JP2983840B2 - 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 plurality of audio broadcasting systems, and can be used for a television receiver such as a television receiver and a video tape recorder.

[0002]

2. Description of the Related Art First, before describing a conventional example, a broadcasting system will be described.

FIG. 4a shows a Japanese television broadcasting system (terrestrial wave).
FIG. 3 is a diagram showing a video carrier frequency P and an audio carrier frequency S
FIG. In other words, in the Japanese television receiving system, the video carrier frequency P is 4.5 from any channel in any channel.
A carrier having a frequency lower by (MHz) is FM-modulated to be a voice carrier frequency S. Therefore, normally, when demodulating audio using this, the difference in frequency is 4.5 (MH).
Demodulation is enabled in z).

In the French television receiving system, as shown in FIGS. 4B and 4C, the audio signal is FM-modulated at a frequency separated by 6.5 (MHz) from the video carrier frequency P. In the UHF band, the audio carrier frequency S1 is higher than the video carrier frequency P, as in the L type,
In the L band, the audio carrier frequency S1 is lower than the video carrier frequency P as in the L 'type.

[0005] In France, neighboring countries such as Germany and Switzerland need to receive signals. for that reason,
A receiving circuit configuration as shown in FIG. 5 (here, an example of a television receiver is shown) is used.

First, a tuner 1 receives a video signal including an audio signal input from an antenna in response to a control signal for receiving a broadcast of a specific frequency from a channel selection circuit (for example, a channel selection CPU) 21. The video signal, which is a signal, is converted into an intermediate frequency video signal (for example, an IF signal). This IF signal is passed through a preamplifier 2 to a video filter (surface acoustic wave filter: Surface Acou).
It is inputted to each of a sictic WaveFilter (hereinafter, referred to as SAF) 14, an FM audio SAF 3, and an L-type / L'-type conversion circuit 9 '.

First, the video signal system will be described. Video SAF
At 14, a specific band is extracted and output to the amplifier circuit 15. This specific band is, for example, a band having characteristics as shown in FIG. 6 in Japan. That is, it is possible to stably extract only the frequency of the channel signal band necessary for the subsequent amplification circuit. In this figure, an audio carrier frequency exists at a frequency of 54.25 (MHz), and a video carrier frequency exists at a frequency of 58.75 (MHz). A filter having a frequency characteristic indicated by a solid line is constituted by this SAF. Can be.

In France, 33.4 (MH
The voice carrier frequency is 38.9 (MHz) at the frequency of z).
, And a filter having this frequency characteristic can be constituted by the SAF 14. The extracted video signal is output from an oscillation circuit 17 oscillated at a frequency (58.75 MHz in Japan, 38.9 MHZ in France) determined by an oscillation adjustment circuit 18 composed of a parallel resonance circuit composed of a coil and a capacitor. Detection is performed by the video detection circuit 16 according to the control signal.
The video signal after the detection is subjected to various processes by a video processing circuit 19.
Is displayed as an image on the video display device 20 such as a CRT, and can be viewed by a viewer.

On the other hand, the audio signal system is as follows.
The audio signal having passed through the FM-SAF 3 whose frequency characteristic is shown in FIG. 7A is input to the mixing circuit 5 via the amplifier circuit 4.
In the mixing circuit 5, the frequency is converted at a frequency of 38.9 (MHz) in France, and an audio signal can be obtained.

The FM-SAF 3 extracts an FM-modulated audio signal frequency of 33.4 (MHz) and digitally modulates (actually, PCM-modulated) NICAM (N).
ear Instantaneous Compamd
Audio Multiplex is omitted) 33.05 (MHz) is extracted from the audio signal (5.85 (MHz) away from the video carrier frequency P). Where N
ICAM audio signal is ± 2 around 33.05 (MHz)
It has a band of 00 (KHz). This NICAM broadcast is scheduled to start broadcasting in 1995 from France.

Therefore, a digital NICAM signal and an analog audio signal are obtained from the mixing circuit 5,
The AM signal is demodulated by a NICAM demodulation circuit 6 from a digital signal to a first analog audio signal, and the analog audio signal is FM-converted through a ceramic filter 7 for reducing unnecessary bands.
Demodulation by detection is performed to obtain a second analog audio signal. This second analog audio signal is used for broadcasting in countries such as Germany and Switzerland adjacent to France,
With these circuit configurations, it is possible to receive broadcasts from Germany, Switzerland, etc., even in France. Here, the reason why the PCM and the FM audio signal are processed in different systems is that there is no composite IC that can process the PCM and the FM audio signal.

In the case of France, as described above, L
Since the frequencies of video and audio are different from each other, such as the L and L 'types, an L / L' conversion circuit 9 'is required to use a common circuit. The L / L 'conversion circuit 9' converts an L'-type frequency to an L-type using an L'-converted signal output by a selected channel of the tuning circuit 21.

Since the converted frequencies are all L-type frequencies, the AM-SA having the frequency band shown in FIG.
An audio signal having a frequency of 32.4 (MHz) AM-modulated in F10 can be extracted. The audio signal after extraction is A
The signal is AM-demodulated by the M demodulation circuit 11 'to become a third analog audio signal.

The first, second or first and third audio signals are switched by a signal from a channel selection circuit 21 in an audio processing circuit 12, and the audio reproduction means 13 such as a speaker is used.
a and 13b.

Next, the L / L 'conversion circuit 9' will be specifically described with reference to FIG. As described above, since the circuit 11 converts the L'-type frequency to the L-type, when the L-type frequency, that is, the channel of the VH band and the UHF band is selected by the channel selection circuit 21, This circuit 9 'allows the input signal to pass through as it is, and has an L' type frequency, that is, VL
When a channel of the band frequency is selected by the tuning circuit 21, this circuit 9 'performs the following operation.

In FIG. 8, a and b are explanations of the L-type frequency, and FIG. 8A shows the frequency inputted to the tuner 1 and is determined for each channel (the channel of the VL band and the UHF band). The local oscillation frequency can be obtained from the tuning circuit 21 to obtain the frequency of the IF band shown in FIG.

FIGS. 3C, 3D and 3E illustrate the L 'type frequency, and FIG. 3C shows the frequency input to the tuner 1 and is determined by each channel (VH band channel). The local oscillation frequency obtained from the tuning circuit 21 is
It is possible to obtain the frequency shown in FIG.

However, since the L 'type oscillates the local oscillation frequency at a position 38.9 (MHz) away from the audio carrier frequency S1 and 32.4 (MHz) away from the video carrier frequency P, In FIG. 4D converted to the IF band, the position of the audio carrier frequency S1 and the position of the video carrier frequency P are opposite to those in FIG.

That is, as shown in FIG. 2D, the frequency conversion is performed again at the second local oscillation frequency of 71.3 (MHz). This 71.3 (MHz) is 32.4 (MH
38.9 (MHz) away from the video carrier frequency P of z) and 32.4 (MHz) away from the audio carrier frequency S1 of 38.9 (MHz). Therefore, when the frequency is converted at the second local oscillation frequency, the frequency becomes the same as that in FIG.

Therefore, in the subsequent processing, processing can be performed at a constant frequency.

Here, in this conventional example, an AM-SAF 10 as shown in FIG. 7B is used, and detailed characteristics are shown in FIG.
As shown in the figure, the voice carrier frequency S1 is 32.4 (M
Hz).

As described above, the NICAM audio signal has a frequency band of ± 200 (KHz) around 33.05 (MHz), and the difference from the frequency closest to the audio carrier frequency S1 is 450 (KHz). Has become. Therefore, the NICAM audio signal passes through the AM-SAF 10, and the amplitude of the digital signal NICAM audio signal is also detected by the AM demodulation circuit 11 'at the subsequent stage. Will be. P
When processing CM and FM signals, the frequency is 5.5 MHz
Or 2nd. Of 5.85 MHz. Using the SIF band, I
By inserting a BPF before the C demodulator, it is possible to remove an interference signal other than the desired signal, so that good reception performance can be ensured. On the other hand, when the AM signal is processed by the conventional technique, the frequency is 1st. Using SIF band,
Since a broadband detector is used without using a BPF in the preceding stage of the IC detector, an interference signal (A) such as a NICAM signal is used.
When a NICAM signal interferes with M voice), the characteristics of the AM detector deteriorate.

Therefore, as a solution, AM-S
A method of narrowing the frequency characteristics of the AF 10 is conceivable. However, it is very difficult to develop a SAF having a characteristic of trapping frequencies separated by 450 (KHz) in a 30 (MHz) band, and even if possible, considerable accuracy is required and adjustment is difficult.

[0024]

When the NICAM broadcast (France), which is scheduled to be started in 1995, is started, the present invention aims to demodulate the AM signal of the current broadcast and to demodulate the adjacent digital signal. The NICAM audio signal is erroneously demodulated, and an unnecessary signal is output as the audio signal.

[0025]

According to the present invention, there is provided a receiving apparatus for receiving high-frequency transmission in which an audio signal in a second band adjacent to an audio signal in a first band is used as the same channel. Intermediate frequency converting means for converting the frequency into an intermediate frequency; first filtering means for extracting the intermediate frequency audio signal in the first band and the intermediate frequency audio signal in the second band converted to the intermediate frequency; and the first filtering means. Low-frequency conversion means for converting the signal extracted in step 1 into a low-frequency audio signal by a control signal of a predetermined frequency, a first band filter for extracting the first band audio signal from the low frequency audio signal, and a first band filter First demodulating means for demodulating a signal from the filter, a second band filter for extracting the audio signal of the second band from the low frequency audio signal,
A second demodulating means for demodulating a signal from the band-pass filter, a switching means for switching an output between the first demodulating means and the second demodulating means, and a sound reproducing apparatus for reproducing an output sound of the switching means An apparatus is provided.

According to the present invention, the first audio signal AM-modulated in the first band and the second audio signal digitally modulated in the second band adjacent to the first audio signal are co-channeled with the video signal. A receiving apparatus for receiving a broadcast transmitted by high-frequency modulation, an intermediate-frequency converting means for converting the transmitted high-frequency signal to an intermediate frequency, and an intermediate-frequency audio signal of the first band converted to the intermediate frequency. A first filter for extracting the intermediate frequency audio signal of the second band, a second filter for extracting the video signal converted to the intermediate frequency, and reproducing the intermediate frequency video signal by a control signal of a predetermined frequency. Video conversion means for converting the signal extracted by the first filter means into an audio signal in a low frequency range by the control signal; A first band filter for extracting the first band audio signal from the low frequency audio signal; first demodulating means for demodulating the signal from the first band filter; and a digital audio of the second band from the low frequency audio signal Provided is a receiving device comprising: a second demodulating unit for demodulating a signal; a switching unit for switching an output between the first demodulating unit and the second demodulating unit; and an audio reproducing device for reproducing an output audio of the switching unit. Things.

The present invention further provides a first audio signal AM-modulated in a first band, a second audio signal digitally modulated in a second band adjacent to the first audio signal, and a second audio signal adjacent to the first audio signal. Filter means for passing all the signals on which the third audio signal FM-modulated in the third band and the high frequency carrier are passed, and converting the high frequency carried signal into a low frequency audio signal by a control signal of a predetermined frequency. Low frequency conversion means, a first band filter for extracting only the first band audio signal from the low frequency audio signal, first demodulation means for AM demodulating the signal from the first band filter, and low frequency audio signal A second demodulating means for digitally demodulating the signal, a third band filter for extracting the third band audio signal from the low frequency audio signal, and an FM decoding of the signal from the first band filter. A third demodulating means for performing a switching operation for selectively switching an output of the first demodulating means, the second demodulating means, and the third demodulating means; an audio reproducing apparatus for reproducing an output audio of the switching means; It is an object of the present invention to provide a receiving apparatus including a selection unit for controlling switching of the switching unit.

[0028]

According to the present invention, since an AM-modulated audio signal is converted into a low-frequency band and then extracted by an AM filter, only a desired frequency can be extracted.

[0029]

FIG. 1 is a circuit block diagram of the present invention. still,
The same portions as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted.
Since the video signal system is the same, the description is omitted.

In the audio signal system, the IF obtained from the preamplifier 2
The signal is sent to the FM / AM-SAF via the L / L 'conversion circuit 9.
22. The L / L 'conversion circuit 9 has the same configuration as the conventional circuit 9' and performs the same processing. F
The M / AM-SAF 22 is a filter having a frequency characteristic as shown in FIG.
3.4 (MHz), a digital signal NICAM audio signal frequency of 33.05 (MHz), and an AM-modulated audio signal frequency of 33.4 (MHz).

The passed signal is input to the mixing circuit 5 via the amplifying circuit 4 and processed in the same manner as in the conventional example, so that an audio signal can be obtained.

Therefore, a digital signal NICAM signal and an analog audio signal (FM modulated audio signal and AM modulated audio signal) are obtained from the mixing circuit 5.
The ICAM signal is demodulated by a NICAM demodulation circuit 6 from a digital signal to a first analog audio signal. The FM-modulated audio signal of the analog signal is demodulated by FM detection via a ceramic filter 7 for reducing an unnecessary band to obtain a second analog audio signal.

Further, the AM-modulated audio signal of the analog signal is passed through a ceramic filter 23 for dropping an unnecessary band.
Demodulation by M demodulation is performed to obtain a third analog audio signal. Here, the ceramic filter 23 has characteristics as shown in FIG. In other words, it is a characteristic of passing an AM-modulated frequency of 6.5 (MHz).
The frequency 5.85 (MHz) of the CAM audio signal is removed. In addition, the characteristic is such that frequencies in the range of ± 200 (KHz), which is the band frequency of the NICAM audio signal, are removed.

Then, 6.5 (MH) is applied to the AM demodulation circuit 11.
The third audio signal is obtained by demodulation in a frequency band much lower than that of the related art such as z).

Therefore, the third audio signal is converted into a digital NICAM by the filter 23 and the AM demodulation circuit 11.
There is no influence of the signal, and no unnecessary sound is reproduced when the third sound signal is reproduced.

The first, second or first and third audio signals (the audio signals broadcasted in different countries) are switched by the signal from the channel selection circuit 21 in the audio processing circuit 12, and the audio signal from a speaker or the like is output. The data is reproduced by the reproducing means 13a and 13b.

[0037]

According to the present invention, the AM audio signal adjacent to the digital audio signal is passed through a filter at a low frequency and demodulated, so that the digital audio signal does not undergo AM demodulation. A sound signal free from unnecessary components such as noise can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a frequency characteristic diagram of the SAF used in the present invention.

FIG. 3 is a frequency characteristic diagram of a filter used in the present invention.

FIG. 4 is a diagram showing a television broadcasting system in each country.

FIG. 5 is a circuit block diagram showing a conventional example.

FIG. 6 is a diagram illustrating frequency characteristics of a Japanese video SAF.

FIG. 7 is a diagram illustrating frequency characteristics of a conventional FM-SAF and AM-SAF.

FIG. 8 is a diagram illustrating L / L ′ conversion.

FIG. 9 is a detailed diagram illustrating frequency characteristics of a conventional AM-SAF.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 tuner 2 preamplifier 3 FM-SAF 4 amplifying circuit 5 mixing circuit 6 NICAM demodulation circuit 7 filter 8 FM detection circuit 9 L / L 'conversion circuit 10 AM-SAF 11 AM demodulation circuit 12 audio processing circuit 13 audio reproduction processing means 14 video SAF 15 Amplifier circuit 16 Video detection circuit 17 Oscillation circuit 18 Oscillation adjustment circuit 19 Video processing circuit 20 Video display device 21 Tuning circuit 22 FM / AM-SAF 23 Filter

Claims (3)

(57) [Claims] 1. A second band adjacent to an AM audio signal of a first band.
A receiving apparatus for receiving a high-frequency transmission in which a band of the NICAM audio signal is the same channel; an intermediate frequency converting means for converting the transmitted high-frequency audio signal into an intermediate frequency; First filter means for extracting a frequency audio signal and an intermediate frequency audio signal of the second band; low frequency conversion means for converting the signal extracted by the first filter means into a low frequency audio signal by a control signal of a predetermined frequency A first band-pass filter for extracting the first band AM audio signal from the low-frequency audio signal; a first demodulation unit for demodulating a signal from the first band-pass filter; A second bandpass filter for extracting a band of the NICAM audio signal; a second demodulation means for demodulating a signal from the second bandpass filter; And switching means for switching the output of said second demodulating means and the first demodulating means, the receiving apparatus comprising a sound reproducing apparatus for reproducing an output audio of said changeover switching means. 2. An AM audio signal that has been AM-modulated in a first band and a NICAM audio signal that has been digitally modulated in a second band adjacent to the AM audio signal are transmitted together with a video signal by high-frequency modulation as the same channel. An intermediate frequency converting means for converting a transmitted high-frequency signal into an intermediate frequency; and an intermediate frequency between the intermediate frequency audio signal in the first band and the second band converted into the intermediate frequency. First filter means for extracting a high-frequency audio signal and the intermediate-frequency video signal by a control signal of a predetermined frequency.
Video conversion means for converting a signal extracted by the first filter means into a low-frequency audio signal with the control signal; and a first band from the low-frequency audio signal. A first bandpass filter for extracting the audio signal of the first bandpass filter, a first demodulation unit for demodulating the signal from the first bandpass filter, and a second demodulation unit for demodulating the digital audio signal of the second band from the low frequency audio signal. A receiving device comprising: switching means for switching the output of the first demodulating means and the second demodulating means; and an audio reproducing apparatus for reproducing the audio output from the switching means. 3. An AM audio signal AM-modulated in a first band, a NICAM audio signal digitally modulated in a second band adjacent to the first audio signal, and a NICAM audio signal in a third band adjacent to these audio signals. Filter means for passing all signals on which the FM-modulated FM audio signal and the high-frequency carrier have been passed; low-frequency conversion means for converting the high-frequency-carried signal into a low-frequency audio signal by a control signal of a predetermined frequency; A first band filter for extracting only the first band audio signal from the low frequency audio signal; a first demodulation unit for AM demodulating the signal from the first band filter; a digital demodulation from the low frequency audio signal A second demodulating means for performing the following; a third band filter for extracting the third band FM audio signal from the low frequency audio signal; and a FM demodulation of the signal from the third band filter. A third demodulating unit that performs switching; a switching unit that selectively switches an output of the first demodulating unit, the second demodulating unit, and the third demodulating unit; an audio reproducing device that reproduces an audio signal output from the switching unit; A receiving device comprising: switching means for controlling switching of the switching means.