JPH0374849B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a FET power amplification device, and particularly to a FET power amplification device using a field effect transistor (abbreviated as FET) used in a single sideband (abbreviated as SSB) multiplex radio device. This paper relates to a multi-stage FET linear power amplifier.

(b) Prior art and problems FETs were not used as linear power amplifiers for conventional SSB multiplex radio equipment because they could only obtain small amounts of power, and traveling wave tubes were used exclusively. This has led to problems in that the device is large, consumes a lot of power, and is expensive.

(c) Purpose of the Invention The present invention has been made in view of the problems of the prior art described above, and provides an SSB multiplex radio device that is stable against environmental changes and can be used up to near saturation output.
The purpose is to provide a FET linear power amplification device.

(d) Structure of the Invention The object of the invention is to divide an input signal by a first dividing means, detect a part and output it as an input-side detected voltage, and divide the remaining part by the first dividing means. , an input side monitor section that outputs it as is, and a second dividing means placed after the input side monitor section, which divides the input signal and amplifies a part with an internal amplifier to obtain a distorted output signal. a distortion compensation circuit that extracts only the distortion component from the distorted output signal and superimposes it on the remaining portion divided by the second dividing means to generate a signal including the distortion compensation component; and a control signal to be applied. a first variable attenuation portion that applies an attenuation amount to the output of the distortion compensation circuit using
a power amplifier that amplifies the signal including the distortion compensation signal output from the first variable attenuation section and sends out an output signal with suppressed distortion components; an output side monitor section which divides the signal by a dividing means, detects a part and outputs it as an output side detected voltage, and outputs the remaining part divided by the third dividing means as it is, and the input side detected voltage and the output side. A power amplifier device comprising a differential amplifier that sends out a control signal using a side detection voltage to maintain a gain of the entire power amplifier device including the distortion compensation circuit and the power amplifier at a predetermined value, A second variable attenuation section is provided that uses the applied control signal to give an attenuation amount to the signal output from the input side monitor section and sends it to the distortion compensation circuit, the second variable attenuation section , the amount of attenuation is changed by the control signal so that the amount of change in the distortion component generated in the power amplifier is equal to the amount of change in the distortion compensation component generated in the distortion compensation circuit, and the first variable attenuation portion is , SSB multiplexing characterized in that the control signal changes the attenuation by an amount obtained by subtracting the attenuation change of the second variable attenuation portion from the attenuation change that compensates for the gain change. This is accomplished by providing a FET linear power amplifier for wireless equipment.

(e) Embodiment of the invention FIG. 1 shows a block connection diagram of an embodiment of the invention.

In the figure, 1 and 6 are directional couplers, 2 and 4 are variable attenuation parts, 7 and 10 are detectors, 8 and 9 are DC amplifiers, 11 is a differential amplifier, and 3 is a distortion compensation circuit. , 5 represents a FET power amplifier, and 12 and 13 represent an input terminal and an output terminal, respectively.

These parts are connected as follows.

The input terminal 12 is connected to the output terminal 13 via the directional coupler 1, variable attenuator 2, distortion compensation circuit 3, variable attenuator 4, FET power amplifier 5, and directional coupler 6.
connected to. Further, terminal 1 of the differential amplifier 11 is connected to terminal 1 of the directional coupler 1 via the detector 7, and terminal 2 is connected to the terminal 1 of the directional coupler 1 through the detector 7.
is connected to the terminal 1 of the variable attenuator 2 via the DC amplifier 8 and to the terminal 1 of another variable attenuator 4 via another DC amplifier 9, and the terminal 3 is connected to the terminal of the directional coupler 6 via the detector 10. 1, respectively.

Note that the dotted line portion is the portion added in the present invention.

FIG. 2 shows a more detailed block connection diagram of the distortion compensation circuit 3 of FIG.

FET for SSB multiplex radio device connected like this
The operation of the linear power amplifier is as follows.

The input signal applied to the input terminal 12 is divided into two parts by the directional coupler 1 , one part is detected by the detector 7 and then applied to the differential amplifier 11 . The remaining portion passes through the variable attenuator 2 and is then applied to the distortion compensation circuit 3.

A more specific block diagram of the distortion compensation circuit 3 is shown in Part 2.
Since it is shown in the figure, the operation of the distortion compensation circuit 3 will now be explained.

The input signal that has passed through the variable attenuator 2 as described above is applied to the hybrid circuit 20 from the terminal 40, where it is divided into two parts, and one part passes through the attenuator 21 and the delay circuit 22 and is sent to the terminal 1 of the hybrid circuit 23. added to. On the other hand, the remaining part is divided into two by the hybrid circuit 24, and one part is connected to the FET amplifier 2.
5, the amplified and distorted output signal is extracted. This distorted output signal is applied to terminal 1 of hybrid circuit 28 through variable attenuator 26. The other portion is directly applied to the terminal 3 of the same hybrid circuit 28 through the variable phase shifter 27.

Since the hybrid circuit 28 combines the two signal components applied to terminals 1 and 3 with opposite phases,
When the variable attenuator 26 and the variable phase shifter 27 are set to cancel the input signal applied to the FET amplifier 25, only the distortion component generated by the FET amplifier 25 can be taken out to the output terminal 2 of the hybrid circuit 28.

This distortion component is removed by the variable attenuator 2 regardless of the input signal.
6 and variable phase shifter 27, the amplitude and phase can be changed using variable attenuator 29 and variable phase shifter 30.
The signal is input to terminal 3 of the hybrid circuit 23 through the terminal 3 of the hybrid circuit 23.

Therefore, the two signals inputted to terminals 1 and 3 of this hybrid circuit 23 are combined, and a distorted signal is obtained at terminal 41.

This distorted signal is applied to a multi-stage FET power amplifier 5 via a variable attenuator 4 shown in FIG.
By setting the variable attenuator 29 and the variable phase shifter 30 so as to cancel out the distortion components generated here, the distortion components included in the output wave of the multi-stage FET power amplifier 5 can be canceled out.

Next, the multistage FET power amplifier 5 and the output terminal 13
A directional coupler 10 is installed between the is obtained. Since the output signal level changes in the same way as the input signal level changes, the output of the differential amplifier 11 remains constant.

Here, the amount of distortion of the power amplifier 5 composed of multi-stage FETs is a combination of the distortions of each stage.

Therefore, when the gain changes due to temperature changes, etc., even if the output is kept constant, the operating point of the FET amplifier in the previous stage changes, so the amount of distortion in that part changes, and the amount of combined distortion changes.

On the other hand, the amount of distortion in the distortion compensation circuit 3 is determined by the FET amplifier 25.
Varies depending on the input level. So, for example
Assuming that the gain of the FET power amplifier 5 decreases by 3 dB and the distortion increases by 1 dB, in order to keep the gain of the FET power amplifier 5 constant, the total attenuation of the variable attenuators 2 and 4 needs to be decreased by 3 dB. .

Also, in order to increase the distortion by 1 dB, the input of the FET amplifier 25 needs to be increased by 0.5 dB, so the attenuation amount of the variable attenuator 2 is 0.5 dB, and the attenuation amount of the variable attenuator 4 is 0.5 dB.
By selecting the gains of the DC amplifiers 8 and 9 so as to reduce the distortion by 2.5 dB, it is possible to stabilize the gain and the amount of distortion.

(f) Effect of the Invention As explained above, according to the present invention, the distortion generated in the FET linear amplifier and the distortion generated in the distortion signal generation circuit included in the distortion compensation circuit are controlled to be used for stabilizing the gain. By suppressing with voltage, a FET linear power amplifier for SSB multiplex radio equipment with constant gain and low distortion can be obtained.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a more detailed diagram of the distortion compensation circuit included in FIG. 1. In the figure, 1 and 6 are directional couplers, 2 and 4 are variable attenuators, 7 and 10 are detectors, 3 is a distortion compensation circuit, 5 is a FET power amplifier, and 8 and 9 are DC amplifiers. , and 11 indicate a differential amplifier, respectively.

Claims (1)

[Claims] 1. An input side that divides an input signal by a first dividing means, detects a part and outputs it as an input-side detected voltage, and outputs the remaining part divided by the first dividing means as it is. A monitor part, which is arranged after the input side monitor part, divides the input signal by a second dividing means, amplifies a part by an internal amplifier, obtains a distorted output signal, and then outputs the distorted signal. a distortion compensation circuit that extracts only the distortion component from the output signal and superimposes it on the remaining portion divided by the second dividing means to generate a signal including the distortion compensation component; a first variable attenuation section that gives an attenuation amount to the output of the distortion compensation circuit; and an output in which a distortion component is suppressed by amplifying a signal including a distortion compensation signal output from the first variable attenuation section. A power amplifier that sends out a signal; an output signal sent from the power amplifier is divided by a third dividing means, a part is detected and outputted as an output side detection voltage, and the remaining part is divided by the third dividing means. The output side monitor section outputs the output as is, and the gain of the entire power amplification device including the distortion compensation circuit and the power amplifier is set to a predetermined value by using the input side detection voltage and the output side detection voltage. In a power amplification device having a differential amplifier that sends out a control signal that maintains the distortion, the distortion compensation circuit uses the applied control signal to attenuate the signal output from the input side monitor section. a second variable attenuation section that transmits a signal to the control signal;
The amount of attenuation is changed so that the amount of change in the distortion component generated by the power amplifier is equal to the amount of change in the distortion compensation component generated by the distortion compensation circuit, and the first variable attenuation portion is configured to:
From the attenuation change that compensates for the gain change, the second
Only the amount excluding the attenuation change of the variable attenuation part of
It is characterized by a configuration that changes the amount of attenuation.
FET linear power amplifier for SSB multiplex radio equipment.