JPH04302232A - Signal level circuit - Google Patents

Abstract

PURPOSE:To obtain a signal level always proportional to an input level at a satellite broadcasting receiver and to exactly adjust a parabolic antenna based on this signal level. CONSTITUTION:A level detecting circuit 35 prepares the signal level always proportional to the reception level based on a control signal (a) and a level detecting signal (b). By inputting this signal level to a process computer, the exact trend of the reception level can be recognized at all times. Thus, the antenna is always exactly adjusted.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] This invention relates to satellite broadcasting (hereinafter referred to as BS).
) relates to a signal level circuit that detects the reception level in a receiving device.

0003

2. Description of the Related Art Generally, the signal level of received radio waves is used as a guideline for adjusting the direction of a parabolic antenna for BS reception. A method for determining the signal level from received radio waves will be explained below with reference to the drawings.

FIG. 6 is a block diagram showing the configuration of a BS receiving circuit. In this figure, the BS-IF signal output from the outdoor converter is input to an automatic gain control circuit (hereinafter referred to as AGC) 21 via an input terminal 20. Further, 15V power is supplied to the outdoor converter from the input terminal 20 via the coil 34. BS input to AGC21
-IF signal is gain-controlled, amplified by an amplifier 22, and supplied to a tunable band pass filter (hereinafter referred to as BPF) 23. This tunable BPF23 is a microcomputer 3
The pass band is changed by the control signal supplied from 1. The signal that has passed through the tunable BPF 23 is input to the mixer 24. Also, mixer 24 has VCO 29.
An output signal is also input, and the two input signals are mixed and output to the SAW filter 25.

[0005] The SAW filter 25 removes unnecessary waves from the input signal and outputs only necessary signals to the AGC 26 . AGC 26 adjusts the amplitude of the input signal and outputs it to demodulation circuit 27 and control circuit 28. The demodulation circuit 27 demodulates the video signal from the input signal and outputs the video signal to the output terminal 32.

The demodulation circuit 27 also outputs a signal indicating the degree of frequency detuning to the microcomputer 31. By the way, the output signal of the VCO 29 mentioned above is also input to the prescaler 30. The prescaler 30 divides the input signal,
This frequency-divided signal is output to the microcomputer 31. The microcomputer 31 outputs a control signal for controlling the VCO 29 and the tunable BPF 23 based on the two input signals.

The aforementioned control circuit 28 outputs two control signals for controlling the AGCs 21 and 26, respectively, based on the amplitude of the input signal. It also outputs a level detection signal indicating the reception level. The parabolic antenna was adjusted based on this level detection signal.

FIG. 7 shows the relationship between the level voltage, which is the voltage of the level detection signal, and the BS-IF signal input level. Here, when the input level is less than or equal to α, the change in level voltage with respect to the change in input level is large, so adjustment of the parabolic antenna is relatively easy. However, the input level is α
In the above case, the change in level voltage with respect to the change in input level is very small. For this reason, it was quite difficult to make fine adjustments to accurately point the parabolic antenna toward the satellite.

[0009]

As described above, the level detection signal has conventionally been used as a guide for adjusting the parabolic antenna. Here, when the input level is less than α shown in FIG. 7, the change in level voltage with respect to the input level is large, so adjustment of the parabolic antenna is relatively easy. However, when the input level is α or more, the change in level voltage with respect to the input level is very small, so it is quite difficult to make fine adjustments to accurately point the parabolic antenna toward the satellite.

The present invention is intended to eliminate the above problems, and aims to provide a signal level proportional to the input level, and to accurately adjust a parabolic antenna based on this signal level.

[Configuration of the invention]

0012

[Means for Solving the Problems] The present invention provides a first amplitude control means that receives a signal output from an outdoor converter and controls the amplitude of the signal to be constant, and an output signal of the first amplitude control means. an amplification means that takes as an input and amplifies this signal; a first filter that takes an output signal of the amplification means as an input and can change the frequency band to be passed; and a local oscillation signal generating means that outputs a local oscillation signal. and a mixing means which receives the output signal of the first filter means and the output signal of the local signal generation means and mixes these signals; and a mixing means which receives the output signal of the mixing means and outputs the required frequency. The second band passes only the signal in the band.
a second amplitude control means that receives the output signal of the second filter means as an input and controls the amplitude of the signal to be constant; demodulation means for demodulating and outputting the video signal by performing FM demodulation on the signal and outputting a detuning degree signal indicating the degree of detuning of the frequency of the input signal; and an output signal of the second amplitude control means. is input, and from this signal, two control signals for controlling the first and second amplitude control means are generated and output, and when the level of the signal input to the first amplitude control means is small, a control means for outputting a level detection signal that changes in proportion to the level of the signal; and a control signal for controlling a first amplitude control means and a level detection signal among the signals output from the control means, as inputs; level detection means for generating and outputting a signal level that changes in proportion to the level of the signal input to the first amplitude control means from these signals; and inputting the output signal of the local signal generation means; A frequency dividing means for dividing and outputting this signal; an output signal of the frequency dividing means and a detuning degree signal outputted from the demodulating means are input, and the frequency of the output signal of the local signal generating means; By providing a control means for outputting a control signal for controlling the pass frequency band of the first filter means, it is possible to provide a signal level proportional to the reception level.

[0013]

[Operation] The level detection means receives a control signal for controlling the second amplitude control means and a level detection signal. By processing these signals with the level detection means, a signal level proportional to the level of the signal input to the first amplitude control means is generated.

[0014]

EMBODIMENTS Before describing embodiments of the present invention, a parabolic antenna adjustment system for adjusting a parabolic antenna based on a signal level will be described. FIG. 5 is a block diagram showing the configuration of the parabolic antenna adjustment system.

In this figure, a BS signal collected by a parabolic antenna 10 is frequency-converted by a BS converter 11 and then input to a BS receiver 12 . The BS receiver 12 processes the input signal, outputs the video signal to the TV monitor 13, and outputs the signal level to the process computer 15. Process computer 15 outputs a control signal for controlling antenna drive amplifier 14 based on the signal level. The antenna drive amplifier 14 changes the direction of the parabolic antenna 10 based on the control signal. On the other hand, information regarding the orientation of the parabolic antenna 10 is input to the process computer 15 via the antenna drive amplifier 14. In this way, the direction of the parabolic antenna 10 is adjusted.

Next, a receiving circuit that generates a signal level inside the BS receiver 12 will be explained with reference to FIG. In this figure, the BS- output from the outdoor converter
The IF signal is input to the AGC 21 via the input terminal 20. In addition, the outdoor converter has a 15V power supply connected to the coil 34.
It is supplied from the input terminal 20 via.

After gain control, the BS-IF signal input to the AGC 21 is amplified by the amplifier 22, and the BS-IF signal is amplified by the tunable BP.
Supplied to F23. The tunable BPF 23 changes its passband in response to a control signal supplied from the microcomputer 31. The signal that has passed through the tunable BPF 23 is input to the mixer 24. Also, mixer 24 has V
The output signal of CO29 is also input, and the two input signals are mixed and output to the SAW filter 25.

The SAW filter 25 removes unnecessary waves from the input signal and outputs only necessary signals to the AGC 26. AGC 26 adjusts the amplitude of the input signal and outputs it to demodulation circuit 27 and control circuit 28. The demodulation circuit 27 demodulates the video signal from the input signal and outputs the video signal to the output terminal 32.

The demodulation circuit 27 also outputs a signal indicating the degree of frequency detuning to the microcomputer 31. By the way, the output signal of the VCO 29 mentioned above is also input to the prescaler 30. The prescaler 30 divides the input signal,
This frequency-divided signal is output to the microcomputer 31. The microcomputer 31 outputs a control signal for controlling the VCO 29 and the tunable BPF 23 based on the two input signals.

The aforementioned control circuit 28 outputs two control signals for controlling the AGCs 21 and 26, respectively, based on the amplitude of the input signal. It also outputs a level detection signal indicating the reception level. This level detection signal b and AGC2
A control signal a for controlling the signal level 1 is input to the level detection circuit 35. This level detection circuit 35 generates a signal level proportional to the accurate reception level and outputs it to the output terminal 33.

Next, a circuit for generating a signal level from the aforementioned control signal a and level detection signal b will be explained. FIG. 2 is an explanatory diagram for explaining a first embodiment of the present invention, and FIG. 3 is an explanatory diagram for explaining a second embodiment. Further, FIG. 4 is a circuit diagram showing the circuit of the third embodiment.

First, a first embodiment will be explained with reference to the drawings. In FIG. 2, (A) is a circuit diagram showing the circuit of the first embodiment, and (B) is a characteristic diagram showing the characteristics of the circuit in (A).

In FIG. 2(A), the input terminal 40 is connected to the resistor 4.
It is connected to one end of 1. The other end of resistor 41 is resistor 42
and an inverting input terminal of the operational amplifier 43. The other end of the resistor 42 is connected to an output terminal 44 and an output terminal of the operational amplifier 43. On the other hand, the input terminal 45 is connected to the resistor 4
6. The other end of resistor 46 is resistor 47
and a non-inverting input terminal of the operational amplifier 43. The other end of the resistor 47 is connected to a reference potential point.

A control signal a is input to the input terminal 40,
A level detection signal b is input to the input terminal 45. The voltage relationship with respect to the input level of these control signal a and level detection signal b is shown in FIG. 2(B). From this figure, when the input level is smaller than β, the voltage of the control signal a is constant, but the voltage of the level detection signal b increases in proportion to the input level. On the other hand, when the input level is greater than β, the voltage of the control signal a decreases in proportion to the input level, but the voltage of the level detection signal b remains constant.

The signal level c output from the output terminal 44 at this time is shown by the solid line in FIG. 2(B). From this figure, although the slope of the signal level c changes depending on whether the input level is larger than β or smaller, it always increases in proportion to the input level.

Next, a second embodiment will be explained with reference to the drawings. In FIG. 3, (A) is a circuit diagram showing the circuit of the second embodiment, and (B) is a characteristic diagram showing the characteristics of the circuit in (A).

The circuit shown in FIG. 3(A) is similar to that in FIG. 1(A). The difference is that the level detection signal b is input to the input terminal 40.
is input, and the control signal a is input to the input terminal 45. In this case, the signal level d always decreases in inverse proportion to the input level, contrary to the first embodiment. By inverting and reading this signal using the process computer 15, an accurate reception level can be read.

Furthermore, a circuit diagram of the third embodiment is shown in FIG. This is obtained by adding an inverting amplifier circuit to the circuit shown in FIG. 3(A). The output terminal of the operational amplifier 43 is connected to a resistor 50. The other end of this resistor 50 is connected to an inverting input terminal of an operational amplifier 52 and a resistor 51. The other end of the resistor 51 is connected to an output terminal of an operational amplifier 52 and an output terminal 53. On the other hand, the non-inverting input terminal of the operational amplifier 52 is connected to resistors 48 and 49. A certain constant voltage Vcc is supplied to the other end of the resistor 48. The other end of the resistor 49 is connected to a reference potential point. The characteristics of the signal level c' at this time are similar to those shown in FIG. 2(B).

The process computer 15 to which these signal levels are input, regardless of the magnitude of the input level,
You can know the trend of input level. This allows accurate antenna adjustment at all times.

As described above, the level detection circuit 35 always creates a signal level proportional to the received level based on the control signal a and the level detection signal b. The process computer 15 to which this signal level is input can know the exact trend of the received level. This allows accurate antenna adjustment at all times.

[0031]

As described above, the level detection circuit 35 always creates a signal level proportional to the received level based on the control signal a and the level detection signal b. The process computer 15 to which this signal level is input can know the exact trend of the received level. This ensures accurate antenna adjustment at all times.

[Brief explanation of drawings]

[Fig. 1] Block diagram showing the configuration of the present invention

FIG. 2 is an explanatory diagram illustrating a first embodiment of the level detection circuit 35.

FIG. 3 is an explanatory diagram illustrating a second embodiment of the level detection circuit 35.

FIG. 4 is a circuit diagram showing a third embodiment of the level detection circuit 35;

[Figure 5] Block diagram showing the configuration of a system that adjusts the orientation of a parabolic antenna

[Figure 6] Block diagram showing the conventional configuration

[Fig. 7] Explanatory diagram explaining conventional level detection voltage

[Explanation of symbols]

21, 26...AGC 22...Amplifier 23... Tunable BPF 24...Mixer 25...SAW filter 27...Demodulation circuit 28...Control circuit 29...VCO 30...Prescaler 31...Microcomputer 35...Level detection circuit

Claims (1)

[Claims] 1. A first amplitude control means that receives a signal output from an outdoor converter as an input and controls the amplitude of this signal to be constant; an amplification means for amplifying; a first filter means that receives the output signal of the amplification means and can change the frequency band to be passed; a local signal generation means for outputting a local signal; and the first filter. a mixing means that receives the output signal of the means and the output signal of the local signal generating means and mixes these signals; and a mixing means that receives the output signal of the mixing means and passes only signals in a necessary frequency band. a second filter means; a second amplitude control means that receives the output signal of the second filter means as an input; and a second amplitude control means that controls the amplitude of the signal to be constant; , demodulation means for demodulating and outputting the video signal by performing FM demodulation on the signal and outputting a detuning degree signal indicating the degree of detuning of the frequency of the input signal; and the second amplitude control means. Taking an output signal as an input, generating and outputting two control signals for controlling the first and second amplitude control means from this signal, and when the level of the signal input to the first amplitude control means is small. , a control means for outputting a level detection signal that changes in proportion to the level of this signal, and a control signal for controlling the first amplitude control means and a level detection signal among the signals output from this control means. and level detection means for generating and outputting a signal level that changes in proportion to the level of the signal input to the first amplitude control means from these signals, and inputting the output signal of the local signal generation means. A frequency dividing means for dividing and outputting this signal, an output signal of this frequency dividing means and a detuning degree signal output from the demodulating means are input, and the frequency of the output signal of the local oscillator signal generating means is and control means for outputting a control signal for controlling the pass frequency band of the first filter means.