JPH08125554A - Automatic distortion compensation circuit - Google Patents

Abstract

PURPOSE: To stably secure the amplifying efficiency of a power amplifier and to automatically compensate the nonlinear distortion of the power amplifier highly efficiently by automatically following and saving even when the mutual modulating distortion of the power amplifier changes. CONSTITUTION: A distortion generation part from one side of a distributor 12a by way of a linear compensation circuit 11 to a variable amplifier circuit 18 compensate nonlinear distortion generated at the power amplifier 22 and generates a predistortion signal provided with an amplitude and a phase for compensating mutual modulating distortion from an original signal. Then, a synthesizing part including a synthesizer 13a synthesizes the predistortion signal to be the original signal to send to the power amplifier 22. A control part including a phase comparing circuit 35 and an amplitude comparing circuit 34 to which the output signal of the power amplifier 22 is feedback-transmitted from a directional coupler 23 controls the amplitude and the phase of the predistortion signal based on mutual modulating distortion components extracted from the power amplifier 22 so as to minimize the mutual modulating distortion components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic distortion compensation circuit having an analog power amplifier of high frequency application type and suppressing intermodulation distortion generated in a power amplifier to which an original signal containing multiple high frequency components is input.

[0002]

2. Description of the Related Art Conventionally, as a technique for compensating for intermodulation distortion in a power amplifier as represented by this type of automatic distortion compensating circuit, for example, the mutual distortion disclosed in Japanese Patent Laid-Open No. 59-17736. A modulation distortion automatic compensation circuit is mentioned. Here, a technique is provided in which a filter for absorbing intermodulation distortion is provided at the output section of the power amplifier to fixedly suppress the intermodulation distortion component radiated from the antenna, or the output backoff of the power amplifier is sufficiently set in advance. A technique for variably suppressing intermodulation distortion generated in a power amplifier by a linearity compensation circuit as a compensation circuit is disclosed.

[0003]

When variably compensating for the intermodulation distortion by the above-described automatic intermodulation distortion compensation circuit, the output efficiency of the power amplifier deteriorates because the output backoff of the power amplifier is sufficiently taken. There is a problem. Further, since the amount of compensation in the linearity compensating circuit is large, the characteristics are likely to vary particularly with temperature, and there is a problem in the reliability of the circuit. Further, even if the non-linear distortion of the power amplifier can be automatically compensated, the change of the intermodulation distortion cannot be automatically tracked and compensated. When exchanging or adjusting, it is necessary to adjust the entire compensation circuit without fail, which is a problem in terms of maintenance.

The present invention has been made to solve the above problems, and its technical problem is that the amplification efficiency of the power amplifier is stably ensured and the intermodulation distortion of the power amplifier changes. However, it is still another object of the present invention to provide an automatic distortion compensating circuit capable of automatically suppressing tracking and highly accurately compensating for nonlinear distortion of a power amplifier.

[0005]

According to the present invention, an automatic distortion compensating circuit for suppressing intermodulation distortion generated in a high frequency applied power amplifier to which an original signal containing multiple high frequency components is input is generated in the power amplifier. A distortion generating section for compensating the non-linear distortion, and generating a predistortion signal having an amplitude and a phase for canceling the intermodulation distortion from the original signal, and a power amplifier combining the predistortion signal with the original signal. A synthesizing section for sending to
An automatic distortion compensation circuit having a control unit for controlling the amplitude and phase of the predistortion signal based on the intermodulation distortion component extracted from the power amplifier so that the intermodulation distortion component is minimized is obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The automatic distortion compensating circuit of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of an automatic distortion compensation circuit according to an embodiment of the present invention.

This automatic distortion compensating circuit suppresses intermodulation distortion generated in the power amplifier 22 to which an original signal containing multiple high frequency components is input, and the high frequency application type power amplifier 22 is provided.
In addition to compensating for the non-linear distortion that occurs in, the pre-distortion signal having the amplitude and phase for canceling the intermodulation distortion is generated from the original signal, and the pre-distortion signal is combined into the original signal. A combining unit for sending to the power amplifier 22, and the power amplifier 22.
And a control unit for controlling the amplitude and phase of the predistortion signal based on the intermodulation distortion component extracted from the above so as to minimize the intermodulation distortion component.

Of these, the distortion generating section is connected to the input terminal 41, and the linearity compensating circuit 11 for compensating the non-linear distortion of the original signal and the first signal distributing the original signal in which the non-linear distortion is compensated are distributed. Divider 12a and second divider 12 which further divides one of the original signals distributed by the first distributor 12a.
b, a first linear amplifier 15a that linearly amplifies one of the original signals distributed by the second distributor 12b, and a non-linear one of the original signals distributed by the second distributor 12b. A non-linear amplifier 16 for amplifying, a first phase shift circuit 14b for phase-shifting the other of the original signals non-linearly amplified by the non-linear amplifier 16, and an original signal linearly amplified by the first linear amplifier 15a. A first combiner 13 for combining one of the two of the original signals phase-shifted by the first phase shift circuit 14b.
b, a second linear amplifier 15b for linearly amplifying the combined signal combined by the first combiner 13b, and a second phase shift circuit for phase-shifting the combined signal linearly amplified by the second linear amplifier 15b. 17 and a variable attenuator circuit 18 for variably attenuating the combined signal phase-shifted by the second phase shift circuit 17 and outputting it as a predistortion signal.

Further, the synthesizing unit combines the predistorted signal and the other one of the original signals distributed by the first distributor 12a with the phase shifted and delayed by the phase shift circuit 14a and the delay circuit 19, respectively. The second combiner 13a for combining and the power amplifier 2 for frequency-converting the combined signal combined by the second combiner 13a
2 and a mixer 21 for sending to 2.

Further, the control unit is connected to the output terminal 42 and is coupled to the output side of the power amplifier 22 to branch a part of the output signal from the power amplifier 22, and a directional coupler 23. A down converter 31 for extracting an intermodulation distortion component from the output signal branched by the sex coupler 23;
A detection circuit 32 for detecting the output signal from the down converter 31, a filtering circuit 33 for filtering the output signal from the detection circuit 32, and a phase of the output signal from the filtering circuit 33 for the second phase shift circuit 17 The phase comparison circuit 35 for compensating and controlling the phase of the combined signal by comparing it with the phase of the combined signal phase-shifted by, and the amplitude of the combined signal variably attenuated by the variable attenuation circuit 18 for the amplitude of the output signal from the filtering circuit 33. And an amplitude comparison circuit 34 for compensating and controlling the amplitude of the combined signal.

The operation of this automatic distortion compensation circuit is as follows:
A video intermediate frequency modulated wave (hereinafter abbreviated as VIF), a video color carrier (hereinafter abbreviated as IFS), and an audio intermediate frequency modulated wave (hereinafter abbreviated as AIF) input as an original signal from 1.
The main signal, which is a composite wave of the above, is compensated by the compensation circuit 11 for the nonlinearity of the power amplifier 22 at the final stage, and then distributed by the first distributor 12a. One of the distributed signals has a phase shift circuit 14a.
Then, the signal is input to one input terminal of the second combiner 13a via the delay circuit 19. The other signal distributed by the first distributor 12a is again distributed by the second distributor 12b. One of the signals distributed by the second distributor 12b is input to one input terminal of the first combiner 13b via the first linear amplifier circuit 14a. The other signal distributed by the second distributor 12b becomes a distortion signal containing an intermodulation distortion component in the non-linear amplifier 16, and passes through the first phase shift circuit 14b to produce the first signal.
Is input to the other input terminal of the synthesizer 13b.

At the two input terminals of the first combiner 13b, the distortion signal containing the intermodulation distortion component by the non-linear amplifier 16 is supplied to the first linear amplification circuit 15a by the first phase shift circuit 14b. It is adjusted so that the phase difference becomes 180 ° with respect to the signal input after that. The outputs from the first linear amplifier circuit 15a and the non-linear amplifier 16 are adjusted with the same gain with respect to the main signal. Therefore, the main signal components applied to the two input terminals of the first combiner 13b have the same amplitude and a phase difference of 180 °, and cancel the main signal components. Therefore, the signal component generated at the output terminal of the first combiner 13b is only the intermodulation distortion component having a phase difference of 180 ° from the output signal of the first linear amplification circuit 15a. This intermodulation distortion component is supplied to the second linear amplification circuit 15
b, and then the second phase shift circuit 17 and variable attenuation circuit 1
The predistortion signal is input to the other input terminal of the second combiner 13a via 8.

Of the two input signal components of the second combiner 13a, the one input via the phase shift circuit 14a and the delay circuit 19 is the same component as the main signal input to the input terminal 41. On the other hand, the predistortion signals input through the variable attenuation circuit 18 are adjusted so that the phases thereof differ by 180 °. Therefore, the signal generated at the output terminal of the second combiner 12a is composed of the main signal and the signal of the intermodulation distortion component having a phase difference of 180 ° from that of the main signal, and after the combined signal is frequency-converted by the mixer 21. , To the power amplifier 22. At this time, intermodulation distortion occurs in the power amplifier 22,
This intermodulation distortion component is generated in the same phase as the main signal input to the power amplifier 22, and is 180 ° out of phase with the intermodulation distortion component included in the input signal. or,
Since the intermodulation distortion component is determined by the frequency and wave number of the carrier of the main signal input to the input terminal 41, the intermodulation distortion component input to the power amplifier 22 and the intermodulation distortion component generated by the main signal are Have the same frequency.
Therefore, in the power amplifier 22, the signals cancel each other out,
As a result, the output of the power amplifier 22 is such that the intermodulation distortion component is suppressed.

On the other hand, the directional coupler 23 provided between the output side of the power amplifier 22 and the output terminal 42 is for monitoring the output signal of the power amplifier 22, and this directional coupler 23 is provided. Output signal from the down converter 3
After frequency conversion by 1, the detector 32 and the filtering circuit 33
Then, the intermodulation distortion component of the necessary portion is extracted by passing through. The phase of the output signal including the extracted intermodulation distortion component is detected by the phase comparison circuit 35 and the second phase shift circuit 17 is detected.
, The amplitude (level) of the output signal is detected by the amplitude comparison circuit 34, and the variable attenuation circuit 18 is set to the power amplifier 22.
The intermodulation distortion component output from is automatically controlled to be the minimum.

[0016]

As described above, according to the automatic distortion compensating circuit of the present invention, the intermodulation distortion having the amplitude and phase for canceling and compensating the intermodulation distortion generated in the power amplifier from the original signal is compensated. Since the predistortion signal of the component is created and the phase and amplitude of this predistortion signal are controlled and added to the original signal in antiphase, the intermodulation distortion is not affected by the frequency and the number of multiplexing of the original signal The nonlinear distortion of the power amplifier can be automatically compensated with high accuracy after automatically suppressing the tracking. As a result, the amplification efficiency of the power amplifier is stably secured, and automatic tracking is suppressed even when the intermodulation distortion of the power amplifier changes, so that the power amplifier is replaced or adjusted, or the characteristics of the power amplifier change over time. Even if this occurs, it is no longer necessary to adjust the entire compensation circuit, which facilitates maintenance. Further, since the linearity compensating circuit included in this automatic distortion compensating circuit has a small amount of compensation, variations in characteristics due to temperature and the like are less likely to occur, and reliability of the compensating circuit is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an automatic distortion compensation circuit according to an embodiment of the present invention.

[Explanation of symbols]

 11 Linearity Compensating Circuit 12a, 12b Divider 13a, 13b Combiner 14a, 14b Phase Shifting Circuit 15a, 15b Linear Amplifier 16 Non-Linear Amplifier 17 Phase Shifting Circuit 18 Variable Attenuating Circuit 19 Delay Circuit 21 Mixer 22 Power Amplifier 23 Directional Coupling Device 31 Down converter 32 Detection circuit 33 Filtering circuit 34 Amplitude comparison circuit 35 Phase comparison circuit 41 Input terminal 42 Output terminal

Claims (2)

[Claims] 1. An automatic distortion compensating circuit for suppressing intermodulation distortion generated in a high frequency application type power amplifier to which an original signal containing multiple high frequency components is input, while compensating for non-linear distortion generated in the power amplifier, A distortion generator that generates a predistortion signal having an amplitude and a phase for canceling the intermodulation distortion from the original signal, and a combination that combines the predistortion signal with the original signal and sends the combined signal to the power amplifier. And a control unit for controlling the amplitude and phase of the predistortion signal based on the intermodulation distortion component extracted from the power amplifier so that the intermodulation distortion component is minimized. Automatic distortion compensation circuit. 2. The automatic distortion compensating circuit according to claim 1, wherein the distortion generating unit includes a linearity compensating circuit 11 for compensating for the non-linear distortion of the original signal and an original signal for which the non-linear distortion is compensated. A first distributor 12a for distributing, a second distributor 12b for further distributing one of the original signals distributed by the first distributor 12a, and a distributor for the second distributor 12b. A first linear amplifier 15a that linearly amplifies one of the original signals, and a non-linear amplifier 16 that non-linearly amplifies the other of the original signals distributed by the second distributor 12b.
A first phase shift circuit 14b for shifting the other of the original signals non-linearly amplified by the non-linear amplifier 16 and one of the original signals linearly amplified by the first linear amplifier 15a. And a first combiner 13b for combining the other one of the original signals phase-shifted by the first phase shift circuit 14b, and the combined signal combined by the first combiner 13b is linearly amplified. A second linear amplifier 15b, a second phase shift circuit 17 for shifting the phase of the combined signal linearly amplified by the second linear amplifier 15b, and a combined signal phase-shifted by the second phase shift circuit 17. And a variable attenuator circuit 18 for variably attenuating the predistortion signal and outputting the predistortion signal as the predistortion signal. A second combiner 13a for combining the phase-shifted and delayed ones; The synthesis signal synthesized by the second combiner 13a to frequency conversion made mixer 21 for delivery to the power amplifier 22, the control unit, the power amplifier 2
A directional coupler 23 that is coupled to the output side of 2 and branches a part of the output signal from the power amplifier 22, and the intermodulation distortion component is extracted from the output signal that is branched by the directional coupler 23. A down converter 31, a detection circuit 32 for detecting an output signal from the down converter 31, and a filtering circuit 33 for filtering an output signal from the detection circuit 32.
And the phase of the output signal from the filtering circuit 33 to the second
A phase comparison circuit 35 that compares the phase of the combined signal phase-shifted by the phase shift circuit 17 of FIG.
An amplitude comparison circuit 34 for comparing the amplitude of the output signal from the filtering circuit 33 with the amplitude of the composite signal variably attenuated by the variable attenuation circuit 18 and compensating and controlling the amplitude of the composite signal. Automatic distortion compensation circuit.