JP2000115660A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To receive standard television signals and high definition television signals. SOLUTION: For NTSC signals, a single superheterodyne system for converting them into IF signals in a third mixer and separating a tuned channel from the IF signals in an IF filter for the NTSC signals is used. Also, for the high-definition television signals, a double superheterodyne system for turning them to first IF signals >=10 GHz in a first mixer 10, turning the first IF signals to second IF signals equal to the IF signals of the NTSC signals in a frequency band and separating a tuned channel from the second IF signals in the IF filter 15 for the high definition television signals which is a SAW filter is used. For the IF filter 11 for supplying the first IF signals from the first mixer 10, the band-pass filter of intra-band flatness and low group delay deviation is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver capable of receiving a high-definition television signal and a normal television signal, and more particularly to a signal compressed as a high-definition television signal into a 6 MHz band. And a receiving apparatus for commonly receiving an NTSC signal having a 6 MHz band as a normal television signal.

[0002]

2. Description of the Related Art In recent years, conventional television broadcasting (N
In addition to TSC, PAL, etc.), establishment of a high-definition television broadcasting system is being promoted in each country. Along with this, there has been a need for a receiving apparatus that has little deterioration in image quality and sound room when receiving a high-definition television signal. FIG.
3 shows a conventional single superheterodyne television receiver. In the figure, 1 is a signal input terminal, 2 is a tuning signal input terminal, 4 is a video and audio signal output terminal, 17 and 21 are variable tuning circuits, 18 and 20 are variable attenuators, 19 is an RF amplifier, and 22 is an RF amplifier. Frequency converter, 23,
25 is an IF amplifier, 24 is an IF filter, 26 is a local oscillator, 29 is a low-pass filter, 31 is a PLL (phase locked loop) circuit, and 34 is an AM demodulator. Hereinafter, description will be made using an NTSC signal as a standard TV signal as an example.

A desired signal of an RF signal AM-modulated with an NTSC signal input from a signal input terminal 1 follows a oscillating frequency of a local oscillator 26 and changes a center frequency of a pass band of the RF signal. At 21, the signal is selectively passed, and the desired signal is appropriately amplified or attenuated by the variable attenuators 18 and 20 and the RF amplifier 19 so as to have a desired reception level. In the frequency converter 22, a signal that oscillates at a frequency corresponding to a desired channel according to a tuning signal input from the tuning signal input terminal 2.
The signal is mixed with a local oscillation signal from a local oscillator 26, which forms a feedback by the LL circuit 31 and the low-pass filter 29, and outputs a 45 MHz band IF signal. The IF signal is amplified by first and second IF amplifiers 23 and 25, and an IF filter 24 composed of a SAW filter or the like.
Passes only a desired band, and is demodulated by the AM demodulator 34 to output baseband video and audio signals. A
GC is performed using the inside of the AM demodulator 34 and the variable attenuators 18 and 20. The AFC is performed by finely adjusting the oscillation frequency of the local oscillator 26.

[0004]

However, the above-mentioned receiving apparatus receives a normal television signal such as NTSC, and does not consider receiving a high-definition television signal. Also, it is not considered to receive both a normal television signal and a high definition television signal.

An object of the present invention is to provide a receiving apparatus capable of receiving a digital television signal, and in particular, capable of receiving a signal compressed in a 6 MHz band.

[0006]

To achieve the above object, the present invention converts a received digital television signal to a frequency substantially equal to an intermediate frequency signal for a standard television and outputs the converted signal. The configuration includes a frequency conversion unit and an extraction unit that extracts a signal of a predetermined channel from an output signal from the frequency conversion unit and outputs the signal.

According to this configuration, the received digital television signal is converted by the frequency conversion means into a frequency substantially equal to the intermediate frequency signal for the standard television, so that the digital television signal can be received. In addition, a signal of a predetermined channel is extracted by the extracting means from the output signal from the frequency converting means. The output signal from the frequency converting means is substantially equal to the intermediate frequency signal for standard television. Since the signals have the same frequency, it is possible to use a SAW filter equivalent to a SAW filter used for receiving a standard television signal as the extracting means.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first preferred embodiment of a receiving apparatus according to the present invention.

In FIG. 1, 1 is a signal input terminal, 2 is a channel selection signal input terminal, 3 is a high definition television signal input terminal, 4 is an NTSC video and audio signal output terminal, 5 is a distributor, and 6 is an input. Filters, 7, 9, 18, and 20 are variable attenuators; 8, 19 are first and second RF amplifiers;
, 11 is a first IF filter, and 12 is a first I filter.
F amplifier, 13 a second mixer, 14 a first IF amplifier, 15 a high-definition television signal IF filter,
6 is a second IF amplifier, 17 and 21 are tunable circuits,
2 is a third mixer, 23 is a third IF amplifier, 24 is N
IF filter for TSC signal, 25 is a fourth IF amplifier,
26 is a third local oscillator, 27 is a first local oscillator, 2
8, a second local oscillator; 29, 30 low-pass filters; 31, 32, PLL circuits; 33, a high-definition television signal demodulator; 34, an NTSC signal AM demodulator;
5 is a signal level detector for high definition television signals, 36
Is a low-pass filter, and 37 is an AGC voltage amplifier.
In this figure, parts performing the same operations as in FIG. 13 are assigned the same reference numerals as in FIG. 13 and their explanation is omitted.

When an NTSC signal is input, the signal processing is the same as the signal processing described in the conventional example, and the description is omitted here. From the signal input terminal 1, an RF signal modulated by an NTSC signal and an original signal of a high-definition television are subjected to A / D conversion, data compression, and a 6 MHz band digitally modulated by QAM (quadrature axis amplitude modulation) or the like. The high-definition television RF signal is input and distributed by the distributor 5.
The band is divided into an F band and a UHF band (the VHF band is sometimes divided into a low band, a middle band, and a high band), and a band including a desired channel is selectively passed. The desired channel is appropriately amplified or attenuated by the variable attenuators 7 and 9 and the RF amplifier 8 so as to have a desired signal level, and input to the first mixer 10. In the first mixer 10, feedback is performed by a PLL circuit 32 and a low-pass filter 30 having a built-in reference oscillator and a frequency divider so as to oscillate at a frequency corresponding to a desired channel according to a tuning signal input from a tuning signal input terminal 2. It mixes with the local oscillation signal from the formed local oscillator 27 and outputs a first IF signal. 1st IF
The signal frequency is used to reduce the intermodulation interference of the received signal.
Set to be equal to or higher than the upper limit frequency of the V transmission band. In particular,
In consideration of mutual interference disturbance due to the first local oscillation signal, the second local oscillation signal and its higher harmonic signal, the frequency is 1 GHz or more, 1.2 GHz band, 1.7 GHz band, and 2.6 GHz.
Band, 3 GHz band, etc. The first IF signals set in these frequency bands are selectively passed by the first IF filter 11. Demodulation of high definition television signal is NT
It requires more accurate demodulation than the SC signal. In order not to deteriorate the demodulation characteristics of the high definition television signal, the first I
As the F filter, a bandpass filter having in-band flatness and low group delay deviation is used. The first IF signal is the first I signal
After being amplified by the F amplifier 12, it is input to the second mixer 13. The second mixer mixes with the local oscillation signal from the second local oscillator 28 and outputs a second IF signal. The second IF signal frequency is 45M, the same as when receiving the current NTSC signal.
Hz band. The second IF signal is supplied to the first IF amplifier 14
After that, the signal is input to a high-definition television signal IF filter 15 composed of a SAW filter or the like. The IF filter passes only the band of the desired receiving channel. When receiving a high definition television signal, the second IF
The desired receiving channel is amplified by the amplifier 16, input to the high-definition television signal demodulator 33, demodulated according to the modulation method, and output from the output terminal 3 as the data-compressed high-definition television signal. The output signal is input to a digital signal processing circuit that performs data expansion, D / A conversion, and the like, and outputs video, audio, or data to a high-definition television. On the other hand, when receiving an NTSC signal,
A desired receiving channel is amplified by the fourth IF amplifier 25 and NT
The signal is input to the SC signal AM demodulator 34, AM demodulated, and the baseband video and audio signals are output from the output terminal 4. When the AGC receives a high-definition television signal, the AGC detects a signal branched from the output of the second IF amplifier 16 with a signal level detector 35, and a low-pass filter 36.
The AGC voltage is generated by the AGC voltage amplifier 37 and applied to the variable attenuators 7 and 9. In the case of receiving an NTSC signal, the variable attenuators 18 and 20 perform the shortage inside and inside the AM demodulator 34. The AFC uses the respective AFC voltages from the high-definition television signal demodulator 33 and the NTSC signal AM demodulator 34 to fine-tune the oscillation frequencies of the second local oscillator 28 and the third local oscillator 26. Do. As will be described later, the case where the high-definition television signal is transmitted on the same channel as the NTSC signal is also considered, and in order to avoid interference from the NTSC signal, a high-energy video and audio carrier in the NTSC signal is used. In the vicinity of the color sub-carrier, the signal shown in FIG. 7 in which the spectrum of the high-definition television signal is not arranged in advance is used, or the high-definition television signal demodulator 33 removes the carrier and the sub-carrier of the NTSC signal. It is necessary to provide a notch filter.

As described above, the receiving apparatus of the present embodiment can not only receive an NTSC signal and a high-definition television signal, but also can demodulate a high-definition television signal with high accuracy. is there.

FIG. 2 is a block diagram showing a second embodiment of the receiving apparatus according to the present invention. In this figure, parts performing the same operations as in FIG. 1 are assigned the same reference numerals as in FIG. 1 and their explanation is omitted.

The second embodiment is designed to reduce the circuit scale. That is, in the first embodiment, the first local oscillator 27 and the PLL are used for high-definition television signals.
Circuit 32, a third local oscillator 26 and P
The desired reception channel is set to the first IF using the LL circuit 31.
It controls the frequency of the local oscillation signal to be converted into a signal or an IF signal.
Whereas the fine adjustment using the C voltage is performed by the second local oscillator 28, in the present embodiment, as shown in FIG. 2, the local oscillator 26 and the PLL circuit 31 are shared, and the AFC voltage is used. Fine adjustment is also performed by switching the AFC voltage from the high-definition television signal demodulator 33 and the NTSC signal AM demodulator 34 in the PLL circuit 31 according to the received signal.
6 is performed.

In the second embodiment, in addition to the effects described in the first embodiment, the local oscillator and the PLL circuit are shared by the high-definition television signal processing unit and the NTSC signal processing unit, so that the circuit scale is reduced. As a result, it is possible to obtain a simple channel selecting means in which the frequency is controlled only by the local oscillator 26.

FIG. 3 is a block diagram showing a third preferred embodiment of the receiving apparatus according to the present invention. In this figure, parts performing the same operations as in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS. 1 and 2, and description thereof is omitted.

The third embodiment also takes into account a reduction in circuit scale. That is, in the first and second embodiments, the first mixer 10, NT for the high-definition television signal is used.
The frequency conversion for converting the desired reception channel into the first IF signal or the IF signal is performed by using the third mixer 22 for the SC signal.
As shown in (1), the frequency conversion is performed by sharing the mixer 10.

In the third embodiment, in addition to the effects described in the first and second embodiments, the mixer 10 is shared between the high-definition television signal processing section and the NTSC signal processing section, so that the circuit scale is reduced. Reduction can be achieved.

Although not shown, one of the first IF amplifier 14 and the third IF amplifier 23 is shared by the high-definition television signal processing section and the NTSC signal processing section, so that the same effect as described above is obtained. The effect is obtained.

FIG. 4 is a block diagram showing a fourth preferred embodiment of the receiving apparatus according to the present invention. In this figure, parts performing the same operations as those in the embodiment shown in FIG. 2 are assigned the same reference numerals as in FIG. 2 and their explanation is omitted. In the figure, reference numeral 39 denotes a fourth mixer, 40 denotes a fourth local oscillator, and 50 denotes a baseband high-definition television signal demodulator.

The fourth embodiment is characterized in that a high-definition television signal is further subjected to frequency conversion of the second IF signal into baseband and demodulation. In other words, in the second embodiment, the second definition is applied to the high definition television signal.
After the second IF signal of the 45 HMz band output from the mixer 13 is amplified by the first and second IF amplifiers 14 and 16 and the band is selected by the high-definition television signal IF filter 15, the high-definition television signal In the fourth embodiment, the signal is input to the demodulator 33 for demodulation according to the modulation method. In the fourth embodiment, as shown in FIG. It mixes with a local oscillation signal in the 45 HMz band from the local oscillator 40 to output a baseband high definition television signal. This signal is converted to a low-pass filter 41.
, And demodulation is performed by the baseband high-definition television signal demodulator 50. In the fourth embodiment, in addition to the effects described in the first and second embodiments, a high-definition television signal can be demodulated in a low-frequency baseband. The configuration is simplified.

FIG. 5 is a block diagram showing a fifth preferred embodiment of the receiving apparatus according to the present invention. In this figure, parts performing the same operations as those of the embodiment shown in FIG. 4 are assigned the same reference numerals as those in FIG. In the figure, 31 is a PLL circuit not including a reference oscillator, and 42 is a frequency divider.

In the fifth embodiment, as shown in FIG. 5, the oscillation signal of the fourth local oscillator 40 is frequency-divided and used as a reference oscillation signal of a PLL circuit 31 for controlling the oscillation frequency of the local oscillator 26. It is characterized by using. The fourth mixer 39 that converts the frequency of the IF signal of the high-definition television signal into baseband requires a local oscillation signal with high frequency accuracy. Therefore, the fourth local oscillator 40 constitutes an oscillation circuit having high frequency stability using a crystal oscillator, a SAW resonator, or the like. For this reason, instead of the reference oscillator included in the PLL circuit 31 in the second embodiment,
The frequency of the oscillation signal of the fourth local oscillator 40 is divided by the frequency divider 42.

In the fifth embodiment, in addition to the effects described in the fourth embodiment, the oscillation signal of the fourth local oscillator 40 is frequency-divided by the frequency divider 42 and used as the reference oscillation signal of the PLL circuit 31. Since it is used, the circuit scale of the oscillator portion of the receiving device can be reduced, and the high-definition television signal can be demodulated with high accuracy.

Hereinafter, more specific embodiments will be described with reference to the drawings based on the format of a high definition television signal.

FIG. 6 is a block diagram showing a sixth embodiment of the receiving apparatus according to the present invention, and FIG. 7 is a signal band diagram supplementing the sixth embodiment. In FIG. 6, parts performing the same operations as those in the embodiment shown in FIG. 5 are denoted by the same reference numerals as in FIG. 5, and description thereof will be omitted. In the drawing, reference numeral 60 denotes a first IF filter for a high-definition television signal, 61 denotes a second IF filter for a high-definition television signal, and 62 denotes a fifth IF filter.
An amplifier 63 is a fifth mixer, 64 and 65 are low-pass filters, and 66 and 67 are baseband signal amplifiers.

In the sixth embodiment, a high-definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving a TSC signal. FIG. 7 shows the frequency spectrum of the high-definition television signal, the video and audio carriers (fv, fs) and the color subcarrier (fc) of the NTSC signal for comparison. The format of a high-definition television signal to be compressed to a signal band of 6 MHz is being studied in the United States and the like. 506-508, 1992 Annual Conference of the Institute of Television Engineers of Japan.
Consideration is also given to the case where a high-definition television signal is transmitted on the same channel as the NTSC signal. In order to avoid interference from the NTSC signal, a high-energy video and audio carrier in the NTSC signal is placed near the carrier in advance. It has been proposed to use the signal shown in FIG. 7 which does not place the spectrum of the definition television signal. FIG. 7 shows the transmission of a QAM-high-definition television signal by dividing the signal below the video carrier frequency of the NTSC signal into a high-priority signal (HP unit) and dividing the signal above the video carrier frequency into other signals (SP unit). Signal format. This sixth embodiment is similar to FIG.
As shown in FIG. 7, a first IF filter 60 for a high-definition television signal composed of a SAW filter is converted from the second IF signal of the high-definition television signal subjected to the dual frequency conversion.
And the second IF filter 61, the HP section, SP
After the parts are divided and amplified by the second IF amplifier 16 and the fifth IF amplifier 62, the fourth mixer 39 and the fifth mixer 6
In step 3, the frequency is converted to the baseband. The HP unit and the SP unit converted to the baseband pass through the low-pass filters 64 and 65, respectively, and then pass through the baseband signal amplifier 6
In steps 6 and 67, the desired signal level is input to the high-definition television signal demodulator 50 and demodulated. Although the first IF filter 60 and the second IF filter 61 for high-definition television signals are each configured by a separated SAW filter, band separation can be performed by a filter configured on the same substrate. is there.

The sixth embodiment has the effects described in the fifth embodiment, and further divides the high-definition television signal of the signal band shown in FIG. Signal processing, it is possible to sufficiently reduce interference between both bands and interference from NTSC signals transmitted on the same channel.

FIG. 8 is a block diagram showing a seventh embodiment of the receiving apparatus according to the present invention. In this figure, parts performing the same operations as in the embodiment shown in FIG. 6 are assigned the same reference numerals as those in FIG. 6 and their explanation is omitted. In the figure, 70 is a first QAM detector, 71 is a second QAM detector, and 72 and 73.
Is a 90-degree phase shifter, 74 is a first carrier and clock recovery circuit, 75 is a second carrier and clock recovery circuit,
76 is a fifth oscillator, 77 is a sixth oscillator, 78 is AF
The C voltage generation circuit 51 is a data demodulator. This seventh
As shown in FIG. 8, the embodiment of the present invention converts the SA from the second IF signal of the
The first for high definition television signal composed of W filter
The HP and SP sections of the high definition television signal are separated by the IF filter 60 and the second IF filter 61, and the second IF amplifier 16 and the fifth IF amplifier 62
After being amplified by the first and second QAM detectors 70 and 71, the oscillation signals of the fifth and sixth oscillators 76 and 77 are phase-shifted by the 90-degree phase shifters 72 and 73, respectively. Detection is performed using two signals having a phase difference of degrees. At this time, A
The oscillating frequency of the local oscillator 26 is controlled by the FC voltage generation circuit 78, and the frequency control is performed so that the first and second carrier and clock recovery circuits 74 and 75 can recover the carrier and clock signals in the best condition. The detected signal is input to the data demodulator 51 and demodulated. Although the oscillation frequency of the local oscillator 26 is controlled here, a configuration for controlling the oscillation frequency of the second local oscillator 28 or a configuration for controlling the oscillation frequencies of the fifth and sixth oscillators 76 and 77 may be used.

The seventh embodiment has the effects described in the sixth embodiment and performs QAM demodulation on the HP and SP sections of the high-definition television signal in the signal band shown in FIG. Therefore, it is possible to further reduce the interference between the two bands and the interference from the NTSC signal transmitted on the same channel, thereby enabling more accurate data demodulation. Further, by controlling the oscillation frequency of the local oscillator 26, QA
Since the M demodulation is performed, it is possible to demodulate a high-precision television signal with high accuracy.

FIG. 9 is a block diagram showing an eighth embodiment of the receiving apparatus according to the present invention, and FIG. 10 is a signal band diagram supplementing the eighth embodiment. In FIG. 9, parts performing the same operations as those in the embodiment shown in FIG. 2 are assigned the same reference numerals as those in FIG. In the figure, reference numeral 52 denotes a high-definition television signal demodulator.

In the eighth embodiment, a high-definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving an NTSC signal. FIG. 10 shows the frequency spectrum of the high-definition television signal and the video and audio carrier waves (f
v, fs) and the color subcarrier (fc). The figure is 6M
FIG. 4 is a signal band diagram using quaternary vestigial sideband amplitude modulation (VSB) as another digital modulation format of a high-definition television signal compressed to a signal band of Hz. In the eighth embodiment, as shown in FIG. 9, an IF filter 1 for a high-definition television signal in which a second IF signal of a high-definition television signal subjected to dual frequency conversion is constituted by a SAW filter.
5 and the signal is amplified by the second IF amplifier 16, and then, similarly to the IF signal of the NTSC signal, the AM demodulator 34
And demodulate. When the NTSC signal is demodulated, a demodulated signal is output from the AM demodulator 34. When the high-definition television signal is demodulated, the demodulated signal is further input to the high-definition television signal demodulator 52 and demodulated. In addition,
In order to reduce interference from the NTSC signal transmitted on the same channel, the AM demodulator 34 is provided with a notch filter which operates at the time of receiving a high definition television signal and removes the carrier and the subcarrier of the NTSC signal. . Also,
The input filter 6 is provided with a band-pass filter having a bandwidth corresponding to one channel and varying the center frequency of the pass band following the oscillation frequency of the local oscillator 26, so that a strong electric field can be disturbed compared to the desired reception signal. Even when a signal is input, occurrence of interference is reduced.

In the eighth embodiment, in addition to the effects described in the second embodiment, the high-definition television signal is also AM-modulated.
It can be performed by using a signal demodulator, and the control of the AGC voltage and the AFC voltage can be commonly performed, so that the circuit configuration of the receiving apparatus can be simplified and the circuit scale can be reduced. Although the high-definition television signal IF filter 15 and the NTSC signal IF filter 24 are separately provided in the eighth embodiment, the residual sideband width and roll-off characteristics of the high-definition television signal and the NTSC signal are provided. Are similar, both can be shared, and the circuit scale is further reduced.

FIG. 11 is a block diagram showing a ninth embodiment of the receiving apparatus according to the present invention, and FIG. 12 is a signal band diagram supplementing the ninth embodiment. In this figure, parts performing the same operations as those in the embodiment shown in FIGS. 2 and 8 are denoted by the same reference numerals as those in FIGS. 2 and 8, and description thereof is omitted. In the figure, reference numeral 53 denotes a data demodulator for a high definition television signal.

In the ninth embodiment, a high-definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving an NTSC signal. FIG. 12 shows the frequency spectrum of a high-definition television signal and the video and audio carrier waves (f
v, fs) and the color subcarrier (fc). The figure is 6M
FIG. 11 is a signal band diagram using 16-level or 32-level QAM modulation as another format of a high-definition television signal compressed to a signal band of Hz. In the ninth embodiment, as shown in FIG. 11, a second IF signal of a high-definition television signal subjected to dual frequency conversion is selected by an IF filter 15 for a high-definition television signal constituted by a SAW filter. After passing through and amplifying by the second IF amplifier 16, the first QAM
The detector 70 shifts the phase of the oscillation signal of the fifth oscillator 76 by the 90-degree phase shifter 72 and detects the two signals having a phase difference of 90 degrees from each other. At this time, the AFC voltage generation circuit 78
To control the oscillation frequency of the local oscillator 26, and the first and second
The frequency control is performed so that the carrier and clock signal recovery in the carrier and clock recovery circuits 74 and 75 is in the best state. The detected signal is input to the data demodulator 53 and demodulated. Although the oscillation frequency of the local oscillator 26 is controlled here, a configuration for controlling the oscillation frequency of the second local oscillator 28 or a configuration for controlling the oscillation frequency of the fifth oscillator 76 may be used. Also, N transmitted on the same channel
In order to reduce interference from the TSC signal, a QAM detector 7
0 has a notch filter for removing the carrier and subcarrier of the NTSC signal.

In the ninth embodiment, in addition to the effect described in the second embodiment, since the QAM demodulation is performed by controlling the oscillation frequency of the local oscillator 26, the demodulation of a high-precision high-definition television signal can be performed. It becomes possible.

The embodiment described so far is based on the NTS
Although the C signal and the high-definition television signal are input from the signal input terminal 1 and distributed by the distributor 5, the same effect can be obtained by providing two input terminals and inputting to each signal processing unit. Is obtained.

In the embodiments described above, the receivers for receiving NTSC signals and high-definition television signals are mainly used in TV and VTR equipment. However, the receivers are used for communication such as digital communication. The same effect can be obtained by applying to the field.

[0039]

As described above, according to the present invention,
A digital television signal compressed to a 6 MHz band and transmitted can be received, and when extracting a signal of a predetermined channel from the received digital television signal, the digital television signal is converted to a current standard television signal. Since it is an intermediate frequency signal having a frequency substantially equal to that of the intermediate frequency signal, it is used for receiving a current standard television signal as extraction means for extracting a signal of a predetermined channel from the received digital television signal. A SAW filter equivalent to a SAW filter can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a receiving device according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the receiving device according to the present invention.

FIG. 3 is a block diagram showing a third preferred embodiment of a receiving device according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the receiving device according to the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of the receiving device according to the present invention.

FIG. 6 is a block diagram showing a sixth embodiment of the receiving device according to the present invention.

FIG. 7 is a signal band diagram supplementing the sixth embodiment shown in FIG. 6;

FIG. 8 is a block diagram showing a seventh embodiment of the receiving device according to the present invention.

FIG. 9 is a block diagram showing an eighth embodiment of the receiving device according to the present invention.

FIG. 10 is a signal band diagram supplementing the eighth embodiment shown in FIG.

FIG. 11 is a block diagram showing a ninth embodiment of a receiving device according to the present invention.

FIG. 12 is a signal band diagram supplementing the ninth embodiment shown in FIG.

FIG. 13 is a block diagram illustrating an example of a conventional receiving device.

[Explanation of symbols]

Reference Signs List 1 signal input terminal 2 tuning signal terminal 3 high definition television signal output terminal 4 NTSC signal output terminal 5 distributor 7, 9, 18, 20 variable attenuator 8, 19 first and second RF amplifier 10 first mixer DESCRIPTION OF SYMBOLS 11 1st IF filter 12 1st IF amplifier 13 2nd mixer 14 1st IF amplifier 15, 60, 61 IF filter for high definition television signals 16 2nd IF amplifier 17, 21 Variable tuning circuit 22nd 3 mixer 23 third IF amplifier 24 NTSC signal IF filter 25 fourth IF amplifier 26 third local oscillator 27 first local oscillator for high-definition television signal 28 second local oscillator 29, 30, 36, 41, 64, 65 Low-pass filter 31, 32 PLL circuit 33, 50, 51, 52, 53 Demodulator for high definition television signal 34 demodulator for NTSC signal 35 level detector for high definition television signal 37 AGC voltage amplifier 39 fourth mixer 40 fourth local oscillator 42 frequency divider 62 fifth IF amplifier 63 fifth mixer 66, 67 base Band signal amplifier 70, 71 QAM detector 72, 73 90-degree phase shifter 74, 75 Carrier and clock recovery circuit 76, 77 Reference oscillator 78 AFC voltage generator

Claims (7)

[Claims] 1. A receiving apparatus for receiving a digital television signal, comprising: converting a received digital television signal into a frequency substantially equal to an intermediate frequency signal for a standard television, and outputting the converted signal. And a extracting means for extracting a signal of a predetermined channel from an output signal from the frequency converting means and outputting the signal. 2. The digital television signal is 6M
The receiving device according to claim 1, wherein the receiving device has a frequency band of Hz. 3. The receiving apparatus according to claim 1, wherein the digital television signal is subjected to quadrature axis amplitude modulation. 4. The receiving apparatus according to claim 1, wherein said frequency conversion means performs frequency conversion in two stages. 5. The first frequency converter, wherein the frequency converter converts a received digital television signal into a higher frequency than the digital television signal, and outputs the converted signal. 2. The receiving apparatus according to claim 1, further comprising a second frequency converting means for converting an output signal from the first frequency converting section into a frequency substantially equal to an intermediate frequency signal for standard television and outputting the converted signal. 6. The receiving apparatus according to claim 1, wherein said extracting means is a SAW filter. 7. The receiving apparatus according to claim 1, further comprising PLL means for controlling an oscillation frequency of a local oscillator in said frequency converting means.