JPH01176105A - Nonlinear distortion compensation circuit - Google Patents

Abstract

PURPOSE:To improve the compensation characteristic of an amplifier to be compensated by adopting the circuit such that a frequency converter is provided on each of a linear path and a nonlinear path connected in parallel and the phase of a carrier supplied to the frequency converter is made adjustable. CONSTITUTION:As input signal voltage increases, an amplifier 18 enters the nonlinear region at first, the output amplitude ratio of a signal e1 is represented in a vector oB, a combined output ec is expressed in oc, the amplitude is increased by DELTAc in comparison with that at the linear operation and the phase is advanced by DELTAtheta. As a result, the amplitude nonlinearity -DELTAc and the phase nonlinearity -DELTAtheta generated in an amplifier 19 to be compensated are canceled and the linear processing of the input/output is attained at an output terminal 103. In this case, the amplitude of the signal eb is selected by an attenuator 16 and the synthesized phase angle of ea, eb is selected by a delay line 23 so as to best compensate the nonlinearity of the amplifier 19 to be compensated. Thus, the compensation effect of the amplifier to be compensated is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonlinear distortion compensation circuit for reducing nonlinear distortion generated in an amplifier or a frequency converter.

[Conventional technology]

Conventionally, the negative feedback method has been known as this type of nonlinear distortion compensation method, but the pre-form nonlinear distortion method is one of the nonlinear distortion compensation methods that is effective in high frequency bands where the negative feedback method cannot be applied. There is a compensation law. That is, this method assumes the nonlinear characteristics of the compensated amplifier, and connects nonlinear circuits having nonlinear characteristics opposite to the nonlinear characteristics in cascade to make the overall input/output characteristics linear.

The configuration of this conventional circuit is shown in FIG. In the figure, 101 is an input terminal, 102 is an output terminal of a nonlinear distortion compensation circuit, 9 is a compensated amplifier, 103 is a general output terminal, 3 is a distributor,
4 is a combiner, 5 and 6 are attenuators, and 7 and 8 are amplifiers.

In this configuration example, amplifiers 7 and 8 exhibit almost the same characteristics, but the input level of amplifier 7 is lower than that of amplifier 8 due to attenuator 5, and the amplifier performs linear operation and eliminates nonlinear distortion. There have been no outbreaks. On the other hand, the input level of amplifier 8 is higher than that of amplifier 7 (it performs nonlinear operation as an amplifier and generates nonlinear distortion. By combining with a phase difference close to the opposite phase, an output that cancels out the nonlinear characteristics of the subsequent compensated amplifier is obtained at the terminal 102.

[Problem that the invention seeks to solve]

In the conventional circuit described above, the circuit configuration is simple, but the phase angle of the two signals when combining the outputs of the linear path (including amplifier 7) and the nonlinear path (including amplifier 8) is 3 and the characteristics of the synthesizer 4, there is a problem in that the nonlinear distortion compensation effect of the compensated amplifier as a whole is also limited.

An object of the present invention is to provide a nonlinear distortion compensation circuit that solves the above-mentioned problems.

[Means for Solving the Problems] The nonlinear distortion compensation circuit of the present invention is configured by connecting in parallel a signal path having a circuit with linear characteristics and a signal path having a circuit with nonlinear characteristics. Each of them is provided with a frequency converter, and the phase of the carrier wave supplied to these frequency converters can be adjusted.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. Input terminal 1
The input signal supplied to 01 is split into two by a divider 13, and one of the branched signals is sent to a mixer (frequency converter) 21.
Bandpass filter 25. the attenuator 15 and the amplifier 17, and the mixer 22. Bandpass filter 26. After passing through an amplifier 18 and an attenuator 16, they are combined by a combiner 14, and the output of the nonlinear distortion compensation circuit is obtained at an output terminal 102. This output is input to the compensated amplifier 19, and the total output is output to the output terminal 103.

In such a configuration, the input/output characteristics of the path including the amplifier 17 and the path including the amplifier 18 exhibit linear operation (straight line 111) and nonlinear operation (curve 112) as shown in FIG.
The attenuation amount of attenuators 15 and 16 is selected so that Here, in FIG. 2, the horizontal axis shows the input amplitude at the input terminal 101, and the vertical axis shows the output amplitude at the terminals 104 and 105, respectively.

The carrier waves of mixers 21 and 22 are supplied from the same signal source 20, and the frequencies of the output signals of both mixers completely match. Further, by changing the electrical length of the delay line 23 inserted between the signal source 20 and the mixer 22, the phase difference between the output signals of both mixers can be changed from 0° to 360°.

The outputs of these two amplifiers are combined into a combiner 1 with approximately opposite phases.
4, it is possible to produce a nonlinear characteristic that is almost the opposite of that of a normal amplifier, as shown by the curve 113 in FIG. Bandpass filters 25 and 26 are for removing unnecessary waves generated by the mixer.

Next, the operation of the circuit of the present invention will be explained. FIG. 3 is a vector diagram for explaining the operating principle of the circuit shown in FIG. 1. When normalized by the input signal amplitude, the signal at the output terminal 102 of the synthesizer 14 [is the point 1 that has passed through the mixer 21
It is expressed as the sum of the signal core of point 04 and the signal core of point 105 that has passed through mixer 22, and is e, +e, = ec. When the input signal voltage is low and both paths are operating linearly, the signal is represented by vector 2.

On the other hand, when the input signal voltage increases, the amplifier 18 first enters the nonlinear region, the output amplitude ratio of the signal i decreases as represented by the vector
Compared to the linear operation, the amplitude is larger by ΔC and the phase is also advanced by Δθ.

As a result, the amplitude nonlinearity expressed by −ΔC and the phase nonlinearity expressed by −Δθ generated in the compensated amplifier 19 are canceled out, and the input/output characteristics at the output terminal 103 can be linearized.

In this case, in the embodiment shown in FIG. 1, the amplitude of eb is selected by the attenuator 16, and the combined phase angle of Ishi and Gei is selected by the delay line 23 so as to best compensate for the non-linearity of the compensated amplifier 19. do.

FIG. 4 shows another embodiment of the present invention, in which an attenuator 15 is placed before the mixer 21, and bandpass filters 25 and 26 for removing unnecessary waves generated by the mixer are placed after both mixers 21 and 22. It is structured as follows.

The operation in this embodiment is similar to that in FIG.

〔Effect of the invention〕

As explained above, in the present invention, a frequency converter is provided in each of the linear path and the nonlinear path connected in parallel, and the phase of the carrier wave supplied to these frequency converters can be adjusted. It is possible to change the phase difference between the two nonlinear paths independently of the signal frequency and over a wide band, improving the compensation characteristics of the compensated amplifier and making it effective as a nonlinear compensation circuit with a frequency conversion function. It has the effect of becoming.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a diagram showing the input/output characteristics of the circuit of Fig. 1, and Fig. 3 is a signal vector diagram for explaining the operating principle of the circuit of the present invention. , FIG. 4 is a circuit diagram of another embodiment of the present invention, and FIG. 5 is a circuit diagram of a conventional nonlinear distortion compensation circuit. 1... Input terminal, 2... Output terminal, 3... Distributor, 4... Combiner, 5.6... Attenuator, 7, 8...
Amplifier, 9...Compensated amplifier, 13...Distributor, 1
4...Synthesizer, 15.16...Attenuator, 17.18
...Amplifier, 19...Compensated amplifier, 20...Carrier signal source, 21°22...Mixer (frequency converter)
, 23...Delay line, 25.26...Band filter,
101...Input terminal, 102...Nonlinear distortion compensation circuit output terminal, 103...Compensated amplifier output terminal. Figure 3; xi Empress Meyari Middle ≦ Work *1 Tank Nobaba A Shang Kuzu

Claims (1)

[Claims] (1) In a nonlinear distortion compensation circuit configured by connecting in parallel a signal path having a circuit with linear input/output characteristics and a signal path having a circuit with nonlinear input/output characteristics, and compensating for the nonlinear characteristics of the compensated circuit. A nonlinear distortion compensation circuit, characterized in that two frequency converters sharing a carrier wave signal source are provided in each of the two signal paths, and the phase of the carrier wave supplied to these frequency converters can be adjusted.