JPS60241305A - Distortion compensating system - Google Patents

Abstract

PURPOSE:To reduce the passing loss of signal components by operating a directional coupler in the output terminal as a synthesizer for signal components and operating this directional coupler as a canceller for distortion components. CONSTITUTION:Output signal components of a distortion extracting circuit 12 are a composite signal including distortion components and signal components. This composite signal is amplified by a distortion amplifier 8 and is inputted to a 1/4 wavelength directional coupler 13 provided in the output terminal. Respective amplitudes and phases of signal components and distortion components are selected properly to operate the coupler as the synthesizer for signal components and operate it as the canceller for distortion components. As the result, the passing loss of signal components is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a feed-forward distortion compensation system for compensating distortion of a nonlinear amplifier.

<Prior Art and Problems> As a conventional distortion compensation system of this type, there is one shown in FIG. 1, for example. In the figure, 1 is a nonlinear amplifier, 2, 3.
5 is a directional coupler, 4 and 6 are delay lines, 7 is a combiner, 8 is a distortion amplification width, 9 is an absorption resistor, 10 is a variable attenuator, and 11 is a variable phase shifter. First, by inputting a portion of the input signal and a portion of the output signal of the nonlinear amplifier 1 to the combiner 7 in opposite phases, only the distortion components generated in the nonlinear amplifier 1 are extracted. Next, the distortion component is amplified by the distortion component amplifier 8 and inputted to the directional coupler 5 at the output end at an appropriate level, and the directional coupler 5 cancels out the distortion component contained in the output signal. This realizes distortion compensation. At this time, the gain and output level of the distortion amplifier 8 are determined by the amount of coupling between the directional couplers 3 and 5. 1. Normally, the coupling amount of the directional coupler 5 is less than 10 dB, and the gain of the distortion amplifier 8 is also set to 40 to 50 dB. The level distribution of the distortion compensation circuit is made as described above to perform distortion compensation and at the same time to minimize the transmission loss of the main line.

However, with a directional coupler 5 of about 10 dB, the theoretical passing loss of the main line is about 0.5 dB (6 J), which is absorbed by the absorption resistor 9, and the higher the output power, the more power loss that cannot be ignored. The disadvantage is that it is not. Also 1
If the coupling degree of the connection 5 is set to 20 dB or more, the passing loss is reduced, but on the other hand, this leads to an increase in the output level and gain of the distortion amplifier 8, and the number of amplification stages of the distortion amplifier 8 increases.As a result, the delay line 4 increases. There is also the disadvantage that the passing loss of the main line (which is quite long) increases accordingly.

<Object of the Invention> An object of the present invention is to provide a distortion compensation method capable of reducing passage loss of a directional coupler of a main line while maintaining a distortion compensation function.

<Configuration of the Invention> The configuration of the present invention is that in a distortion compensation method in which distortion compensation of a nonlinear amplifier is performed by a directional coupler provided at the output end, the output signal of the nonlinear amplifier and the input signal of the nonlinear amplifier are When combining the composite signal of the extracted distortion component and signal component with the output signal using the above directional coupler, select the amplitude and phase of each of the signal component and distortion component, and select the directional coupler at the output end. The above problem is solved by employing a distortion compensation system that operates as a combiner for signal components and as a canceller for distortion components.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 2 to 4.

In FIG. 2, 1 is a non-linear amplifier, 2 and 3 are directional couplers, 4 and 6 are delay lines, 8 is a distortion amplifier, and 9 is an absorption resistor, all of which are the same as in the prior art. 12 is a distortion extraction circuit, and 13 is a directional composite signal at the output end. The composite signal amplified by the distortion amplifier 8 is sent to a 174-wavelength directional coupler 13 provided at the output end of the compensation circuit.
is input. FIG. 3 shows a quarter wavelength wavelength directional device 13.

A main signal is input from terminal A, and a composite signal is input from terminal C. In this case, if the amplitude and phase of each of the signal component and distortion component of the composite signal input from terminal C are appropriately selected, the signal components will be in-phase combined only at the B terminal, and canceled at the D terminal. Further, the distortion components can be in-phase combined only at the D terminal and canceled at the B terminal.

In this way, the passage loss of the quarter-wavelength directionality device 13 for the signal component is ignored, and conversely, it operates as a combiner for the signal component.

Here, the phase relationship between the signal component and the distortion component of the composite signal may be such that the phase relationship between the signal component and the distortion component of the main signal is opposite to each other. Therefore, the distortion extraction circuit 12 outputs a signal component and a distortion component. Of these, the distortion component is the component coupled from the output side of the nonlinear amplifier 1 and is output as is, and the signal component is the signal coupled from the input side of the amplifier 10. Since it is only necessary to output the components, for example, the signal components from the input side of the amplifier 1 may be combined so that the amplitude thereof is larger and the phase thereof is opposite to that of the signal component from the output side of the amplifier 1.

Or, according to the circuit configuration shown in FIG. 4, the signal component coupled from the input side of the amplifier 1 is inputted to the terminal (B), and is first divided into 92 parts by the divider 14, and one is divided into 92 parts by the terminal 0). The input distorted signal is combined with the synthesizer 7 and only the distorted component is outputted to the terminal (c), while the other output signal passes through the variable attenuator 10 and the variable phase shifter 11 and is outputted to the terminal (c). Finally, the synthesizer 7 synthesizes only the distortion components of the multi-terminal (C) and outputs the output terminal (
e) Outputs a composite signal of signal components and distortion components. If the distortion extraction circuit shown in FIG. 4 is used, the phase relationship between the distortion component and the signal component can be varied, so there is no need to use the quarter wavelength wavelength directional coupler 13 as shown in FIG. 2, and a normal directional coupler may be used. By adjusting the variable phase shifter 11, the directional coupler can operate as a combiner for signal components and as a canceller for distortion components.

<Effects of the Invention> As explained above, the distortion compensation system of the present invention has the above-described configuration, so that ``the directional coupler at the output end is used as a combiner for signal components and as a combiner for distortion components. Since the signal component can be operated as a canceller against the directional coupler, the signal component is not absorbed by the absorbing resistance of the directional coupler, and as a result, the passing loss of the signal component can be reliably reduced. There is an effect that it can be done.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional distortion compensation method, FIG. 2 is a circuit diagram showing a distortion compensation method according to an embodiment of the present invention, and FIG. 3 is a circuit diagram showing an example of a 1/4 direction genitalia. FIG. 4 is a circuit diagram showing an example of a distortion extraction circuit. 1...Non-linear amplifier 12...Distortion extraction circuit 13...1/4 wavelength wavelength directional device Applicant: NEC Corporation

Claims (1)

[Claims] In a distortion compensation method in which distortion compensation of a nonlinear amplifier is performed by a directional coupler provided at the output end, the output signal of the nonlinear amplifier, the distortion component and signal extracted from the input signal and output signal of the nonlinear amplifier are used. When a composite signal of components is combined by the above directional coupler, the amplitude and phase of each of the signal component and distortion component are selected, and the directional coupler at the output end is used as a combiner for the signal component, or as a combiner for the signal component. A distortion compensation method characterized by operating as a canceller for distortion components.