JP3058646B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention receives a BS (Satellite Broadcasting) signal transmitted using an FM modulation method and an AM-modulated TV signal in the VHF / UHF band. Related to a receiving device.

[Conventional technology]

A general receiving system receives a BS signal, which is down-converted from an FM-modulated SHF band satellite broadcast signal and frequency-converted to a 1 GHz band intermediate frequency signal, and a VHF / UHF band TV signal (including CATV). In this case, since the frequency band of each broadcast wave signal is different, a separate receiving circuit is required, the configuration becomes complicated, and the operation is not easy.

Therefore, for example, as a solution to these problems, as a receiving device using the same receiving circuit for satellite broadcasting and TV broadcasting,
As described in Japanese Patent Application Laid-Open No. 57-39628, a receiving device that converts a BS signal to a frequency of an empty channel in the UHF or VHF band and causes the TV signal receiving circuit to receive the frequency-converted BS signal together with a TV signal is disclosed. Are known.

[Problems to be solved by the invention]

Among the above-mentioned prior arts, in the former, the BS signal, T
When a V signal is received, it is necessary to separately select a BS signal and a TV signal, which not only complicates the operation but also increases the circuit size of the receiving device.

If both the BS signal receiving circuit and the TV signal receiving circuit are incorporated in a television receiver, video tape recorder, etc., many terminals are required to redistribute the BS signal and TV signal. And the operation becomes complicated.

Further, of the above-mentioned conventional techniques, the latter has the following problems.

That is, the BS signal is converted to the frequency of an empty channel in the UHF or VHF band, and the frequency-converted BS signal is transmitted to the TV together with the TV signal.
In a receiving apparatus for receiving a signal by a signal receiving circuit, a pass band of a filter provided in the TV signal receiving circuit is about 20 MHz in order to pass a TV signal. However, since the band of the BS signal is a wide band of 27 MHz, passing the frequency-converted BS signal through the filter deteriorates the signal,
As a result, there has been a problem that the demodulation characteristics of the BS signal deteriorate.

Further, as an application example of the receiving apparatus, for example, a BS signal is converted into a frequency of an empty channel in the UHF or VHF band, and the frequency-converted BS signal and the TV signal (including the CATV) are both transmitted by the same cable. When transmitting and distributing to a plurality of receivers for TV signal reception, in one receiver, a local oscillation signal leaks from another receiver, and the leaked local oscillation signal is converted to a frequency-converted BS signal. Band (ie, UHF
Band or VHF band), causing interference.

An object of the present invention is to provide a receiving device which can receive a BS signal and a TV signal, has a simple circuit configuration, and is excellent in operability.

Another object of the present invention is to provide a receiving apparatus capable of receiving a BS signal and a TV signal, having a small frequency fluctuation, and obtaining a good demodulated signal.

Still another object of the present invention is to provide a receiving device which has an input terminal for inputting an RF signal obtained by mixing a BS signal and a TV signal, and an output terminal for outputting, and has a simple circuit configuration and excellent operability. Is to do.

[Means for solving the problem]

In order to achieve the first of the above objectives,
In the present invention, at least one of the RF amplifier circuit, the AGC circuit, the frequency conversion circuit, the voltage-controlled oscillator, and the tuning circuit is used commonly for receiving a TV signal and receiving a BS signal.

In order to achieve the second object, means for switching the control sensitivity when changing the control voltage for the voltage controlled oscillator in accordance with the AFS signal voltage from the demodulation circuit between the time of receiving a TV signal and the time of receiving a BS signal. Was provided.

Further, in order to achieve a third object, an RF signal input terminal for inputting an RF signal formed by mixing a received TV signal and a BS signal, and a branch circuit for splitting the input RF signal into two parts A branching circuit that receives one of the two branched RF signals and separates the signal into a TV signal and a BS signal; an amplifier circuit that amplifies and outputs the separated BS signal; A combining circuit for combining the BS signal output from the circuit and the separated TV signal, and an RF obtained by combining in the combining circuit.
An RF signal output terminal for outputting a signal is provided.

[Action]

In the present invention, an RF amplifier circuit, an AGC circuit, a frequency conversion circuit,
At least one of the voltage-controlled oscillator and the tuning circuit is used commonly for receiving a TV signal and for receiving a BS signal to control a voltage-controlled oscillator (a local oscillator of a superheterodyne tuner) and a variable filter. Accordingly, it is possible to obtain a receiver having a simple circuit configuration and excellent operability and capable of receiving a BS signal and a TV signal.

In addition, the control voltage for the voltage controlled oscillator is
When changing according to the S signal voltage, the control sensitivity is switched between the time of receiving the TV signal and the time of receiving the BS signal by the means, so that a stable receiving operation can be performed and a good demodulated signal can be obtained.

Also, the above-described RF signal input terminal, branch circuit, branching circuit, amplifier circuit, synthesis circuit, RF signal output terminal,
Is provided, an input terminal for inputting an RF signal obtained by mixing a BS signal and a TV signal, and an output terminal for outputting the RF signal, and a receiving device with improved operability can be obtained.

Also, even if a signal mixed with a TV signal and BS signal is input,
Since an appropriately selected IF signal can be obtained by filter switching and oscillation frequency band switching and then demodulated, one input of a TV / BS signal becomes possible.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

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

The receiving device shown in FIG. 1 is a PAL T
The receiving device receives a V-BS signal and outputs a video and audio signal or a data signal as a demodulated signal.

In FIG. 1, 1 is an RF signal input terminal, 2 is a demultiplexer, 3
Is an AGC circuit, 4 is a first RF amplifier circuit, 5 is a first variable (tuned) BPF, 6 is a first AGC amplifier circuit, 7 is a branching circuit, 8 is a second variable (tuned) BPF, 9 is the third variable (tuned) BPF, 10 is the fourth
Variable (tuning) BPF, 11 is a first frequency conversion circuit, 12 is a second frequency conversion circuit, 13 is a voltage controlled oscillator for BS, 14 is a VHF
Voltage-controlled oscillator, 15 for UHF voltage-controlled oscillator, 16, 17 for IF
Amplification circuit, 18 is a fixed IF band BPF for BS, 19 is a fixed I band for TV
F band BPF, 20 is a FM (signal) demodulation circuit for BS, 21 is an AM demodulation circuit for TV, 26 is an audio FM demodulation circuit, 22 is a filter for data or PCM audio signal, 23 is a video output switching circuit, 24 Is an audio signal demodulation switching circuit, 25 is an AFS voltage superposition circuit, 30 is an AGC switching circuit, 1
00 is a tuning key, 101 is a microcomputer circuit (control circuit), 102 is a voltage synthesizer tuning circuit, 103 is a memory, 230 is an oscillation switching circuit, 33 is an audio output terminal, 34 is a PCM audio output terminal, and 35 is a video output. Terminal.

FIG. 2 is a block diagram showing a detailed circuit configuration of the demodulation circuit of FIG.

The FM demodulation circuit 20 includes an IF amplification circuit 202, a phase comparator 203, an LPF
(Reduced filter) 205, demodulation signal amplifier 206, PLLCO demodulation VCO
(Voltage control oscillator) 204, voltage terminal 2 of PLLM demodulation VCO 204
07, a power supply terminal 208 of a circuit other than the PLLM demodulation VCO 204.

The AM demodulation circuit 21 includes an IF demodulation circuit 211 and a phase comparator 21.
2, VCO (voltage controlled oscillator) 213 for carrier recovery, AM quadrature detection circuit 214, amplifier 215, power supply terminal 21 for VCO 213 for carrier recovery
7. It is composed of a power supply terminal 218 other than the carrier recovery VCO 213.

The case of receiving a TV signal will be described first with reference to FIGS.

The demultiplexing circuit 2 is composed of a UHF signal of about 470 MHz to 850 MHz and an
The VHF signal in the 0 to 470 MHz band and the BS signal in the 960 to 1750 MHz band are switched to perform band selection and demultiplexing.

When the channel number of the VHF signal is selected by the tuning key 100, the first AGC amplifier circuit 6 and the second frequency converter 6 are controlled by a control signal from the microcomputer circuit (control circuit) 101 according to the selected channel number. Circuit 12, VHF voltage controlled oscillator 1
4. The power supply of the second IF amplifier 17 is turned on.

Further, the oscillation switching circuit 230 is operated, and the AM switching circuit shown in FIG.
Only the VHO (voltage controlled oscillator) 213 for synchronous quadrature detection carrier recovery of the demodulation circuit 21 starts oscillating.

That is, the oscillation switching circuit 230 switches the power supply between the PLLM demodulation VCO 240 of the FM demodulation circuit 20 and the carrier recovery VCO 213 of the AM demodulation circuit 21 to start and stop oscillation.

The VHF signal from the demultiplexing circuit 2 is band-selected by the first variable BPF 5, amplified or attenuated by the first AGC amplifier circuit 6, and further band-selected by the fourth variable BPF 10, and is converted by the frequency conversion circuit 12. It mixes with the oscillation signal from the VHF voltage controlled oscillator 14 to output a normal IF signal (about 38 MHz). This TV
The IF signal is amplified by the second IF amplifier 17, further band-selected by the fixed BPF 19, and modulated by the AM demodulation circuit 21 by AM signal detection by quadrature detection.

That is, in the AM demodulation circuit 21, after the TV / IF signal is amplified by the IF amplification circuit 211, a part of the output is compared in phase with the carrier reproduction VCO 213 by the phase comparator 212, and is synchronized with the carrier of the TV / IF signal,
Obtain a carrier reproduction oscillation signal that is orthogonal (out of phase with the carrier at 90 °). The AM quadrature detection circuit 214 performs AM quadrature detection on the carrier reproduced oscillation signal and the TV / IF signal from the IF amplification circuit 211, and after detection, amplifies the amplified signal with the amplifier 215 and outputs the demodulated signal.

Next, after the audio signal is removed by a filter (not shown), the switching circuit 23 is switched by a control signal from the microcomputer circuit 101 and output. At this time, the switching circuit 24 inputs the demodulated signal to the FM demodulation circuit 26, extracts a signal in the audio band (around 6.5 MHz) by a filter (not shown), performs FM demodulation, and outputs it as an audio signal. .

In the voltage synthesizer tuning circuit 102, tuning voltage data corresponding to the channel number selected by the tuning key 100 is read from the memory 103, a tuning voltage is generated, and AFS (automatic frequency control) from the AM demodulation circuit 21 is generated. Variable BPF5, 10 and voltage-controlled oscillator 1
The band and oscillation frequency of 4 are controlled. This tuning operation is the same not only when receiving a VHS signal but also when receiving a UHF / BS signal.

Next, when receiving a UHF signal, compared to when receiving a VHF signal,
First RF amplifier circuit 4, AGC circuit 3, voltage controlled oscillator 15
Operates, and the microcomputer circuit 101 controls so that the power supplies of the first AGC amplifier circuit 6 and the voltage controlled oscillator 14 are turned off. At this time, the AGC switching circuit 30 performs switching control so that the AGC circuit 3 operates with an AGC (automatic gain control) signal from the AM demodulation circuit 21.

The UHF signal whose band has been selected by the branching circuit 2 is amplified or attenuated by the AGC circuit 3 and the first RF amplifier circuit 4 according to the input level. After that, the signal is demultiplexed (or switched) by the demultiplexing circuit 7 and the band is selected by the third variable BPF 9, and then mixed with the oscillation signal from the UHF voltage controlled oscillator 15 by the second frequency conversion circuit 12. To the IF signal of
The video signal and the audio signal are output by demodulation by the AM demodulation circuit 21 in the same manner as the VHF signal. Next, the case where the BS signal is received will be described with reference to FIGS.

When the BS signal is received, the oscillation switching circuit 230 is operated, the oscillation of the carrier recovery VCO 213 of the AM demodulation circuit 21 is stopped, and the PLLM demodulation VCO (voltage controlled oscillator) 204 of the FM demodulation circuit is used instead.
Start oscillation. Further, the first frequency conversion circuit 11, B
The first voltage-controlled oscillator 13 for S and the first IF amplifier circuit 16 are controlled so as to be turned on, and the second frequency converter 12 and the voltage-controlled oscillator 15 that were turned on when receiving the UHF signal. In addition to turning off the power of the second IF amplifying circuit 17, the AGC switching circuit 30 switches the AGC circuit 3 to operate according to the AGC signal from the FM demodulation circuit 20.

The BS signal is subjected to band selection (or demultiplexing) by the demultiplexing circuit 2, and then is amplified and attenuated by the AGC circuit 3 and the first RF amplifier circuit 4 according to the input signal level. The band is selected by the variable BPF 8 and the electronically controlled oscillator 13 for BS
Mixed with the oscillation signal from the first frequency conversion circuit 11,
It is converted to a normal IF signal (about 480 MHz).

This IF signal is amplified by the first IF amplifying circuit 16 and fixed BPF 18
After the band is selected in, the FM demodulation circuit 20 demodulates the signal by PLLFM detection.

That is, in the FM demodulation circuit 20, the FM-modulated BS / IF signal is amplified by the IF amplifier 202, the phase of the output of the PLLFM demodulation VCO 204 is compared with the phase of the phase comparator 203, and the high-frequency component of the comparison output signal is removed by the LPF 205. The signal is amplified by the IF amplification circuit 206, the output is output as a demodulated signal, and the signal is re-input to the oscillation frequency control terminal of the PLLM demodulation VCO 204, that is, FM demodulation is performed by the so-called PLLFM demodulation method.

The output demodulated signal is output as a video signal via the switching circuit 23 after the audio signal is removed by a filter (not shown). The audio signal of the demodulated output of the BS signal is FM-modulated in the same band as the TV signal demodulated signal (approximately 6.5 MHz, depending on the method). The demodulated signal is demodulated by the audio FM demodulation circuit 26 via the switching circuit 24. And output it. When the audio signal of the BS signal is PCM-modulated, the signal is output from the PCM audio output terminal via the filter 22.

 The above embodiment will be described in more detail.

FIG. 3 is a circuit diagram showing a more detailed circuit configuration of the AFC voltage superposition circuit 25. 251 to 253 are bias resistors, 256, 257
Is an analog switching FET, and 258 and 259 are gate terminals.

When a BS signal is received, the switching FET 257 is turned off at zero potential (negative potential) at the terminal 259, a positive voltage is applied to the terminal 258, and the FET 256 is turned on. From the FM demodulation circuit 20
The AFS voltage is superimposed on the tuning voltage from the voltage synthesizer 102 by the resistor 252 to control the frequency.

When a TV signal is received, a zero potential (negative potential) is applied to the terminal 258, the FET 256 is turned off, a positive voltage is applied to the terminal 259, the FET 257 is turned on, and the AFS voltage from the AM demodulation circuit 21 is supplied to the resistor 253. To control the frequency by superimposing it on the tuning voltage.

At this time, the voltage controlled oscillators for BS and TV (VHF.UHF)
At 4,15, the control sensitivity to tuning voltage is about 3 for BS
On the other hand, control sensitivity to AFS voltage is also different. Therefore, according to the amount of change of the AFS voltage with respect to the frequency in the FM demodulation circuit 20 and the AM demodulation circuit 21, the resistors 251, 252, 253
By properly setting the resistance value and resistance ratio of
Sufficient frequency (fluctuation correction) control operation can be performed for the frequency fluctuation of the local oscillation circuit (not shown) of the converter and the voltage control oscillators 13, 14, and 15 of the receiving device, and stable IF signal frequency accuracy can be obtained. Therefore, a good demodulated signal can be obtained.

In this embodiment, the VCO 20 for PLL detection of the FM demodulation circuit 20 is used.
4 and the power supply of the carrier recovery VCO 213 of the AM demodulation circuit 21 are switched by the oscillation switching circuit 230 to start and stop the oscillation.This is because the AM demodulation circuit 20 operates while the AM demodulation circuit 20 is operating. When the oscillation signal from the carrier recovery VCO 213 of the circuit 21 leaks into the FM demodulation circuit 20 or the AM demodulation circuit 21 is operating, the oscillation signal from the PLLFM demodulation VCO 204 of the FM demodulation circuit 20 is This is to prevent the leakage of the fluid into the device and the occurrence of interference.

Here, as a method of starting / stopping the oscillation of each VCO 204, 213, as described above, in addition to a method of starting / stopping the oscillation by turning on / off the power supply thereof, and a method of starting / stopping the oscillation in each VCO 204, 213, respectively. A method of starting and stopping oscillation by increasing or decreasing the Q of the circuit is also conceivable.

As another method, a method of turning on / off the power supply of each of the demodulation circuits 20 and 21 to start and stop the oscillation of each of the VCOs 204 and 213 can be considered. In this case, a relatively large power supply is used. Turn on the power of the operating demodulation circuits 20 and 21.
Since the circuit is turned off, there is a problem that a certain time is required until the circuit operation completely starts or stops. On the other hand, the two methods described above have the advantage that the tuning operation can be performed at high speed because there is no such problem.

According to the present embodiment as described above, UHF and BS
At the time of signal reception, the AGC circuit 3 and the RF amplifier circuit 4 are used in common, and the band selection circuit 102 is also used in all bands. A receiving device with excellent operability, such as being able to receive a signal mixed with a signal from one terminal and performing a common channel selection operation, can be obtained. In addition, the AFS control range has been optimized when receiving BS and TV signals, so that the frequency fluctuation is small and a good demodulated signal can be obtained.In addition, when the BS and TV sound transmission systems share the same modulation method and the same frequency band, Is advantageous in that a receiver having a simpler circuit configuration can be obtained by using a common audio demodulation circuit.

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

In FIG. 4, description of those performing the same operations as in the first embodiment is omitted. In addition, 27 is a filter switching circuit, 31
Is a second RF amplifier circuit, and 5 'is a fifth variable BPF, which performs the same band selection as the first variable BPF 5 shown in FIG.
30 'is an AGC switching circuit, which is A when receiving VHF and UHF signals.
The AGC signal from the M demodulation circuit 21 and the AGC signal from the FM demodulation circuit 20 when receiving the BS signal are switched and applied to the AGC circuit 3, respectively, to perform gain control.

Each band of VHF / UHF / BS is selected by the filter switching circuit 27, and the AGC circuit 3 attenuates the gain. At the time of BS / UHF reception, the same operation as the embodiment shown in FIG. 1 is performed,
At the time of VHF reception, after passing through the AGC circuit 3 inserted into the input, the band of the VHF signal is selected by the fifth variable BPF 5 ′ and amplified by the RF amplifier circuit 31. Thereafter, the same receiving operation as in the embodiment shown in FIG. 1 is performed.

In this embodiment, since the AGC circuit 3 is used in common, the circuit configuration becomes simpler. Also, this AGC circuit 3
Is constructed using a pin (PIN) diode, a stable impedance characteristic and a good distortion characteristic over a wide band can be obtained as compared with the dual gate FET normally used for the AGC amplifier circuit 6 of the embodiment shown in FIG. It has the effect that it can be done.

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

In FIG. 5, components performing the same operations as those in the embodiment of FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In addition, reference numerals 41 and 42 denote sixth and seventh variable (tuning) BPFs which can be tuned by switching between UHF and VHF signals, and one example of the configuration is disclosed in Japanese Patent Application Laid-Open No. Sho 62-68312. 43 is a control voltage holding circuit,
44 is an AGC setting circuit.

In this embodiment, the VHF and UHF signals are band-switchable by the variable BPFs 41 and 42, and the first AGC amplifier circuit 6 that controls the gain of both the UHF and VHF bands is used to convert the TV signal. Receiving. Further, as an AFS voltage superimposing circuit for superimposing the AFG voltage on the tuning voltage, an AFS voltage superimposing circuit for TV 25 ′ and an AFS voltage superimposing circuit 25 ″ for BS are provided. It is configured to separately supply to the receiving system.

By the way, in general, when the level of a TV signal is considerably higher than the level of a BS signal, when a BS signal is received, in a variable BPF or the like, in particular, the sum of two or three times higher harmonics of a UHF signal or between UHF signals is used. A spurious interference signal such as a signal occurs, which leaks out and appears in the band of the BS signal, sometimes causing beat interference.

Therefore, in the present embodiment, at the time of receiving the BS signal, the control voltage holding circuit 43 changes the TV signal receiving system regardless of the voltage input from the TV AFS voltage superimposing circuit 25 '.
Fix the voltage output to 42 etc. to a fixed value (for example, 0V
), And the variable BPFs 41 and 42 are switched to the VHF band and tuned out of the band of the TV signal.

Also, when receiving a BS signal, the first of the TV signal receiving system
If the AGC circuit 6 is simply turned off and rested, the AGC circuit 6 operates in an unstable manner, causing distortion,
The signal may be adversely affected.

Therefore, in the present embodiment, even when the BS signal is received, the TV
A power supply voltage is applied to the first AGC amplifier circuit 6 of the signal receiving system to allow the first AGC amplifier circuit 6 to operate normally and to prevent the distortion from occurring.
The voltage applied to the AGC amplifier circuit 6 is fixed at a constant value by the C setting circuit 44 so that the gain attenuation in the AGC amplifier circuit 6 is maximized.

As a result, according to the present embodiment, at the time of receiving a BS signal, it is possible to prevent the occurrence of distortion in the AGC amplifier circuit 6, compensate for the insufficient amount of signal isolation, and reduce the beat interference due to spurious interference signals. It has the effect of being able to do it.

When receiving a TV signal, the control voltage holding circuit 43
And the operation of the AGC setting circuit 44 are stopped, and the tuning voltage obtained by superimposing the AFS voltage from the AFS voltage superimposing circuit 25 'is applied to the variable BPFs 41 and 42 of the TV signal receiving system.
, The voltage from the AM demodulation circuit 21 is applied as it is.

FIG. 6 is a block diagram showing a fourth embodiment of the present invention.

In FIG. 6, those performing the same operation as the embodiment of FIG. 1 or FIG. 5 will not be described. In addition, 50 is a switching circuit, 52 is a demultiplexing circuit, and 51 is a third frequency conversion circuit. In this embodiment, as compared with the embodiment shown in FIG. The signal band is commonly used and has a simpler configuration. Where the switching circuit
50 is supplied to the third frequency conversion circuit 51 from the second variable BPF 8
The BS signal and the VHS and UHF signals from the seventh variable BPF 42 are selected and input. Further, the demultiplexing circuit 52 converts the signal from the third frequency conversion circuit 51 into a TV-IF signal (about 38 MHz) and a BS-IF signal.
-Demultiplex to IF signal (about 480 MHz).

According to this embodiment, there is an effect that the circuit configuration is further simplified as compared with the embodiment of FIG.

FIG. 7 is a block diagram showing only a main part in a fifth embodiment of the present invention. That is, FIG. 7 shows the RF signal input unit and the RF signal output unit.

In FIG. 7, 60 is a branch circuit, 61 is an LPF, 62 is a BPF,
63 and 64 are RF amplifiers, 65 is a synthesis circuit, and 200 is an RF signal output terminal.

The RF signal in which the BS signal and the TV signal are mixed is input to the branch circuit 60, where it is branched into two. At this time, the distribution loss on one side is kept small, and the distribution loss on the other side is slightly large.

Next, of the two branched signals, the RF signal whose distribution loss is suppressed to a small value is input to the branch circuit 2 and then transmitted to another circuit.

For RF signals with a relatively large distribution loss, two more
The signal is input to the TV signal LPF 61 and the BS signal BPF 62. As a result, a TV signal is derived from the TV signal LPF 61 and a BS signal is derived from the BS signal BPF 62, respectively.

Next, the TV signal from the TV signal LPF 61 is a low-gain RF signal.
Amplified by the amplifier circuit 63 and input to the synthesis circuit 65,
The BS signal from the BS signal BPF 62 is amplified by the RF amplifier circuit 64 having a higher gain than the RF amplifier circuit 63 and is input to the synthesis circuit 65. Then, the input TV signal and BS signal are combined by a synthesis circuit.
The signals are combined at 65 and output from the RF signal output terminal 200 as an RF signal.

In the receiving apparatus of this embodiment, during operation, the RF signal in which the BS signal and the TV signal are combined is transmitted to another BS signal or the TV signal receiving apparatus.
The signal can be redistributed without loss.

Also, since the BS signal has a high frequency, the loss that occurs during the transmission of cables and the like and the loss around the terminals increase, and the signal level is often low.
The signal often has a large signal level. Therefore, if the RF signal from the branch circuit 60 is not separated into a BS signal and a TV signal, and is amplified as it is, spurious interference due to second and third-order distortion may occur in the BS signal.

Therefore, in this embodiment, in order to avoid this, as described above, the RF signal from the branch circuit 60 is separated into a BS signal and a TV signal, and the RF signal for the TV signal is amplified with respect to the BS signal. 63
That is, the signal is amplified by the RF amplifier circuit 64 having a higher gain.

In each of the embodiments described above, the BS / TV signal format is described as being limited to PAL. However, the SECAM system may be used, and the voice modulation signal of the demodulated signal may be 5.5 MHz. Also, the audio modulation method may be an AM modulation method.
It is only necessary to use the demodulation method.

Also, the case where the TV signal receives all the signals in the VHF / UHF band has been described, but the reception of only the signal in the VHF band or only the signal in the UHF band does not hinder the effectiveness of each embodiment. On the contrary, there is an effect that a simple receiving device can be obtained.

Further, although a voltage synthesizer tuning system is used as the tuning device, the same effect can be obtained by using a button tuning system for switching a tuning volume row or a tuning system using a PLL synthesizer.

Further, in the BS signal receiving system, the variable BP
Although F8 is used, when the band of the BS signal is narrow, using a fixed BPF or simply a variable trap circuit does not impair the gist of the present invention.

Furthermore, in each embodiment, one voltage controlled oscillator is used for the BS signal, one for the VFH for the TV signal,
One for FH, three in total, but one for BS signal
VFH and UFH, one for TV signal and one for TV signal, and only one for BS signal and TV signal.
It is not necessary to use only one of them, and in each case, the same effect as that obtained in each embodiment can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the RF amplification circuit, the AGF
By using the circuit, the frequency conversion circuit, and the tuning circuit in common, a receiving device having a simple configuration can be obtained. Further, even if an RF signal obtained by mixing a BS signal and a TV signal is input, an IF signal appropriately selected by filter switching and oscillation frequency band switching can be obtained. Therefore, RF that mixes BS and TV signals
Since a single system of signal input is possible, a receiver having good operability can be obtained in combination with the system of the channel selection circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
1 is a block diagram showing a detailed circuit configuration of the demodulation circuit of FIG. 1, FIG. 3 is a circuit diagram showing a detailed circuit configuration of the AFS voltage superposition circuit of FIG. 1, and FIG. 4 is a second embodiment of the present invention. FIG. 5 is a block diagram showing a third embodiment of the present invention, FIG. 6 is a block diagram showing a fourth embodiment of the present invention, and FIG. 7 is a fifth embodiment of the present invention. FIG. 4 is a block diagram showing only a main part in the embodiment of FIG. 1 RF signal input terminal, 3 AGC circuit 4 RF amplifier circuit, 20 FM demodulation circuit 21 AM demodulation circuit, 26 FM audio demodulation circuit 25 AFS voltage superposition circuit 11, 12 51, frequency conversion circuit 102, voltage synthesizer tuning circuit 60, branch circuit 101, microcomputer circuit (control circuit) 200, RF signal output terminal

Continuation of the front page (56) References JP-A-2-29184 (JP, A) JP-A-58-14684 (JP, A) JP-A-58-14685 (JP, A) JP-A-3-64217 (JP) JP-A-3-153117 (JP, A) JP-A-3-6194 (JP, A) JP-A-57-39628 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H04N 5/38-5/46 H04N 7/20

Claims (4)

(57) [Claims] 1. An RF amplifier circuit (hereinafter, referred to as an RF amplifier circuit), an automatic gain control circuit (hereinafter, referred to as an AGC circuit), a frequency conversion circuit, a voltage controlled oscillator, an FM demodulation circuit, an AM demodulation circuit, and a channel selection circuit. And a television broadcast signal (hereinafter, referred to as
TV signal) and satellite broadcast signal (BS signal)
And a receiver for outputting each demodulated signal, wherein the tuning circuit is used commonly for receiving a TV signal and for receiving a BS signal, and outputs a control voltage for a voltage-controlled oscillator. ,
The FM demodulation circuit and the AM demodulation circuit each output a frequency control signal voltage (hereinafter, referred to as an AFS signal voltage), and the voltage control oscillator is used commonly for receiving a TV signal and for receiving a BS signal. The oscillation frequency is controlled by a voltage obtained by changing the control voltage for the voltage controlled oscillator according to the AFS signal voltage, and the control voltage for the voltage controlled oscillator is changed according to the AFS signal voltage. A receiving device comprising a switching means for switching the control sensitivity between the time of receiving a TV signal and the time of receiving a BS signal. 2. An RF amplifier circuit (hereinafter, referred to as an RF amplifier circuit), an automatic gain control circuit (hereinafter, referred to as an AGC circuit), a frequency conversion circuit, a voltage controlled oscillator, an FM demodulation circuit, an AM demodulation circuit, and a channel selection circuit. And a television broadcast signal (hereinafter, referred to as
TV signal) and satellite broadcast signal (BS signal)
And a receiver for outputting each demodulated signal, wherein the tuning circuit is used commonly for receiving a TV signal and for receiving a BS signal, and outputs a control voltage for a voltage-controlled oscillator. ,
The FM demodulation circuit and the AM demodulation circuit each output an AFS signal voltage, and the voltage controlled oscillator includes a TV voltage controlled oscillator used when receiving a TV signal and a BS voltage controlled oscillator used when receiving a BS signal. The voltage controlled oscillator for the TV and the BS are controlled by a voltage obtained by changing the control voltage for the voltage controlled oscillator according to the AFS signal voltage.
The oscillation frequency of each of the voltage-controlled oscillators is controlled, and the control sensitivity for changing the voltage-controlled oscillator control voltage in accordance with the AFS signal voltage is switched between when a TV signal is received and when a BS signal is received. A receiving device comprising means. 3. An RF amplifier circuit (hereinafter, referred to as an RF amplifier circuit), an automatic gain control circuit (hereinafter, referred to as an AGC circuit), a frequency conversion circuit, a voltage controlled oscillator, an FM demodulation circuit, an AM demodulation circuit, and a tuning circuit. And a television broadcast signal (hereinafter, referred to as
TV signal) and satellite broadcast signal (BS signal)
And a receiver that outputs each demodulated signal, wherein at least one of the RF amplifier circuit, the AGC circuit, the frequency conversion circuit, the voltage-controlled oscillator, and the channel selection circuit, when receiving a TV signal, In a receiving device used in common with the reception of a BS signal, the AM demodulation circuit is a voltage controlled oscillator for carrier recovery, and the FM demodulation circuit is a voltage controlled oscillator for phase locked loop FM detection (hereinafter, PLLFM detection). Voltage-controlled oscillator), and when receiving a TV signal,
A receiver provided with means for stopping oscillation of a voltage-controlled oscillator for PLLFM detection and oscillation of the voltage-controlled oscillator for carrier wave reproduction when a BS signal is received. 4. A high-frequency amplifier circuit (hereinafter, referred to as an RF amplifier circuit), an automatic gain control circuit (hereinafter, referred to as an AGC circuit), a frequency conversion circuit, a voltage-controlled oscillator, an FM demodulation circuit, an AM demodulation circuit, and a channel selection circuit. And a television broadcast signal (hereinafter, referred to as
TV signal) and satellite broadcast signal (BS signal)
And a receiver that outputs each demodulated signal, wherein at least one of the RF amplifier circuit, the AGC circuit, the frequency conversion circuit, the voltage-controlled oscillator, and the channel selection circuit, when receiving a TV signal, An RF signal input terminal for inputting a high-frequency signal (hereinafter, referred to as an RF signal) configured by mixing a received TV signal and a BS signal, and A branch circuit for branching the RF signal into two,
One of the split RF signals is input, and a TV signal and
A demultiplexing circuit that separates the BS signal into a BS signal; an amplification circuit that amplifies and outputs the separated BS signal; and a combining circuit that combines the BS signal output from the amplification circuit and the separated TV signal. And an RF signal output terminal for outputting an RF signal obtained by combining in the combining circuit.