JP2799105B2 - Satellite broadcast 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 satellite broadcast receiver for receiving satellite broadcasts, and more particularly to a satellite broadcast receiver having a simplified configuration.

[0002]

2. Description of the Related Art A conventional satellite broadcast receiving apparatus of this type will be described below with reference to FIGS.

[0003] A conventional satellite broadcast receiving apparatus comprises a converting means 1 for converting a carrier signal in a 12 GHz band transmitted from a satellite into a first intermediate frequency in a 1 GHz band, and an intermediate signal selected from the signal converted into the first intermediate frequency. Frequency (Intermed
iate Frequency) signal (hereinafter, selected IF
And a gain control means 3 for controlling the gain of the selected IF signal.
And the selected IF signal whose gain has been controlled is FM
(Frequency Modulation) demodulation means 4 for demodulating and outputting as a baseband signal, and filter means for extracting only a no-signal band E between the video signal band C and the audio carrier band D in FIG. 6 from the baseband signal. A band pass filter (hereinafter referred to as BPF) 6; P. Amplifying circuit 7 for amplifying the signal of no-signal band E extracted at F6
A peak detection circuit 8 which is a conversion means for peak-detecting an output signal of the amplification circuit 7 and converting the output signal into a DC level signal;
Non-linear amplifier 9 for non-linearly amplifying the DC level signal
And the output of the non-linear amplifier 9 is input as a detection signal of the signal strength received by the parabolic antenna 12, and the A / D
After the conversion, an arithmetic processing circuit 10 which is a detecting means comprising a microcomputer or the like for performing an arithmetic processing for converting to a number from 0 to 99 corresponding to the signal strength, and the arithmetic processing circuit 1
A display circuit 11 is provided for displaying the detection signal calculated at 0 on a display device (not shown) such as a CRT or the like with numerals from 0 to 99.

In the above configuration, the converting means 1 includes a parabolic antenna 12 and a BS (Broad Casting).
ng Satellite) converter 13.

The tuning means 2 includes a high frequency amplifier (hereinafter, referred to as RF amplifier) 14, a high frequency attenuator (hereinafter, referred to as RF-ATT) 15, a filtering amplifier (hereinafter, referred to as FILTER amplifier) 16, , PLL (Ph
case Locked Loop) Local oscillation circuit 17
And a mixer 18 having one input terminal connected to the output terminal of the FILTER amplifier 16 and the other input terminal connected to the output terminal of the PLL local oscillation circuit 17.

Also, gain control means 3
Are a FILTER 19 having an RF-ATT 15, a FILTER amplifier 16, a mixer 18 and an input terminal connected to an output terminal of the mixer 18, an intermediate frequency amplifier (hereinafter referred to as an IF amplifier) 20, and an output terminal. RF AGC (Automatic Cai) connected to PF-ATT15
n Control) circuit 21 to form an AGC loop.

Further, the demodulation means 4 has a SAW (Surface) having an input terminal connected to the output terminal of the IF amplifier 20.
Acoustic Wave) FILTER22,
IF amplifier 23; P. PLL F connected to F6 and a video and audio signal processing circuit (not shown)
And an M demodulator 24.

The satellite broadcast receiving apparatus constructed as described above converts the carrier signal of the 12 GHz band transmitted from the satellite received by the parabolic antenna 12 of the conversion means 1 into the first intermediate frequency of the 1 GHz band by the BS converter 13. To
After being amplified by the RF amplifier 14 of the tuning means 2, the mixer 1
At 8, the signal of the desired channel is selected by mixing with the signal from the PLL local oscillation circuit 17, and the frequency is converted.
Obtain the F signal. Next, after the selected IF signal is amplified by the IF amplifier 20 of the gain control means 3, RF A
The signal amplitude of the input signal is detected by the GC circuit 21 and the PF-
By feeding back to the ATT 15, AGC (automatic gain control) is performed so that the level of the signal to the modulation means 4 in the next stage does not fluctuate due to the level of the input signal.

Then, the baseband signal is obtained by performing the FM demodulation processing in the PLL FM demodulator 24 of the demodulation means 4.
As shown in FIG. 6, when the parabolic antenna 12 is at an appropriate position, the video signal band C and the audio signal as shown by the broken line A are shown in FIG.
Has a large signal level in the carrier band D,
In the no-signal band E between the video signal band C and the Audio carrier band D, the signal level becomes small,
When the parabolic antenna 12 is at an improper position, it has a constant noise signal level irrespective of the frequency band as shown by the solid line B.

Next, a baseband signal is input to a video / audio signal processing circuit (not shown), P.
At F6, only the baseband signal in the no-signal band E is extracted, amplified by the amplifier circuit 7, peak-detected (ie, AC-DC converted) by the peak detection circuit 8 to output a DC level, and then output to the nonlinear amplifier 9. Nonlinear amplification,
Since the output level of the baseband signal in the non-signal band E is higher when the parabolic antenna 12 is at an improper position than when it is at an appropriate position, the output of the non-linear amplifier 9 is shown in FIG. As described above, the signal strength is inversely proportional to the signal strength received by the parabolic antenna 12. Therefore, the next-stage arithmetic processing circuit 10
After the A / D conversion of the output (detection signal) of the non-linear amplifier 9 at 0, the signals 0 to 9 corresponding to the signal strength (proportional relationship)
An arithmetic process for converting into numbers up to 9 is performed.

The detection signal calculated by the arithmetic processing circuit 10 in the display circuit 11 is displayed on a display device (not shown) as a number from 0 to 99 so that it can be received by the parabolic antenna 12. The user can be notified of the signal strength to be performed, and the user adjusts the mounting position of the parabolic antenna 12 so that the number of the display device (not shown) increases.

[0012]

However, in the above-mentioned conventional satellite broadcast receiving apparatus, the output (detection signal) of the non-linear amplifier is inversely proportional to the signal strength received by the parabolic antenna. The processing circuit requires an arithmetic operation such as an inversion operation for displaying a numerical value from 0 to 99 in proportion to the signal strength, and there is a problem that the system becomes complicated.

[0013]

SUMMARY OF THE INVENTION A satellite broadcast receiving apparatus according to the present invention comprises an inverting DC amplifier for inverting and amplifying a DC level output obtained by converting a baseband signal in a no-signal band.

[0014]

The satellite broadcast receiving apparatus according to the present invention has an inverted DC
Since the amplifier amplifies and inverts the DC level output obtained by converting the baseband signal in the no-signal band, the load on the detection means at the next stage can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the satellite broadcast receiving apparatus according to the present invention will be described below with reference to FIGS. 1 to 4. The same parts as those in the above conventional example will be described using the same reference numerals.

The satellite broadcast receiving apparatus of the present invention converts a 12 GHz band carrier signal transmitted from a satellite to a first 1 GHz band signal.
Conversion means 1 for converting to an intermediate frequency, and tuning means 2 for obtaining a selected IF signal from the signal converted to the first intermediate frequency
2, gain control means 3 for controlling the gain of the selected IF signal, demodulation means 4 for FM-demodulating the selected IF signal subjected to the gain control and outputting it as a baseband signal, and FIG.
Is a filter means for extracting only a non-signal band (shown by E in FIG. 2) between the video signal band C and the audio carrier band D in B. P. F6; P. Amplifying circuit 7 for amplifying the signal of no-signal band E extracted at F6
A peak detection circuit 8 which is a conversion means for peak-detecting an output signal of the amplification circuit 7 and converting the output signal into a DC level signal;
An inverting DC amplifier 29 for amplifying the DC level signal and performing a DC level shift in a range of 1 to 5 V in accordance with an operation of a pulse generation circuit 30 described later; Is input as a detection signal of the signal strength received by the parabolic antenna 12, and after A / D conversion, based on the detection signal, a switch drive pulse having a different duty ratio as shown in FIG. A pulse generating circuit 30 which is a detecting means composed of a microcomputer or the like for outputting a signal, a switch 32 for controlling the intermittent output of the voice band oscillator 31 in accordance with the switch driving pulse, and a signal intensity controlled by the switch 32. Speaker (not shown) that responds to the intermittent sound
And an audio output terminal 33 for outputting to

In the above configuration, the conversion means 1 comprises a parabolic antenna 12 and a BS converter 13.

The tuning means 2 includes an RF amplifier 14 and
RF-ATT15, FILTER amplifier 16, PL
It comprises an L local oscillation circuit 17 and a mixer 18 having one input terminal connected to the output terminal of the FILTER amplifier 16 and the other input terminal connected to the output terminal of the PLL local oscillation circuit 17.

Also, gain control means 3
Is a FILTER 19 having an RF-ATT 15, a FILTER amplifier 16, a mixer 18 and an input terminal connected to an output terminal of the mixer 18, an IF amplifier 20, and an RF having an output terminal connected to the PF-ATT 15. AGC circuit 21
And an AGC loop is formed.

Further, the demodulating means 4 has a SAW FILTER 2 having an input terminal connected to the output terminal of the IF amplifier 20.
2, the IF amplifier 23, and the output terminal P. F6 and a PL connected to a video and audio signal processing circuit (not shown)
And an LFM demodulator 24.

The satellite broadcast receiving apparatus constructed as described above converts the carrier signal of 12 GHz band transmitted from the satellite received by the parabolic antenna 12 of the conversion means 1 to the first intermediate frequency of 1 GHz band by the BS converter 13. After the signal is converted and amplified by the PF amplifier 14 of the tuning means 2, the signal is mixed with the signal from the PLL local oscillation circuit 17 by the mixer 18 to select the signal of the desired channel, frequency-converted, and the selected IF signal. Get. Next, the IF amplifier 2 of the gain control means 3
0, the selected IF signal is amplified, and the RFAGC circuit 21 detects the signal amplitude of the input signal, and
By feeding back to 5, the AGC (automatic gain control) is applied so that the level of the signal to the next-stage demodulation means 4 does not fluctuate due to the level of the input signal.

The baseband signal is obtained by the FM demodulation processing in the PLL demodulator 24 of the demodulation means 4. The output characteristic of the baseband signal is as shown in FIG. When it is in the position, it has a large signal level in the video signal band C and the Audio carrier band D as shown by a broken line A, but in the non-signal band E between the video signal band C and the Audio carrier band D, The signal level becomes small, and when the parabolic antenna 12 is at an improper position, it has a constant noise signal level regardless of the frequency band as shown by the solid line B.

Next, a baseband signal is input to a video / audio signal processing circuit (not shown), P.
At F6, only the baseband signal in the no-signal band E is taken out, amplified by the amplifier circuit 7, peak-detected (ie, AC-DC converted) by the peak detection circuit 8 to output DC level, and then inverted DC amplifier 29. And performs a DC level shift in the range of 1 to 5 V corresponding to the operation of the pulse generation circuit 30. The output level of the baseband signal in the non-signal band E is such that the parabolic antenna 12 is at an appropriate position. The output of the inverting DC amplifier 29 is proportional to the signal intensity received by the parabolic antenna 12 in the range of 1 to 5 V as shown in FIG. It is a relationship.

After the output (detection signal) of the inverting DC amplifier 29 is A / D-converted by the pulse generation circuit 30, the magnitude of the input voltage is determined based on the DC level of the detection signal as shown in FIG. A switch drive pulse having a duty ratio that changes in proportion to the switch drive pulse is output, and the switch 32 is closed when the switch drive pulse is turned on to change the open / close operation period of the switch 32 according to the duty ratio of the switch drive pulse. , Voice band oscillator 31
The intermittent output of is controlled, and the intermittent sound corresponding to the signal strength received by the parabolic antenna 12 from the sound output terminal is output to a speaker (not shown), thereby notifying the user of the signal strength. The user adjusts the mounting position of the parabolic antenna 12 so that the sound of a speaker (not shown) is not interrupted.

In the above embodiment, since the user is notified of the signal strength received by the parabolic antenna 12 by voice, the user can adjust the mounting position of the parabolic antenna 12 to be mounted outdoors by himself / herself. Even if there is, work can be performed easily.

[0026]

Since the satellite broadcast receiving apparatus of the present invention has the above-described configuration, the inverting DC amplifier inverts and amplifies the DC level output obtained by converting the baseband signal in the no-signal band. The load on the detection means can be reduced, and the system can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a satellite broadcast receiving apparatus of the present invention.

FIG. 2 is a frequency characteristic diagram of a baseband signal output level in one embodiment of the satellite broadcast receiving apparatus of the present invention.

FIG. 3 is a diagram showing a relationship between signal strength and output of an inverting DC amplifier in one embodiment of the satellite broadcast receiving apparatus of the present invention.

FIG. 4 is a diagram showing a relationship between an output of an inverting DC amplifier and a switch drive pulse in one embodiment of the satellite broadcast receiving apparatus of the present invention.

FIG. 5 is a block diagram showing a conventional satellite broadcast receiving apparatus.

FIG. 6 is a frequency characteristic diagram of a baseband signal output level in a conventional satellite broadcast receiving device.

FIG. 7 is a diagram illustrating a relationship between signal strength and output of a nonlinear amplifier in a conventional satellite broadcast receiving apparatus.

[Explanation of symbols]

 4 demodulation means 6 B. P. F 8 Peak detection circuit 12 Parabolic antenna 29 Inverting DC amplifier 30 Pulse generation circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 1/16

Claims (1)

(57) [Claims] 1. A demodulator for demodulating a carrier signal transmitted from a satellite into a baseband signal, a filter for extracting a non-signal band of the baseband signal, and a rectifier for rectifying the signal extracted by the filter. A satellite broadcast receiving apparatus comprising: a rectifier for converting to a DC level; and a detector for detecting a signal strength for determining a mounting position of an antenna based on the DC level rectified by the rectifier. Inverting D for inverting and amplifying level output
A satellite broadcast receiving device comprising a C amplifier.