JP3128371B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver capable of receiving a high-definition television signal and a normal television signal, and more particularly to a signal compressed as a high-definition television signal into a 6 MHz band. Movement in the United States has been seen, so such a 6MH
A high-definition television signal band-compressed to z and a standard television signal having a 6 MHz band as a normal television signal (not only the NTSC system, but also a standard television signal by another AM-modulated system). Including)
, And a receiving device that can receive in common.

[0002]

2. Description of the Related Art In recent years, with the expansion of television broadcasting, CATV broadcasting, and the like, multichannel broadcasting has been promoted. Along with this, a receiving apparatus having a frequency conversion unit of a double superheterodyne system capable of reducing intermodulation interference and the like even at the time of multi-channel reception has come to be used.

FIG. 13 is a block diagram showing such a conventional double 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, 5 is an input filter (BPF), and 6 and 8 are variable attenuators (A
GC), 7 is an RF amplifier, 9 is a first mixer, 10 is a first mixer.
The local oscillator 12 is a first IF amplifier.

Further, 13 is a second mixer, 14 is a second local oscillator, 15 is a first IF amplifier, 17 is an IF filter (BPF), 20 is a second IF amplifier, 22 is a low-pass filter (LPF), 23 is a PLL (phase locked loop) circuit, 34 is an AM demodulator (NTSC demo)
d. IC), 71 is a first IF filter.

An AM-modulated RF signal of an NTSC television signal (hereinafter, may be simply referred to as an NTSC signal) input from a signal input terminal 1 is divided by an input filter 5 into a desired channel. Are selectively passed through the filter 5. For the desired channel, the variable attenuator 6 is set to a desired reception level.
8 and the RF amplifier 7 appropriately amplify or attenuate
It is input to the mixer 9.

In the first mixer 9, a PLL circuit 23 and a low-pass filter 22 form feedback so as to oscillate at a frequency corresponding to a desired channel in response to a tuning signal input from a tuning signal input terminal 2. Oscillator 1
0 and the variable attenuators 6, 8 and R
The signal is mixed with the NTSC signal appropriately amplified or attenuated by the F amplifier 7 to output a first IF signal.

Specifically, the PLL circuit 23 has a reference signal therein, compares the reference signal with a local oscillation signal from the local oscillator 10, and outputs an error signal to the local oscillator 10 via the low-pass filter 22. By doing so, the oscillation frequency of the local oscillator 10 is controlled so that the error signal becomes zero, and the tuning signal is selected by performing an action such as dividing the reference signal used for comparison. Do stations.

The first IF signal is selectively passed through a first IF filter 71 and amplified by a first IF amplifier 12,
It is input to the second mixer 13. In the second mixer 13, the signal is mixed with the local oscillation signal from the second local oscillator 14,
Outputs IF signal. The second IF signal is amplified by the first and second IF amplifiers 15 and 20, and only a desired band is passed by an IF filter 17 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. The AGC uses the AM demodulator 34
And the variable attenuators 6 and 8 are used. Also, AFC
Performs fine adjustment of the oscillation frequency of the second local oscillator 14 with the AFC signal output from the AM demodulator 34.

[0009]

However, the above-mentioned receiving apparatus is for receiving a standard television signal such as an NTSC television signal, and does not consider receiving a high definition television signal. not to mention,
No consideration has been given to selectively receiving both the standard television signal and the high-definition television signal.

An object of the present invention is to provide a receiving apparatus capable of selectively receiving both a standard television signal and a high-definition television signal compressed and broadcast to the same bandwidth as that of the standard television signal. To provide.

[0011]

In order to achieve the above object, the present invention provides a double super heterodyne type receiving apparatus having first and second mixers.
As a filter, a bandpass filter having in-band flatness characteristics and low group delay deviation characteristics that does not deteriorate the demodulation of a high-definition television signal is used. As a second IF filter, a standard television signal such as an NTSC television signal is used. A SAW filter for a signal and a SAW filter for a high-definition television signal are used, and as a demodulation unit, a demodulator for a high-definition signal is provided in addition to the AM demodulator for a standard television signal.

[0012]

According to the above arrangement, both a standard television signal and a high definition television signal can be received. Also,
The first IF filter is shared for the standard television signal and the high-definition television signal, and the second IF filter and the demodulator are separately provided for the standard television signal and the high-definition television signal. Since the dual frequency conversion unit of the heterodyne system can be used for both signals, the circuit scale can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the description of the embodiments, a television signal according to the NTSC system will be described as an example among various standard systems such as the NTSC system, the PAL system, and the SECAM system. In the following description, a television signal according to the NTSC system is simply referred to as NTS.
Sometimes called C signal.

FIG. 1 is a block diagram showing a receiving apparatus according to a first embodiment of the present invention. 1, reference numeral 1 denotes a signal input terminal of a television signal, 2 denotes a channel selection signal input terminal, 3 denotes a high-definition television signal output terminal, and 4 denotes an NTS.
Video and audio signal output terminals for C system, 5 is an input filter (BPF), 6 and 8 are variable attenuators (AGC), 7 is RF
An amplifier, 9 is a first mixer, 10 is a first local oscillator, 11
Is a first IF filter (BPF), and 12 is a first IF amplifier.

13 is a second mixer, 14 is a second local oscillator, 15 is a first IF amplifier, 16 is an IF filter (BPF) for high definition television signals, 17 is an IF filter (BPF) for NTSC signals, 19 Is the second IF amplifier,
20 is a third IF amplifier, 27 is an AFC for NTSC signal
An AFC voltage switching circuit (AFC SW) for switching between a voltage and an AFC voltage for a high-definition television signal in accordance with a desired reception signal and outputting the same.

Reference numeral 33 denotes a high-definition television signal demodulator (Digital demod. IC), and reference numeral 34 denotes an NTS.
AM demodulator for C signal (NTSC demod. IC),
40 is a signal level detector (D) for a high-definition television signal.
ET), 41 is a low-pass filter (LPF), 42 is A
A GC voltage amplifier 43 switches an AGC voltage for an NTSC signal and an AGC voltage for a high-definition television signal in accordance with a desired reception signal and outputs the AGC voltage.
SW).

Next, the circuit operation will be described. Signal input terminal 1
A / D conversion of an RF signal AM-modulated with an NTSC signal and an original signal of a high-definition television, followed by data compression and high-definition television having a 6 MHz band modulated by QAM (quadrature axis amplitude modulation) or the like. John's RF signal is input, and the input filter 5 uses the VHF band, UHF band (and VHF band).
Sometimes a band is divided into low, mid and high bands. ), And selectively passes a band including a desired channel.

The desired channel is appropriately amplified or attenuated by the variable attenuators 6 and 8 and the RF amplifier 7 so as to have a desired signal level, and is input to the first mixer 9. In the first mixer 9, feedback is provided by a PLL circuit 23 having a built-in reference oscillator and a frequency divider and a low-pass filter 22 so as to oscillate at a frequency corresponding to a desired channel according to a tuning signal input from the tuning signal input terminal 2. It mixes with the local oscillation signal from the formed local oscillator 10 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 mutual interference interference caused by the first local oscillation signal, the second local oscillation signal, and harmonic signals thereof, a frequency of 1 GHz or more, a band of 1.2 GHz, and a frequency of 1.7 GHz are used.
Band, 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.

The first IF filter is used for the first IF signal of the high-definition television signal and the NTSC signal.
A band-pass filter having a flatness characteristic within a band and a low group delay deviation characteristic that does not degrade the demodulation characteristics of a high definition television signal that requires more accurate demodulation than a TSC signal is used. The first IF signal is amplified by the first IF amplifier 12 and then input to the second mixer 13. The second mixer 13 mixes with the local oscillation signal from the second local oscillator 14,
A second IF signal is output.

The second IF signal frequency is set to the same 45 MHz band as when receiving the current NTSC signal. After the second IF signal is amplified by the first IF amplifier 15 and branched, the IF filter 1 for a high-definition television signal composed of a SAW filter or the like is used.
6 and the NTSC signal IF filter 17. Each IF filter passes only the band of the desired reception channel.

When a high-definition television signal is received, a desired reception channel is amplified by the second IF amplifier 19 and input to the high-definition television signal demodulator 33 to perform demodulation according to the modulation method. A data-compressed high-definition television signal is output from an 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 an NTSC signal,
The desired receiving channel is amplified by the third IF amplifier 20 and NT
The signal is input to the SC signal AM demodulator 34, AM demodulated, and the baseband video and audio signals are output from the output terminal 4.

When receiving a high definition television signal, the AGC detects a signal branched from the output of the second IF amplifier 19 with a signal level detector 40, and detects an AGC voltage with a low-pass filter 41 and an AGC voltage amplifier 42. Generated by the AGC voltage switching circuit 43 and the variable attenuators 6, 8
Is applied. When receiving an NTSC signal, A
The inside of the M demodulator 34 and the shortage inside the M demodulator 34 are performed using the variable attenuators 6 and 8.

The AFC switches and outputs the AFC voltage from the high-definition television signal demodulator 33 and the NTSC signal AM demodulator 34 in accordance with the received signal.
The oscillation frequency of the second local oscillator 14 is finely adjusted using a C voltage switching circuit.

As will be described later, it is considered that the high definition television signal is transmitted on the same channel as the NTSC signal. In this case, in order to avoid interference from the NTSC signal, the energy in the NTSC signal is reduced. In the vicinity of the high video carrier (frequency fv), the audio carrier (frequency fs) and the chrominance subcarrier (frequency fc), the spectrum of the high-definition television signal (the spectrum HP of the high priority information, the spectrum HP of the standard information, And a notch filter for removing the carrier and subcarrier of the NTSC signal is provided in the high-definition television signal demodulator 33. That is necessary.

AGC (automatic gain control) is performed by the variable attenuators 6 and 8. However, when the interference of the high-definition television signal during the gain control is sufficiently small, a dual gate FET or the like is connected to the RF amplifier 7. It is also possible to adopt a configuration in which the amplification degree is controlled by using.

As described above, the receiving apparatus of the present embodiment shown in FIG. 1 can not only receive the NTSC signal and the high-definition television signal, but also can
TSC signal and high-definition television signal
By separately providing an F filter and a demodulator for NTSC signals and high-definition television signals, the double frequency conversion unit of the double superheterodyne system can be shared for both signals, reducing the circuit scale and improving operability. And a receiver excellent in the above is obtained.

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

This embodiment has a feature in the channel selection method. That is, in the first embodiment, the first local oscillator 10 uses the PLL circuit 23 to set the desired reception channel to the first I-channel.
The frequency of the local oscillation signal to be converted into the F signal is controlled,
While the fine adjustment using the FC voltage was performed by the second local oscillator 14, in the present embodiment, the first local oscillation signal and the second
The local oscillation signal is mixed by the third mixer 21, and the signal of the difference frequency is compared by the PLL circuit 23.
Control the oscillation frequency of the
High-definition television signal demodulator 3 in LL circuit 23
3. The oscillation frequency of the first local oscillator 10 is controlled by switching the AFC voltage from the NTSC signal AM demodulator 34 according to the received signal.

In the present embodiment, in addition to the effects described in the first embodiment, frequency control is performed by utilizing the fact that the difference between the first local oscillation signal frequency and the second local oscillation signal frequency is kept constant. A simple channel selection means performed by only one local oscillator 10 is obtained.

FIG. 3 is a block diagram showing a receiving apparatus according to a third embodiment of the present invention. In FIG.
1 and 2 are denoted by the same reference numerals as those in FIGS. 1 and 2, and description thereof is omitted.
In FIG. 3, reference numeral 30 denotes a fourth mixer, 31 denotes a third local oscillator, and 60 denotes a baseband high-definition television signal demodulator.

This embodiment is characterized in that the high-definition television signal is further frequency-converted from the second IF signal to baseband and demodulated.

That is, in the second embodiment (FIG. 2), the second IF signal of the 45 MHz band output from the second mixer 13 is converted by the first and second IF amplifiers 15 and 19 for the high definition television signal. Amplified, high definition television signal IF
After the band is selected by the filter 16, the signal is input to the high-definition television signal demodulator 33 and demodulated according to the modulation method.
The IF signal is mixed with a 45 MHz band local oscillation signal from the third local oscillator 31 to output a baseband high definition television signal. This signal is selectively passed by a low-pass filter 32 and demodulated by a high-definition television signal demodulator 60 in a base band.

In this 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. 4 is a block diagram showing a receiving apparatus according to a fourth embodiment of the present invention. In the figure, parts performing the same operations as those of the embodiment shown in FIG.
The same reference numerals are given to those, and the description is omitted. In FIG.
24 is a PLL circuit that does not include a reference oscillator, and 28 is a frequency divider.

The present embodiment is characterized in that the frequency of the oscillation signal of the third local oscillator 31 is divided and used as the reference oscillation signal of the PLL circuit 24 for controlling the oscillation frequency of the first local oscillator 10. The fourth mixer 30, which converts the frequency of an IF signal of a high-definition television signal to baseband, requires a local oscillation signal with high frequency accuracy. Therefore, the third local oscillator 31 constitutes an oscillation circuit having high frequency stability using a crystal oscillator, a SAW resonator, or the like. Therefore, instead of the reference oscillator included in the PLL circuit 23 in the third embodiment (FIG. 3), the oscillation signal of the third local oscillator 31 is divided by the frequency divider 28 and used.

In this embodiment, in addition to the effects described in the third embodiment, the oscillation signal of the third local oscillator 31 is divided by the frequency divider 28 and used as the reference oscillation signal of the PLL circuit 24. The circuit scale of the oscillator portion of the device can be reduced, and high-definition television signals can be demodulated with high accuracy.

FIG. 5 is a block diagram showing a receiving apparatus according to a fifth embodiment of the present invention. In the figure, parts performing the same operations as those of the embodiment shown in FIG.
The same reference numerals are given to those, and the description is omitted. In FIG.
25 is a low-pass filter, and 26 is a PLL circuit not including a reference oscillator.

In this embodiment, the oscillation frequency of the second local oscillator 14 is controlled by a PLL circuit 26 and a low-pass filter 25, and the third local oscillator is used as a reference oscillation signal of the PLL circuit 26 as in the fourth embodiment. It is characterized in that the oscillation signal of 31 is divided by a frequency divider and used.

In this embodiment, in addition to the effects described in the fourth embodiment (FIG. 4), the oscillation frequency of the second local
The LL circuit 26 and the low-pass filter 25 enable high-accuracy control, and enable high-accuracy demodulation of high-definition television signals. The PLL circuit 24 and the second local oscillator 14 that divide the frequency of the oscillation signal of the third local oscillator 31 by the frequency divider 28 to control the oscillation frequency of the first local oscillator 10
Is used as a reference oscillation signal of the PLL circuit 26 for controlling the oscillation frequency of the receiving device, so that the circuit scale of the oscillator portion of the receiving device can be reduced.

As described above, NTS is used as a standard television signal.
Although the description has been made assuming that the C signal is used, a PAL signal, a SECAM signal, or the like is used as another standard television signal, and the signal is commonly received with a high-definition television signal compressed to a bandwidth equal to the signal band. Of course, the above-described effects can be obtained.

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 receiving apparatus according to a sixth embodiment of the present invention. In FIG. 6, parts performing the same operations as those of the embodiment shown in FIG.
The same reference numerals are given to those, and the description is omitted. In FIG.
70 is a first IF filter for a high-definition television signal, 18 is a second IF filter for a high-definition television signal, 35 is a fourth IF amplifier, 36 is a fifth mixer,
Reference numerals 7 and 71 denote low-pass filters, and reference numerals 38 and 39 denote baseband signal amplifiers.

FIG. 7 is a signal band diagram showing the relationship between the signal band of the high definition television signal and that of the standard television signal in the embodiment of FIG. That is, FIG. 7 shows, for comparison, the frequency fv of the video carrier of the NTSC signal, the frequency fs of the audio carrier, and the frequency fc of the color subcarrier in the frequency spectra HP and SP constituting the high definition television signal.

The format of a high-definition television signal to be compressed to a signal band of 6 MHz is being studied in the United States and the like. 506-508, The Institute of Television Engineers of Japan 1992
It is described in detail in annual conferences and so on. Consideration is also given to the case where the high-definition television signal is transmitted on the same channel as the NTSC signal. In this case, in order to avoid interference from the NTSC signal, the video carrier fv and the audio carrier fs having high energy in the NTSC signal are used. Near
The spectrum of the high-definition television signal (HP, S
It has been proposed to use the signal constellation shown in FIG. 7 without P).

In FIG. 7, the video carrier fv of the NTSC signal is composed of the spectrums HP and S of the high-definition television signal.
It will be noted that the valley at the boundary of P and the audio carrier fs of the NTSC signal are located at the rightmost valley of the spectrum SP of the high definition television signal, respectively.

The signal constellation shown in FIG. 7 is NTSC as a spectrum constellation of a high-definition television signal subjected to QAM.
A signal band having a high priority, for example, a signal band including an error correction code (HP) is set below the video carrier frequency fv of the signal.
Section), and other standard signal bands (SP sections) are assigned to the video carrier frequency fv or higher,
In the end, a signal format in which a high-definition television signal is divided into an HP unit and an SP unit and transmitted is shown.

The embodiment shown in FIG. 6 is a high definition television signal having a baseband signal band shown in FIG.
It is characterized by receiving an NTSC signal.
In the present embodiment (FIG. 6), the second IF signal (output of 15) of the high-definition television signal subjected to the dual frequency conversion is converted into the SA signal.
The first for high definition television signal composed of W filter
The above-described signal spectrum HP and SP sections are separated by the IF filter 70 and the second IF filter 18 and amplified by the second IF amplifier 19 and the fourth IF amplifier 35. Each of the five mixers 36 performs frequency conversion to baseband.

The HP section and the SP section converted to the base band pass through low-pass filters 71 and 37, respectively, and are inputted to a high-definition television signal demodulator 60 as desired signal levels by base band signal amplifiers 38 and 39. And demodulate. Although the first IF filter 70 and the second IF filter 18 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 present embodiment (FIG. 6) has the same effects as those of the fourth embodiment (FIG. 4), and also performs the high frequency television signal of the signal band shown in FIG. Since the signal processing is performed by dividing the band, 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 receiving apparatus according to a seventh embodiment of the present invention. In the figure, parts performing the same operations as those of the embodiment shown in FIG.
The same reference numerals are given to those, and the description is omitted. In FIG.
50 is a first QAM detector, 51 is a second QAM detector, 52 and 53 are 90-degree phase shifters, 54 is a first carrier and clock recovery circuit, 55 is a second carrier and clock recovery circuit, 56 is a fourth oscillator, 57 is a fifth oscillator, 58 is an AFC voltage generation circuit, and 61 is a data demodulator.

In this embodiment, the second IF signal (output of 15) of the high-definition television signal subjected to the dual frequency conversion is obtained from
The HP section and the SP section of the high definition television signal are separated by a first IF filter 70 and a second IF filter 18 for a high definition television signal constituted by a SAW filter, and the second IF amplifier 19 and Fourth IF amplifier 3
After amplification at 5, the first and second QAM detectors 50 and 51 respectively shift the oscillated signals of the fourth and fifth oscillators 56 and 57 at 90-degree phase shifters 52 and 53 to each other. 90
Detection is performed using two signals having a phase difference of degrees.

At this time, the oscillation frequency of the first local oscillator 10 is controlled by the AFC voltage generation circuit 58, and the carrier and clock signal regeneration in the first and second carrier and clock regeneration circuits 54 and 55 is in the best condition. Frequency control as described above. The detected signal is input to the data demodulator 61,
Demodulate. Although the oscillation frequency of the first local oscillator 10 is controlled here, a configuration for controlling the oscillation frequency of the second local oscillator 14 or a configuration for controlling the oscillation frequencies of the fourth and fifth oscillators 56 and 57 may be used.

This embodiment has the effects described in the sixth embodiment (FIG. 6), and also performs QAM demodulation on the HP and SP sections of the high-definition television signal in the signal band shown in FIG. Therefore, it is possible to further reduce the interference between the two bands and the interference from the NTSC signal transmitted on the same channel, thereby enabling more accurate data demodulation.
Also, by controlling the oscillation frequency of the first local oscillation signal,
Since demodulation is performed, demodulation of a high-precision high-definition television signal becomes possible.

FIG. 9 is a block diagram showing a receiving apparatus according to an eighth embodiment of the present invention. In FIG. 9, parts performing the same operations as those of the embodiment shown in FIG.
The same reference numerals are given to those, and the description is omitted. In FIG.
Reference numeral 62 denotes a high-definition television signal demodulator (Digita
l Signal Process).

FIG. 10 is a signal band diagram showing the relationship between the signal band of a high definition television signal and that of a standard television signal in the embodiment of FIG. That is, the present embodiment shown in FIG. 9 is characterized by receiving a high-definition television signal having the baseband signal band shown in FIG. 10 and an NTSC signal.

FIG. 10 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, as in FIG. FIG. 10 is a signal band diagram using quaternary vestigial sideband amplitude modulation (VSB) as another format of a high definition television signal compressed to a 6 MHz signal band.

In this embodiment (FIG. 9), the second IF signal (output of 15) of the high-definition television signal subjected to the dual frequency conversion is selected by the high-definition television signal IF filter 16 constituted by a SAW filter. After passing through and amplifying by the second IF amplifier 19, the signal is input to the AM demodulator 34 and demodulated similarly to the second IF signal of the NTSC signal.

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 62. Perform demodulation.

Note that NTSC transmitted on the same channel
In order to reduce interference from the signal, a notch filter is provided in the AM demodulator 34 when a high-definition television signal is received, and the carrier and the subcarrier of the NTSC signal are removed. Further, the input filter 5 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 first local oscillator 10, and comparing with the desired reception signal. Even when a strong electric field interference signal is input, the occurrence of interference is reduced.

In this embodiment, in addition to the effects described in the first embodiment (FIG. 1), since a high-definition television signal is also AM-modulated, a part of the demodulation of the high-definition signal is partially demodulated for the NTSC signal. AGC voltage and A
The control of the FC voltage can be commonly performed, so that the circuit configuration of the receiving device is simplified and the circuit scale can be reduced.

In this embodiment, the IF filter 16 for a high-definition television signal and the IF filter 1 for an NTSC signal are used.
7 is provided separately, but high-definition television signals and NTS
When the residual sideband width and roll-off characteristics of the C signal are similar, both can be shared, and the circuit scale is further reduced.

FIG. 11 is a block diagram showing a receiving apparatus according to a ninth embodiment of the present invention. In FIG.
1 and 8 are denoted by the same reference numerals as those in FIGS. 1 and 8, and description thereof is omitted. In FIG. 11, reference numeral 63 denotes a data demodulator (Digit
al demod. IC).

FIG. 12 is a signal band diagram showing the relationship between the signal band of a high definition television signal and that of a standard television signal in the embodiment of FIG. The present embodiment shown in FIG. 11 is characterized by receiving a high-definition television signal having the baseband signal band shown in FIG. 12 and an NTSC signal.

FIG. 12 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, as in FIG. FIG. 12 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 this embodiment (FIG. 11), the second IF signal of the high-definition television signal subjected to the dual frequency conversion is selectively passed through the high-definition television signal IF filter 16 composed of a SAW filter. After being amplified by the IF amplifier 19, the first QAM detector 50 outputs the signal to the fourth oscillator 56.
Is phase-shifted by a 90-degree phase shifter 52 and detected using two signals having a phase difference of 90 degrees from each other.

At this time, the oscillation frequency of the first local oscillator 10 is controlled by the AFC voltage generation circuit 58, and the carrier and clock signal regeneration by the first and second carrier and clock regeneration circuits 54 and 55 is in the best condition. Frequency control as described above. The detected signal is input to the demodulator 63 and demodulated.

Although the oscillation frequency of the first local oscillator 10 is controlled here, a configuration for controlling the oscillation frequency of the second local oscillator 14 or a configuration for controlling the oscillation frequency of the fourth oscillator 56 may be used. Also, N transmitted on the same channel
In order to reduce interference from the TSC signal, the first QAM detector 50 is provided with a notch filter for removing the carrier and subcarrier of the NTSC signal.

In this embodiment, in addition to the effects described in the first embodiment (FIG. 1), since the QAM demodulation is performed by controlling the oscillation frequency of the first local oscillation signal, a high-precision high-definition television signal is obtained. Can be demodulated.

[0071]

According to the present invention, in a receiving apparatus of a double super heterodyne system, a high-definition television which transmits a standard television signal such as an NTSC signal and the like by being compressed to a bandwidth equal to that of a standard television signal. And a receiving device capable of receiving the signal.

Further, the first IF filter is used commonly for a standard television signal such as an NTSC signal and the like for a high definition television signal, and the second IF filter and the demodulator are used for a standard television signal such as an NTSC signal and the like. Since the dual frequency conversion unit of the double superheterodyne system can be shared for both signals by separately providing the television signal for the fine television signal, the circuit scale can be reduced.

Also, due to the configuration of the high definition television signal band, for example, in the case of a high definition television signal subjected to VSB modulation of four values, the second IF filter and a part of the demodulator are set to NT
Because it can be shared with standard television signals such as SC signals,
Further, the circuit configuration of the receiving device is simplified, and the circuit scale can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention.

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

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

7 is a signal band diagram showing a relationship between a signal band of a high definition television signal and that of a standard television signal in the embodiment of FIG. 6;

FIG. 8 is a block diagram showing a seventh embodiment of the present invention.

FIG. 9 is a block diagram showing an eighth embodiment of the present invention.

10 is a signal band diagram showing a relationship between a signal band of a high definition television signal and that of a standard television signal in the embodiment of FIG. 9;

FIG. 11 is a block diagram showing a ninth embodiment of the present invention.

12 is a signal band diagram showing a relationship between a signal band of a high definition television signal and that of a standard television signal in the embodiment of FIG. 11;

FIG. 13 is a block diagram showing a conventional double superheterodyne television signal receiving apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal input terminal, 2 ... Selection signal input terminal, 3 ... High-definition television signal output terminal, 4 ... NTSC signal output terminal, 6,8 ... Variable attenuator, 7 ... RF amplifier, 9 ... First mixer, 10 first local oscillator, 11 first IF filter, 12 first IF amplifier, 13 second mixer, 14
Second local oscillator, 15... First IF amplifier, 16, 18
... IF filter for high definition television signal, 17 ... NT
IF filter for SC signal, 19 second IF amplifier, 2
0: third IF amplifier, 21: third mixer, 22, 2
5, 32, 37, 41, 71 ... low-pass filter, 2
3, 24, 26: PLL circuit, 28: frequency divider, 30: fourth mixer, 31: third local oscillator, 33, 60, 61,
62, 63 ... demodulator for high definition television signal, 34 ...
NTSC signal demodulator, 36 fifth mixer, 40 high-definition television signal level detector, 42 AGC voltage amplifier, 43 AGC voltage switching circuit, 50, 51 QA
M detector, 52, 53: 90-degree phase shifter, 54, 55: carrier and clock recovery circuit, 56, 57: reference oscillator, 58: AFC voltage generator, 71: first IF filter for NTSC signal.

Claims (8)

(57) [Claims] 1. An RF signal input terminal (1), an input filter (5) that divides an input signal input through the terminal into bands and selectively passes a predetermined band, and an input filter that passes through the input filter. An RF amplifier (6, 7, 8) for amplifying or attenuating the signal of the predetermined band including the desired signal to a desired signal level, and is input via a channel selection signal input terminal (2) for channel selection. A first local oscillator (10) whose oscillation frequency is controlled by a PLL circuit (23) depending on tuning information;
A first oscillator that receives a local oscillation signal from the first local oscillator and a signal in the predetermined band including a desired signal from the RF amplifier, converts the desired signal into a first IF signal, and outputs the first IF signal; A frequency converter (9), a first IF filter (11) for selectively passing the first IF signal, a first IF amplifier (12) for amplifying the first IF signal passed through the filter, and a second local oscillator ( 1
4) inputting a local oscillation signal from the second local oscillator and a first IF signal from the first IF amplifier;
A second frequency converter (13) that converts the IF signal into a second IF signal and outputs the second IF signal; a second IF amplifier (15) that amplifies the second IF signal from the second frequency converter; A second IF filter for selectively passing the second IF signal; a second IF signal for passing the second IF filter and demodulating the second IF signal; and fine-tuning the oscillation frequency of the second local oscillator. AFC voltage and the RF amplifier (6,
And a standard demodulator (34) for outputting an AGC voltage for controlling the degree of amplification of (7, 8), wherein the NTSC television is connected to the RF signal input terminal. When an AM-modulated standard television signal such as a television signal (hereinafter simply referred to as a standard signal) and a high-definition television signal are input, as components for selectively receiving both signals, The various circuits from the RF signal input terminal (1) to the second IF amplifier (15), which are commonly used, and a high-definition television signal connected to the output of the second IF amplifier (15) for a high-definition television signal 2nd IF
A high-definition demodulator (33) for inputting and demodulating the second IF signal passed through the second high-definition IF filter; and a high-definition high-pass filter passed through the second high-definition second IF filter. A detector (40) for receiving and detecting the second IF signal
And a low-pass filter (4) that passes the output of the detector.
1), a high-definition amplifier (42) for amplifying the output of the low-pass filter to a desired voltage value, and an AGC output when the high-definition television signal is received. An AGC voltage switching circuit (43) for switching the AGC voltage from the standard demodulator (34) and supplying the AGC voltage to the RF amplifier when receiving a standard signal as a voltage; The AFC voltage output from the high-definition demodulator (33) when receiving a signal, the AFC voltage output from the standard demodulator (34) when receiving a standard signal, An AFC voltage switching circuit (27) for switching and outputting to the second local oscillator (14) for fine-tuning the oscillation frequency. 2. An RF signal input terminal (1), an input filter (5) that divides an input signal input through the terminal and selectively passes a predetermined band, and an input filter that passes through the input filter. An RF amplifier (6, 7, 8) for amplifying or attenuating the signal of the predetermined band including the desired signal to a desired signal level, and is input via a channel selection signal input terminal (2) for channel selection. A first local oscillator (10) whose oscillation frequency is controlled by a PLL circuit (23) depending on tuning information;
A first oscillator that receives a local oscillation signal from the first local oscillator and a signal in the predetermined band including a desired signal from the RF amplifier, converts the desired signal into a first IF signal, and outputs the first IF signal; A frequency converter (9), a first IF filter (11) for selectively passing the first IF signal, a first IF amplifier (12) for amplifying the first IF signal passed through the filter, and a second local oscillator ( 1
4) inputting a local oscillation signal from the second local oscillator and a first IF signal from the first IF amplifier;
A second frequency converter (13) that converts the IF signal into a second IF signal and outputs the second IF signal; a second IF amplifier (15) that amplifies the second IF signal from the second frequency converter; A second IF filter for selectively passing a second IF signal; a second IF signal having passed through the second IF filter; demodulating the input signal; an AFC voltage for the PLL circuit; A standard demodulator for outputting an AGC voltage for controlling the amplification degree of (6, 7, 8) (34)
A double super heterodyne type receiving apparatus comprising: a standard television signal (hereinafter simply referred to as a standard signal) modulated by AM such as an NTSC television signal at the RF signal input terminal; When the signals are input, the circuits from the RF signal input terminal (1) shared by the two signals to the second IF amplifier (15) as components for selectively receiving the two signals. A second high-definition second IF connected to the output of the second IF amplifier (15) for a high-definition television signal;
A high-definition demodulator (33) for inputting and demodulating the second IF signal passed through the second high-definition IF filter; and a high-definition high-pass filter passed through the second high-definition second IF filter. A detector (40) for receiving and detecting the second IF signal
And a low-pass filter (4) that passes the output of the detector.
1), a high-definition amplifier (42) for amplifying the output of the low-pass filter to a desired voltage value, and an AGC output when the high-definition television signal is received. An AGC voltage switching circuit (43) that switches the AGC voltage from the standard demodulator (34) and supplies the AGC voltage to the RF amplifying unit when receiving a standard signal as the voltage; A third signal for inputting the oscillation signal (10) and the second local oscillation signal (14) and outputting a signal having a frequency difference between the signals;
A frequency conversion circuit (21), and the PLL circuit that controls the oscillation frequency of the first local oscillator (10) so as to keep the difference frequency output from the third frequency conversion circuit constant. When the AFC voltage for the high-definition television signal output from the high-definition television demodulator (33) and the AFC voltage output from the standard demodulator are taken in and the high-definition television signal is received, the former is used. And a PLL circuit for fine-tuning the oscillation frequency of the first local oscillator (10) by switching each of them when a standard signal is being received. 3. An RF signal input terminal (1), an input filter (5) that divides an input signal input through the terminal and selectively passes a predetermined band, and an input filter that passes through the input filter. An RF amplifier (6, 7, 8) for amplifying or attenuating the signal of the predetermined band including the desired signal to a desired signal level, and is input via a channel selection signal input terminal (2) for channel selection. A first local oscillator (10) whose oscillation frequency is controlled by a PLL circuit (23) depending on tuning information;
A first oscillator that receives a local oscillation signal from the first local oscillator and a signal in the predetermined band including a desired signal from the RF amplifier, converts the desired signal into a first IF signal, and outputs the first IF signal; A frequency converter (9), a first IF filter (11) for selectively passing the first IF signal, a first IF amplifier (12) for amplifying the first IF signal passed through the filter, and a second local oscillator ( 1
4) inputting a local oscillation signal from the second local oscillator and a first IF signal from the first IF amplifier;
A second frequency converter (13) that converts the IF signal into a second IF signal and outputs the second IF signal; a second IF amplifier (15) that amplifies the second IF signal from the second frequency converter; A second IF filter for selectively passing a second IF signal; a second IF signal having passed through the second IF filter; demodulating the input signal; an AFC voltage for the PLL circuit; A standard demodulator for outputting an AGC voltage for controlling the amplification degree of (6, 7, 8) (34)
A double super heterodyne type receiving apparatus comprising: a standard television signal (hereinafter simply referred to as a standard signal) modulated by AM such as an NTSC television signal at the RF signal input terminal; When the signals are input, the circuits from the RF signal input terminal (1) shared by the two signals to the second IF amplifier (15) as components for selectively receiving the two signals. A second high-definition second IF connected to the output of the second IF amplifier (15) for a high-definition television signal;
A filter (16); a third local oscillator (31); a local oscillation signal output from the third local oscillator; and a second IF signal from the second high-definition IF filter, and a second IF signal. A fourth frequency converter (30) for converting to a baseband signal, and a high-definition demodulator (60) for inputting and demodulating a baseband high-definition television signal from the fourth frequency converter
A detector (40) for receiving and detecting the second high-definition IF signal passed through the second high-definition IF filter (16);
And a low-pass filter (4) that passes the output of the detector.
1), a high-definition amplifier (42) for amplifying the output of the low-pass filter to a desired voltage value, and an AGC output when the high-definition television signal is received. An AGC voltage switching circuit (43) that switches the AGC voltage from the standard demodulator (34) and supplies the AGC voltage to the RF amplifying unit when receiving a standard signal as the voltage; A third signal for inputting the oscillation signal (10) and the second local oscillation signal (14) and outputting a signal having a frequency difference between the signals;
A frequency conversion circuit (21), and the PLL circuit that controls the oscillation frequency of the first local oscillator (10) so as to keep the difference frequency output from the third frequency conversion circuit constant. When the AFC voltage for the high-definition television signal output from the high-definition television demodulator (60) and the AFC voltage output from the standard demodulator are taken in and the high-definition television signal is received, the former is used. And a PLL circuit for fine-tuning the oscillation frequency of the first local oscillator (10) by switching between the two when a standard signal is being received. 4. The receiving device according to claim 1, wherein said first IF filter comprises a dielectric filter. 5. The receiving apparatus according to claim 1, wherein said first IF filter comprises a SAW filter. 6. The receiving apparatus according to claim 1, wherein the second IF filter for high definition is an SA.
A receiving device comprising a W filter. 7. The receiving device according to claim 3, wherein the third local oscillator (31) is formed of an oscillation circuit using a crystal oscillator, and divides a local oscillation signal output from the third local oscillator. The PLL circuit (24) through a container (28)
Wherein the local oscillation signal is used in place of the reference signal generation source existing in the PLL circuit. 8. A receiving apparatus according to claim 1, wherein the high-definition television signal and an AM-modulated standard television signal such as an NTSC television signal are supplied to a common input terminal (1). A receiving device for inputting from a device.