JPH02131606A - Nonlinear compensation circuit - Google Patents

Abstract

PURPOSE:To widen a nonlinear compensation enable level range by providing a means detecting an input signal and an attenuator control circuit controlling the attenuation of distortion in response to the detected output. CONSTITUTION:A nonlinear compensation circuit 4 is connected to a distortion generator 11 generating a distortion in response to an input signal level as a nonlinear signal generator and an attenuator 12 attenuating the signal in series. The level of the input signal is detected by a detection circuit 5 and the attenuator 12 controlled by an attenuator control circuit 6 controls a level of a nonlinear signal in response to the detection output to control the distortion characteristic of the nonlinear compensation circuit in matching with the distortion characteristic of the amplifier. As a result, the distortion characteristic (chained lines) of the nonlinear compensation device is controlled in matching with the distortion characteristic (solid lines) of the amplifier and excellent distortion is obtained over a wide signal level range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonlinear compensation circuit, and particularly to a nonlinear compensation circuit that achieves distortion improvement over a wide signal level range.

[Conventional technology]

Conventionally, this type of nonlinear compensation circuit has a configuration in which a nonlinear signal corresponding to an input signal level is generated by a nonlinear signal generator, set to a desired level by an attenuator, and combined with a linear signal. That is, as shown in FIG. 2, the nonlinear compensation circuit 3 is inserted between the input terminal l and the output terminal 2, and connects in series a distortion generator l1 and an attenuator l2 that generate distortion according to the input signal level. The phase shifter l3 and the delay line 14 are connected in series and connected in parallel. In this case, the amount of attenuation of the attenuator is set by the attenuator adjustment circuit 6A, but once set, it is not particularly variable.

[Problems to be Solved by the Invention] By the way, in an actual field effect transistor (FET) amplifier, as shown in Fig. 3, when the distortion characteristics are expressed as, for example, third-order intermodulation distortion, up to a certain level, the third-order However, at higher levels, it tends to increase with a slope of 3rd order or higher. Furthermore, as shown in FIG. 4, the distortion characteristics of the distortion generator tend to gradually become saturated when the input signal level exceeds a certain level.

Therefore, like the conventional nonlinear compensation circuit described above,
In the case where the amount of distortion of the nonlinear compensation circuit is determined by setting the attenuator l2 fixedly to compensate for the nonlinearity of the amplifier at a certain operating point, the amount of distortion of the nonlinear compensation circuit is determined. It becomes difficult to compensate for nonlinearity.

In other words, as shown in Figure 6, which shows how distortion of an amplifier is improved by a conventional nonlinear compensation circuit, when the signal level exceeds a certain value, the distortion characteristics of the amplifier (solid line) and the nonlinear compensator (iN line) no longer match. , the amount of distortion improvement decreases. For this reason,
Conventional nonlinear compensation circuits have a problem in that the range of levels that can be compensated for nonlinearity is narrow.

An object of the present invention is to provide a nonlinear compensation circuit with a wide range of nonlinear compensable levels. (Means for Solving the Problems) The nonlinear compensation circuit of the present invention generates distortion according to a human input signal, attenuates this distortion, and synthesizes it into a linear signal to compensate for the distortion. and an attenuator control circuit that controls the amount of distortion attenuation according to the detected output.

[Effect]

With the above configuration, the amount of attenuation of the generated distortion can be controlled according to the input signal, and compensation can be achieved over a wide level range by matching the distortion characteristics of the compensation circuit to the distortion characteristics of the amplifier to be compensated. [Example] Next, the present invention will be described with reference to the drawings.

Figure 1 shows a nonlinear compensation circuit according to an embodiment of the present invention. A directional coupler 3 and a nonlinear compensation circuit 4 are inserted between the input terminal 1 and the output terminal 2, a part of the signal inputted by the directional coupler 3 is taken in, and the signal is detected by the detection circuit 5 to control the attenuator. circuit 6
The detection output is sent to. On the other hand, the nonlinear compensation circuit 4 includes a distortion generator l1 that serves as a nonlinear signal generator and generates distortion according to the input signal level, and an attenuator l2 that attenuates this signal, which are connected in series.

These are connected in parallel to a circuit in which the phase shifter 13 and the delay line l4 are connected in series, and the nonlinear signal made to a predetermined level by the attenuator l2 is synthesized with a linear signal.

The attenuation amount of the attenuator l2 is controlled by a control signal output from the attenuator control circuit 6. According to this configuration, the level of the input signal is detected by the detection circuit 5, and the level of the nonlinear signal is controlled in the attenuator 12 controlled by the attenuator control 1n circuit 6 according to the detected output, as shown in FIG. The distortion characteristics of the nonlinear compensation circuit shown in Figure 3 are controlled to match the distortion characteristics of the amplifier shown in Figure 3. As a result, as shown in Figure 5, the distortion characteristics of the nonlinear compensator (dashed line) are controlled to match the distortion characteristics of the amplifier (solid line), and a good amount of distortion improvement is achieved over a wide signal level range. It turns out that you are getting it.

It goes without saying that the signal input to this compensation circuit may be either the input signal or the output signal of the amplifier. [Effects of the Invention] As explained above, the present invention includes means for detecting an input signal and an attenuator control circuit that controls the amount of attenuation of distortion according to the detected output. The amount of attenuation of the amplifier can be controlled according to the input signal, and the distortion characteristics can be matched to the distortion characteristics of the amplifier to be compensated, so that the distortion of the amplifier can be suitably improved over a wide level range.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a circuit diagram of a conventional nonlinear compensation circuit, Fig. 3 is a diagram showing power versus distortion characteristics in an FET amplifier, and Fig. 4 is a diagram of a distortion generator. FIG. 5 is a diagram showing power versus distortion characteristics, FIG. 5 is a diagram showing characteristics of distortion compensation according to the present invention, and FIG. 6 is a diagram showing characteristics of conventional distortion compensation. l...Input terminal, 2...Output terminal, 3...Nonlinear compensation circuit, 4...Directional coupler, 5...Detector, 6
...Attenuator control circuit, 6A...Attenuator adjustment circuit, l
1... Distortion generator, 12... Attenuator, 13... Phase shifter, l4... Delay line. Figure 1 Figure 6, Entering bonito Figure 3 Figure 4

Claims (1)

[Claims] 1. In a circuit that generates distortion according to an input signal, attenuates the distortion, and synthesizes it into a linear signal to compensate for the distortion, the circuit includes means for detecting the input signal, and detecting the distortion according to the detection output. and an attenuator control circuit that controls the amount of attenuation of the nonlinear compensation circuit.