JP2000244597A - Non-linear distortion compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide satisfactory and stable distortion compensation characteristics even when a transmission power is changed by switching compensation coefficient ROM corresponding to the transmission power in the case of use for the transmission system of a radio communication system. SOLUTION: Plural compensation coefficient ROM 103 are prepared and the respective compensation coefficient ROM 103 store compensation coefficients calculated on the basis of transmission powers at plural levels within the range of transmission power control. When performing non-linear distortion compensation, the compensation coefficient ROM capable of obtaining the best distortion compensation characteristics corresponding to the transmission power at the point of time is selected in accordance with a control signal from a transmission power control part 110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear distortion compensator for use in a communication device of a radio communication system and for compensating for non-linear distortion generated in a transmission system.

[0002]

2. Description of the Related Art Non-linear distortion generated in a transmission power amplifier in a wireless communication system includes distortion of an amplitude component called input amplitude / output amplitude non-linearity (AM / AM) and input amplitude / output amplitude non-linearity.
There is a phase component distortion called output phase non-linearity (AM / PM), and these non-linear distortions deteriorate the transmission characteristics. To reduce the nonlinear distortion, a transmission power amplifier with high linearity may be used, but from the viewpoint of power efficiency,
Generally, a transmission power amplifier that generates nonlinear distortion is used.

Conventionally, as a method of compensating for this nonlinear distortion, there is a method called a pre-distortion method. This is a method in which distortion for compensating for nonlinear distortion generated in a transmission power amplifier is given to a transmission signal in advance. In addition, a nonlinear distortion compensator can be realized with a simple configuration.

FIG. 5 shows an example of a configuration of a conventional nonlinear distortion compensating apparatus using a predistortion method. Reference numeral 501 denotes a transmission quadrature baseband signal; 502, a power calculation unit;
3 is a compensation coefficient calculator, 504 is a nonlinear distortion compensator, 505
Is a D / A converter, 506 is a quadrature modulator, 507 is a transmission power amplifier, and 508 is an antenna.

[0005] The power value of the transmission quadrature baseband signal 501 is calculated by a power calculation unit 502, and a compensation coefficient for compensating for nonlinear distortion is calculated by a compensation coefficient calculation unit 503 based on the power value. The nonlinear distortion compensator 504 uses the compensation coefficient output from the compensation coefficient calculator 503 to transmit the transmission orthogonal baseband signal 501.
Is added to compensate for the nonlinear distortion. As a result, a linear transmission signal in which the nonlinear distortion has been canceled appears at the output of the transmission power amplifier 507.

However, since the compensation coefficient calculation unit 503 requires a huge amount of operation to calculate the compensation coefficient, usually the compensation coefficient calculated in advance is stored in the ROM, and the power of the transmission baseband signal is stored. A method of reading the result based on the value to reduce the amount of calculation has been adopted.

[0007]

However, in the above-described method of storing the compensation coefficient in the ROM, the compensation coefficient calculated based on the fixed transmission power is stored in the ROM. In this case, the distortion compensation characteristics deteriorate. One of the methods for solving this problem is to multiply the power value of the transmission baseband signal by a coefficient corresponding to the transmission power, as described in Japanese Patent Application Laid-Open No. Although there is a method of adjusting the reading position, there is a problem that a coefficient multiplication unit that performs an operation according to the transmission power is required, and the amount of operation increases.

According to the present invention, in a nonlinear distortion compensator using a pre-distortion method, by changing a compensation coefficient ROM according to transmission power, a good and stable distortion can be obtained with a small amount of calculation even when the transmission power is changed. The purpose is to obtain compensation characteristics.

[0009]

According to the present invention, a plurality of compensation coefficient ROMs are prepared, and each compensation coefficient ROM has a plurality of levels within a range of transmission power control. Is stored in advance. When performing non-linear distortion compensation, a compensation coefficient ROM that provides the best distortion compensation characteristic is selected according to the transmission power at that time, based on a control signal from the transmission power control unit. The number of compensation coefficient ROMs is determined according to a required distortion compensation characteristic, a control range of transmission power, and the like.

Thus, a nonlinear distortion compensator having good and stable distortion compensation characteristics can be obtained with a small amount of computation even when the transmission power is changed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a plurality of compensation coefficient storage means for storing compensation coefficients used for compensating a transmission quadrature baseband signal based on its power value. Variable gain amplifying means for amplifying the quadrature modulated output; outputting a control signal for selecting one from the plurality of compensation coefficient storage means; and outputting a gain control signal for controlling the gain of the variable gain amplifying means. This is a nonlinear distortion compensating device having transmission power control means for performing the above operation, and has an effect that a good distortion compensation characteristic can be obtained with a small amount of calculation even when the transmission power is changed.

According to a second aspect of the present invention, there is provided a power calculator for calculating a power value of a transmission quadrature baseband signal, and a plurality of compensation coefficient ROMs (Read Only Memory) for storing compensation coefficients read based on the power value. ), A non-linear distortion compensator that performs non-linear distortion compensation of a transmission orthogonal baseband signal using the compensation coefficient, a D / A converter that performs an analog conversion of an output of the non-linear distortion compensator, and the D / A converter And a variable gain amplifier for amplifying the output of the quadrature modulator, and a compensation coefficient RO to be used.
A transmission power control unit that outputs a control signal for switching M and changes the gain of the variable gain amplifier, and provides good distortion compensation characteristics even when the transmission power is changed. It has the action of:

Further, as in the invention according to claim 3,
3. The nonlinear distortion compensator according to claim 2, further comprising a variable gain amplifier between the nonlinear distortion compensator and the D / A converter, the gain being changed by a control signal from the transmission power controller. Thus, the second embodiment has the same operation as that of the second embodiment, and also has the operation that the resolution of the D / A converter can be effectively used even when the compensation coefficient ROM is switched.

According to a fourth aspect of the present invention, there is provided a power calculation unit for calculating a power value of a transmission quadrature baseband signal, a plurality of compensation coefficient ROMs for storing compensation coefficients read based on the power value, A nonlinear distortion compensator that performs nonlinear distortion compensation on a transmission orthogonal baseband signal using a coefficient, a quadrature modulator that orthogonally modulates an output of the nonlinear distortion compensator, and a D / A that converts an output of the quadrature modulator into an analog signal.
A nonlinear amplifier having a converter, a variable gain amplifier for amplifying an output of the D / A converter, and a transmission power control unit for outputting a control signal for switching a compensation coefficient ROM to be used and changing a gain of the variable gain amplifier; This is a distortion compensator, which performs digital processing on the quadrature modulation unit, so it can remove quadrature errors and DC offsets that lead to degradation of distortion compensation characteristics, and provide good distortion compensation even when the transmission power is changed. It has the effect that characteristics can be obtained.

Further, as in the invention according to claim 5,
5. The nonlinear distortion compensator according to claim 4, further comprising a variable gain amplifier whose gain changes according to a control signal from the transmission power controller between the quadrature modulator and the D / A converter. In addition to having the same operation as that of the fourth aspect, the present invention has the effect that the resolution of the D / A converter can be effectively used even when the compensation coefficient ROM is switched.

According to a sixth aspect of the present invention, there is provided a wireless communication system using the nonlinear distortion compensator according to any one of the first to fifth aspects. In addition, a system having a nonlinear distortion compensator having good and stable distortion compensation characteristics can be constructed with a small amount of calculation.

An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a transmitting apparatus using a nonlinear distortion compensating apparatus according to an embodiment of the present invention. 101 is a quadrature baseband signal, 10
2 is a power calculator, 103 is a compensation coefficient ROM, 104 is a nonlinear distortion compensator, 105 is a D / A converter, 106 is a quadrature modulator, 107 is a variable gain amplifier, 108 is a transmission power amplifier, 109 is an antenna, 110 Is a transmission power control unit.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the power value of the transmission quadrature baseband signal 101 is calculated by the power calculator 1
The compensation coefficient for compensating for the nonlinear distortion is called from the compensation coefficient ROM 103 using the power value as an address. A plurality of compensation coefficient ROMs are prepared, and each ROM stores a compensation coefficient with the best distortion compensation characteristic according to the value of the transmission power. Then, based on the control signal from the transmission power control unit 110, the optimum compensation coefficient ROM is selected for the transmission power at that time. The number of the compensation coefficient ROMs 103 is determined according to a required distortion compensation characteristic, a control range of transmission power, and the like.

In the nonlinear distortion compensating section 104, distortion for compensating for nonlinear distortion is added to the transmission orthogonal baseband signal 101 using the compensation coefficient output from the compensation coefficient ROM 103. The orthogonal baseband signal having undergone the nonlinear distortion compensation is converted into an analog signal by the D / A converter 105, and is subjected to orthogonal modulation by the orthogonal modulation unit 106 to generate a modulated signal.

The modulated signal output from quadrature modulator 106 is amplified by variable gain amplifier 107, and the gain of variable gain amplifier 107 is adjusted by a control signal from transmission power controller 110. Then, the output of variable gain amplifier 107 is amplified to a required level in transmission power amplifier 108 and transmitted from antenna 109.

By the above operation, even when the transmission power is changed, a good and stable distortion compensation characteristic can be obtained without requiring many operations.

In FIG. 1, a switch used for switching the compensation coefficient ROM is of a type that is turned on / off for each compensation coefficient ROM. Instead of these switches, one switch is used. A switch of a type for selecting one compensation coefficient ROM may be provided.

(Embodiment 2) FIG. 2 is a block diagram showing a configuration of a transmitting apparatus using a nonlinear distortion compensating apparatus according to an embodiment of the present invention. 201 is a quadrature baseband signal, 20
2 is a power calculator, 203 is a compensation coefficient ROM, 204 is a nonlinear distortion compensator, 205 is a variable gain amplifier, and 206 is D
/ A converter, 207 is a quadrature modulator, 208 is a variable gain amplifier, 209 is a transmission power amplifier, 210 is an antenna,
11 is a transmission power control unit.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the power value of the transmission quadrature baseband signal 201 is calculated by the power calculator 2
The compensation coefficient for compensating for the nonlinear distortion is called from the compensation coefficient ROM 203 using the power value as an address. A plurality of compensation coefficient ROMs are prepared, and each ROM stores a compensation coefficient with the best distortion compensation characteristic according to the value of the transmission power. Then, based on the control signal from the transmission power control unit 211, the optimum compensation coefficient ROM is selected for the transmission power at that time. The number of compensation coefficient ROMs 203 is determined according to a required distortion compensation characteristic, a control range of transmission power, and the like.

In the nonlinear distortion compensator 204, distortion for compensating for nonlinear distortion is added to the transmission orthogonal baseband signal 201 using the compensation coefficient output from the compensation coefficient ROM 203. The non-linear distortion-compensated quadrature baseband signal is supplied to the D / A converter 2 in the variable gain amplifier 205.
It is amplified to a maximum input level of 06. The gain of variable gain amplifier 205 is adjusted by a control signal from transmission power control section 211.

The orthogonal baseband signal converted into an analog signal by the D / A converter 206 is output to the orthogonal modulator 20.
At 7, orthogonal modulation is performed to generate a modulation signal. The modulation signal output from quadrature modulation section 207 is applied to variable gain amplifier 2
08, the gain of the variable gain amplifier 208 is adjusted by a control signal from the transmission power control unit 211.
The output of the variable gain amplifier 208 is amplified to a required level in the transmission power amplifier 209, and
Sent from 0.

With the above operation, even when the transmission power is changed, a good and stable distortion compensation characteristic can be obtained without requiring much calculation, and even when the compensation coefficient ROM is switched, D The resolution of the / A converter can be used effectively.

In FIG. 2, as the switch used for switching the compensation coefficient ROM, a switch which is turned on / off for each compensation coefficient ROM is arranged. Instead of these switches, one switch is used. A switch of a type for selecting one compensation coefficient ROM may be provided.

(Embodiment 3) FIG. 3 is a block diagram showing a configuration of a transmitting apparatus using a nonlinear distortion compensating apparatus according to an embodiment of the present invention. 301 is a quadrature baseband signal, 30
2 is a power calculator, 303 is a compensation coefficient ROM, 304 is a nonlinear distortion compensator, 305 is a quadrature modulator, and 306 is D / A.
A converter, 307 is a variable gain amplifier, 308 is a transmission power amplifier, 309 is an antenna, and 310 is a transmission power control unit.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the power value of the transmission quadrature baseband signal 301 is calculated by the power calculator 3
The compensation coefficient for compensating for the nonlinear distortion is called from the compensation coefficient ROM 303 using the power value as an address. A plurality of compensation coefficient ROMs are prepared, and each ROM stores a compensation coefficient with the best distortion compensation characteristic according to the value of the transmission power. Then, based on the control signal from the transmission power control unit 310, the optimum compensation coefficient ROM is selected for the transmission power at that time. The number of the compensation coefficient ROMs 303 is determined according to a required distortion compensation characteristic, a control range of transmission power, and the like.

In the nonlinear distortion compensator 304, distortion for compensating for nonlinear distortion is added to the transmission orthogonal baseband signal 301 using the compensation coefficient output from the compensation coefficient ROM 303. The orthogonal baseband signal subjected to the nonlinear distortion compensation is orthogonally modulated in the orthogonal modulation section 305 to generate a modulated signal.

The modulated signal output from quadrature modulating section 305 is analog-converted by D / A converter 306, and the analog-converted modulated signal is amplified by variable gain amplifier 307. The gain of variable gain amplifier 307 is adjusted by a control signal from transmission power control section 310. The output of the variable gain amplifier 307 is
At 8, the signal is amplified to a required level and transmitted from the antenna 309.

According to the above operation, even when the transmission power is changed, good and stable distortion compensation characteristics can be obtained without requiring many operations, and the quadrature modulation section is performed by digital processing. Thus, the quadrature error and DC offset are removed, and the distortion compensation characteristics are improved.

In FIG. 3, as the switch used for switching the compensation coefficient ROM, a switch which is turned on / off for each compensation coefficient ROM is arranged. Instead of these switches, one switch is used. A switch of a type for selecting one compensation coefficient ROM may be provided.

(Embodiment 4) FIG. 4 is a block diagram showing a configuration of a transmitting apparatus using a nonlinear distortion compensating apparatus according to an embodiment of the present invention. 401 is a quadrature baseband signal, 40
2 is a power calculator, 403 is a compensation coefficient ROM, 404 is a nonlinear distortion compensator, 405 is a quadrature modulator, 406 is a variable gain amplifier, 407 is a D / A converter, 408 is a variable gain amplifier, and 409 is a transmission power amplifier. , 410 is an antenna, 4
11 is a transmission power control unit.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the power value of the transmission quadrature baseband signal 401 is
The compensation coefficient for compensating for the nonlinear distortion is called from the compensation coefficient ROM 403 using the power value as an address. A plurality of compensation coefficient ROMs are prepared, and each ROM stores a compensation coefficient with the best distortion compensation characteristic according to the value of the transmission power. Then, according to the control signal from the transmission power control unit 411, the optimum compensation coefficient ROM is selected for the transmission power at that time. The number of the compensation coefficient ROMs 403 is determined according to a required distortion compensation characteristic, a control range of transmission power, and the like.

The nonlinear distortion compensator 404 adds distortion for compensating for nonlinear distortion to the transmission quadrature baseband signal 401 using the compensation coefficient output from the compensation coefficient ROM 403. The orthogonal baseband signal, for which nonlinear distortion has been compensated, is orthogonally modulated in an orthogonal modulation section 405 to generate a modulated signal. The modulated signal output from the quadrature modulator 405 is supplied to the D / A converter 4 in the variable gain amplifier 406.
It is amplified to a maximum input level of 07. The gain of variable gain amplifier 406 is adjusted by a control signal from transmission power control section 411.

The modulated signal converted into an analog signal by the D / A converter 407 is amplified by the variable gain amplifier 408, and the gain of the variable gain amplifier 408 is adjusted by a control signal from the transmission power control section 411. Then, the output of variable gain amplifier 408 is amplified to a required level in transmission power amplifier 409 and transmitted from antenna 410.

With the above operation, even when the transmission power is changed, a good and stable distortion compensation characteristic can be obtained without requiring much calculation, and even when the compensation coefficient ROM is switched, D The resolution of the / A converter can be effectively used, and the quadrature modulation unit is digitally processed, so that quadrature errors and DC offsets are removed, thereby improving distortion compensation characteristics.

In FIG. 4, as the switch used for switching the compensation coefficient ROM, a switch which is turned on / off for each compensation coefficient ROM is arranged. Instead of these switches, one switch is used. A switch of a type for selecting one compensation coefficient ROM may be provided.

[0042]

As described above, according to the present invention, a case where a plurality of compensation coefficient storage means are prepared and the transmission power is changed by selecting an optimum compensation coefficient storage means according to the transmission power. Also, a non-linear distortion compensator having good and stable distortion compensation characteristics can be obtained with a small amount of calculation.

Further, by providing a variable gain amplifier in the preceding stage of the D / A converter, the gain is adjusted so that the input signal to the D / A converter becomes the maximum input level, thereby switching the compensation coefficient ROM. Even in this case, the resolution of the D / A converter can be used effectively.

Further, by performing the quadrature modulator by digital processing, the quadrature error and DC offset are removed, and the distortion compensation characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a nonlinear distortion compensator according to an embodiment of the present invention;

FIG. 2 is a configuration block diagram of a nonlinear distortion compensator according to an embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a nonlinear distortion compensator according to an embodiment of the present invention;

FIG. 4 is a block diagram illustrating a configuration of a nonlinear distortion compensator according to an embodiment of the present invention;

FIG. 5 is a configuration block diagram of a conventional nonlinear distortion compensator.

[Explanation of symbols]

 Reference Signs List 101 transmission orthogonal baseband signal 102 power calculation unit 103 compensation coefficient ROM 104 nonlinear distortion compensation unit 105 D / A converter 106 orthogonal modulation unit 107 variable gain amplifier 108 transmission power amplifier 109 antenna 110 transmission power control unit 201 transmission orthogonal baseband signal 202 Power calculation unit 203 Compensation coefficient ROM 204 Nonlinear distortion compensation unit 205 Variable gain amplifier 206 D / A converter 207 Quadrature modulation unit 208 Variable gain amplifier 209 Transmission power amplifier 210 Antenna 211 Transmission power control unit 301 Transmission quadrature baseband signal 302 Power Calculation section 303 Compensation coefficient ROM 304 Nonlinear distortion compensation section 305 Quadrature modulation section 306 D / A converter 307 Variable gain amplifier 308 Transmission power amplifier 309 Antenna 310 Transmission power control section 401 Baseband signal 402 power calculating section 403 compensates the coefficient ROM 404 nonlinear distortion compensating section 405 quadrature modulator 406 variable gain amplifier 407 D / A converter 408 variable gain amplifier 409 the transmission power amplifier 410 antenna 411 transmission power control unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Masayuki Orihashi 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Inside Matsushita Giken Co., Ltd. (72) Akihiko Matsuoka 3-chome, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa No.10 No.1 Matsushita Giken Co., Ltd. F-term (reference) 5K004 AA05 FF02 FF05 5K046 AA05 DD13 EE06 EE32 EE51 EF23 EF26 EF46

Claims (6)

[Claims] A plurality of compensation coefficient storage means for storing a compensation coefficient used for compensating a transmission quadrature baseband signal based on a power value thereof; a variable gain amplifying means for amplifying quadrature-modulated output; A transmission power control means for outputting a control signal for selecting one from the plurality of compensation coefficient storage means and outputting a gain control signal for controlling the gain of the variable gain amplifying means. 2. A power calculator for calculating a power value of a transmission quadrature baseband signal, and a plurality of compensation coefficient ROMs (Res) storing compensation coefficients read out based on the power value.
ad Only Memory), a non-linear distortion compensator for performing non-linear distortion compensation on a transmission orthogonal baseband signal using the compensation coefficient, and a D / D converter for converting the output of the non-linear distortion compensator to analog.
An A converter, a quadrature modulator for quadrature modulating the output of the D / A converter, a variable gain amplifier for amplifying the output of the quadrature modulator, and a control signal for switching a compensation coefficient ROM to be used. A nonlinear distortion compensator comprising: a transmission power controller for changing a gain of a variable gain amplifier. 3. The variable gain amplifier according to claim 2, further comprising a variable gain amplifier whose gain is changed by a control signal from a transmission power control unit, between the nonlinear distortion compensating unit and the D / A converter. Nonlinear distortion compensator. 4. A power calculator for calculating a power value of a transmission quadrature baseband signal; a plurality of compensation coefficient ROMs for storing compensation coefficients read based on the power value;
A nonlinear distortion compensator that performs nonlinear distortion compensation on a transmission orthogonal baseband signal using the compensation coefficient; a quadrature modulator that orthogonally modulates an output of the nonlinear distortion compensator; A / A converter, a variable gain amplifier that amplifies the output of the D / A converter, and a transmission power control unit that outputs a control signal for switching a compensation coefficient ROM to be used and changes the gain of the variable gain amplifier. Non-linear distortion compensating device. 5. The non-linear amplifier according to claim 4, further comprising a variable gain amplifier between the quadrature modulator and the D / A converter, the gain of which changes according to a control signal from the transmission power controller. Distortion compensator. 6. A wireless communication system using the nonlinear distortion compensator according to claim 1.