JPH06224672A - Power amplifier - Google Patents

Abstract

PURPOSE:To provide the power amplifier which is highly efficient and has a satisfactory linearity by controlling a level compressor and an efficient power amplifier in accordance with an input signal level. CONSTITUTION:A level detector 1, a level compressor 2, a power amplifier 3, and a voltage control circuit 4 are provided. The input signal is inputted to a conventional power amplifier 3 after being preliminarily compressed. That is, the signal corresponding to the input signal level detected by the level detector 1 is not only inputted to the conventional power control circuit 4 for improvement of efficiency but also used as the control signal of the level compressor 2. In this case, the inclination of input/output characteristics of the level compressor 1 is so set that input/output characteristics of a conventional power amplifier a voltage control circuit are compensated, and thereby, the inclination of synthetic input/output characteristics is 1:1 and a satisfactory linearity is realized. The level compressor 2 used in this case utilizes the saturation characteristic of the amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the efficiency of a high frequency power amplifier, and more particularly to the structure of a high efficiency and low distortion power amplifier.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a configuration of a conventional power amplifier, in which 1 is a level detector, 3 is a power amplifier, and 4 is a voltage control circuit.

Next, the operation will be described. The power amplifier in the high frequency band has a relatively low efficiency, and therefore various techniques for increasing the efficiency are used. In the power amplifier shown here, as a basic principle, the applied voltage is changed according to the output signal level so that optimum efficiency is always obtained. FIG. 7 shows the principle. When the voltage applied to the power amplifier is changed, the input / output characteristics of the amplifier change according to the voltage. Generally, in the case of FET, high voltage, high gain and high output are obtained, and at low voltage, Low gain and low output. However, the point of maximum efficiency is immediately before the output level reaches saturation, and at the same output level, it is highly efficient to use the voltage as low as possible. Therefore,
The ideal characteristic is a straight line connecting the points immediately before each saturation shown in FIG. 7, and it is necessary to control the voltage applied to the power amplifier according to the input signal level. In order to realize this, in the configuration diagram shown in FIG. 6, the voltage controller 4 is controlled according to the input signal level detected by the level detector 1,
The voltage applied to the power amplifier 3 is changed so that the power amplifier 3 always operates with high efficiency.

[0004]

Since the conventional power amplifier is constructed as described above, it is optimum for high efficiency operation. However, as shown in FIG. 7, as shown in FIG. Is not proportional to 1: 1 and is unsuitable as a pass-through amplifier, and has many distortion components.
There is a problem that it is not suitable for amplification of multi-wave signals.

The present invention has been made in order to solve the above-mentioned problems, and while ensuring a highly efficient operation,
The purpose is to obtain a power amplifier that can obtain good input / output characteristics and linearity.

[0006]

The power amplifier according to the present invention is such that an input signal is compressed in advance and then input to a conventional power amplifier.

[0007]

In the power amplifier according to the present invention, the signal pre-compressed by the level compressor is used as the input of the conventional power amplifier, and a good input / output characteristic is realized as a whole.

[0008]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a level detector, 2
Is a level compressor, 3 is a power amplifier, and 4 is a voltage control circuit.

A signal corresponding to the input signal level detected by the level detector 1 is input to the conventional power control circuit 4 for improving efficiency and is also used as a control signal for the level compressor 2. . FIG. 5 shows the principle of this device. By setting the slope of the input / output characteristic of the level compressor in a form that compensates the input / output characteristic of the conventional power amplifier plus voltage control circuit, the slope of the total input / output characteristic becomes 1: 1 and a good Linearity can be realized. The level compressor used here utilizes the saturation characteristic of the amplifier.

Embodiment 2. FIG. 2 is a diagram showing another embodiment of the present invention, in which the level compressor 5 is controlled by the output of the voltage control circuit 4 controlled by the control signal from the level detector. . This level compressor utilizes the fact that the FET in the microwave band has characteristics of low voltage, low gain, and high voltage, high gain. FIG. 4 shows a principle diagram of the level compressor 5. The applied voltage is controlled in accordance with the input signal level so that the gain is large when the input signal is small and the gain is small when the input signal is large, so that the characteristics shown by the solid line in the figure are obtained.

Embodiment 3. FIG. 3 shows another embodiment of the present invention, in which 6 is an externally controlled level compressor, and 7 is a level compressor.
Is a memory holding / reading circuit. In this example,
According to the output of the level detector 1, the memory holding / reading circuit 7
Is output to the level compressor 6 and the voltage control circuit 4 to control each of them to an optimum value.

[0012]

As described above, according to the present invention, the level compressor and the high efficiency power amplifier are configured to be controlled according to the input signal level, so that high efficiency and good linearity can be achieved. There is an effect that a power amplifier having the same can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a power amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a power amplifier according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a power amplifier according to a third embodiment of the present invention.

FIG. 4 is a diagram showing an operating principle of a level compressor.

FIG. 5 is a diagram showing an operating principle of the power amplifier of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional power amplifier.

FIG. 7 is a diagram showing an operating principle of a conventional power amplifier.

[Explanation of symbols]

 1 level detector 2 level compressor 3 power amplifier 4 voltage control circuit 5 level compressor 6 according to another embodiment 6 level compressor 7 according to another embodiment 7 memory holding / reading circuit

Claims (3)

[Claims] 1. A level detector, a level compressor connected to the level detector, a power amplifier connected to the level compressor, and a voltage applied to the power amplifier are controlled by a control voltage from the level detector. And a voltage control circuit for controlling the power amplifier. 2. A power comprising a level detector, a level compressor connected to the level detector, a power amplifier connected to the level compressor, and a voltage control circuit controlled by a control signal of the level detector. In the amplifier, the voltage applied to the level compressor and the power amplifier is controlled by a level detection signal from the level detector. 3. The electric power according to claim 2, wherein the level compressor and the voltage control circuit are controlled by a storage / readout circuit which reads out data stored in advance by a level detection signal from the level detector. amplifier.