JP3495656B2 - Receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates is a receiving apparatus capable of receiving high-definition television signal, in particular, receive the <br/> No. signals compressed in the band of 6MHz as high definition television signals Receiving device

[0002]

2. Description of the Related Art In recent years, conventional television broadcasting (N
In addition to TSC, PAL, etc., establishment of high-definition television broadcasting systems is being promoted in each country. Along with this, also in the receiving device, a receiving device in which image quality and sound room deterioration at the time of receiving a high-definition television signal is small has been required. Figure 1
FIG. 3 shows a conventional single super-heterodyne television receiver. In the figure, 1 is a signal input terminal, 2 is a channel selection 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,
Reference numeral 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. In addition, hereinafter, an NTSC signal will be used as a standard TV signal for explanation.

Of the RF signal AM-modulated by the NTSC signal inputted from the signal input terminal 1, a desired signal follows the oscillation frequency of the local oscillator 26, and the center frequency of its pass band is variable. The signal is selectively passed at 21, 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, and input to the frequency converter 22. In the frequency converter 22, the tuning signal input from the tuning signal input terminal 2 oscillates at a frequency corresponding to the desired channel.
The LL circuit 31 and the low-pass filter 29 mix with the local oscillation signal from the local oscillator 26, which forms feedback, and outputs an IF signal in the 45 MHz band. The IF signal is amplified by the first and second IF amplifiers 23 and 25, and is also an IF filter 24 including a SAW filter or the like.
Then, only a desired band is passed and demodulated by the AM demodulator 34, and baseband video and audio signals are output. A
The GC is performed using the inside of the AM demodulator 34 and the variable attenuators 18 and 20. Further, the AFC finely adjusts the oscillation frequency of the local oscillator 26.

[0004]

However, the above-mentioned receiving device receives an ordinary television signal such as NTSC, and does not consider the reception of a high-definition television signal. Nor is it considered to receive both a normal television signal and a high definition television signal.

An object of the present invention, a child receiving a high definition television signal, in particular to provide a possible receiving receiving apparatus a signal which has been compressed in the band of 6MHz as high definition television signal.

[0006]

In order to achieve the above object, the present invention has a single superheterodyne system for processing an NTSC signal and a first and a second mixer for processing a high definition television signal. The double super-heterodyne system is used. Regarding the double super-heterodyne system, the first IF signal frequency is 1 GHz.
z is set to z or more, a band pass filter having in-band flatness and low group delay deviation that does not deteriorate demodulation of a high definition television signal is used for the first IF filter, and a high definition television signal is used as the second IF filter. For SAW,
A high-definition television signal demodulator was provided as a demodulator.

According to this structure, it is possible to provide a receiving device capable of receiving the NTSC signal and the high definition television signal. In addition, the tuning circuit, the local oscillator, the first mixer NT
Shared when receiving SC signals and high definition television signals,
The second IF filter or IF filter and demodulator is set to N
By separately providing each of the TSC signal and the high-definition television signal, it is possible to configure a receiving device that receives the NTSC signal and the high-definition television signal with a reduced circuit scale.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

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

In the figure, 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 and 19 are first and second RF amplifiers, and 10 is first
Mixer, 11 is the first IF filter, and 12 is the first I filter.
F amplifier, 13 is a second mixer, 14 is a first IF amplifier, 15 is a high definition television signal IF filter, 1
6 is a second IF amplifier, 17 and 21 are variable tuning circuits, 2
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 the figure, parts that perform the same operations as in FIG. 13 are assigned the same numbers as in FIG. 13 and their explanations are omitted.

When the NTSC signal is input, the signal processing is the same as the signal processing described in the conventional example, and therefore the description thereof is omitted here. From the signal input terminal 1, an RF signal AM-modulated by an NTSC signal and a high-definition television original signal are A / D converted, data-compressed, and digitally modulated by QAM (quadrature axis amplitude modulation) to obtain a 6 MHz band The RF signal of the high-definition television that it has is input and distributed by the distributor 5, and the RF signal of the high-definition television is VH by the input filter 6.
The F band and the UHF band (further, the VHF band may be divided into a low band, a middle band, and a high band in some cases), 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 provided by a low pass filter 30 and a PLL circuit 32 having a built-in reference oscillator and frequency divider so as to oscillate at a frequency corresponding to a desired channel by a tuning signal input from a tuning signal input terminal 2. The local oscillation signal from the formed local oscillator 27 is mixed and the first IF signal is output. First IF
In order to reduce intermodulation interference of received signals, the signal frequency is used for terrestrial transmission band of NTSC television signals and CAT.
It is set above the upper limit frequency of the V transmission band. In particular,
In consideration of mutual interference and interference due to the first local oscillation signal, the second local oscillation signal, and harmonic signals thereof, 1.2 GHz band, 1.7 GHz band, 2.6 GHz at 1 GHz or higher.
Band, 3 GHz band, etc. The first IF signal set in these frequency bands is selectively passed by the first IF filter 11. High-definition television signal demodulation is NT
It requires more accurate demodulation than the SC signal. Since the demodulation characteristics of the high definition television signal are not deteriorated, 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
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 the second IF signal. The second IF signal frequency is 45M, which is the same as when receiving the current NTSC signal.
Hz band. The second IF signal is transferred to the first IF amplifier 14
After being amplified by, the signal is input to the high-definition television signal IF filter 15 including a SAW filter or the like. Only the band of the desired reception channel is passed by the IF filter. When receiving a high-definition television signal, the second IF
The desired reception channel is amplified by the amplifier 16 and input to the high-definition television signal demodulator 33, demodulated according to the modulation system, and the data-compressed 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, etc., and outputs video and audio or data to a high definition television. On the other hand, when receiving an NTSC signal,
The fourth IF amplifier 25 amplifies the desired reception channel and NT
It is input to the SC signal AM demodulator 34, AM demodulated, and baseband video and audio signals are output from the output terminal 4. When receiving a high-definition television signal, the AGC detects a signal branched from the output of the second IF amplifier 16 with the signal level detector 35, and outputs the low-pass filter 36,
The AGC voltage is generated by the AGC voltage amplifier 37 and applied to the variable attenuators 7 and 9. Further, when the NTSC signal is received, the variable attenuators 18 and 20 are used to compensate for 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 finely adjust the oscillation frequencies of the second local oscillator 28 and the third local oscillator 26. To do. As will be described later, a high-definition television signal is considered in the case of being transmitted on the same channel as the NTSC signal, and in order to avoid interference from the NTSC signal, a video and audio carrier with high energy in the NTSC signal is used. In the vicinity of the color subcarrier, the signal shown in FIG. 7 in which the spectrum of the high-definition television signal is not arranged in advance is used, and the carrier and subcarrier of the NTSC signal are removed by the high-definition television signal demodulator 33. It is necessary to provide a notch filter.

As described above, the receiving apparatus of this embodiment is capable of not only receiving the NTSC signal and the high definition television signal, but also capable of demodulating the 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 the figure, parts that perform the same operations as in FIG. 1 are assigned the same numbers as in FIG. 1 and their explanations are omitted.

The second embodiment takes into consideration the reduction of 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, third local oscillator 26 and P for NTSC signals
The LL circuit 31 is used to set the desired reception channel to the first IF.
Control the frequency of the local oscillation signal that is converted into a signal or an IF signal, and when receiving a high-definition television signal, the AF
While fine adjustment using the C voltage was 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. For fine adjustment, the AFC voltage from the high-definition television signal demodulator 33 and the NTSC signal AM demodulator 34 is switched in the PLL circuit 31 in accordance with the received signal, and the local oscillator 2
6 oscillation frequency control is performed.

In the second embodiment, in addition to the effect described in the first embodiment, the high-definition television signal processing unit and the NTSC signal processing unit share the local oscillator and the PLL circuit, thereby reducing the circuit scale. It is possible to achieve a reduction, and it is possible to obtain a simple tuning unit that controls the frequency only by the local oscillator 26.

FIG. 3 is a block diagram showing a third embodiment of the receiving apparatus according to the present invention. In the figure, parts that perform the same operations as in FIG. 1 and FIG. 2 are assigned the same numbers as in FIG. 1 and FIG.

This third embodiment also takes into consideration the reduction of the 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 was used to perform frequency conversion for converting the desired reception channel into the first IF signal or the IF signal, in the third embodiment, FIG.
As shown in, the mixer 10 is shared and frequency conversion is performed.

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

Although not shown in the figure, by sharing either one of the first IF amplifier 14 and the third IF amplifier 23 in the high definition television signal processing section and the NTSC signal processing section, the same as above. The effect is obtained.

FIG. 4 is a block diagram showing a fourth embodiment of the receiving apparatus according to the present invention. In the figure, parts that perform the same operations as in the embodiment shown in FIG. 2 are assigned the same numbers as in FIG. 2 and their explanations are omitted. In the figure, 39 is a fourth mixer, 40 is a fourth local oscillator, and 50 is a baseband high-definition television signal demodulator.

The fourth embodiment is characterized in that the high-definition television signal is subjected to frequency conversion of the second IF signal to the base band and demodulation is performed. That is, in the second embodiment, the second
After the second IF signal in the 45 HMz band output from the mixer 13 is amplified by the first and second IF amplifiers 14 and 16 and band-selected by the high-definition television signal IF filter 15, the high-definition television signal is obtained. In the fourth embodiment, as shown in FIG. 4, the fourth IF mixer outputs the second IF signal and the fourth IF signal to the second IF signal. 45 MHz band from the local oscillator 40,
It mixes with a local oscillation signal in a standard frequency band such as the 58 MHz band and outputs a baseband high-definition television signal. This signal is selectively passed by the low pass filter 41,
Baseband high-definition television signal demodulator 50
Demodulate with.

In the fourth embodiment, in addition to the effects described in the first and second embodiments, demodulation of a high definition television signal can be performed in a low frequency base band. The demodulator configuration is simplified.

FIG. 5 is a block diagram showing a fifth embodiment of the receiving apparatus according to the present invention. In the figure, parts that perform the same operations as in the embodiment shown in FIG. 4 are assigned the same numbers as in FIG. 4 and their explanations are 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 divided and used as the reference oscillation signal of the PLL circuit 31 for controlling the oscillation frequency of the local oscillator 26. It is characterized by using. The fourth mixer 39, which frequency-converts the IF signal of the high-definition television signal to the baseband, requires a local oscillation signal with high frequency accuracy. Therefore, the fourth local oscillator 40 constitutes an oscillation circuit having a high frequency stability using a crystal oscillator, a SAW resonator, or the like. Therefore, instead of the reference oscillator included in the PLL circuit 31 in the second embodiment,
The oscillation signal of the fourth local oscillator 40 was divided by the divider 42.

In the fifth embodiment, in addition to the effect described in the fourth embodiment, the oscillation signal of the fourth local oscillator 40 is 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 part of the receiving device can be reduced, and high-definition television signal can be demodulated with high accuracy.

A more specific embodiment will be described below 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. 6, parts that perform the same operations as in the embodiment shown in FIG. 5 are assigned the same numbers as in FIG. 5 and their explanations are omitted. In the figure, 60 is a first IF filter for high definition television signals, 61 is a second IF filter for high definition television signals, and 62 is 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.

The sixth embodiment is 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 video and audio carriers (fv, fs) and color subcarriers (fc) of the NTSC signal for comparison in the frequency spectrum of the high definition television signal. The format of high-definition television signals compressed to a signal band of 6 MHz has been studied in the United States and the like, and for example, Mr. Fukui, “Trends in Next Generation Television Systems in Europe and America” pp. 506-508, and the Television Society of Japan 1992 Annual Conference.
High-definition television signals are also considered when they are transmitted on the same channel as the NTSC signal. In order to avoid interference from the NTSC signal, high-definition television signals should be pre-set near the video and audio carriers with high energy in the NTSC signal. It has been proposed to use the signal shown in FIG. 7 in which the spectrum of the high definition television signal is not placed. FIG. 7 shows a high-definition television signal that has been QAM-divided and transmitted by dividing the video carrier frequency of the NTSC signal into a high-priority signal (HP section) and the signal higher than the video carrier frequency (SP section). Signal format. This sixth embodiment is shown in FIG.
As shown in, the first IF filter 60 for the high-definition television signal formed by the SAW filter from the second IF signal of the high-definition television signal subjected to the double frequency conversion.
And the second IF filter 61 causes the HP section, SP
After being divided into parts 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 respective frequencies are converted to baseband. The HP section and the SP section converted to the baseband pass through the low-pass filters 64 and 65, respectively, and then, the baseband signal amplifier 6
At 6, 67, a 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 composed of separate SAW filters, band separation is possible even with filters formed on the same substrate. is there.

The sixth embodiment has the effects described in the fifth embodiment, and the high-definition television signal in the signal band shown in FIG. Since the signal processing is performed by the above, it is possible to sufficiently reduce the interference between both bands and the interference from the NTSC signal 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 the figure, parts that perform the same operations as in the embodiment shown in FIG. 6 are assigned the same numbers as in FIG. 6 and their explanations are omitted. In the figure, 70 is a first QAM detector, 71 is a second QAM detector, and 72, 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, and 78 is an AF.
A C voltage generation circuit, 51 is a data demodulator.

In the seventh embodiment, as shown in FIG. 8, the second IF signal of the high-definition television signal subjected to the double frequency conversion is used for the high-definition television signal composed of the SAW filter. The first IF filter 60 and the second IF filter 61 separate the HP section and the SP section of the high definition television signal, and after amplifying them by the second IF amplifier 16 and the fifth IF amplifier 62, respectively. In 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 to have a phase difference of 90 degrees with each other. The signal is used for detection. At this time, the AFC voltage generation circuit 78 controls the oscillation frequency of the local oscillator 26, and frequency control is performed so that the carrier and clock signal regeneration in the first and second carrier and clock regeneration circuits 74 and 75 is in the best state. To 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, the oscillation frequency of the second local oscillator 28 may be controlled or the oscillation frequencies of the fifth and sixth oscillators 76 and 77 may be controlled.

The seventh embodiment has the effects described in the sixth embodiment, and QAM demodulation is performed on the HP portion and the SP portion of the high definition television signal in the signal band shown in FIG. 7, respectively. Therefore, the interference between both bands and the interference from the NTSC signal transmitted on the same channel can be further reduced, and the data demodulation with higher accuracy can be performed. In addition, by controlling the oscillation frequency of the local oscillator 26, the QA
Since M demodulation is performed, it becomes possible to demodulate a highly accurate high definition television signal.

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 this eighth embodiment. 9, parts that perform the same operations as in the embodiment shown in FIG. 2 are assigned the same numbers as in FIG. 2 and their explanations are omitted. In the figure, 52 is a demodulator for high definition television signals.

The eighth embodiment is a high-definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving an NTSC signal. 10, the frequency spectrum of the high-definition television signal is similar to that of FIG. 7, and the video and audio carrier waves (f
v, fs) and the color subcarrier (fc) are shown. The figure shows 6M
FIG. 6 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, a high-definition television signal IF filter 1 in which the second IF signal of the double-frequency-converted high-definition television signal is configured by a SAW filter.
After selectively passing the signal through the second IF amplifier 16 and amplifying it by the second IF amplifier 16, the AM demodulator 34 is operated in the same manner as the IF signal of the NTSC signal.
Input to and demodulate. When the NTSC signal is demodulated, the demodulated signal is output from the AM demodulator 34, but when the high-definition television signal is demodulated, it is further input to the high-definition television signal demodulator 52 to perform demodulation. In addition,
In order to reduce the interference from the NTSC signal transmitted on the same channel, the AM demodulator 34 is provided with a notch filter for removing the carrier wave and the subcarrier wave of the NTSC signal, which operates when receiving the high definition television signal. . Also,
The input filter 6 is provided with a bandpass filter having a bandwidth of one channel and varying the center frequency of its pass band by following the oscillation frequency of the local oscillator 26, thereby disturbing a strong electric field as compared with a desired received signal. Even when a signal is input, the occurrence of interference is reduced.

In the eighth embodiment, in addition to the effects described in the second embodiment, since the high definition television signal is also AM-modulated, a part of the demodulation of the high definition signal is performed by the NTSC.
The signal demodulator can be used, and the AGC voltage and the AFC voltage can be commonly controlled, so that the circuit configuration of the receiving device can be simplified and the circuit scale can be reduced. Further, 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. If they are similar to each other, they 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 this ninth embodiment. In the figure, parts that perform the same operations as in the embodiment shown in FIGS. 2 and 8 are assigned the same numbers as in FIGS. 2 and 8 and their explanations are omitted. In the figure, 53 is a data demodulator for high definition television signals.

The ninth embodiment is a high-definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving an NTSC signal. 12, the frequency spectrum of the high-definition television signal is similar to that of FIG. 7, and the video and audio carrier waves (f
v, fs) and the color subcarrier (fc) are shown. The figure shows 6M
FIG. 6 is a signal band diagram using 16-value 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, the second IF signal of the high-definition television signal subjected to the double frequency conversion is selected by the IF filter 15 for the high-definition television signal which is configured by the SAW filter. After passing through and amplifying by the second IF amplifier 16, the first QAM
In the detector 70, the oscillation signal of the fifth oscillator 76 is phase-shifted by the 90-degree phase shifter 72 and is detected using two signals having a phase difference of 90 degrees. At this time, the AFC voltage generation circuit 78
The oscillation frequency of the local oscillator 26 is controlled by the first and second
The frequency is controlled so that the carrier and clock signal reproduction by the carrier and clock recovery circuits 74 and 75 of FIG. The detected signal is input to the data demodulator 53 and demodulated. Although the oscillation frequency of the local oscillator 26 is controlled here, the oscillation frequency of the second local oscillator 28 may be controlled or the oscillation frequency of the fifth oscillator 76 may be controlled. Also, N transmitted on the same channel
To reduce the interference from the TSC signal, the QAM detector 7
At 0, a notch filter is provided to remove the carrier and subcarrier of the NTSC signal.

In the ninth embodiment, in addition to the effect described in the second embodiment, since the oscillation frequency of the local oscillator 26 is controlled to perform the QAM demodulation, it is possible to accurately demodulate a high-definition television signal. It will be possible.

The embodiments described above are 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 them to the respective signal processing units. Is obtained.

Further, in the above-mentioned embodiments, the use as the receiving device for receiving the NTSC signal and the high-definition television signal is mainly described in the TV and VTR equipment, but the receiving device is used for communication such as digital communication. Similar effects can be obtained when applied to the field.

[0041]

As described above, according to the present invention ,
The high definition television signal to be transmitted is compressed in the band of 6 MHz can be provided that can be received receiver.

[Brief description of 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 a receiving device according to the present invention.

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

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

FIG. 5 is a block diagram showing a fifth embodiment of a 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 which complements the sixth embodiment shown in FIG.

FIG. 8 is a block diagram showing a seventh embodiment of a 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 complementary to the eighth embodiment shown in FIG.

FIG. 11 is a block diagram showing a ninth embodiment of the 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 showing an example of a conventional receiving device.

[Explanation of symbols]

1 signal input terminal 2 channel selection 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 11 1st IF filter 12 1st IF amplifier 13 2nd mixer 14 1st IF amplifier 15, 60, 61 High-definition television signal IF filter 16 2nd IF amplifier 17, 21 Variable tuning circuit 22 3 mixer 23 third IF amplifier 24 NTSC signal IF filter 25 fourth IF amplifier 26 third local oscillator 27 first local oscillator 28 high-definition television signal second local oscillator 29, 30, 36, 41, 64, 65 Low-pass filter 31, 32 PLL circuit 33, 50, 51, 52, 53 High-definition television signal demodulator 34 NTSC signal For demodulator 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 For baseband 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

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Nagashima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Video Media Research Laboratory (56) Reference JP-A-1-168125 (JP, A) Kaihei 2-234518 (JP, A) JP 1-300717 (JP, A) JP 1-236736 (JP, A) JP 63-76592 (JP, A) JP 54-18208 ( JP, A) JP 60-66528 (JP, A) JP 62-292028 (JP, A) JP 61-212923 (JP, A) JP 3-284015 (JP, A) JP 56-140746 (JP, A) JP-A 61-77455 (JP, A) JP 58-23022 (JP, B1) Noboru Taga, Tatsuya Ishikawa, Susumu Komatsu, "A Study of QPS K Demodulation System", Television Society Technical Report, Japan, August 22nd, 1991 Sun, Vol. 15, No. 46, p. 19-24 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/38-5/46 H04B 1/26 H04L 27/38

Claims (8)

(57) [Claims] 1. A digital television signal Film image signal and the audio signal, which are data compressed and the standard television signal
And a standard television signal received by the digital television.
The vision signal and the standard television signal are transmitted
A first frequency converted to a first frequency lower than the frequency
A predetermined channel is selected from the output signals of the conversion means and the first frequency conversion means.
First extraction means for extracting and outputting a channel signal, and a standard television set for demodulating the output signal of the first extraction means.
The digital signal demodulation means and the received digital television signal are transferred to the first frequency band.
Second frequency conversion means for converting to a frequency substantially equal to the wave number and outputting, and a first frequency conversion means for extracting and outputting a signal of a predetermined channel from the output signals of the second frequency conversion means . The second extractor and the output signal of the second extractor are converted to a frequency lower than the output signal of the second frequency converter and output.
Third frequency conversion means, and a digital signal demodulating the output signal of the third frequency conversion means
And a receiver demodulating means . 2. The digital television signal is 6 MHz.
The receiving apparatus according to claim 1, having the frequency band of. 3. The receiving apparatus according to claim 1, wherein the digital television signal is QAM-modulated. 4. The receiving apparatus according to claim 1, wherein the second frequency converting means frequency-converts the digital television signal in two stages. 5. The receiving apparatus according to claim 1, wherein the second extracting means is a SAW filter. 6. The receiving apparatus according to claim 1, further comprising PLL means for controlling an oscillation frequency of a local oscillator in the second frequency converting means. 7. A based on the output signal of the second extracting means
The receiving apparatus according to claim 1, further comprising an AGC unit that performs GC. 8. The receiving apparatus according to claim 1, further comprising an AFC unit that performs AFC based on the output signal of the digital demodulation unit.