JPH0797733B2 - Non-linear distortion compensation circuit for power amplifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a circuit for compensating the nonlinear distortion characteristic generated in an electron tube used for power amplification, and relates to the power level of an input signal, that is, the operating power level of a power amplifier. Regardless of which, it relates to a method for always obtaining the best nonlinear distortion compensation characteristic.

[Conventional technology]

Conventionally, in this type of non-linear distortion compensating circuit, a non-linear distortion generating circuit 6 is mounted in the main line system as shown in FIG.
Then, the non-linear distortion signal generated from the non-linear distortion generation circuit 6 according to the power level of the input signal is combined with the subsequent power amplifier 10 so as to always be in a reverse phase at a constant ratio, and the non-linear distortion as a whole. The characteristics are compensated.

[Problems to be solved by the invention]

In the above-described conventional non-linear distortion compensation circuit, the degree of coupling between the non-linear distortion generation circuit 6 and the power amplifier 10 is constant. Therefore, only when the non-linear distortion generation circuit 6 and the power amplifier 10 have the same degree (ratio) of non-linear distortion generation, the best non-linear distortion compensation characteristic as a whole is obtained regardless of the power level of the input signal. It is possible to obtain.

However, in general, an electron tube such as a traveling wave tube is used for a power amplifier, whereas a solid-state power amplifier is used for a non-linear distortion generation circuit for compensating the non-linear distortion for downsizing and power reduction. However, their nonlinear distortion characteristics are often different. Therefore, the best compensation characteristics are not always obtained depending on the magnitude of the power level of the input signal, and in some cases, the characteristics may be worse than the characteristics of the power amplifier alone.

[Means and Actions for Solving Problems]

A nonlinear distortion compensating circuit according to the present invention includes a circuit for branching an input signal into a main line system and a branch line system, a circuit for detecting a power level of a branched main line system input signal, and an input of the branched branch line system. A variable attenuator that performs amplitude correction on the signal and a variable phaser that performs phase correction, and distortion characteristics related to the amplitude and phase of the power amplifier are given in advance, and based on the distortion characteristics and the detection signal of the power level detection circuit. A control circuit for controlling the variable attenuator and the variable phaser so as to obtain an optimum attenuation amount and phase amount for compensating for the distortion characteristic, and an input passing through the variable attenuator and the variable phaser. A non-linear distortion generation circuit that generates a non-linear distortion signal corresponding to the signal, and a combining circuit that combines the non-linear distortion signal with the branched main line signal, and the power level of the branched input signal. Always it is made possible to obtain the best non-linear distortion compensation characteristic by combining an input signal to produce a non-linear distortion signal optimal to the entire distortion compensation mainline by the amplitude and phase both sides according to Le.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the present invention. The high frequency signal input to the high frequency signal input terminal 1 is divided into a main line system and a branch line system by the directional coupler 2 that functions as a branch circuit. The high frequency signal of the branch line system is further branched by the directional coupler 3, and then one is sent to the nonlinear distortion generating circuit 6 through the variable attenuator 4 and the variable phase shifter 5. The other signal branched by the directional coupler 3 is sent to a power level detection circuit 7 including a detector, a linear amplifier, etc.,
The power level is detected. The voltage signal detected by the power level detection circuit 7 is input to the control circuit 8.

The control circuit 8 is previously provided with the amplitude characteristic and the phase characteristic of the output with respect to the power level of the input signal in the power amplifier 10. These characteristics and the voltage signal corresponding to the input level from the power level detection circuit 7 are given. The bias signals to the variable attenuator 4 and the variable phase shifter 5 are output from
The control operation is always performed so that the amplitude and phase of the distortion characteristic of the power amplifier 10 are opposite to those of the distortion characteristic of the power amplifier 10. The non-linear distortion signal thus generated in the non-linear distortion generating circuit 6 is combined with the high frequency signal of the main line system in the directional coupler 9 and sent to the subsequent power amplifier 10. The non-linear distortion generated in the power amplifier 10 is canceled by being combined in advance with the non-linear distortion generated in the non-linear distortion generation circuit 6 to improve the non-linear distortion characteristic as a whole. become.

In this case, it is clear that each non-linear distortion component has exactly the same amplitude and exactly the opposite phase in terms of phase, which leads to the best compensation characteristics. Therefore, in the present invention, based on the amplitude and phase characteristics of the power amplifier 10 given in advance by the control circuit 8 from the power level of the input signal detected by the power level detection circuit 7, the optimum value corresponding to each characteristic is obtained. A bias signal is output so as to adjust the variable attenuator 4 and the variable phase shifter 5 so as to generate a non-linear distortion component having an opposite phase. That is, the power level detection circuit 7 detects the magnitude of the power level of the input signal to detect the power level.
Knowing the operation level of 10, the control circuit 8 drives the variable attenuator 4 in order to generate a non-linear distortion component corresponding to it and generate the maximum compensation characteristic in terms of amplitude. Control. Further, by knowing the operation level of the power amplifier 10, the absolute phase change amount at that operation level is detected. Therefore, the absolute phase of the non-linear distortion generated by the non-linear distortion generating circuit 6 is adjusted by driving the variable phase shifter 5 by the control circuit 8 based on this phase change amount, and the phase difference at the time of synthesis is accurately reversed. By setting the phase, the highest compensation characteristic in terms of phase is obtained.

〔The invention's effect〕

As described above, according to the present invention, in the non-linear distortion compensation circuit of the power amplifier, when the non-linear distortion signal from the non-linear distortion generation circuit is combined with the input signal to the power amplifier, the characteristics in both the amplitude and the phase. It is possible to always obtain the best compensation characteristic regardless of the power level of the input signal, by varying the value corresponding to the operating level of the power amplifier.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a non-linear distortion compensation circuit according to the present invention, and FIG. 2 is a system diagram of a conventional non-linear distortion compensation circuit. 2, 3 ... Directional coupler, 4 ... Variable attenuator, 5 ... Variable phaser, 6 ... Non-linear distortion generation circuit, 7 ... Power level detection circuit, 8 ... Control circuit, 9 ... Directional coupler, 10 ... Power amplifier.

Claims (1)

[Claims] 1. A circuit for branching an input signal into a main line system including a power amplifier and a branch line system for compensating the non-linear distortion of the power amplifier, and a power level of the input signal of the branched branch line system. Circuit, a variable attenuator for performing amplitude correction on the input signal of the branched branch line system, a variable phaser for performing phase correction, and distortion characteristics related to the amplitude and phase of the power amplifier are given in advance, and the distortion A control circuit for controlling the variable attenuator and the variable phaser so that an optimum attenuation amount and phase amount for compensating for the distortion characteristic are obtained based on a characteristic and a detection signal of the power level detection circuit; A non-linear distortion generation circuit that generates a non-linear distortion signal corresponding to an input signal that has passed through the variable attenuator and the variable phase shifter; Nonlinear distortion compensating circuit constituted power amplifier and a combining circuit for combining the line distortion signal.