JPH01884A - Receiving machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] C. The present invention, which is applied to the field of practical application, is a first
This invention relates to a receiver to which a second frequency modulated signal obtained by transforming the main carrier wave is supplied with a frequency modulated signal and an image (a multiplexed signal of No. 3).

(Summary of the Invention) The present invention provides a first
In a receiver that is supplied with a second frequency modulated signal obtained by modulating the main carrier wave with a multiplexed signal of a frequency modulated signal and a video signal, the subcarrier wave is used to perform flu transmission of the second frequency converted signal. By displaying the noise ratio (hereinafter referred to as rC/NJ), C/N can be displayed satisfactorily.

(Conventional technology) FIG. 6 shows an example of a satellite broadcasting receiver.

In the figure, (1o) is a broadcasting satellite, and the ku hand from this broadcasting satellite (10) < 12GHz band -11,
7~12.2GIIz) or C band (4GI
Iz band -3,7~4,2GHz) satellite broadcasting signal s
ss is supplied to the S/'U converter (13) via the IIs antenna (1).

This S/Ll converter (■3) converts the frequency, and both the KU band and C band have a frequency of 950 to 1.4.
The first intermediate frequency signal SIF+ is 50 M 11 z. That is, the local frequency for frequency conversion in the S/IJ converter (13) is lO
, fixed at 75GIIZ, 2.75GH in C hand
It is fixed at 2. Although Fig. 6 shows only one system of BS antenna and S/U converter, in reality, different systems are used for KU punt reception and C band reception.
An S antenna and an S/Ll converter are used alternately.

The satellite broadcasting signal 5) is, for example, as shown in FIG.
Video ('r' No. 5 Sν, the general transmission wave of 6.8M1iz in the upper frequency band of this video signal Sν is the audio signal SA F'
A carrier wave in the Hλ band or 4Gtlz band is FM-modulated with a signal obtained by multiplying the 1·゛M audio signal SΔFM with M variations.

In addition, the signal 5IFI from the S/U converter (13) is transmitted to the cable (14), booster (15) and cable (1
6) to the indoor co-unit 1-(1'/). In other words, the signal S+r from the S/U converter (13)
t passes through the first intermediate frequency amplifier (18) to the second mixer (
19). This second oscillator (19) is supplied with a local signal from the 20th oscillator (20), and the (*j+S IF' L
For example, the second intermediate frequency signal 5 of 402.78 MIIz
Converted to IF2. In this case, the microcomputer for channel selection (hereinafter referred to as "microcomputer for channel selection") (21)
The frequency of the local signal is changed under the control of , and the receiving equal channel is selected.

Further, the signal 5IF2 from the second mixer (19) is passed through the second intermediate frequency filter (22) and the second intermediate frequency amplifier (23).
) and 8G (: [l-''M demodulation via 1 path (24)) 5 (25) and demodulated to obtain a multiplexed signal between the video signal Sv and the 1.M audio signal SAP. The video signal Sv obtained from this FM demodulator (25) is led out to the output terminal (2'/) via the video signal processing circuit (26).

Further, the t'M speech signal SAFM obtained from the l-'M demodulator (25) is passed through a bandpass filter (28).
- It is supplied to the M demodulator (29) and demodulated to obtain the audio signal SΔ. The audio signal S obtained from this FM demodulator (29) is led out to an output terminal (31) via an audio signal processing circuit (30).

Mata, in this receiver, the M unit (
17) is displayed.

That is, the voltage QC from the GG circuit (24) is supplied to the display signal forming circuit (32).

Then, when detecting C/H, the 20th Cu oscillator (20
) is shifted to a nearby frequency in addition to the normal tuning state. In this case, AGC voltage VA
GC corresponds to human signal power (regarded as transmission power) when the frequency of the local signal is in the normal tuning state, and corresponds to noise power when the frequency of the local signal is shifted to a nearby frequency. Become something. In the display signal forming circuit (32), ^GC'rTi pressure VAGC
A C/N display signal is formed based on the
), and the C/N is displayed on this display (33).

[Problem that the invention seeks to solve]

In the example shown in Fig. 6, noise power data is obtained by shifting the frequency of the local signal from the 20th Cull oscillator (20) to a nearby frequency in addition to the normal tuning state. When other signals are present, correct noise power data cannot be obtained, and there is a possibility that accurate C/N cannot be displayed.

Moreover, in the example of FIG. 6, the AGC voltage VAGC is used, and the cable (14) is connected between the S/U converter (3) and the indoor unit 1-(17).

Depending on the 41i type in (16), the length, and the gain of the booster (15), even if the C/N is originally close, the GC voltage VAGC cannot be obtained equally, and even if there are no other signals at nearby frequencies (and In addition, in the example shown in Figure 6, the frequency of the local signal is shifted when measuring noise power, so there was a problem that both video and audio were interrupted during that time. .

In view of these points, the present invention makes it possible to display accurate C/N using UJ function, and also uses video for displaying C/N.

This ensures that the audio will not be interrupted.

Means for Solving Problem C] The present invention provides a first frequency modulated signal SAFM in which the subcarrier is frequency modulated with the audio signal S8 and a second frequency modulated signal SAFM in which the main carrier is modulated in Lk, and a video signal Sv. Frequency modulation signal 5I of
F2 is supplied, and the second frequency modulated signal 5IF2 is applied to the first
The demodulator (25) demodulates the first frequency modulated signal SA.
The receiver obtains the FM and video signal Sv, and demodulates the first frequency modulation signal SAFM obtained by the first demodulator (25) with the second demodulator (29) to obtain the audio signal SΔ. Then, the output signal of the second demodulator (29) is supplied to a filter (1) having an out-of-band passband of the warehouse signal.
and the output signal of this rectifier circuit (3)
The C/N of the frequency modulated signal 5IF2 is displayed.

(Function) - In the connected configuration, the level of noise included in the output signal of the second demodulator (29) is equal to
This corresponds to the C/N of M. Moreover, the level of the carrier wave of this first frequency modulated signal -'8S8FM, that is, the sub) general transmission wave is the sub-level of the main carrier wave. Since the deviation of the transmitted wave is constant, it is constant, and the noise level corresponds to the C/N of the second frequency modulation signal 5IF2. Therefore, the output signal of the rectifier circuit (3) corresponds to the C/N of the second frequency modulation signal 5IF2 (SIF). 5IF2 C/N is not displayed well.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the same figure, the output signal of the FMM demodulator 29) has a passband outside the audio signal band (for example, the center frequency is 100K).
Hz and a bandpass filter (1) with a bandwidth of 20 Hz > Hz, which bandpass filter (1)
The output signal of is supplied to a rectifier circuit (3) via an amplifier (2). The output signal of this rectifier circuit (3) is supplied as a display signal to a display device (5) via an amplifier (4).

The rest of the structure is the same as the example shown in FIG.

In this example, since the bandpass filter (1) has a pass band outside the band of the audio signal, its output signal is a part of the triangular noise generated by the 1.mm MM demodulator 29 (of the bandpass filter (1) The level of this noise is l- which is supplied to the FM receiver (29).
' M neck line + S Ap ) 40C/N is determined.

Furthermore, the level of the forward transmission to the M fp+signal S8F supplied to F M
The FM audio signal S8 for the 11I transmission of the intermediate frequency signal 5IF2 changes linearly due to carrier wave deviation (audio subcarrier deviation) M(1). For example, when the deviation changes from 2M+lz to 4M)Iz, the level doubles. In other words, since the audio subcarrier deviation is constant, the FM audio signal SAFM
The level of the 1M transmission wave is constant.

On the other hand, the noise level of the FM demodulator (25) is a part of the triangular noise (noise within the band of the bandpass filter (28)) generated by the FM demodulator (25). ) of the second intermediate frequency signal 5IF2 supplied to
/N. In this case, if designed correctly, the first intermediate frequency amplifier (18) of the indoor unit (17)
) to the manual power of the FM demodulator (25)
The C/N of the second intermediate frequency signal 5IF2 supplied to the FM demodulator (25) is sufficiently small, and the C/N of the first intermediate frequency signal 5IF1 supplied to the indoor unit (17) is sufficiently small.
It can be considered as N.

Therefore, the level of noise U of the FM sound signal W S AF M supplied to the FM fifm unit (29) is lower than the level of noise U of the first intermediate frequency signal 5IFI supplied to the indoor unit (17).
Determined by N.

From the above, the output from the bandpass filter (1) is ♀
(The rails of the 6th row, and therefore the rails of the output signal of the rectifier circuit (3), are the first
The C/N of the intermediate frequency signal 5LFL is 6 times higher than that of the intermediate frequency signal 5LFL. Therefore, the display (5) displays the C/N of the first intermediate frequency e times 5IFI that is supplied lj to the indoor unit (17) by the output signal of the rectifier circuit (3).

In this way, according to this example, a display signal corresponding to the C/N of the first intermediate frequency signal 5IFI supplied to the indoor unit (7) is obtained, and the C/N is thereby displayed.
Accurate display can be performed. Figure 2 shows that the noise level of the signal 5IFI supplied to the indoor Unison 1-(17) is 1138 dfJm/llz and 120 dBm/Hz.
This figure shows the relationship between C/N and the output signal of the rectifier circuit (3) when the noise L/H varies, but the change in the output type j is small, and the C/N It can be seen that a signal corresponding to N = 1 can be obtained.

Further, according to this example, since the video signal thread and the audio signal thread are not affected in obtaining the display signal, there is no interruption in the video and audio signals.

Next, FIGS. 3 to 5 show other embodiments of the present invention, and in these FIGS. 3 to 5, the same reference numerals are given to Hl However, the detailed explanation will be omitted.

In the example in FIG. 3, the signal corresponding to the C/N of the first intermediate frequency signal 5IF1 supplied to the indoor unit (l'l) outputted from the rectifier I II (3+) is sent to the amplifier (4).
and the channel selection microcomputer (21) via the A/D converter (6).
). Then, based on this signal, a display signal is generated by the channel selection microcomputer (21), and is supplied to the display (5) via the table > 1 signal (bal)/A converter (7) and displayed. C/N is displayed on the device (5). Also,
A switching control signal is generated from the tuning microcomputer (2) based on a signal corresponding to the C/N of the first width frequency signal 5IFI, and this switching control signal is transmitted via the D/A converter (8). and is supplied to the second width frequency filter (22). In this case, the passband of the second intermediate frequency filter (22) is set to, for example, 30M11Z, but when the C/N becomes 10 dB or less, it is switched to, for example, 20M11Z.

According to the example in FIG. 3, it is possible to obtain the same effects as in the example in FIG.
The S/N of ν can be improved.

In addition, the example in Figure 4 uses a time-sharing system, and the FM is only used at certain times.
This is an example in which a sound shore signal SAFM exists. That is, in the example of FIG. 4, the output signal of the l-'M demodulator (25) is supplied to the sub-primary general transmission detection circuit (9), and the output signal of this detection circuit (9) is sent to the tuning microcomputer. (21). Then, on the channel selection Mac/C controller (21),
When the lvi tone signal SAFM is present, a display signal and a warning signal 111 are generated, and the same operation as in the example in FIG. 3 is performed. Note that when the FM monophonic signal SAFM does not exist, for example, the C/N display and pass range 4) when the FM audio signal SAFM is present are maintained as they are.

Also,! In the example in Figure 145, the audio signal processing circuit (3
A muting circuit (
40) is connected. Further, the output signal of the rectifier circuit (3) is supplied to the comparator (41) to output the base /I11 voltage VREF.
compared to The output signal of this comparator (41) is then supplied as a control signal to the '%j--ting circuit (40). In this case, when the C/N becomes smaller than a predetermined value, a muting state is entered.

According to the example in FIG. 5, in addition to obtaining the same effect as the example in FIG. 1, when the C/N decreases, the audio signal is muted to prevent the generation of noisy audio. There are profits that can be made.

〔Effect of the invention〕

According to the present invention described above, the C
Since a display signal corresponding to /N is obtained and C/N is displayed using this, accurate display can be performed. Further, since the video signal line and the audio signal system are not affected in obtaining the display signal, it is possible to avoid interruption of the video and audio for display.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the same, FIGS. 3 to 5 are block diagrams showing other embodiments of the present invention, and FIG. 7 is a diagram showing a configuration of a conventional example, and FIG. 7 is a diagram showing an example of a satellite broadcast signal. (1) and (28) are band pass filters, (3) is a rectifier circuit, (5) is a display, (17) is an indoor unit, (
25) and (2!]) are FM restorers.

Claims (1)

[Scope of Claims] A second frequency modulated signal obtained by modulating the main carrier wave is supplied with a multiplexed signal of a first frequency modulated signal obtained by frequency modulating the subcarrier wave with an audio signal and a video signal, and the second frequency modulated signal is supplied by modulating the main carrier wave, The signal is demodulated by a first demodulator to obtain the first frequency modulated signal and the video signal, and the first frequency modulated signal obtained by the first demodulator is demodulated by a second demodulator. In the receiver for obtaining the audio signal, the output signal of the second demodulator is supplied to a filter having a passband outside the band of the audio signal, the output signal of this filter is supplied to a rectifier circuit, and the output signal of the second demodulator is supplied to a rectifier circuit. A receiver characterized in that the output signal of the circuit indicates the carrier-to-noise ratio of the second frequency modulated signal.