JP3495662B2 - Receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital television
Receiving the television signal, especially the analog television signal
The present invention relates to a receiver using the same transmission band . [0002] 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 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 transmission frequency of a local oscillator 26 and varies 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 by 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 an LL circuit 31 and a 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 the 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. AFC is performed by finely adjusting the oscillation frequency of the local oscillator 26. [0004] However, the above-mentioned receiving apparatus receives an analog television signal such as NTSC, and does not consider receiving a digital television signal . An object of the present invention is to provide a digital television signal.
Issue, especially for analog television
An object of the present invention is to provide a receiving device that uses the same transmission band as a signal . [0006] In order to achieve the above object, the present invention is applied to an analog television signal.
Digital television having a bandwidth substantially equal to the bandwidth
A receiving device for receiving a television signal, comprising:
For the vision signal, the video signal and the audio signal are data compressed.
A signal consisting of Te, the received digital television signal is converted into an intermediate frequency signal is substantially equal frequency used Anal log television signal, a first frequency converting means for outputting, the first Extracting means for extracting a signal of a predetermined channel including a video signal and an audio signal from an output signal from the frequency converting means and outputting the signal; and outputting an output signal from the extracting means to the first frequency converting means. A second frequency converting means for converting the output signal to a lower frequency than the output signal and outputting the converted signal; and a demodulating means for demodulating the output signal from the second frequency converting means.
The frequency conversion means detects an oscillation signal having a phase difference of 90 degrees from each other, thereby converting the output signal from the extraction means into a baseband signal. According to such a configuration, the received digital
The television signal is the same as the digital television signal.
Used for analog television signals using the same transmission band.
To a frequency substantially equal to the intermediate frequency signal
Therefore, it is possible to receive digital television signals
And an output signal from the first frequency conversion means.
Extract the signal of the specified channel from the signal
However, the output signal from the first frequency conversion means is
Analog using the same transmission band as digital television signals
And intermediate frequency signals used in television signals.
Since the signal has a frequency equal to
Used to receive analog television signals
Using a SAW filter similar to the SAW filter
enable. Further, the predetermined channel extracted by the extracting means may be used.
The channel signals are mutually converted by the second frequency conversion means.
Detection using an oscillation signal having a phase difference of 90 degrees
Is converted to a lower baseband signal
Since the signal is demodulated by the demodulation means,
High-precision demodulation is possible with simple demodulation 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 is a second local oscillator, 29 and 30 are low-pass filters, 31 and 32 are PLL circuits, 33 is a high-definition television signal demodulator, 34 is an NTSC signal AM demodulator, 3
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 those in FIG. 13 are denoted by the same reference numerals as those in FIG. NTS as an analog television signal
When the C signal is input, the signal processing is the same as the signal processing described in the conventional example, and the description is omitted here. Signal input terminal 1
A / D conversion is performed on the RF signal AM-modulated with the NTSC signal and the original signal of the high-definition television, and the data is compressed.
6 MH digitally modulated by AM (quadrature axis amplitude modulation) etc.
An RF signal of a high-definition television having a frequency band of z is input and distributed by a distributor 5. (May be divided into a band, a middle band, and a high band.) And selectively passes a band including a desired channel. 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. The first mixer 10 includes a PLL circuit 3 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.
2. The signal is mixed with a local oscillation signal from a local oscillator 27 formed by forming a feedback by a low-pass filter 30,
Is output. The first IF signal frequency is set to be equal to or higher than the upper limit frequency of the terrestrial transmission band of the NTSC television signal or the CATV transmission band in order to reduce intermodulation interference of the received signal. More specifically, in consideration of the mutual interference by the first local oscillation signal, the second local oscillation signal, and the harmonic signal thereof, the frequency range is 1 GHz or more and 1.2 GHz band.
It is set to a 1.7 GHz band, a 2.6 GHz band, a 3 GHz band, or the like. The first IF signals set in these frequency bands are selectively passed by the first IF filter 11. Demodulation of high definition television signals requires more accurate demodulation than NTSC signals. In order not to deteriorate the demodulation characteristics of the high-definition television signal, a band-pass filter having in-band flatness and low group delay deviation is used as the first IF filter. The first IF signal is amplified by a first IF amplifier 12 and then input to a second mixer 13. In the second mixer, the second
And a local oscillation signal from the local oscillator 28 to output a second IF signal. The second IF signal frequency is the current NT
It is the same 45 MHz band as when receiving the SC signal. Second IF
After the signal is amplified by the first IF amplifier 14, 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 reception channel. When a high-definition television signal is received, the desired receiving channel is amplified by the second IF amplifier 16, input to the high-definition television signal demodulator 33, demodulated according to the modulation method, and subjected to data compression. The high-definition television signal is output from the output terminal 3. 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, NTSC
When a signal is received, the desired receiving channel is amplified by the fourth IF amplifier 25, input to the NTSC signal AM demodulator 34, AM-demodulated, and the baseband video and audio signals are output from the output terminal 4. You. The AGC detects a signal branched from the output of the second IF amplifier 16 by a signal level detector 35 when receiving a high definition television signal, and generates an AGC voltage by a low-pass filter 36 and an AGC voltage amplifier 37. This is performed by applying the voltage to the variable attenuators 7 and 9. When receiving an NTSC signal, the AM demodulator 3
The variable attenuators 18 and 20 are used to perform the inside and the shortage inside of 4. The AFC uses the respective AFC voltages from the high-definition television signal demodulator 33 and the NTSC signal AM demodulator 34 to generate a second local oscillator 28, a third
The oscillation frequency of the local oscillator 26 is finely adjusted. In addition,
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.
In order to avoid interference from the TSC signal, the signal shown in FIG. 7 in which the spectrum of the high-definition television signal is not arranged in advance near the high-energy video and audio carriers and the color subcarrier in the NTSC signal may be used. It is necessary to provide the high-definition television signal demodulator 33 with a notch filter for removing the carrier and subcarrier of the NTSC signal. 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 receiving channel is set to the first IF using the LL circuit 31.
The frequency of the local oscillation signal to be converted into a signal or an IF signal is controlled.
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 PLL circuit 31 is shared with the local oscillator 26, and the AFC voltage is used. The 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 in accordance with 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 those 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 high-definition television signals is used.
While the third mixer 22 for the SC signal is used to perform the frequency conversion for converting the desired reception channel into the first IF signal or the IF signal, the third embodiment employs FIG.
As shown in (1), the mixer 10 is shared to perform frequency conversion. 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 unit and the NTSC signal processing unit, 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 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 in the embodiment shown in FIG. 2 are assigned the same reference numerals as those 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 the 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
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 MHz 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, the demodulation of a high-definition television signal can be performed in a low-frequency baseband. The configuration is simplified. FIG. 5 is a block diagram showing a receiving apparatus according to a fifth embodiment of the present invention. In this figure, parts performing the same operations as in the embodiment shown in FIG. 4 are assigned the same reference numerals as those in FIG. 4 and their explanation is omitted. 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. Therefore, in place of the reference oscillator included in the PLL circuit 31 in the second embodiment,
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 figure, 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.
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 compressed to a signal band of 6 MHz has been 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 signal and a high-energy carrier in the NTSC signal are placed beforehand. It has been proposed to use the signal shown in FIG. 7 without arranging the spectrum of the definition television signal. FIG. 7 shows the transmission of a QAM-high-definition television signal by dividing the video carrier frequency below the NTSC signal into a high-priority signal (HP unit) and 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, this HP unit, 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, frequency conversion to baseband is performed. The HP unit and the SP unit, which have been converted to the baseband, pass through the low-pass filters 64 and 65, respectively, and then pass through the baseband signal amplifier 6
At 6 and 67, the signal level is input to the high-definition television signal demodulator 50 as a desired signal level 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 those in the embodiment shown in FIG. 6 are denoted by the same reference numerals as those in FIG. 6, and description thereof is omitted. In the figure, reference numeral 70 denotes a first QAM detector, 71 denotes 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. In the seventh embodiment, as shown in FIG. 8, a second IF signal of a high-definition television signal subjected to dual frequency conversion is converted to a second IF signal for a high-definition television signal constituted by a SAW filter. The HP section and the SP section of the high-definition television signal are separated by the first IF filter 60 and the second IF filter 61, and are amplified by the second IF amplifier 16 and the fifth IF amplifier 62, respectively. The first and second QAM detectors 70 and 71 shift the phases of the oscillation signals of the fifth and sixth oscillators 76 and 77 by 90-degree phase shifters 72 and 73 and have a phase difference of 90 degrees from each other. Detect using the signal. At this time, the AFC voltage generation circuit 78 controls the oscillation frequency of the local oscillator 26, and the first and second carrier and clock recovery circuits 74 and 75 control the frequency so that the carrier and clock signal recovery is in the best state. Do. 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, and to perform more accurate data demodulation. Also, by controlling the oscillation frequency of the local oscillator 26, QA
Since the M demodulation is performed, it is possible to demodulate a high-definition 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. 2 and their explanation is omitted. 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 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. 4 is a signal band diagram using quaternary residual 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 amplified by the second IF amplifier 16, and then, like the IF signal of the NTSC signal, the AM demodulator 34
And demodulate. When the NTSC signal is demodulated, the 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 that 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 stronger electric field than the desired reception signal is disturbed. 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, since a high-definition television signal is also AM-modulated, part of the demodulation of the high-definition signal is performed by NTSC.
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 device 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- or 32-value 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
Controls the oscillation frequency of the local oscillator 26,
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
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 effects 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 devices. The same effect can be obtained even when applied to the field. As described above, according to the present invention,
Digital television signals can be received,
Use the same transmission band as the analog television signal
It can be a receiving device. Also, demodulation with simple configuration
This enables high-accuracy demodulation. In addition, extraction means
Used to receive analog television signals
Using a SAW filter similar to the SAW filter
It becomes possible.

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. 11; FIG. 13 is a block diagram illustrating an example of a conventional receiving device. [Description of Signs] 1 signal input terminal 2 channel selection signal terminal 3 high definition television signal output terminal 4 NTSC signal output terminal 5 distributors 7, 9, 18, 20 variable attenuators 8, 19 first and second RF amplifiers Reference Signs List 10 first mixer 11 first IF filter 12 first IF amplifier 13 second mixer 14 first IF amplifier 15, 60, 61 high-definition television signal IF filter 16 second IF amplifier 17, 21 Variable tuning circuit 22 Third mixer 23 Third IF amplifier 24 NTSC signal IF filter 25 Fourth IF amplifier 26 Third local oscillator 27 First local oscillator 28 for high definition television signal Second local oscillator 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 4 NTSC signal demodulator 35 High-definition television signal level detector 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 amplifiers 70, 71 QAM detectors 72, 73 90-degree phase shifters 74, 75 Carrier and clock recovery circuits 76, 77 Reference oscillator 78 AFC voltage generator

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshio Nagashima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Media Research Laboratory, Hitachi, Ltd. (56) References JP-A-63-76592 (JP, A) JP-A-54-18208 (JP, A) JP-A-60-66528 (JP, A) JP-A-62-292028 (JP, A) JP-A-61-212923 (JP, A) JP-A-3-284015 ( JP, A) JP-A-56-140746 (JP, A) JP-A-61-77455 (JP, A) JP-B-58-23022 (JP, B1) JP-A-6-505378 (JP, A) Noboru Taga , Tatsuya Ishikawa, Susumu Komatsu, "A Study of QPSK Demodulation System", Television Society Technical Report, Japan, August 22, 1991, Vol. 15, No. 46, p. 19-24 (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 5/38-5/46 H04B 1/26

Claims (1)

(57) A reception apparatus for receiving the Patent Claims 1. A digital television signal, said digital television signal is a signal video signal and audio signal, which are data compression, A first frequency conversion unit that converts the received digital television signal into a frequency substantially equal to an intermediate frequency signal used for demodulation of an analog television signal, and outputs the converted signal; Extracting means for extracting a signal of a predetermined channel including a video signal and an audio signal from the output signal and outputting the signal; and an output signal of the extracting means having a phase difference of 90 degrees from each other.
A second frequency converting means for converting a frequency lower than the output signal of said first frequency converting means by using an oscillation signal of a demodulating means for demodulating an output signal from the second frequency converting means, said first 2 according to the output signal from the frequency conversion means.
A means for controlling the frequency in the first frequency conversion means;
Receiving apparatus characterized by comprising a stage.