JPH11205057A - Automatic output control amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic output control amplifier with which the deterioration of a distortion characteristic in an output signal level is prevented and also power consumption will not be increased, by removing a second variable attenuator for controlling an output level from a main signal line. SOLUTION: A main signal line is provided with an amplifier for amplifying an input signal 1 coupler 6 for and outputting the output signal from the amplifier 1 taking-out a part of the signal and a first variable attenuator 4 which is connected at the preceding stage of the coupler 6 and which holds the output level constant the attenuated quantity of with is varied by the output signal from a differential amplifier 8. In addition, a feedback signal line is provided with the differential amplifier 8, which feedback the level of the signal which is taken-out from the coupler 6 and detected with a threshold so as to variably control the first variable alternator 4. A second variable attenuator 5 for controlling the output level of the automatic output control amplifier is connected to the main signal line and the feedback signal line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic output control amplifier, and more particularly to an automatic output control amplifier suitable for use in a repeater mounted on a satellite.

[0002]

2. Description of the Related Art In a satellite communication system, when receiving a signal from an earth station, an automatic output control amplifier is provided in a repeater in order to absorb a change in signal level due to a change in propagation loss between the earth station and the satellite. Often introduced. In addition, it is necessary to operate with the transmission power varied according to the line usage status.In this case, the transmission power of the repeater is varied by varying the output signal level of the automatic output control amplifier in the repeater. Let me.

FIG. 2 is a block diagram showing an example of a conventional automatic output control amplifier. The conventional automatic power control amplifier shown in FIG. 2 includes amplifiers 1 and 2 and first and second variable attenuators 14.
And 15, a coupler 6, a detector 7, a differential amplifier 8, and an output level controller 9. And
In this automatic output control amplifier, the input signal is amplified by the amplifiers 1 and 2, passes through the coupler 6, and is output after being attenuated by the second variable attenuator 5. The coupler 6 extracts a part of the signal, and the detector 7 detects the extracted signal and outputs a detection voltage. The differential amplifier 8 differentially amplifies the detection voltage and the threshold, and controls the amount of attenuation of the first variable attenuator 4. As a result, the detector 7
Is always controlled to a voltage determined by the threshold, so that the input signal level of the detector 7, that is, the output signal level of the coupler 6, is always controlled to be constant.

As described above, since the output signal level of the coupler 6 is controlled to be constant by the first variable attenuator 14, the amount of attenuation of the second variable attenuator 5 is varied by the output level controller 9. Thereby, the output signal level of the automatic output control amplifier can be controlled. At this time, if the command signal is transmitted from the earth station, the transmission power of the repeater in the satellite can be controlled on the earth.

However, in the conventional automatic output control amplifier, the second variable attenuator 5 is connected to the subsequent stage of the coupler 6, that is, to the main signal line, and there is an insertion loss, so that the output signal level of the amplifier 2 is automatically adjusted. It must be higher than the output end of the power control amplifier. In general, when the same amplifier is used, the distortion characteristic is degraded when the output signal level is increased. Therefore, there is a problem that the distortion characteristic is degraded as it is.

In order to obtain the same distortion characteristics, it is necessary to use a higher output amplifier in accordance with the increase in the signal level, but in this case, the power consumption increases. Needless to say, in a satellite or the like, an increase in power consumption must be avoided as much as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to prevent a deterioration in a distortion characteristic of an output signal level and to increase power consumption by removing a second variable attenuator from a main signal line. It is an object of the present invention to provide an automatic power control amplifier that does not bring about.

[0008]

In order to achieve the above object, an automatic output control amplifier according to the present invention comprises an amplifier for amplifying an input signal, an output signal from the amplifier, and a part of the signal. And a main signal line having a first variable attenuator connected at a stage preceding the coupler and having an attenuation variable by an output signal from a differential amplifier described later, and a signal extracted from the coupler. Automatic output including a detector for detection, and a feedback signal line having a differential amplifier for comparing and amplifying a signal level and a threshold output from the detector and variably controlling the first variable attenuator. In the control amplifier, a configuration in which a second variable attenuator that performs output control in the automatic output control amplifier is connected to the feedback signal line. And Aru.

In this case, a preferable example is claim 2.
The automatic output control amplifier described above is configured so that the second variable attenuator is connected between a coupler and a detector in the feedback signal line and is variable by an output level controller.

With this configuration, the variable attenuator functioning to keep the output signal level constant when the input signal level changes can be removed from the main signal line (after the coupler). Therefore, the output of the amplifier in the main signal line can be used effectively, and even when the input signal level changes, the output signal level is maintained at a constant level, without deteriorating the distortion characteristics of the output signal level. The level of the output signal can be controlled. Further, an increase in power consumption caused by using a high-output amplifier is prevented.

Preferably, an amplifier is connected between the second variable attenuator and the detector, so that the signal output from the second variable attenuator is amplified in the detector. Can be sent to

The automatic output control amplifier of the present invention is used in a transponder mounted on a satellite, and the output level controller is controlled by an external command signal, particularly, a command signal from an earth station. By making the attenuation of the variable attenuator variable, the earth station can control the transmission power of the onboard satellite transponder.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a block diagram of an automatic output control amplifier according to one embodiment of the present invention. The automatic output control amplifier shown in FIG. 1 includes amplifiers 1 and 2 for amplifying an input signal with a certain gain, a first variable attenuator 4 connected between the amplifiers 1 and 2, and an output of the amplifier 2. Coupler connected to the side to take out part of the input signal
An amplifier 3 for amplifying a signal taken out from the coupler 6 through a second variable attenuator 5, a detector 7 for outputting a detection voltage proportional to the level of the amplified signal, and an output from the detector 7. And a differential amplifier 8 that compares the applied voltage with a threshold, amplifies the difference signal, outputs the amplified signal to the first variable attenuator 4, and controls the amount of attenuation of the first variable attenuator. An output level controller 9 for varying the amount of attenuation of the second variable attenuator 5 is provided.

Here, the amplifiers 1 and 2, the first variable attenuator 4 and the coupler 6 form a main signal line, and the second variable attenuator 5, the amplifier 3, the detector 7, and the differential The amplifier 8 forms a feedback signal line.

The automatic output control amplifier having such a configuration operates as follows. Now, assuming that the input signal level increases, the input signal level of the coupler 6 also increases. As a result, the level of the signal partially extracted from the coupler 6 also increases, and passes through the second variable attenuator 5 and the amplifier 3 as it is and the input signal level of the detector 7 increases.
Then, the output voltage of the detector 7 increases in proportion to the signal level, the difference from the threshold increases, and the output voltage from the differential amplifier 8 increases. The voltage increases and the attenuation increases. That is, the total gain of the amplifiers 1 and 2 and the first variable attenuator 4 decreases, and the output signal level becomes constant.

On the other hand, when the input signal level decreases, the signal level partially extracted from the coupler 6 also decreases, the output voltage of the differential amplifier 8 decreases, and the attenuation of the first variable attenuator 4 decreases. The total gain of the first variable attenuator 4 increases, and the output signal level becomes constant.

That is, this automatic output control amplifier operates so that the output voltage of the detector 7 always becomes a voltage determined by the threshold of the differential amplifier 8, and the output level of the coupler 6, that is, the automatic output control amplifier Output level becomes constant. Also, since the second variable attenuator is not connected to the subsequent stage (main signal line) of the coupler 6,
There is no insertion loss due to this second variable attenuator.

When the output level controller 9 controls the amount of attenuation of the second variable attenuator 5, the second variable attenuator 5
, The output level of the coupler 6, that is, the output level of the automatic output control amplifier changes. An output level controller 9 for varying the second variable attenuator 5 operates according to an external command signal. When this automatic output control amplifier is used in a repeater mounted on a satellite, the amount of attenuation of the second variable attenuator 5 can be varied via an output level controller 9 by a command signal from an earth station. .

According to the present invention, the second variable attenuator 5 is configured to be connected to the feedback signal line instead of the main signal line, thereby preventing the distortion characteristic of the output signal level from deteriorating and reducing the consumption. An automatic power control amplifier that does not cause an increase in power can be obtained. Therefore, in the automatic output control amplifier of the present invention, if the second variable attenuator 5 is connected to the feedback signal line, the connection position or quantity of the amplifier 3 in the feedback signal line or the detector 7
Are not limited to those in the above embodiment.

[0020]

As described above, according to the automatic output control amplifier of the present invention, the output signal level can always be kept constant even if the input signal level changes, contributing to the improvement of the line reliability. be able to.

Further, by varying the output signal level, the output signal level can be set according to the line use request, and the power consumption can be effectively utilized. Further, since there is no variable attenuator for controlling the output level on the main signal line, the output of the amplifier is output as it is, so that power consumption is not wasted.

[Brief description of the drawings]

FIG. 1 shows a block diagram of an automatic output control amplifier according to one embodiment of the present invention.

FIG. 2 shows a block diagram of a conventional automatic power control amplifier.

[Explanation of symbols]

 1, 2, 3 amplifier 4 first variable attenuator 5 second variable attenuator 6 coupler 7 detector 8 differential amplifier 9 output level controller

Claims (6)

[Claims] An amplifier for amplifying an input signal, a coupler for outputting an output signal from the amplifier and extracting a part of the signal, and an output signal from a differential amplifier, which is connected at a preceding stage of the coupler and is connected to the coupler, A main signal line having a first variable attenuator whose attenuation is varied by a detector, a detector for detecting a signal taken out from the coupler, and a signal level and a threshold output from the detector for comparison and amplification. A feedback signal line having a differential amplifier for variably controlling the first variable attenuator, and a second variable attenuator for performing output control in the automatic output control amplifier, An automatic output control amplifier connected in a feedback signal line. 2. The automatic output control amplifier according to claim 1, wherein the second variable attenuator is connected between a coupler and a detector in the feedback signal line and is variable by an output level controller. 3. The automatic output control amplifier according to claim 2, wherein an amplifier is connected between said second variable attenuator and said detector. 4. The automatic output control amplifier according to claim 2, wherein the output level controller changes the amount of attenuation of the second variable attenuator according to a command signal from the outside. 5. An automatic output control amplifier, wherein the automatic output control amplifier according to claim 2, 3 or 4 is used in a satellite transponder. 6. An automatic output control amplifier according to claim 4, wherein an external command signal for controlling said output level controller is transmitted from an earth station.