JPH0425222A - Automatically level controlled system - Google Patents

Abstract

PURPOSE:To decrease a deviation among signals in a synthesis wave by using the same level detector for detecting the output level of each modulator. CONSTITUTION:A selector 30 is selected so as to detect the level of a modulator 11 and a level detector 60 detects the output level of the modulator 11. The detected value is latched and the selector 30 is selected to detect a level of a modulator 12 and a level control circuit 22 is controlled so that the level is the same as the detected level of the modulator 11. Similarly, level control circuits 22-2n are controlled so that the level of modulators 13-1n is made the same level as the modulator 11 and the cycle is repeated periodically. Thus, the output level deviation of the modulators 11-1n is independent of the absolute accuracy of the detector 60 and decreased to the level resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic level control system, and more particularly to an automatic level control system for transmission output in a transmitter of a satellite communication earth station.

[Conventional technology]

FIG. 2 shows an example of a satellite communication earth station using the conventional automatic level control method.

In this conventional example, the modulator 211. Level control circuit 212. Interface circuit (INTFC) 213. C
Indoor device 201 including PU 214 and interface circuit 215. High power amplifier (HPA) 216. Outdoor device 202 including level detector 217 and antenna (ANT)
203.

Automatic level control is provided from the outdoor device 202 to the antenna 203.
The purpose of this invention is to prevent communication from being cut off due to the reception level of the other station exceeding the receivable range due to changes in the level of the signal output to the device due to changes in the temperature of the device.

Therefore, the output of the HPA 216 at the final stage of the outdoor device 202 is monitored by the level detector 217, and the output level information is sent to the indoor device 202 via the INTFCs 215 and 213.
communicates with the CPU 214 of. The CPU 214 sends a control signal to the level control circuit 212 to correct the change in the output level.

[Problem to be solved by the invention]

The conventional automatic level control method described above is effective in a transmitting device with one modulator, but in the case of a configuration with multiple modulators whose outputs are combined and sent to an outdoor device, each of the individual modulators is Due to their unique characteristics, it is difficult to obtain the same level of output even with the same control signal. Also,
In order to correct this, each modulator is provided with an individual level detector, and even if the detected values are corrected to be at the same level, the deviation in each output level largely depends on the absolute precision of the detector.

As described above, the conventional automatic level control system has a drawback that, in the case of a configuration including a plurality of modulators, the deviation between each signal in the composite wave is large.

[Means to solve the problem]

The automatic level control system of the present invention includes a plurality of modulators whose output levels can be controlled by control signals, a selection means for sequentially and periodically repeating branch outputs of the outputs of these modulators, and a selection means that branches out the outputs of these modulators. The control device includes a level detector to which the detected signal is input, control means to generate the control signal based on the detection signal from the level detector, and combining means to combine the outputs of the modulator.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

The satellite communication earth station according to this embodiment includes an indoor device 101, an outdoor device 102. It is composed of an antenna 103.

In the indoor device 101, the modulators 11 to 1n receive the input signal 81.
A modulation signal modulated by ~Sn is generated, and these modulation signals pass through the level control circuits 21 to 2n and the selector 30, and are synthesized by the hybrid 40, and the INTFC
50 and is sent to the outdoor device 103. Further, a part of the output from the modulators 11 to 1n is inputted to the level detector 60 through the selector 30.

In the outdoor device 102 , a signal input through the INTFC 80 is amplified by the HPA 90 and sent to the antenna 103 . It also includes a level detector 100 for measuring the output level of the HPA 90.

Next, the automatic level control operation of this embodiment will be explained.

First, check the output level of HPA90 using level detector 10.
0 and notifies the CPtJ 70 of the indoor device 101 via the INTFC 80°50. The CPU 70 compares the information with the value specified by itself, and provides control signals to the level control circuits 21 to 2n so as to achieve the required output level.

Next, the selector 3 is set so that the level of the modulator 11 can be detected.
0, and the level detector 60 detects the output level of the modulator 11. Hold the detected value and selector 30
is switched to detect the level of the modulator 12, and the level control circuit HFI 22 is controlled so that the detected value becomes the same as the detected value of the modulator 11. Similarly, modulator 13 to modulator 1n
The level control circuits 22 to 2n are also controlled to have the same level as the modulator 11. The operation at J here is one cycle, and when this one cycle is completed, it returns to the beginning again, detects the output level of the HPA 90, and in addition to correcting changes due to the influence of the temperature of the HPA 90, outputs of the modulators 11 to 1n. The level change of the composite wave caused by controlling each level control circuit 21 to 2n to make the level the same is corrected.

By periodically repeating this cycle, the modulator 1
The output level deviation of 1 to 1n is not related to the absolute accuracy of the level detector 60 and can be reduced to its level resolution.

〔Effect of the invention〕

As explained above, the present invention uses the same level detector to detect the output level of each modulator. This has the effect of reducing the signal deviation between each signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an example of a conventional automatic level control system. 11-1n...Modulator, 21-2n...Level control circuit, 30...Selector, 40...Hybrid, 50...Interface circuit, 60...Level detector, 70... CPU, 80... Interface circuit, 90... HPA, 100... Level detector, 101... Indoor device, 102... Outdoor device, 1
03...Antenna.

Claims (1)

[Claims] A plurality of modulators whose output levels can be controlled by control signals, a selection means for sequentially and periodically repeating branch outputs of the outputs of these modulators, and a level detector into which the signals branched by the selection means are input. An automatic level control method comprising: a control means for generating the control signal based on a detection signal from the level detector; and a synthesis means for synthesizing the outputs of the modulator.