JPH05260483A - Tuner unit - Google Patents

Abstract

PURPOSE:To allow the unit to be immune to interference by a BS signal by providing a means attenuating a high frequency component included in an oscillation signal from a variable frequency oscillator on the way of a line leading the oscillation signal from the oscillator to a frequency converter. CONSTITUTION:Low pass filters 118, 117 are inserted between TV signal use voltage controlled oscillators 120, 119 and TV signal frequency converters 115, 116 to attenuate an oscillation signal. Moreover, a BS signal attenuation circuit 110 is provided between a BS signal input terminal 101 and a BS signal use frequency converter 114 to suppress leakage of a BS signal to the frequency converters 115, 116 at the reception of a TV signal. That is, a VHF signal use RF signal processing system is arranged between the BS signal use RF signal processing point and the UHF signal use RF signal processing point by using low pass filters 118, 117 and a BS signal attenuation circuit 110 to suppress leakage of the BS signal from the BS signal use RF signal processing system to the UHF signal use RF signal processing system.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a broadband tuner. More specifically, a BS signal as an intermediate frequency signal obtained by receiving and down-converting a satellite broadcast signal (including a communication satellite) adopting the FM modulation method, and AM modulation in the VHF and UHF bands. The terrestrial television broadcast signal (including CATV) is input,

When receiving a satellite broadcast signal, a BS-IF, which is a second intermediate frequency signal, in a frequency converter from an oscillation signal from a variable frequency oscillator and the BS signal.
When generating and outputting a signal and receiving a terrestrial television broadcast signal, a TV-IF signal which is an intermediate frequency signal in a frequency converter from the oscillation signal from the voltage controlled variable frequency oscillator and the terrestrial television broadcast signal. The present invention relates to a tuner unit (that is, a wideband tuner) that produces and outputs a signal.

[0003]

2. Description of the Related Art A BS signal as an intermediate frequency signal obtained by down-converting (frequency-converting) an FM-modulated satellite broadcast signal and an AM-modulated terrestrial television broadcast signal (including CATV) in the VHF and UHF bands. In the case of receiving the signal and the like by a general receiving system, there are drawbacks that different tuner circuits are required because the frequency bands of the broadcast wave signals are different, the configuration is complicated, and the operation is not easy.

Therefore, for example, as a solution to these drawbacks, a part of the tuner circuit is used for satellite broadcasting and terrestrial television broadcasting (hereinafter, terrestrial television broadcasting may be simply referred to as TV broadcasting). A receiver has been proposed. As an example thereof, as described in Japanese Patent Laid-Open No. 3-211979, at least one of a tuning circuit, a high frequency amplifier circuit and a mixing circuit is used when receiving a BS signal and a TV. There is known a receiving device that is commonly used for signal reception.

[0005]

The above-mentioned prior art has the following problems. That is, when the BS signal and the TV signal are received by a general receiving system, when the TV signal is received,
If the BS signal leaks into the TV signal frequency converter,
A difference signal between the harmonic component (the fundamental wave in some cases) of the oscillation signal of the signal voltage controlled variable oscillator and the BS signal is generated in the TV signal frequency converter, and depending on the reception frequency, this is in the TV-IF signal band. The problem is overlap and interference.

This interference will be described using the Japanese channel as an example. TV-IF frequency of Japan channel is 57MHz
When the UHF 17ch RF signal (497 MHz) is received, the oscillation frequency is 554 MHz. At this time, BS
When the 1-ch signal (1049 MHz) leaks into the frequency converter, the difference signal with the double harmonic of the oscillator, 1108 MHz, becomes 59 MHz and overlaps with the TV-IF signal band to cause interference.

Further, a difference signal between the BS 1ch signal and the oscillator oscillation frequency of 554 MHz (1049-554 =
495 MHz), but in this case, it overlaps with the RF signal band. As a result, the signal converted and output by the frequency converter also interferes with the TV-IF signal band.

Further, the oscillating frequency becomes 276 MHz when receiving VHF 12 ch (219 MHz). At this time, if the BS 1 ch signal (1049 MHz) leaks into the frequency converter, harmonics 4104 times higher than that of the oscillator 1104 MHz.
And the difference signal becomes 55 MHz and overlaps with the TV-IF signal band to cause interference.

Further, a BS 7ch signal (1165MH
z) and the 5th harmonic of the oscillator, the difference signal (1165-
276 × 5 = 215 MHz) occurs, but in this case, 1
It overlaps with the 2ch RF signal band. As a result, the signal converted and output by the frequency converter also interferes with the TV-IF signal band.

These disturbances are, for UHF signals,
Since the order of the harmonics that cause the interference is low, the interference harmonic level is high, and the influence of the interference is larger than that of the VHF.

The object of the present invention is to provide the BS shown in the prior art.
Even if the RF signal processing system for signals and a part of the RF signal processing system for TV signals are shared, it is susceptible to interference by BS signals when receiving TV signals. An object of the present invention is to provide a tuner unit capable of wideband reception with a difficult configuration.

[0012]

In order to achieve the above object, according to the present invention, in a tuner, an oscillation signal output terminal of a variable frequency oscillator for TV signals and an oscillation signal input terminal of a frequency converter for TV signals are provided. A means for attenuating the harmonic component of the oscillation signal is provided between them, or when receiving a TV signal, B
A means for attenuating the BS signal is provided between the S signal input terminal and the frequency converter for inputting the BS signal, or at least one of them is adopted.

A low-pass filter is used as the means for attenuating the harmonic components of the oscillation signal, and is connected between the oscillation signal output terminal of the TV signal variable frequency oscillator and the oscillation signal input terminal of the TV signal frequency converter. .. In addition, the frequency converter has a balanced or double-balanced mixer configuration to suppress harmonic components (even order) of the transmission signal generated from the frequency converter itself.

As means for attenuating the input BS signal when receiving the TV signal, the tuning voltage applied to the BS signal variable tuning circuit when receiving the TV signal is an appropriate value, for example, 0V.
In addition, by changing the tuning capacitance of the tuning circuit using a switching diode or the like, a means for attenuating the input BS signal is used so that the tuning frequency point is outside the BS signal frequency band.

Further, in the tuner unit having the RF signal processing system of the three band structure of BS, VHF (including CATV) and UHF, the RF signal processing system for BS signal and the UHF signal which is relatively susceptible to BS signal interference. The RF signal processing system for VHF signals is arranged between the RF signal processing system for VHF signals and the RF signal processing system for BS signals to UHF.
The BS signal jumping into the signal RF signal processing system is suppressed.

[0016]

In the tuner unit of the present invention, the means for attenuating the harmonic components of the oscillation signal from the variable oscillator for TV signals, the BS signal input terminal and the frequency converter to which the BS signal is input when receiving the TV signal are provided. By using at least one of the means for attenuating the BS signal provided therebetween, it becomes possible to prevent the BS signal from interfering with the reception of the TV signal.

Furthermore, according to the present invention, R for BS signals is used.
A frequency converter can be shared between the F signal processing system and the RF signal processing system for TV signals, which has a simple structure and excellent operability, and is a broadband tuner capable of receiving BS signals and TV signals. Units can be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing a first embodiment of the present invention. The tuner shown in FIG. 1 is a wideband tuner unit capable of receiving two types of signals, a TV signal and a BS signal.

The tuner unit shown in FIG. 1 band-selects the input VHF and UHF RF signals and the BS first IF signal (BS signal obtained by down-conversion), and selects the VHF and UHF RF signals by TV-. B to IF signal
This is a tuner unit that outputs the S signal into a BS-IF signal after frequency conversion.

In FIG. 1, 101 is a BS signal input terminal, 102 is a TV signal input terminal, 103 is a demultiplexing circuit, 1
Reference numeral 04 is a high-pass filter, 105 and 106 are VHF (including CATV) and UHF signal input variable tuning circuit, 107 is a BS signal RF amplifier circuit, and 108 and 10, respectively.
Reference numeral 9 is a gain control RF amplification circuit for VHF and UHF signals, and 110 is a BS signal attenuation circuit.

In addition, 111, 112 and 113 are variable double-tuned circuits for BS, VHF and UHF signals, 114, 115 and 116 are first, second and third frequency converters, 117 and 118 are UHF, respectively. , VHF are low-pass filters that attenuate the harmonic components, 119, 120, and 121 are UHF,
A voltage controlled variable oscillator for VHF and BS signals.

Further, 122 is a channel selection circuit, 123 is a channel selection signal input terminal, 124 is a TV-IF synthesis circuit, and 125 is B.
S-IF output terminal, 126 is TV-IF output terminal, 12
7 is a power supply terminal. First, a case of receiving a BS signal will be described with reference to FIG.

By inputting the channel selection signal to the input terminal 123, the channel number of the BS signal is selected, and the channel selection circuit 122 outputs a control voltage for turning off the BS signal attenuating circuit 110. , The RF amplification circuit 107 for BS signal, the voltage controlled variable oscillator 121, and the first frequency converter 114 are turned on.

The BS signal input to the input terminal 101 is
High-pass filter 104 that cuts the UHF and VHF bands
After being amplified by the RF amplification circuit 107, the BS signal attenuation circuit 110 allows the signal to pass without attenuation, and the variable double tuning circuit 111 selects a band. The band-selected signal is converted into a BS-IF signal by the voltage controlled variable oscillator 121 and the first frequency converter 114, and the BS-I signal is obtained.
It is output to the F output terminal 125.

When receiving a TV signal, the tuning circuit 122 outputs a control voltage for turning on the BS signal attenuating circuit 110, and the second and third frequency converters 11 for BS signals are output.
Suppressing the leak to the 5,116. At this time, V
When the channel number of the HF signal is selected, the power supply of the gain control RF amplification circuit 108, the voltage control variable oscillator 120 and the second frequency converter 115 is further turned on.

TV input to the TV signal input terminal 102
With respect to the signal, the VHF and UHF signals are demultiplexed by the demultiplexing circuit 103, and when the VHF signal is selected, the band is selected by the input variable tuning circuit 105 and the gain control RF amplification circuit 10 is selected.
After being amplified or attenuated according to the input level by 8, the band is further selected by the variable double tuning circuit 112,
Voltage controlled variable oscillator 120 and second frequency converter 115
Is converted to a TV-IF signal by way of the synthesis circuit 124 and output to the TV-IF output terminal 126.

A low pass filter 118 is provided between the voltage controlled variable oscillator 120 and the second frequency converter 115.
Is inserted to attenuate the harmonic component of the oscillation signal, which causes interference with the BS signal.

Next, when the UHF signal is selected, VH
The gain control RF amplifier circuit 10 is different from that when the F signal is selected.
9, the voltage controlled variable oscillator 119 and the third frequency converter 116 are operated, and the gain controlled RF amplifier circuit 108, the voltage controlled variable oscillator 120 and the second frequency converter 11 are operated.
Turn off the power of 5.

At this time, the UHF signal demultiplexed by the demultiplexing circuit 103 is band-selected by the input variable tuning circuit 106, amplified or attenuated according to the input level by the gain control RF amplification circuit 109, and then subjected to the variable double tuning. Circuit 1
The band is further selected by 13, and the voltage controlled variable oscillator 1
The signal is converted into a TV-IF signal by 19 and the third frequency converter 116, and is output to the TV-IF output terminal 126 via the synthesizing circuit 124.

At this time, the low-pass filter 117 is inserted between the voltage-controlled variable oscillator 119 and the third frequency converter 116 as in the case of selecting the VHF signal, and BS
The harmonic components of the oscillating signal, which causes interference by the signal, are attenuated.

As can be seen in this embodiment, when the TV signal is received, the BS signal is the TV signal frequency converter 11.
5 or 116, a difference signal between the harmonic component of the oscillation signal of the TV signal voltage controlled variable oscillator 120, 119 corresponding to the converter or the BS signal is generated in the frequency converter 115 or 116 and received. Depending on the frequency, the TV-IF signal band may be overlapped and interference may occur.

As means for suppressing this interference, low-pass filters 118 and 117 are inserted between the TV signal voltage controlled variable oscillator 120 or 119 and the TV signal frequency converter 115 or 116, respectively, so that the oscillation signal A circuit for attenuating the harmonic component and a circuit (BS signal attenuating circuit 110) for attenuating the BS signal between the BS signal input terminal 101 and the first frequency converter 114 for the BS signal at the time of receiving the TV signal are provided. By installing, BS
The signal is the second or third frequency converter 115, 11
There is a means for suppressing the leak into the 6.

Next, the circuits used for the above two suppressing means will be described in more detail. FIG. 2 is a circuit diagram showing a detailed circuit configuration of the low pass filter 118 in FIG.
The coils 201, 203 and the capacitors 202, 204 constitute a low-pass filter, and the voltage-controlled variable oscillator 12
It is possible to attenuate the higher harmonic component of the zero oscillation signal output. Further, the low-pass filter 117 has a similar circuit configuration.

FIG. 3 shows the BS signal attenuating circuit 1 shown in FIG.
10 is a circuit diagram showing a detailed circuit configuration of 10 and a variable double tuning circuit 111. FIG. In FIG. 3, BS variable double tuning circuit 111
Are variable capacitance diodes 315 and 316, resonance inductors 313 and 314, capacitors 303 and 304, and resistor 30.
The resonance inductors 313 and 314 are inductively coupled to each other to form a double tuning circuit, and the capacitance is changed by applying a tuning voltage to the variable capacitance diode via the resistors 308 and 309 to change the tuning frequency. There is. In addition,
The capacitors 301 and 306 are coupling capacitors.

The BS signal attenuator circuit 110 includes a capacitor 3
02, 305, switching diodes 311, 31
2, the resistors 307 and 310, and the changeover switch 317. When the BS signal is received, the changeover switch 3
Reference numeral 17 converts the tuning voltage from the tuning circuit 122 so as to be applied to the variable capacitance diodes 315 and 316 of the BS variable double tuning circuit 111, and performs the band selection operation of the BS signal.

When receiving a TV signal, the changeover switch 3
Reference numeral 17 denotes a constant voltage (0 in FIG. 3) in the variable capacitance diodes 315 and 316 of the BS variable double tuning circuit 111.
V), and the tuning circuit 122,
The switching diodes 311 and 312 are turned on, and the capacitances of the capacitors 302 and 305 are added to the capacitors 303 and 304 of the tuning capacitance.

By these two operations, the tuning frequency point of the BS variable double tuning circuit 111 is changed to outside the BS signal band, and when the TV signal is received, the BS signal is sent to the second or third frequency converter 115, 116. Can be suppressed.

Thus, in addition to the means for switching the tuning capacitance of the BS variable double tuning circuit 111 in accordance with the reception of the TV signal or the BS signal, the inductance of the resonance inductors 313, 314 is switched, or the BS variable double tuning is performed. An attenuator is provided before or after the circuit 111,
The same effect can be obtained by turning this on and off.

FIG. 4 shows an RF signal processing system for BS signals (high-pass filter 10 in the first embodiment shown in FIG. 1).
4, RF amplifier circuit 107, BS signal attenuator circuit 110, variable double tuning circuit 111), RF signal processing system for VHF signals (input variable tuning circuit 105, gain control RF amplifier circuit 10)
8. Variable double tuning circuit 112) and RF for UHF signal
FIG. 6 is a layout diagram showing a signal processing system (input variable tuning circuit 106, gain control RF amplifier circuit 109, variable double tuning circuit 113) as a block layout.

In the layout diagram of FIG. 4, the description of the components that perform the same operation as in the first embodiment is omitted. In addition, 401 is a tuner unit chassis, 402 is an RF signal processing system for BS signals, 403 is an RF signal processing system for VHF signals, 4
Reference numeral 04 is an RF signal processing system for UHF signals.

The RF signal processing system 403 for the VHF signal is arranged between the RF signal processing system 402 for the BS signal and the RF signal processing system 404 for the UHF signal which is relatively susceptible to BS signal interference. , The BS signal from the RF signal processing system 402 for BS signal to the RF signal processing system 404 for UHF signal is suppressed.

As described above, according to the present embodiment, the low-pass filters 118 and 117 and the BS signal attenuating circuit 110 are used, and further, the RF signal processing system for BS signals and the relatively BS signal interference are received. The RF signal processing system for the VHF signal is arranged between the RF signal processing system for the UHF signal and the RF signal processing system for the BS signal from the RF signal processing system for the BS signal to the RF signal processing system for the UHF signal. By trying to suppress the dive,

The BS signal RF signal processing system and the TV signal RF signal processing system, if they are formed on the same unit, can suppress the interference of the BS signal at the time of TV reception, which is a problem. , The TV signal of the desired signal is a weak electric field,
Even if the BS signal of the disturbing signal is a strong electric field, the BS signal is less likely to be disturbed.

FIG. 5 is a block diagram showing a second embodiment of the present invention. In the figure, the description of the same operation as that of the first embodiment is omitted. In addition, 501 and 502 are switching circuits that are turned by receiving VHF, UHF or BS signals, and 503 is a demultiplexing circuit that demultiplexes BS-IF signals and TV-IF signals.

When the BS signal is selected by the tuning signal input to the tuning signal input terminal 123, the tuning circuit 12
2 is a BS whose band is selected by the variable double tuning circuit 111.
So that the signal is directed to the first frequency converter 114,
While switching the switching circuit 501, the oscillation signal from the voltage controlled variable oscillator 121 is transmitted to the first frequency converter 11
The switching circuit 502 is switched so as to lead to 4.

When the VHF signal is selected, the VHF signal band-selected by the variable double tuning circuit 112 is
The switching circuits 502 and 503 are switched so as to be guided to the first frequency converter 114 and the oscillation signal of the voltage controlled variable oscillator 120 is guided to the first frequency converter 114.

Similarly, when the UHF signal is selected, the UHF signal band-selected by the variable double tuning circuit 113 is
The switching circuits 502 and 503 are switched so as to be guided to the first frequency converter 114 and the oscillation signal of the voltage controlled variable oscillator 119 is guided to the first frequency converter 114.

By these operations, the frequency conversion can be performed only by the first frequency converter 114 even at the time of TV reception. The IF signal frequency-converted by the frequency converter 114 is demultiplexed and output by the demultiplexing circuit 503 to the output terminal 125 for the BS-IF signal and the output terminal 126 for the TV-IF signal. The input B
The S, VHF or UHF signal is transmitted to the variable double tuning circuit 11
Until the band is selected by 1, 112 or 113, the same operation as that of the embodiment shown in FIG. 1 is performed.

As described above, since the structure is less likely to be disturbed by the BS signal at the time of TV reception, as in the embodiment of FIG.
Frequency converters for BS, VHF or UHF signals can be shared and the circuit configuration is simplified,
It is possible to obtain a tuner unit having excellent operability by performing common channel selection operations.

FIG. 6 is a block diagram showing a third embodiment of the present invention. In the figure, 601 is an RF input terminal,
The description of the demultiplexing circuit 602 and other components that perform the same operation as that of the second embodiment shown in FIG. 5 is omitted.

BS and T input to the input terminal 601
The V signal is sent to BS, VHF and U by the demultiplexing circuit 602.
After being demultiplexed into the HF signal, the subsequent operation is similar to that of the second embodiment shown in FIG.

According to the present embodiment, since it is resistant to BS signal interference at the time of TV reception, it is possible to receive even if a signal mixed with BS, VHF or UHF signals is inputted from one terminal. In this way, regardless of whether the input TV or BS signal system is one system or two systems as in the first and second embodiments, reception is performed without the BS signal interference. It is possible to obtain a tuner unit with excellent usability.

[0053]

As described above, according to the present invention, the TV
The BS signal processing system and the TV signal processing system can be configured on the same unit by adopting a configuration that is less likely to be affected by the BS signal during reception, and further, the BS signal processing system and the TV signal can be configured. Even when part of the processing system is shared, when receiving TV signals,
It is possible to obtain a tuner unit having a simple configuration and capable of wideband reception, which is unlikely to be disturbed by a BS signal.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a detailed circuit configuration of a low-pass filter in FIG.

3 is a circuit diagram showing a detailed circuit configuration of a BS signal attenuating circuit and a variable double tuning circuit in FIG.

FIG. 4 is a layout diagram showing an embodiment in which the layout of each signal processing system is defined as a modification of the first embodiment shown in FIG.

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

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

[Explanation of symbols]

104 ... High-pass filter, 105, 106 ... Input variable tuning circuit, 107-109 ... RF amplifier circuit, 111-1
13 ... Variable double tuning circuit, 114-116 ... Frequency converter, 119-121 ... Frequency variable oscillator, 122 ... Channel selection circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroyuki Mizukami Inventor Hiroyuki Mizukami 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Visual Media Research Laboratory, Hitachi, Ltd. (72) Inventor Tatsuyuki Hayashi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Incorporated company Hitachi Image Information System

Claims (8)

[Claims] 1. A voltage when a BS signal as an intermediate frequency signal obtained by down-converting a received satellite broadcast signal and a terrestrial television broadcast signal including CATV are input and the satellite broadcast signal is received. In the frequency converter from the oscillation signal from the control variable frequency oscillator and the BS signal, the BS-IF which is the second intermediate frequency signal
When generating and outputting a signal and receiving a terrestrial television broadcast signal, a TV-IF signal which is an intermediate frequency signal in a frequency converter from the oscillation signal from the voltage controlled variable frequency oscillator and the terrestrial television broadcast signal. In the tuner unit for producing and outputting, a harmonic attenuating unit for attenuating a harmonic component included in the oscillation signal from the oscillator is provided on the way of guiding the oscillation signal from the variable frequency oscillator to the frequency converter. A tuner unit featuring. 2. A voltage when a BS signal as an intermediate frequency signal obtained by down-converting a received satellite broadcast signal and a terrestrial television broadcast signal including CATV are input and the satellite broadcast signal is received. In the frequency converter from the oscillation signal from the control variable frequency oscillator and the BS signal, the BS-IF which is the second intermediate frequency signal
When generating and outputting a signal and receiving a terrestrial television broadcast signal, a TV-IF signal which is an intermediate frequency signal in a frequency converter from the oscillation signal from the voltage controlled variable frequency oscillator and the terrestrial television broadcast signal. In the tuner unit for producing and outputting, a tuner is provided with BS signal attenuating means for attenuating the BS signal while the BS signal is being guided to the frequency converter when the terrestrial television broadcast signal is received. unit. 3. The tuner unit according to claim 1, wherein the BS is used when the terrestrial television broadcast signal is received.
A tuner unit, characterized in that BS signal attenuating means for attenuating the BS signal is provided on the way of guiding the signal to the frequency converter. 4. The tuner unit according to claim 1, 2, or 3, wherein the frequency converter comprises a frequency converter having a balanced or double-balanced mixer configuration. 5. A BS signal as an intermediate frequency signal obtained by down-converting a received satellite broadcast signal and a terrestrial television broadcast signal including CATV are input, and first, second, and 3 frequency converter,
A first, a second, and a third variable frequency oscillator, wherein the input BS signal is used as a second intermediate frequency in the first frequency converter by using an oscillation signal from the first variable frequency oscillator. A BS-IF signal which is a signal is generated and output, and VHF or C in the inputted terrestrial television broadcast signal
For the ATV signal, the second frequency converter uses the oscillation signal from the second variable frequency oscillator to generate and output a TV-IF signal, which is an intermediate frequency signal, and outputs the TV-IF signal. For the UHF signal inside, in the tuner unit for producing and outputting a TV-IF signal which is an intermediate frequency signal using the oscillation signal from the third variable frequency oscillator in the third frequency converter, the second unit The oscillation signal from the variable frequency oscillator is applied to the second
In the course of leading to the frequency converter and in the course of leading the oscillation signal from the third variable frequency oscillator to the third frequency converter, the harmonic components contained in the oscillation signal from each oscillator are attenuated respectively. A tuner for attenuating the harmonics, and a BS signal attenuator for attenuating the BS signal while the BS signal is being guided to the frequency converter when the terrestrial television broadcast signal is received. unit. 6. The tuner unit according to claim 5, wherein, for the first, second, and third frequency converters, the first frequency converter is a BS signal frequency converter having the highest frequency. Therefore, the tuner unit is characterized in that the first, second, and third frequency converters are shared by also functioning as the second and third frequency converters. 7. The tuner unit according to claim 5, wherein the BS signal attenuating means receives an RF amplifier circuit for BS signal and an output of the amplifier circuit and inputs a signal band thereof into a BS signal frequency band. A variable tuning circuit for selecting and outputting a signal band, and a detuning means for changing the tuning frequency point of the variable tuning circuit to outside the BS signal frequency band when receiving a terrestrial television broadcast signal. Tuner unit. 8. The tuner unit according to claim 5, 6 or 7, wherein the frequency converter comprises a frequency converter having a balanced or double-balanced mixer configuration.