Feedforward amplifier

Abstract

A delayed input signal from a delay circuit (24) and an output signal are combined by a combiner (51). The output form combiner (51) is converted into a low-frequency signal by a frequency converter (53). Distortion components are extracted from the output from the frequency converter (53) and measured by a power detector (55). A control circuit (56) controls a second vector controller (11) in a distortion cancel loop (102) to minimize the measured distortion components.

Description

technical field [0001] The present invention relates to a feed-forward amplifier for low distortion amplification in the high frequency region. Background technique [0002] Feedforward amplifiers that achieve low distortion characteristics through feedforward distortion compensation are often used as feedforward amplifiers that perform low-distortion amplification in high-frequency regions such as the VHF, UHF, or microwave regions. This kind of feedforward distortion compensation can achieve good distortion compensation in principle, so it has the advantage of being able to form an amplifier with very small distortion. However, when the characteristics of the amplifier change due to ambient temperature or aging, there is a problem that its distortion compensation amount is reduced to significantly deteriorate the distortion characteristics. [0003] In order to solve the above-mentioned problems, a method of injecting a monitor signal into a loop constituting a feedforwar...

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Problems solved by technology

[0028] Since the existing feedforward amplifier is constructed as above, in the feedforward amplifier that controls the feedforward system by injecting the monitor signal into the loop, there is a possibility that the monitor signal that cannot be completely eliminated during the control process will be output from the output terminal. The problem

[0029] In addition, when an output filter is provided to remove the monitor signal, since a large output filter is required and the loss is large, there is a problem of increasing the size of the amplifying device and lowering the efficiency.

[0030] In addition, in the figure 2 In the structure shown in which the monitor signal generator 8 is not provided but the control of the feedforward system that minimizes the above-mentioned distortion is performed by detecting the distortion of the output signal, it is difficult to detect and control the distortion component that is 50dB to 60dB smaller than the signal component, so There is a problem that a distortion detector cannot be realized practically, or even if it can be realized, its circuit structure will be complicated, which will result in an increase in size and price.

[0031] In addition, in the image 3 , Figure 4 In the feedforward amplifier shown, since the signal suppression circuit 22 with a multi-stage structure is used, there is a problem that the device becomes large and complicated.

[0032] In addition, even if the amplification frequency changes slightly, it is necessary to readjust all the vector adjusters and delay circuits of the signal suppression circuit 22, so there is a practically complicated problem.

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