE signal. Demodulated NTS
After the C signal or the MUSE signal is input from the demodulated signal input terminal 50 and the noise is removed by the noise removal filter 52,
The signal is input to the AGC detection circuit 54. At the time of receiving the MUSE signal, the AGC detection circuit 54 performs the peak value AGC detection using the frame pulse which is in the MUSE signal and does not depend on the image content similarly to the clamp period described above.

The signal level of the frame pulse of the MUSE signal is relatively large, and the control sensitivity of the AGC can be improved as compared with the detection using the clamp level. When receiving the NTSC signal, peak value AGC detection using the horizontal synchronization signal of the NTSC signal is performed. With this configuration, the AGC voltage generator can be shared by the MUSE signal and the NTSC signal.

The detected voltage is smoothed by the low-pass filter 55. Since the period of the frame pulse is 30 Hz,
The time constant of the low-pass filter 55 also needs to be set to several tens of seconds or more. Also in this case, as in the specific example of FIG. 10, high-speed level fluctuation such as flutter caused by an airplane or the like, which is seen in terrestrial broadcasting of NTSC signals, cannot be followed.
In the CATV signal, the signal level is relatively stable,
High-speed level fluctuation such as flutter is small, and there is no practical problem.

The AGC voltage smoothed by the low-pass filter 55 is amplified by an AGC voltage amplifier 56 and then output as a gain control voltage of an IF amplifier in a demodulator. Further, the AGC voltage amplification circuit 57 performs amplification and voltage shift, and outputs it as a gain control voltage for an RF amplification circuit or the like in the tuner unit.

According to the present embodiment, the AM-modulated MUS
Since the AGC voltage generator for E signal is configured to detect using the frame pulse, the AGC voltage is generated in the frame pulse period independent of the image content. Therefore, a stable AGC voltage can be obtained even when the APL fluctuates. A demodulation characteristic can be obtained, and the low-pass filter time constant can be switched to be shared with an AGC voltage generator for an AM-modulated NTSC signal using a horizontal synchronization signal. Simplification can be achieved.

When the AGC voltage generator of this embodiment is used, the AGC voltage generator of the embodiment shown in FIGS. 3, 5, and 7 is used.
The GC control circuits 130 and 230 correspond to the AG control circuit shown in FIG.
This is the same as the C control circuits 130 and 230, so that the AGC control circuit can be simplified.

[0093]

According to the present invention, it is possible not only to receive a BS signal, a TV signal, and a CATV signal, but also to
Since the tuner circuit and the tuning means are shared when receiving the V.CATV signal, a receiver having a simple circuit configuration and excellent operability can be obtained.

Also, by using the BS signal demodulation circuit, the NTSC signal AM demodulation circuit, and the MUSE signal AM demodulation circuit, the CATV signal transmission method can be either the AM modulation method or the FM modulation method. Reception is possible whether the television signal system is the NTSC system or the MUSE system.

Further, by providing the local oscillation frequency switching control means, even if the CATV signal transmission method is the AM transmission method or the FM transmission method, the BS signal demodulation processing and the TV / CATV signal demodulation processing are selected and the signal processing is performed. Has the effect that becomes possible.

Also, by providing the MUSE / NTSC discriminating means, high-definition broadcasting can be received. In addition, by providing the AGC system switching circuit (AGC control circuit) and the demodulation circuit switching control means, the CAT is provided.
Even if the V broadcast is a MUSE signal of the AM modulation method, good reception performance can be obtained, and there is an effect that it is possible to receive even a multi-channel Hi-Vision broadcast by CATV.

According to the present invention, a TV signal, a CAT
In a receiving apparatus that receives a V signal and a BS signal and switches and outputs two or more sets of video and audio signals, a TV demodulation signal, a CATV demodulation signal, and a BS demodulation signal are output by sharing a channel selection circuit and a frequency conversion circuit. With TV signal, CA
A TV signal and a BS signal are input from the same terminal. A demodulated signal from a front end having a simple configuration is switched to two or more demodulated signal processing circuits, and the signal is output. Various types of reception are possible, such as receiving a CATV signal, receiving two systems of TV signals, simultaneously receiving TV and BS signals, simultaneously receiving CATV and BS signals, and simultaneously receiving TV and CATV signals.

Furthermore, by using a front end having a simple configuration for inputting a TV signal, a CATV signal, and a BS signal from the same terminal, a small-sized circuit configuration that is easy to use, such as a high-frequency signal input terminal connection is simplified. A receiving device is obtained.

Further, in the demodulation of the TV / CATV signal, by using a keyed pulse or a frame pulse in the AGC voltage generating section, the stable AG can be obtained even when the APL changes.
C voltage is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a left half of a first embodiment of the present invention.

FIG. 2 is a block diagram showing a right half of the first embodiment of the present invention.

FIG. 3 is a block diagram showing a left half of a second embodiment of the present invention.

FIG. 4 is a block diagram showing a right half of a second embodiment of the present invention.

FIG. 5 is a block diagram showing a left half of a third embodiment of the present invention.

FIG. 6 is a block diagram showing a right half of a third embodiment of the present invention.

FIG. 7 is a block diagram showing a left half of a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a right half of a fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a specific example in which the circuit configuration of the TV / CATV signal demodulation circuit in FIGS. 3, 5, and 7 is simplified.

FIG. 10 is a block diagram showing an AGC voltage generator for an AM-modulated MUSE signal in the AGC control circuit shown in FIGS. 3, 5 and 7;

FIG. 11 is a block diagram illustrating an AGC voltage generator for an AM-modulated NTSC signal and a MUSE signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st front end, 2 ... 2nd front end, 24 ... 1st video signal output terminal (current television broadcasting), 26 ... 2nd video signal output terminal (current television broadcasting), 28 ... 1st , A second video signal output terminal (high-definition broadcast), 25 a first audio output terminal (current television broadcast),
27 ... second audio output terminal (current television broadcast), 29 ...
First audio output terminal (high-definition broadcasting), 49 ... second
Audio output terminal (high-definition broadcasting), 101 ... signal input terminal, 100 ... signal distributor, 102 ... first BS-T
V · CATV shared tuner circuit, 202 ... second BS ·
TV / CATV shared tuner circuit, 103 ... first BS
Signal demodulation circuit, 203: second BS signal demodulation circuit, 10
4: first AM demodulation circuit for NTSC signal, 204: second
AM demodulation circuit for NTSC signal, 117.
CATV signal demodulation circuit, 217 ... second TV / CATV
Signal demodulation circuit, 105: AM demodulation circuit for first NTSC signal, 205: AM demodulation circuit for second NTSC signal, 1
16: first MUSE / NTSC discriminating means, 216: second MUSE / NTSC discriminating means, 106: first BS
Signal processing circuit, 206 ... second BS signal processing circuit, 10
7: first MUSE decoder, 207: second MUSE decoder
Decoder 108, first TV signal processing circuit, 208
A second TV signal processing circuit, 118 ... first demodulation circuit switching control means, 218 ... second demodulation circuit switching control means, 119 ... first local oscillation frequency switching control means,
219: second local oscillation frequency switching control means, 11
2. 1st BS / TV / CATV shared channel selection means, 130
... First AGC circuit, 230 ... Second AGC circuit, 21
2 ... second BS / TV / CATV shared channel selection means, 109
... first AM / FM discriminating means, 209 ... second AM / F
M discriminating means, 113 ... keyed pulse control circuit, 114 ...
Demodulation signal switching circuit, 115: video and audio signal switching circuit, 180: wide band SAW filter, 181 ... narrow band SAW filter.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-204287 (JP, A) JP-A-4-196880 (JP, A) JP-A-4-1966881 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H04N 5/46 H04N 7/015 H04N 7/16 H04N 7/20

Claims (6)

(57) [Claims] 1. A receiver for receiving a terrestrial television broadcast signal (hereinafter, referred to as a TV signal), a satellite broadcast signal (hereinafter, referred to as a BS signal), and a CATV broadcast signal (hereinafter, referred to as a CATV signal), comprising: BS / TV / CATV shared tuner circuit (102, 202) for selecting and receiving a signal, BS signal or CATV signal, and BS / TV for sending a tuning command to the shared tuner circuit. A CATV shared channel selecting means (112, 212) and an NTSC-AM demodulation circuit (104, 204) for taking in an IF signal from the shared tuner circuit and demodulating the IF signal if it is an NTSC-AM modulated signal; If it is a MUSE-AM modulation signal, the MUSE-AM demodulation circuit (1) performs the demodulation.
05, 205), which is an NTSC-FM modulated signal or M
BS for demodulating USE-FM modulated signal when it is
A signal demodulation circuit (103, 203) and a gain control (hereinafter referred to as AG) for the shared tuner circuit from each of the demodulation circuits.
AGC control circuit (130, 23) which takes in a voltage, selects and switches the voltage and supplies it to the shared tuner circuit.
0), and at least two TV signal processing circuits (108, 108) that receive demodulated signals output from the respective demodulation circuits in the front end. 208), at least two BSs
A signal processing circuit (106, 206) and at least two systems of MUSE decoders (or MUSE decoders) for MUSE signal processing;
USE-NTSC converters (107, 207) for selectively switching and outputting demodulated signal switching circuits (114); and output signals from the two systems of TV signal processing circuits and two systems of BS signal processing circuits. A signal switching circuit for capturing and outputting the output video signal and audio signal (or data signal) to at least two video signal output terminals (24, 26) and audio signal output terminals (25, 27). 115) and a receiving device characterized in that a TV signal, a BS signal, and a CATV signal can be simultaneously or independently received. 2. A receiving apparatus for receiving a terrestrial television broadcast signal (hereinafter, referred to as a TV signal), a satellite broadcast signal (hereinafter, referred to as a BS signal), and a CATV broadcast signal (hereinafter, referred to as a CATV signal), comprising: BS / TV / CATV shared tuner circuit (102, 202) for selecting and receiving a signal, BS signal or CATV signal, and BS / TV for sending a tuning command to the shared tuner circuit. A CATV common channel selecting means (112, 212) and a TV / CATV signal demodulating circuit (117, 217) for taking in an IF signal from the common tuner circuit and demodulating the IF signal if it is a TV signal or a CATV signal , A BS signal demodulation circuit for demodulating the signal when it is a BS signal (103, 203)
And MUSE / NTSC for determining to which television system the input signal at that time belongs.
Determining means (116, 216);
Whether the TV / CATV signal demodulation circuit is an NTSC system demodulation circuit depends on the result of the discrimination by the discrimination means whether the signal transmitted by the M modulation system belongs to the NTSC system or the MUSE system. Demodulation circuit switching control means (11) for switching to the MUSE type demodulation circuit.
8, 218) and the BS / TV / CATV shared channel depending on the result of the determination by the determination means whether the signal transmitted as the CATV signal is a signal based on the AM modulation method or a signal based on the FM modulation method. Local oscillation frequency switching control means (11) for switching the local oscillation frequency of the
9, 219), and when receiving an AM-modulated MUSE signal, a MUSE
The AGC voltage is generated by using the keyed pulse from the decoder (107, 207), and the tuner AGC voltage output from the BS signal demodulation circuit and the TV / C at the time of receiving the AM-modulated NTSC signal are received.
And the tuner AGC voltage to be output from the ATV signal demodulation circuit.
An AGC control circuit (130, 230) for outputting to the CATV shared tuner circuit; and at least two front ends (1, 2) including: and an output from each of the demodulation circuits in the front end. The demodulated signal is taken in, at least two systems of TV signal processing circuits (108, 208), and at least two systems of BS.
A signal processing circuit (106, 206) and at least two systems of MUSE decoders (or MUSE decoders) for MUSE signal processing;
USE-NTSC converters (107, 207) for selectively switching and outputting demodulated signal switching circuits (114); and output signals from the two systems of TV signal processing circuits and two systems of BS signal processing circuits. A signal switching circuit for capturing and outputting the output video signal and audio signal (or data signal) to at least two video signal output terminals (24, 26) and audio signal output terminals (25, 27). 115) and a receiving device characterized in that a TV signal, a BS signal, and a CATV signal can be simultaneously or independently received. 3. A receiving apparatus for receiving a terrestrial television broadcast signal (hereinafter, referred to as a TV signal), a satellite broadcast signal (hereinafter, referred to as a BS signal), and a CATV broadcast signal (hereinafter, referred to as a CATV signal). BS / TV / CATV shared tuner circuit (102, 202) for selecting and receiving a signal, BS signal or CATV signal, and BS / TV for sending a tuning command to the shared tuner circuit. A CATV common channel selecting means (112, 212) and a TV / CATV signal demodulating circuit (117, 217) for taking in an IF signal from the common tuner circuit and demodulating the IF signal if it is a TV signal or a CATV signal , A BS signal demodulation circuit for demodulating the signal when it is a BS signal (103, 203)
And MUSE / NTSC for determining to which television system the input signal at that time belongs.
Determining means (116, 216);
Whether the TV / CATV signal demodulation circuit is an NTSC system demodulation circuit depends on the result of the discrimination by the discrimination means whether the signal transmitted by the M modulation system belongs to the NTSC system or the MUSE system. Demodulation circuit switching control means (11) for switching to the MUSE type demodulation circuit.
8,218), and when receiving the MUSE signal modulated by AM,
The AGC voltage is generated by using the keyed pulse from the decoder (107, 207), and the tuner AGC voltage output from the BS signal demodulation circuit and the TV / C at the time of receiving the AM-modulated NTSC signal are received.
And the tuner AGC voltage to be output from the ATV signal demodulation circuit.
An AGC control circuit (130, 230) for outputting to the CATV shared tuner circuit; and a CATV signal taken in from the shared tuner circuit to the TV / CATV signal demodulation circuit by an AM modulation method or an FM modulation method. AM to determine whether the signal
/ FM discriminating means (109, 209) and local oscillation frequency switching control means (119, 219) for switching the local oscillation frequency of the tuner circuit shared by BS, TV and CATV depending on the discrimination result by the discriminating means. And at least two front-ends including a demodulation signal output from each of the demodulation circuits in the front-end, and at least two systems of TV signal processing circuits (108, 208). , At least two BSs
A signal processing circuit (106, 206) and at least two systems of MUSE decoders (or MUSE decoders) for MUSE signal processing;
USE-NTSC converters (107, 207) for selectively switching and outputting demodulated signal switching circuits (114); and output signals from the two systems of TV signal processing circuits and two systems of BS signal processing circuits. A signal switching circuit for capturing and outputting the output video signal and audio signal (or data signal) to at least two video signal output terminals (24, 26) and audio signal output terminals (25, 27). 115) and a receiving device characterized in that a TV signal, a BS signal, and a CATV signal can be simultaneously or independently received. 4. A receiver for receiving a terrestrial television broadcast signal (hereinafter, referred to as a TV signal), a satellite broadcast signal (hereinafter, referred to as a BS signal), and a CATV broadcast signal (hereinafter, referred to as a CATV signal), comprising: BS / TV / CATV shared tuner circuit (102, 202) for selecting and receiving a signal, BS signal or CATV signal, and BS / TV for sending a tuning command to the shared tuner circuit. A CATV common channel selecting means (112, 212) and a TV / CATV signal demodulating circuit (117, 217) for taking in an IF signal from the common tuner circuit and demodulating the IF signal if it is a TV signal or a CATV signal , A BS signal demodulation circuit for demodulating the signal when it is a BS signal (103, 203)
And whether the signal transmitted at that time as the CATV signal in the AM modulation system belongs to the NTSC system,
The discrimination information as to whether the data belongs to the E system is transmitted to the BS / TV /
Demodulation circuit switching control means (118, 218) for switching the TV / CATV signal demodulation circuit to the NTSC system demodulation circuit or the MUSE system demodulation circuit, and receiving the AM-modulated signal. When receiving a MUSE signal, the MUSE
The AGC voltage is generated by using the keyed pulse from the decoder (107, 207), and the tuner AGC voltage output from the BS signal demodulation circuit and the TV / C at the time of receiving the AM-modulated NTSC signal are received.
And the tuner AGC voltage to be output from the ATV signal demodulation circuit.
An AGC control circuit (130, 230) for outputting to the CATV shared tuner circuit; and a CATV signal taken in from the shared tuner circuit to the TV / CATV signal demodulation circuit by an AM modulation method or an FM modulation method. Local oscillation frequency switching control means (119) for switching the local oscillation frequency of the BS / TV / CATV shared tuner circuit by receiving information for determining whether the signal is a signal from the BS / TV / CATV shared tuner circuit. , 219), and at least two front-ends (1, 2) including: a demodulation signal output from each of the demodulation circuits in the front-end; , 208), at least two BSs
A signal processing circuit (106, 206) and at least two systems of MUSE decoders (or MUSE decoders) for MUSE signal processing;
USE-NTSC converters (107, 207) for selectively switching and outputting demodulated signal switching circuits (114); and output signals from the two systems of TV signal processing circuits and two systems of BS signal processing circuits. A signal switching circuit for capturing and outputting the output video signal and audio signal (or data signal) to at least two video signal output terminals (24, 26) and audio signal output terminals (25, 27). 115) and a receiving device characterized in that a TV signal, a BS signal, and a CATV signal can be simultaneously or independently received. 5. The receiving device according to claim 1, wherein at least two of said front ends are:
A receiving device characterized in that a TV signal, a BS signal, and a CATV signal are taken in through a common input terminal (101). 6. The receiving device according to claim 2, wherein the TV / CATV signal demodulation circuit comprises:
An AGC voltage generator for generating the tuner AGC voltage; a noise removing filter (52) for receiving the demodulated signal and removing noise and outputting the noise; and an AGC detector for receiving an output of the noise removing filter. A low-pass filter capable of switching a time constant between reception of a MUSE signal and reception of an NTSC signal;
A low-pass filter (55) to which a detection output is input;
An AGC voltage amplifier circuit (56, 57) that receives, amplifies and outputs the output of the low-pass filter.