JP2004104768A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To receive a high definition television signal with high precision. <P>SOLUTION: The high definition television signal is converted into a first IF signal having higher frequency than 10GHz by a first mixer 10, and the fist IF signal is converted into a second IF signal having a frequency band equal to the IF signal of the NTSC signal by a second mixer 13. A double superheterodyne system is used for separating a tuned channel from the second IF signal by an IF filter 15 which is a SAW (surface acoustic wave) filter for the high definition television signal. A bandpass filter having in-band flatness and low group delay deviation is used as an IF filter 11 to be supplied the first IF signal from the first mixer 10. The channel signal abstracted by the IF filter 15 for the high definition television signal is demodulated by a demodulator 50 for the high definition television signal after being converted into a signal having lower frequency band by a fourth mixer 39. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiving device capable of receiving a high-definition television signal and a normal television signal, and particularly to a signal compressed as a high-definition television signal into a 6 MHz band and a normal television signal. The present invention relates to a receiving apparatus for commonly receiving an NTSC signal having a 6 MHz band.
[0002]
[Prior art]
In recent years, in addition to the conventional television broadcasting (NTSC, 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. 13 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 A frequency converter, 23 and 25 are IF amplifiers, 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.
[0003]
The desired signal among the RF signals AM-modulated with the NTSC signal input from the signal input terminal 1 is selected by the variable tuning circuits 17 and 21 which follow the oscillation frequency of the local oscillator 26 and vary the center frequency of the pass band. The signal is appropriately amplified or attenuated by the variable attenuators 18 and 20 and the RF amplifier 19 so that the desired signal has a desired reception level, and is input to the frequency converter 22. In the frequency converter 22, a PLL circuit 31 that oscillates at a frequency corresponding to a desired channel based on a tuning signal input from a tuning signal input terminal 2 and a local oscillator 26 that forms feedback by a low-pass filter 29 are output. It mixes with the local oscillation signal 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, passed through only a desired band by an IF filter 24 composed of a SAW filter or the like, demodulated by an AM demodulator 34, and converted to a baseband signal. Video and audio signals are output. AGC 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]
[Problems to be solved by the invention]
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.
[0005]
An object of the present invention is to receive a high-definition television signal or to receive both a normal television signal and a high-definition television signal. In particular, the present invention has a 6-MHz band as a normal television signal. It is an object of the present invention to provide a receiving apparatus capable of receiving an NTSC signal or a signal compressed to a 6 MHz band as a high definition television signal.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a configuration in which processing of an NTSC signal is performed by a single superheterodyne method and processing of a high-definition television signal is performed by a double superheterodyne method having first and second mixers, For the double superheterodyne method, the first IF signal frequency is set to 1 GHz or more, and the first IF filter has a band pass having a flatness within a band and a low group delay deviation which does not deteriorate the demodulation of a high definition television signal. A high-definition television signal SAW was provided as a second IF filter using a filter, and a high-definition television signal demodulator was provided as a demodulation unit.
[0007]
According to such a configuration, it is possible to provide a receiving device capable of receiving the NTSC signal and the high definition television signal. Further, the tuning circuit, the local oscillator, and the first mixer are shared when receiving the NTSC signal and the high-definition television signal, and the second IF filter or the IF filter and the demodulator are used for the NTSC signal and the high-definition television signal, respectively. , A receiving device that receives an NTSC signal and a high-definition television signal with a reduced circuit scale can be configured.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
FIG. 1 is a block diagram showing a first embodiment of a receiving device according to the present invention.
[0010]
In the figure, 1 is a signal input terminal, 2 is a tuning 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, 6 is an input filter, 7 , 9, 18, and 20 are variable attenuators, 8 and 19 are first and second RF amplifiers, 10 is a first mixer, 11 is a first IF filter, 12 is a first IF amplifier, and 13 is a first IF amplifier. 2 is a first IF amplifier, 15 is an IF filter for a high definition television signal, 16 is a second IF amplifier, 17 and 21 are tunable circuits, 22 is a third mixer, and 23 is a third mixer. , An IF filter for NTSC signal, 25 a fourth IF amplifier, 26 a third local oscillator, 27 a first local oscillator, 28 a second local oscillator, 29 and 30 low-pass filters , 31 and 32 are PLL circuits, 33 High definition TV signal demodulator, 34 AM demodulator for NTSC signal, 35 is a signal level detector for high-definition television signals, 36 is a low pass filter, 37 is the 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.
[0011]
When the 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 RF signal of the high-definition television is input and distributed by the distributor 5, and the RF signal of the high-definition television is input to the input filter 6 in the VHF band, the UHF band (and the VHF band is a low band and a middle band). , May be divided into high bands.), 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. In the first mixer 10, feedback is provided by a PLL circuit 32 and a low-pass filter 30 incorporating a 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. 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 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 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. 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 set to the same 45 MHz band as when the current NTSC signal is received. After the second IF signal is amplified by the first IF amplifier 14, it is input to the 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, when receiving the NTSC signal, the fourth IF amplifier 25 amplifies the desired receiving channel and inputs the amplified signal to the NTSC signal AM demodulator 34 where the signal is AM-demodulated and the baseband video and audio signals are output to the output terminal 4. Output from 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. In the case of receiving an NTSC signal, the inside and outside of the AM demodulator 34 are compensated for by using the variable attenuators 18 and 20. 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 wave 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, or the carrier and the subcarrier of the NTSC signal are removed by the high-definition television signal demodulator 33. It is necessary to provide a notch filter.
[0012]
As described above, the receiving apparatus of the present embodiment can not only receive the NTSC signal and the high-definition television signal, but also can demodulate the high-definition television signal with high accuracy.
[0013]
FIG. 2 is a block diagram showing a second embodiment of the receiving device 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.
[0014]
The second embodiment is designed to reduce the circuit scale. That is, in the first embodiment, the first local oscillator 27 and the PLL circuit 32 are used for high-definition television signals, and the third local oscillator 26 and the PLL circuit 31 are used for NTSC signals. In contrast to the case where the second local oscillator 28 performs fine adjustment using the AFC voltage when receiving a high-definition television signal, the second local oscillator 28 controls In the embodiment, as shown in FIG. 2, the local oscillator 26 and the PLL circuit 31 are shared, and the fine adjustment using the AFC voltage is also performed in the PLL circuit 31 by the high-definition television signal demodulator 33 and the NTSC signal AM demodulation. The oscillation frequency of the local oscillator 26 is controlled by switching the AFC voltage from the unit 34 according to the received signal.
[0015]
In the second embodiment, in addition to the effects described in the first embodiment, the circuit scale can be reduced by sharing the local oscillator and the PLL circuit between the high-definition television signal processing unit and the NTSC signal processing unit. Thus, a simple channel selecting means for controlling the frequency only by the local oscillator 26 can be obtained.
[0016]
FIG. 3 is a block diagram showing a third preferred embodiment of the receiving device 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.
[0017]
This third embodiment also takes into account a reduction in circuit scale. That is, in the first and second embodiments, the first mixer 10 is used for a high-definition television signal, and the third mixer 22 is used for an NTSC signal. In contrast to the frequency conversion for conversion, in the third embodiment, as shown in FIG. 3, the mixer 10 is shared to perform frequency conversion.
[0018]
In the third embodiment, in addition to the effects described in the first and second embodiments, the circuit scale can be reduced by sharing the mixer 10 between the high-definition television signal processing unit and the NTSC signal processing unit. .
[0019]
Although not shown, the same effect as described above can be obtained by sharing one of the first IF amplifier 14 and the third IF amplifier 23 with the high-definition television signal processing unit and the NTSC signal processing unit. Can be
[0020]
FIG. 4 is a block diagram showing a fourth embodiment of the receiving device 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.
[0021]
The fourth embodiment is characterized in that a high-definition television signal is further frequency-converted into a baseband signal and demodulated. That is, in the second embodiment, the second IF signal of the 45 HMz band output from the second mixer 13 is amplified by the first and second IF amplifiers 14 and 16 for the high-definition television signal. After the band is selected by the high-definition television signal IF filter 15, the signal is input to the high-definition television signal demodulator 33 and demodulation is performed according to the modulation method. As shown in FIG. 4, the second IF signal is mixed with a local oscillation signal of a standard frequency band such as a 45 MHZ band or a 58 MHz band from the fourth local oscillator 40 by a fourth mixer to obtain a baseband high-definition television signal. Is output. This signal is selectively passed by a low-pass filter 41 and demodulated by a high-definition television signal demodulator 50 in a base band.
[0022]
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.
[0023]
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.
[0024]
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. Features. 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, the oscillation signal of the fourth local oscillator 40 is divided by the frequency divider 42 instead of the reference oscillator included in the PLL circuit 31 in the second embodiment.
[0025]
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. The circuit scale of the oscillator part of the receiving device can be reduced, and high-definition television signals can be demodulated with high accuracy.
[0026]
Hereinafter, more specific embodiments will be described with reference to the drawings based on the format of a high definition television signal.
[0027]
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, 62 denotes a fifth IF amplifier, 63 denotes a fifth mixer, 64, 65 is a low-pass filter and 66 and 67 are baseband signal amplifiers.
[0028]
The sixth embodiment is characterized in that a high-definition television signal having a baseband signal band shown in FIG. 7 and an NTSC signal are received. 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. In the sixth embodiment, as shown in FIG. 6, a second IF signal of a high-definition television signal subjected to dual frequency conversion is converted into a first IF for a high-definition television signal constituted by a SAW filter. The HP section and the SP section are divided by the filter 60 and the second IF filter 61 and amplified by the second IF amplifier 16 and the fifth IF amplifier 62, and then are respectively separated by the fourth mixer 39 and the fifth mixer 63. Frequency conversion to baseband. The HP section and the SP section converted into the baseband pass through the low-pass filters 64 and 65, respectively, and are input to the high-definition television signal demodulator 50 as desired signal levels by the baseband signal amplifiers 66 and 67 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.
[0029]
The sixth embodiment has the effects described in the fifth embodiment, and performs signal processing by dividing the frequency band after high-definition television signals in the signal band shown in FIG. Therefore, it is possible to sufficiently reduce the interference between the two bands and the interference from the NTSC signal transmitted on the same channel.
[0030]
FIG. 8 is a block diagram showing a seventh embodiment of the receiving device 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, 70 is a first QAM detector, 71 is a second QAM detector, 72 and 73 are 90-degree phase shifters, 74 is a first carrier and clock recovery circuit, 75 is a second carrier and A clock recovery circuit, 76 is a fifth oscillator, 77 is a sixth oscillator, 78 is an AFC voltage generation circuit, and 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 into a first IF 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 filter 60 and the second IF filter 61, and are amplified by the second IF amplifier 16 and the fifth IF amplifier 62. In the second QAM detectors 70 and 71, the oscillation signals of the fifth and sixth oscillators 76 and 77 are phase-shifted by 90-degree phase shifters 72 and 73, and two signals having a phase difference of 90 degrees are used. To detect. 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.
[0031]
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. 7, respectively. 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. In addition, since the QAM demodulation is performed by controlling the oscillation frequency of the local oscillator 26, it is possible to demodulate the television signal with high accuracy and high precision.
[0032]
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.
[0033]
The eighth embodiment is characterized in that a high-definition television signal having a baseband signal band shown in FIG. 10 and an NTSC signal are received. FIG. 10 shows the frequency spectrum of the high-definition television signal, and the video and audio carriers (fv, fs) and the color subcarrier (fc) of the NTSC signal for comparison, as in FIG. FIG. 1 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 6 MHz. In the eighth embodiment, as shown in FIG. 9, 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 signal is input to the AM demodulator 34 and demodulated similarly to the IF signal of the NTSC signal. 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 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. ing. The input filter 6 is provided with a band-pass filter having a bandwidth for one channel and varying the center frequency of the pass band following the oscillation frequency of the local oscillator 26. , The occurrence of interference is reduced.
[0034]
In the eighth embodiment, in addition to the effects described in the second embodiment, since a high-definition television signal is also AM-modulated, a part of the demodulation of the high-definition signal is performed by using an NTSC signal demodulator. The AGC voltage and the AFC voltage can be controlled in common, 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.
[0035]
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.
[0036]
The ninth embodiment is characterized in that it receives a high definition television signal having a baseband signal band shown in FIG. 12 and an NTSC signal. FIG. 12 shows the frequency spectrum of the high-definition television signal, and the video and audio carrier (fv, fs) and the color subcarrier (fc) of the NTSC signal for comparison, as in FIG. FIG. 1 is a signal band diagram using 16- or 32-value QAM modulation as another format of a high-definition television signal compressed to a 6-MHz signal band. 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 detector 70 shifts the phase of the oscillation signal of the fifth oscillator 76 by the 90-degree phase shifter 72, and a phase difference of 90 degrees is obtained. Detection is performed using the two signals. 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 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. Further, in order to reduce interference from the NTSC signal transmitted on the same channel, the QAM detector 70 is provided with a notch filter for removing the carrier and the subcarrier of the NTSC signal.
[0037]
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, it is possible to demodulate a high-precision high-definition television signal. .
[0038]
In the above-described embodiments, the NTSC signal and the high-definition television signal are input from the signal input terminal 1 and distributed by the distributor 5. However, two input terminals are provided and each signal processing is performed. A similar effect can be obtained even when the input is made to the section.
[0039]
In the embodiments described above, the receivers for receiving NTSC signals and high-definition television signals are mainly used in TV and VTR devices. However, the receivers are applied to communication fields such as digital communication. A similar effect can be obtained.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a reception value that can receive an NTSC signal or a high-definition television signal compressed and transmitted in a 6 MHz band. In addition, the tuning circuit, the local oscillator, and the first mixer are shared by the NTSC signal and the high-definition television signal, and the IF filter and the demodulator are separately provided for the NTSC signal and the high-definition television signal. A receiving device that receives an NTSC signal and a high-definition television signal with reduced noise can be configured.
[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.
[Explanation of symbols]
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 The first mixer
11 1st IF filter
12 First IF amplifier
13 Second Mixer
14 1st IF amplifier
15,60,61 IF filter for high definition television signal
16 Second IF amplifier
17,21 Variable tuning circuit
22 Third Mixer
23 Third IF Amplifier
24 IF filter for NTSC signal
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 divider
62 Fifth IF amplifier
63 Fifth Mixer
66,67 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

Claims (8)

A receiving device for receiving a digital television signal,
First frequency conversion means for converting the received digital deviation signal to a frequency substantially equal to the intermediate frequency for a standard television signal and outputting the same;
Extracting means for extracting a signal of a predetermined channel from an output signal of the first frequency converting means and outputting the signal;
A second frequency conversion unit that converts an output signal of the extraction unit to a lower frequency than an output signal of the first frequency conversion unit and outputs the second output signal;
A demodulating means for demodulating an output signal of the second frequency converting means. The receiving device according to claim 1, wherein the digital television signal has a frequency band of 6 MHz. The receiving device according to claim 1, wherein the digital television signal is QAM-modulated. 2. The receiving apparatus according to claim 1, wherein the first frequency converting means converts the frequency of the digital television signal in two stages. The receiving device according to claim 1, wherein the extracting unit is a SAW filter. 2. The receiver according to claim 1, further comprising a PLL unit that controls an oscillation frequency of a local oscillator in the first frequency conversion unit. 2. The receiver according to claim 1, further comprising AGC means for performing AGC based on an output signal of said extracting means. The receiving apparatus according to claim 1, further comprising AFC means for performing AFC based on an output signal of the demodulation means.

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