JPH02145028A - Power amplifier - Google Patents

Abstract

PURPOSE:To make the total gain of a power amplifier constant equivalently and to make an input level of a satellite repeater constant as a result by controlling an input signal level inputted to the power amplifier in response to number of transmission channels. CONSTITUTION:A ROM 7 receiving a transmission control signal is a ROM table generating a level signal for gain control in response to number of operat ing channels, a D/A converter 8 and a filter 9 convert the bit information outputted from the ROM 7 into an analog signal and give the signal to a gain control amplifier 3 as a gain control signal. Gain control information is written in the ROM 7 so that the gain of the gain control amplifier 3 of the pre-stage is g-DELTAG1 when the gain of a power amplifier 4 to which an input signal corre sponding to the unity of the transmission channel number is inputted is G-g+DELTAGT1. It is possible to make the total gain of the power amplifier to be G based on the similar concept as to other transmission channel number and the power amplifier with a constant gain is constituted independently of the transmission channel number.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for controlling the transmission power of a satellite communication earth station.
In particular, the present invention relates to means for stabilizing gain fluctuations of a transmitter caused by an increase or decrease in the number of transmission channels due to nonlinearity of the input/output characteristics of the transmitter.

[Prior art and its problems] A power amplifier generally used in a transmitter is shown in FIG. It has the function to control.

Specifically, in order to control the gain of the composite signal of the transmission signals for each transmission channel that is input to the power amplifier, an amplifier and to set the gain of this amplifier, generate an amplifier gain control signal according to the number of transmission channels. [Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. N transmission signals input from transmission signal input terminals 11, 12, 13 to IN are power-combined by a combiner 2 having N inputs. This composite signal is input to the power amplifier 4 via the gain control amplifier 3, and is power amplified. The power-amplified transmission signal is output from the transmission output terminal 5 as a transmission signal. On the other hand, the transmission control signal input from the transmission control signal input terminals 61, 62, 63 to 6N is a status signal that is, for example, "1" when transmitting and "0" when not transmitting, and is used to determine the number of channels used. It is. The ROM 7 into which these transmission control signals are manually input is a ROM table for generating gain control level signals according to the number of channels used.

The D/A converter 8 and filter 9 convert the bit information output from the ROMB into an analog signal, which is supplied to the gain control amplifier 3 as a gain control signal.

The gain control signal input to the gain control amplifier 3 is set as shown in FIG. 2 and Table 1. FIG. 2 shows that in the output characteristics of the power amplifier 4, the gain changes because the operating point moves according to the number of transmission channels.

Table 1 shows the relationship between the gain of the power amplifier 4 and the gain of the gain control amplifier 3 when the number of transmission channels changes from 1 to 6.

If the gain of the power amplifier 4 when an input signal corresponding to 1 transmission channel is added is G-g+ΔG1, then the gain of the gain control amplifier 3 at the front stage of the power amplifier 4 is g-Δ
If gain control information is written in the ROM 7 so that the gain becomes G1, the total gain of this power amplifier device becomes G.

Based on the same idea regarding the number of other transmission channels, it is possible to set the total gain of the power amplifier to G,
As a result, a power amplification device with a constant gain can be constructed regardless of the number of transmission channels.

Table 1: Gain relationship lock diagram of the power amplifier device; FIG. 2 is a graph showing the input/output characteristics of the power amplifier 4.

11.12.13~IN...Transmission signal input terminal (channel 1°2.3~N) By controlling the input signal level, the total gain of the power amplifier is equivalently kept constant.
As a result, it becomes possible to stabilize the input level of the satellite repeater.

In particular, since the linearity of a power amplifier having a large output power deteriorates, the gain stabilization means for a power amplifier device according to the present invention is effective.

[Brief explanation of the drawing]

FIG. 1 shows the system of the power amplifier of the present invention, including a combiner, a gain control amplifier, a power amplifier, a transmission signal output terminal, 61.62°63~6N...transmission control signal input terminal (channel 1). . 2. 3~N), ? ---ROM (Read Only Memo)
ry, write-only memory), 8-------D/A converter (Digital-Ana
l 0 gl converter), 9...filter.

Claims (1)

[Claims] Includes an amplifier for controlling the gain of a composite signal obtained by combining transmission signals for each transmission channel, and a control circuit that generates an amplifier gain control signal according to the number of transmission channels to set the gain of the amplifier. A power amplification device featuring: