JP2005136758A - Distortion compensating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein an amplification element to be compensated differs from the element configuration of a distortion generator and hence a distortion compensation value cannot be precisely compensated in a distortion compensating device for performing compensation by a conventional predistortion system. <P>SOLUTION: A distortion generating means is provided in the distortion compensating device for compensating distortion generated in an amplifier for amplifying a signal, generates distortion for canceling distortion generated to a signal amplified by the amplifier, and uses the same element as an element for composing the amplifier, thus precisely compensating the distortion generated in the amplifier. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a distortion compensator that compensates for distortion generated in an amplifier when the modulated wave signal is amplified by an amplifier using a predistortion method based on the envelope information of the modulated wave signal, and more particularly to detection accuracy of envelope information The present invention relates to a distortion compensation device that improves the frequency.

For example, a predistortion method is known as a linearization technique of an amplifier. In this method, an envelope is detected by an envelope detector, and distortion generated in the amplifier is compensated based on the detection result. Here, the predistortion method will be described. In the power amplifier used in the transmitter, nonlinearity exists in its input / output characteristics, and as a result of distortion occurring due to the nonlinearity, unnecessary power radiation outside the transmission frequency band occurs, As a result, interference power to other frequency bands is generated. For this reason, in such a power amplifier, it is necessary to suppress the generated distortion.

A power amplifier is a component that consumes a large amount of power. For example, in a base station device of a mobile phone system, the power consumption of the power amplifier accounts for most of the power consumption of the base station device. This is an important issue. However, in order to perform amplification linearly by the power amplifier, it is necessary to operate the power amplifier in a region where the DC-AC conversion efficiency is low. In other words, the improvement in nonlinearity of the power amplifier and the reduction in power consumption are contrary to each other, and it has been difficult to solve both of these problems simultaneously.

Therefore, there is a predistortion method as a method for simultaneously solving both of these problems. The predistortion method is a method of improving distortion by applying distortion that is opposite to distortion generated in a power amplifier (distortion that cancels distortion generated in a power amplifier), for example, from the input stage of the power amplifier. .

In this system, the distortion generator generated on the upstream side of the input section of the power amplifier is configured using a jet key diode having distortion compensation characteristics, a small signal transistor, a small signal FET, or the like.

However, in the conventional distortion compensation device that compensates by the predistortion method, there is a problem that the element configuration of the amplifying element to be compensated and the distortion generator are different and the distortion compensation amount cannot be compensated with high accuracy.

The present invention relates to a distortion compensation apparatus that solves the above-described problems and compensates for distortion generated by an amplifier when the modulated wave signal is amplified by an amplifier using a predistortion method based on envelope information of the modulated wave signal. An object of the present invention is to provide a distortion compensation device that improves the detection accuracy of envelope information.

The distortion compensation apparatus according to claim 1 of the present invention is a distortion compensation apparatus that compensates for distortion generated by an amplifier that amplifies a signal, and that generates distortion for canceling distortion generated for a signal amplified by the amplifier. The strain generating means is configured using an element similar to the element constituting the amplifier.

According to the distortion compensation apparatus of the present invention, distortion generated in an amplifier can be compensated with high accuracy.

Hereinafter, the present invention will be described by way of examples. However, the following examples do not limit the claimed invention, and all combinations of features described in the examples serve as means for solving the invention. It is not always essential.

First, in describing the present invention, an example of a basic configuration of a distortion compensation apparatus to which the present invention can be applied will be described. FIG. 1 is a diagram illustrating an exemplary distortion compensation apparatus according to an embodiment of the present invention. In the distortion compensation apparatus shown in FIG. 1, the transmission signal to be amplified is input to the distortion compensation unit 11 and the power detection unit 13, and the power of the signal is detected by the power detection unit 13, and the detection result is the control unit. 14, the distortion compensation unit 11 is controlled by the control unit 14 so that the distortion compensation characteristic 11 based on the detection result is applied to the signal by the distortion compensation unit 11, and from the control unit 14 After distortion is applied to the signal by the distortion compensator 11 according to the control signal, the signal is amplified by the amplifier 12 and output.

Here, the distortion compensator 11 is, for example, an attenuator (ATT) for attenuating an input signal, a phase shifter for changing the phase shift of the signal, and a reverse characteristic distortion for canceling the distortion generated in the amplifier. It is comprised using the distortion generator which generate | occur | produces. A detailed description of these distortion compensators will be described later. As a method of detecting the power of the signal by the power detection unit 13, various methods such as a method of performing envelope detection and a method of performing a process equivalent to envelope detection by a processor can be used.

The control unit 14 is configured by using, for example, a DSP (Digital Signal Processor), and has a reference table (LUT: Look Up Table) for applying distortion with distortion compensation characteristics. Then, the control unit 14 outputs, for example, attenuator control information and phase shifter control information corresponding to the power of the input signal to the distortion compensation unit 11.

Further, the control unit 14, for example, converts an A / D (Analog to Digital) converter that digitizes a power detection result input as an analog signal from the power detection unit 13, or analogizes a digital control signal for the distortion compensation unit 11. And a D / A (Digital to Analog) converter for outputting to the distortion compensation unit 11.

In the distortion compensation apparatus shown in FIG. 2, a feedback loop is formed in a configuration including the distortion compensation unit 21, the amplification unit 22, the power detection unit 23, and the control unit 25 having the same functions as those shown in FIG. The demodulator 24 is provided. In this transmission power amplification unit, the transmission signal input to the distortion compensation unit 21 and the power detection unit 23 is also input to the control unit 25, and a part of the signal output from the amplification unit 22 is input to the demodulation unit 24. Then, a part of the signal is orthogonally demodulated by the demodulator 24, and the orthogonal demodulation result is input to the controller 25.

In this distortion compensation apparatus, the transmission signal input to the control unit 25 and the quadrature demodulation result are compared by the control unit 25 to detect the distortion component generated in the amplification unit 22, and the detected distortion component is The contents of the reference table are updated by the control unit 25 so as to decrease. By updating such a reference table, for example, it is possible to adapt to a change in the nonlinear characteristic of the amplifying unit 22 caused by a secular change or a temperature change, that is, it is possible to perform adaptive predistortion.

In the distortion compensation apparatus shown in FIG. 3, a feedback loop is formed in a configuration including the distortion compensation unit 31, the amplification unit 32, the power detection unit 33, and the control unit 35 having the same functions as those shown in FIG. The filter 34 is provided. In this distortion compensation apparatus, a part of the signal output from the amplifying unit 32 is input to the filter unit 34, and only a signal in a band in which a distortion component generated in the amplifying unit 32 leaks from the part of the signal to the filter. The extracted distortion component is input to the control unit 35.

In this distortion compensation apparatus, the contents of the reference table are updated by the control unit 35 so that the distortion component input to the control unit 35 is reduced. By updating such a reference table, it is possible to adapt to a change in the nonlinear characteristic of the amplifying unit 32 caused by, for example, aging or temperature change, that is, adaptive predistortion can be performed. Here, the filter part 34 is comprised using a band pass filter (BPF: Band Pass Filter), a mixer, a variable frequency oscillator etc., for example. The above is an example of the basic configuration of a distortion compensation apparatus to which the present invention can be applied.

Next, a configuration example of a distortion compensation unit to which the present invention can be applied will be described. FIG. 4 is a diagram illustrating a configuration example of a distortion compensation unit of a distortion compensation apparatus to which the present invention can be applied. Here, the configuration of the distortion compensator of FIG. 4 is applicable to the distortion compensators 11, 21, and 31 of FIGS. The distortion compensator includes a distortion generator 41 that generates a reverse characteristic distortion for canceling the distortion generated in the amplifier, an attenuator 42 (attenuator: ATT) that attenuates the input signal, and changes the phase shift of the input signal. The phase shifter 43 is configured. Here, as the distortion compensation processing, first, distortion of an inverse characteristic for canceling distortion generated in the amplification unit with respect to the input signal is generated by the distortion generator 43, and distortion is performed on the signal that has generated the distortion. By adjusting the optimum attenuation amount and phase shift amount with the attenuator 42 and the phase shifter, respectively, the distortion generated in the amplifier can be canceled.

Next, an example of the element configuration of the amplification unit of the distortion compensation apparatus to which the present invention can be applied will be described. FIG. 5 is a diagram illustrating an example of an element configuration of an amplification unit of a distortion compensation apparatus to which the present invention can be applied. Here, the configuration of the amplifying unit in FIG. 5 is applicable to the amplifying units 12, 22, and 32 in FIGS. For example, a transistor or FET is used as an element of this amplifier as shown in FIG. 5, and the output is increased by synthesizing the transistor and FET elements in multiple stages in parallel for high output.

Next, an example of an element configuration of a distortion generator of a distortion compensation apparatus to which the present invention can be applied will be described. FIG. 6 is a diagram illustrating an element configuration example of a strain generator of a distortion compensation apparatus to which the present invention can be applied. For example, the distortion generator element is configured by using transistors and FET elements similar to those shown in FIG. 5, and these transistors and FET elements are combined in multiple stages in parallel, and the elements similar to the amplifier are used for distortion. The accuracy of compensation is increased.

As described above, according to the best embodiment of the present invention, the distortion of the amplifier is compensated with high accuracy by configuring the amplification unit and the distortion generator of the distortion compensation apparatus with the same elements. can do.

It is a figure which shows the distortion compensation apparatus of an example of embodiment of this invention. It is a figure which shows the distortion compensation apparatus of an example of embodiment of this invention. It is a figure which shows the distortion compensation apparatus of an example of embodiment of this invention. It is a figure which shows the structural example of the distortion compensation part of the distortion compensation apparatus which can apply this invention. It is a figure which shows the element structural example of the amplification part of the distortion compensation apparatus which can apply this invention. It is a figure which shows the element structural example of the distortion generator of the distortion compensation apparatus which can apply this invention.

Explanation of symbols

11, 21, 31 Distortion compensation unit 12, 22, 32 Amplification unit 13, 23, 34 Power detection unit 14, 25, 35 Control unit 24 Demodulation unit 34 Filter unit 41 Distortion generation unit 42 Attenuator 43 Phase shifter

Claims (1)

In a distortion compensation apparatus that compensates for distortion generated in an amplifier that amplifies a signal,
Comprising distortion generating means for generating distortion for canceling distortion generated for a signal amplified by an amplifier;
The distortion compensation apparatus, wherein the distortion generating means is configured by using an element similar to an element configuring the amplifier.

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