JP2000307353A - High frequency amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform distortion compensation without using an attenuator for the sub-line output of a directional coupler while simplifying the configuration of a distortion compensator by connecting a varactor diode between coupling lines, which constitute the directional coupler, and changing the coupling degree of the directional coupler. SOLUTION: A signal outputted from a directional coupler 1 is inputted to a synthesizer 8 by a delay line 4. The capacitance of a varactor diode 9 is changed so that the power of a signal component from the sub-line output of the directional coupler 2 can be equal with the output signal power of the directional coupler 1. The output of the synthesizer 8 becomes only a distortion signal component generated by a non-linear power amplifier 6 and a signal amplifying this distortion signal component through a linear power amplifier 7 and the distortion signal component of a signal outputted from the main line of the directional coupler 2 through a delay line 5 are combined at the same level with opposite phases while using a varactor diode 10 of a directional coupler 3. The main line output of the directional coupler 3 becomes a signal with no distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high frequency power amplifier,
In particular, it relates to improvement of nonlinear distortion of an amplifier.

[0002]

2. Description of the Related Art Conventionally, in order to extract a distortion component in a distortion compensator of a high-frequency power amplifier, a distortion component is extracted using the coupling degree of a directional coupler having a fixed coupling degree, and the extracted distortion component is extracted. Some of them perform distortion compensation in accordance with Then, a variable attenuator is inserted into the sub-line output of the directional coupler from which the distortion component is extracted, and the level is adjusted by the attenuator.

[0003]

According to the above-mentioned prior art, the circuit scale is large by using an attenuator.
There is a disadvantage that the number of parts increases. An object of the present invention is to realize a high-frequency power amplifier that simplifies the configuration of a distortion compensator and performs distortion compensation without using an attenuator for a sub-line output of a directional coupler for extracting a distortion component of a high-frequency amplifier. is there.

[0004]

According to the present invention, in order to achieve the above object, a varactor diode is connected between coupling lines constituting a directional coupler to change the degree of coupling of the directional coupler. Things.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the high-frequency amplifier according to the present invention will be described below with reference to FIG. A signal input to a high-frequency amplifier having a non-linear compensation circuit for performing distortion compensation by the feedforward method passes through the directional coupler 1, is non-linearly amplified by the non-linear power amplifier 6, and is input to the directional coupler 2. On the other hand, the signal output from the sub-line of the directional coupler 1 is input to the combiner 8 by the delay line 4 so as to be combined with the sub-line output signal of the directional coupler 2 in the opposite phase. At this time, the capacitance of the varactor diode 9 is changed so that the power of the signal component from the sub-line output of the directional coupler 2 is equal to the output signal power of the directional coupler 1. At this time, the output of the synthesizer 8 is
, And the distortion signal component amplified by the linear amplifier 7 and the distortion signal component of the signal output from the main line of the directional coupler 2 and passed through the delay line 5 are: By combining the signals at opposite phases and at the same level using the varactor diode 10 of the directional coupler 3, the signal of the main line output of the directional coupler 3 is output without distortion as a signal without distortion.

[0006]

According to the present invention, a variable attenuator for a feedforward type distortion compensator is not required in a high-frequency amplifier, and the configuration of the high-frequency amplifier is simplified. Further, since the degree of coupling of the directional coupler can be controlled by voltage, it can be applied to automatic electrical control.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

[Explanation of symbols]

1, 2, 3: directional coupler, 4, 5: delay line, 6: nonlinear power amplifier, 7: linear power amplifier, 8: combiner, 9,
10: Varactor diode.

Claims (1)

[Claims] 1. A high-frequency amplifier having a feed-forward type non-linear compensation circuit, wherein the degree of coupling of a directional coupler used in the non-linear compensation circuit is changed using a varactor diode.