JP2002300223A - Method and circuit for compensating nonlinear distortion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an ACPR(adjacent-channel leakage power ratio) characteristic over the entire area of an input power level of a high power amplifier. SOLUTION: This compensation circuit has switches 31 and 32 provided in a feedback loop reaching a distortion superimposing part from a distortion extracting part and for making an inputted signal gas through or stopping the inputted signal, a detector 50 for detecting the input power level of the high power amplifier, and a control circuit 60 for fetching an output of the detector 50 and controlling the switches 31 and 32 so as to turn off the switches 31 and 32 when the input power level of the high power amplifier is not higher than the level of a power which the state a characteristic performs nonlinear distortion compensation control deteriorates more than the state the characteristic stops the control in the characteristic of an adjacent-channel power ratio to the input power of the high power amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrature modulation circuit used in a radio transmitter and the like, and more particularly to a non-linear distortion compensating method for compensating non-linear distortion generated when a baseband signal is quadrature-modulated and then subjected to high power amplification. The present invention relates to a nonlinear distortion compensation circuit.

[0002]

2. Description of the Related Art Conventionally, in a quadrature modulation circuit, after a baseband signal is quadrature-modulated, the modulated signal is amplified with high power.
At this time, non-linear amplification is performed to improve power efficiency, and as a result, non-linear distortion occurs in the amplified modulated signal. Therefore, the generated distortion is compensated to linearize the input / output characteristics. As a conventional method for compensating for such non-linear distortion, there is a pre-distortion type non-linear distortion compensation method as shown in FIG.

[0003] In FIG. 9, baseband signals I and Q pass through a distortion compensating operation unit 1 and are supplied to a D / A converter 2 and a D / A converter 2.
The signal is input to the A converter 3, converted into an analog signal here, and input to the quadrature modulator 4. The baseband signals I and Q input to the quadrature modulator 4 are quadrature-modulated.
The high power amplifier (HPA) 5 amplifies the high power and outputs the result. Here, the compensation data table 7 contains the high power amplifier 5
Compensation data created using the results of measuring the non-linear characteristics at the time of amplification in advance is stored in a table. The power calculator 6 calculates the power of the baseband signals I and Q, and outputs the obtained power to the compensation data table 7.

The compensation data table 7 refers to the table according to the power of the baseband signals I and Q, reads out the corresponding compensation data, and outputs it to the distortion compensation calculation unit 1. As a result, the distortion compensation calculation unit 1 adds in advance the baseband signals I and Q that have not been subjected to the quadrature modulation to the D / A converter by adding distortion having an inverse characteristic to cancel the nonlinear distortion generated in the high power amplifier 4. Output to a few.
Therefore, the modulated signal that has been subjected to high power amplification by the high power amplifier 5 does not include nonlinear distortion.

[0005]

In the above-mentioned conventional predistortion type nonlinear distortion compensation system, the compensation data table is referred to in accordance with the power of the baseband signal. There is a disadvantage that the performance of the entire circuit is easily deteriorated due to variations and temperature changes.

Therefore, as shown in FIG. 10, the output of the high power amplifier 5 is branched by a directional coupler 8, the branched output signal is subjected to quadrature demodulation by a quadrature demodulator 9, and then fed back to a compensation data calculation unit 10. There has been proposed a circuit of such a type. The compensation data calculation unit 10 of this circuit multiplies the coefficient according to the feedback information by the data of a built-in compensation data table (similar to the compensation data table 7 in FIG. 9) to apply a correction to the high power amplifier 5. The compensation data with high accuracy is output to the distortion compensation calculation unit 1 irrespective of the variation in the characteristic and the temperature change to reduce the influence of the above-mentioned defect.

However, any of the above-described circuits generates and utilizes pseudo-nonlinear distortion, and thus does not sufficiently solve the above-mentioned disadvantages. Since the digital operation is performed, the circuit scale is increased, and as a result, the power consumption is also increased. Therefore, particularly in a transmitter using a battery as a power source, there is a problem that the operation time is shortened. In order to solve the above problem, the inventor of the present application has proposed a nonlinear distortion compensation circuit shown in FIG. 7 (Japanese Patent Application No. 2000-233631).
This nonlinear distortion compensating circuit includes a directional coupler or splitter 1.
9, 21, a delay circuit or phase shifter 20, an attenuator 13, a subtractor 14, a quadrature demodulator 15, a phase adjuster 22, amplitude adjusters 23 and 24, and subtracters 16 and 17.

The nonlinear distortion compensating circuit includes a quadrature modulator 11
And a high power amplifier (HPA) 12, a directional coupler or splitter 19 is inserted to split the modulated signal output from the quadrature modulator 11, and the split modulated signal is delayed by a delay circuit or a phase shifter. After the phase is appropriately shifted through the unit 20 so as to match the modulated wave phase of the output signal of the attenuator 13, the signal is input to the subtractor 14.

The output of the high power amplifier 12 is also branched by a directional coupler or divider 21, and the branched output is input to the attenuator 13. Further, the nonlinear distortion component obtained from the subtractor 14 is also input to the quadrature demodulation unit 15 after adjusting its phase through the phase adjuster 22. The baseband nonlinear distortion component output from the quadrature demodulator 15 is also passed through the amplitude adjusters 23 and 24 so that the amplitude of the component becomes appropriate, and then the subtracters 16 and 17 are output.
Has been entered. The nonlinear distortion extraction unit 1A that extracts a nonlinear distortion component from a nonlinear high-power amplified modulation signal includes directional couplers or distributors 19 and 21, delay circuits or phase shifters 20, attenuators 13, and subtracters 14. I have.

The input power level versus ACPR (Adjace) in the high power amplifier 12 of the nonlinear distortion compensating circuit shown in FIG.
nt Channel Power Ratio) characteristic, as shown in FIG.
When the input power level of the high power amplifier 12 becomes lower than a certain input level, there is a problem that the ACPR is deteriorated when the distortion compensation control is performed rather than when the distortion compensation control function is stopped.

The cause is considered as follows. First,
In the high power amplifier 12, the variable delay circuit or the phase shifter 20 and the attenuator 13 in FIG. 7 which are variable at the time of the maximum power output at which the most nonlinear distortion occurs are adjusted so that the distortion-free signal cancels out and becomes minimum. After only the nonlinear distortion component appears at the point a with the highest accuracy, the adjustment points of the delay circuit or the phase shifter 20 and the attenuator 13 are fixed as they are. Therefore, the adjustment point gradually shifts as the output power of the high power amplifier 12 moves away from the adjustment level, so that the undistorted signals canceled out by the subtraction in the subtractor 14 are not completely canceled out, and the subtractor 14 The point a, which is the output terminal of, gradually contains not only the non-linear distortion component but also the distortion-free signal that is the output signal of the transmitter.

As a result, when the input power level of the high power amplifier 12 becomes lower than a certain value, up to the distortion-free desired wave component (signal component) is fed back to the input side of the quadrature modulator 11, and the original signal , The level of the desired wave component is reduced, and it is considered that the ACPR is degraded accordingly. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a nonlinear distortion compensation method and a nonlinear distortion compensation circuit having good ACPR characteristics over the entire input power level of a high power amplifier.

[0013]

According to one aspect of the present invention, there is provided a transmitter for orthogonally modulating a baseband signal and then nonlinearly amplifying the power with a high power amplifier. A nonlinear distortion component is extracted from the high power amplified modulation signal, and the nonlinear distortion component is subjected to quadrature demodulation to a baseband region in a state where the phase of the nonlinear distortion component is adjusted. A non-linear distortion compensation method for compensating for non-linear distortion generated when the non-linear high-power amplification is performed by superimposing the input power on the non-linear high-power amplifier. In the characteristic, the state in which the characteristic performs the nonlinear distortion compensation control is lower than the power level at which the characteristic deteriorates compared to the state in which the control is stopped. In this case, the operation of superimposing a distortion component having a phase opposite to that of the distortion component in the baseband region on the baseband signal is stopped.

According to the first aspect of the present invention, a transmitter that performs nonlinear high-power amplification by a high-power amplifier after quadrature-modulating a baseband signal, extracts a nonlinear distortion component from the nonlinear high-power-amplified modulated signal. Then, when the nonlinear distortion component is subjected to quadrature demodulation to the baseband region with the phase adjusted, and the distortion component having the opposite phase to the distortion component in the baseband region is superimposed on the baseband signal to perform the nonlinear high-power amplification. A nonlinear distortion compensation method for compensating nonlinear distortion occurring in the high power amplifier, wherein the input power level of the high power amplifier is a characteristic of an adjacent channel power ratio to the input power of the high power amplifier, and the characteristic performs nonlinear distortion compensation control. If the power level is lower than the power level that deteriorates compared to the state where the control is stopped, the distortion in the baseband region is reduced. Since the distortion component of the opposite phase component so as to stop the operation to be superimposed on the baseband signal, it is possible to obtain a good ACPR characteristics over the entire input power level of the high power amplifier.

According to a second aspect of the present invention, there is provided a transmitter for quadrature-modulating a baseband signal and then performing non-linear high-power amplification by a high-power amplifier. An extraction unit, a quadrature demodulation unit that performs quadrature demodulation in the baseband region with the nonlinear distortion component being phase-adjusted, and a distortion superimposition unit that superimposes a distortion component having an opposite phase to the distortion component in the baseband region on the baseband signal. A non-linear distortion compensating circuit for compensating for non-linear distortion generated when performing the non-linear high-power amplification, wherein the non-linear distortion compensating circuit passes an input signal provided in a feedback loop from the distortion extraction unit to the distortion superimposition unit. Switch means for allowing or blocking, power detection means for detecting the input power level of the high power amplifier, and captures the detection output of the power detection means, The input power level of the high power amplifier deteriorates in the characteristic of the adjacent channel power ratio with respect to the input power in the high power amplifier when the characteristic performs the nonlinear distortion compensation control as compared with the state where the control is stopped. Control means for controlling the switch means so that the switch means is turned off when the power level is equal to or lower than the power level.

According to the second aspect of the present invention, after the baseband signal is quadrature-modulated, the transmitter amplifies nonlinearly and high-power with the high-power amplifier, and extracts the nonlinear distortion component from the modulated signal that has undergone the nonlinear and high-power amplification. A distortion extracting unit, a quadrature demodulation unit that orthogonally demodulates the nonlinear distortion component into a baseband region with the phase adjusted, and a distortion that superimposes a distortion component having an opposite phase to the distortion component of the baseband region on the baseband signal. And a non-linear distortion compensating circuit for compensating for non-linear distortion generated when the non-linear high-power amplification is performed, wherein the signal is provided in a feedback loop from the distortion extraction unit to the distortion superimposing unit and input. Switch means for passing or blocking the power, power detection means for detecting an input power level of the high power amplifier, and a detection output of the power detection means. In the case where the input power level of the high power amplifier is the characteristic of the adjacent channel power ratio with respect to the input power in the high power amplifier, the state in which the characteristic performs nonlinear distortion compensation control is better than the state in which the control is stopped. Control means for controlling the switch means so that the switch means is turned off when the power level is lower than the deteriorating power level, so that good ACPR characteristics can be obtained over the entire input power level of the high power amplifier. it can.

According to a third aspect of the present invention, there is provided a transmitter for quadrature-modulating a baseband signal and then performing non-linear high-power amplification by a high-power amplifier. An extraction unit, a quadrature demodulation unit that performs quadrature demodulation in the baseband region with the nonlinear distortion component being phase-adjusted, and a distortion superimposition unit that superimposes a distortion component having an opposite phase to the distortion component in the baseband region on the baseband signal. A non-linear distortion compensating circuit for compensating for non-linear distortion generated when the non-linear high-power amplification is performed, comprising: a power detection unit for detecting an input power level of the high-power amplifier; and a detection output of the power detection unit. Capture
The input power level of the high power amplifier deteriorates in the characteristic of the ratio of the adjacent channel power to the input power in the high power amplifier when the characteristic performs the nonlinear distortion compensation control compared to the state where the control is stopped. Control means for controlling the function of any one of a plurality of functional elements provided in a feedback loop from the distortion extracting unit to the distortion superimposing unit to be stopped when the power level is equal to or lower than the power level. It is characterized by the following.

According to the third aspect of the present invention, a transmitter for nonlinearly and high-power-amplifying a baseband signal by a high-power amplifier after quadrature-modulating a baseband signal extracts a nonlinear distortion component from the modulated signal with the nonlinear and high-power amplification. A distortion extracting unit, a quadrature demodulation unit that orthogonally demodulates the nonlinear distortion component into a baseband region with the phase adjusted, and a distortion that superimposes a distortion component having an opposite phase to the distortion component of the baseband region on the baseband signal. A non-linear distortion compensating circuit for compensating for non-linear distortion generated when performing the non-linear high power amplification, wherein the power detecting means detects an input power level of the high power amplifier; and Capturing the detected output, wherein the input power level of the high power amplifier is characterized by the characteristic of the adjacent channel power to input power ratio in the high power amplifier. When the power is lower than the power level in which the nonlinear distortion compensation control is performed compared to the state in which the control is stopped, a plurality of loops provided in a feedback loop from the distortion extraction unit to the distortion superimposition unit are provided. And control means for controlling the function of any one of the functional elements to stop, so that good ACPR characteristics can be obtained over the entire input power level of the high power amplifier.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. A nonlinear distortion compensating circuit according to an embodiment of the present invention extracts a nonlinear distortion component from a modulated signal subjected to nonlinear high power amplification by a transmitter that performs nonlinear high power amplification by a high power amplifier after quadrature modulating a baseband signal. Then, when the nonlinear distortion component is subjected to quadrature demodulation to the baseband region with the phase adjusted, and the distortion component having the opposite phase to the distortion component in the baseband region is superimposed on the baseband signal to perform the nonlinear high-power amplification. A nonlinear distortion compensation method for compensating nonlinear distortion occurring in the high power amplifier, wherein the input power level of the high power amplifier is a characteristic of an adjacent channel power ratio to the input power of the high power amplifier, and the characteristic performs nonlinear distortion compensation control. In the case where the power level is lower than the power level deteriorated from the state in which the control is stopped, It is a circuit for implementing a non-linear distortion compensation method characterized by stopping the operation of superimposing the antiphase distortion components of the distortion component in the baseband signal.

FIG. 1 shows a configuration of a nonlinear distortion compensation circuit according to an embodiment of the present invention. The nonlinear distortion compensating circuit according to the present embodiment is different in configuration from the nonlinear distortion compensating circuit shown in FIG. 7 in that the directional coupler or distributor 19 and the delay circuit or the phase shifter in the nonlinear distortion extracting unit 1A in FIG. Vessel 2
0, and a switch which is electronically controllable between the amplitude adjuster 23 and the subtractor 16 and between the amplitude adjuster 14 and the subtractor 17 respectively. 31 and 32, and a detector 5 between the directional coupler or splitter 30 and the switches 31 and 32.
0, a control circuit 60 is provided, and a directional coupler or distributor 3 is provided.
0 is output to the delay circuit or the phase shifter 20, the other output of the directional coupler or splitter 30 is output to the detector 50, and the control circuit 60 is configured based on the output of the detector 50. Since the switches 31 and 32 are controlled in the same manner, and other configurations are the same, the same reference numerals are given to the same reference numerals, and duplicate description will be omitted.

The switches 31 and 32 are interlocked switches, and are simultaneously controlled to be on or off by the control circuit 60, and are normally controlled to be on. The detector 50 includes, for example, as shown in FIG. 2, a rectifying unit including diodes 501 and 502 for rectifying a nonlinear distortion component input from the input terminal 500, a low-pass filter (LPF) including an inductance 503 and a capacitor 504. And an operational amplifier 505 for amplifying the output of the low-pass filter by DC and outputting the amplified output to the control circuit 60 from an output terminal 506. The switches 31 and 32 correspond to switch means of the present invention, the detector 50 corresponds to power detection means of the present invention, and the control circuit corresponds to control means of the present invention.

The control circuit 60 converts the DC output from the detector 50 into an A / D signal as shown in FIG.
An A / D converter 601 for conversion, a digital comparator 602, and a memo 603 are provided. Memory 603
In the characteristic of the adjacent channel power ratio with respect to the input power of the high power amplifier 12, the state in which the characteristic performs the nonlinear distortion compensation control is more deteriorated than the state in which the control is stopped. Data of the reference power level for determining the power level is stored in advance.
This reference power level is, for example, a curve P indicating the ACPR characteristic with respect to the input power of the high power amplifier 12 when the nonlinear distortion compensation control is performed in FIG. 8, and the curve of the high power amplifier 12 when the nonlinear distortion compensation control is not performed. The input power level of the high power amplifier 12 is set at the intersection with the curve Q indicating the ACPR characteristic with respect to the input power.

The control circuit 60 takes in the output of the detector 50 input via the input terminal 600 and performs A / D conversion on the output of the detector by the A / D converter 601. The digital comparator 602 takes in the output of the A / D converter 601 and switches the switches 31 and 32 when the output value of the A / D converter 601 is equal to or less than the value indicating the reference power level stored in the memory 603 in advance. A control signal for turning off is output to the switches 31 and 32 via the output terminal 604.

Note that the configurations of the detection circuit 50 and the control circuit 60 are not limited to the above configurations, but may be other configurations as long as they have the same function. For example, the control circuit 60 compares the output of the detector 50 input to the non-inverting input terminal via the input terminal 700 with the reference voltage input to the inverting input terminal by the variable resistor 701 that generates the reference voltage. An analog comparator configured with the operational amplifier 702 may be used.

In the above configuration, the baseband signals I,
Q is input to the quadrature modulation unit 11 after subtraction of distortion components e and f described later by the subtracters 16 and 17, respectively.
In the quadrature modulator 11, the π generated by the carrier generator 18
After the carrier having undergone the π / 2 phase shift in the / 2 phase shifter 111 and the baseband signal Q are multiplied in the multiplier 112, the adder 1
14 is input.

The baseband signal I is supplied to the carrier generator 1
After being multiplied by the multiplier 113 with the carrier generated in 8, it is further input to the adder 114, added to the output signal of the multiplier 112, and subjected to quadrature modulation. Quadrature modulated signal i
Is branched by a directional coupler or splitter 19, and one branch output is input to the high power amplifier 12 and the other branch output is input to the directional coupler or splitter 30. Here, it is assumed that the input power level in the high power amplifier 12 is higher than the reference power level stored in the memory 603 described above. Therefore, switch 31,
32 is in an ON state.

One branch output of the directional coupler or splitter 30 is input to a delay circuit or phase shifter 20, and the other branch output is input to a detector 50. The high power amplifier 12 outputs the quadrature modulated signal by nonlinear high power amplification (gain K). The output signal j is branched by the directional coupler or splitter 21, and a part of the output signal j is attenuated. 13 and is attenuated (1 / K) by the amplification gain of the high power amplifier 12 to become an output signal k and a subtractor 14
Is input to In the delay circuit or the phase shifter 20,
The phase of the branch output of the input quadrature modulation signal i is appropriately shifted and input to the subtracter 14 in a state where the phase is adjusted to the modulation wave phase of the output signal of the attenuator 13.

In the subtractor 14, the signal k output from the high power amplifier 12 through the directional coupler or splitter 21 and the attenuator 13 and including the nonlinear distortion is converted from the quadrature modulator 11 into the directional coupler or splitter. The quadrature modulated signal 1 without distortion output via the devices 19 and 30, the delay circuit or the phase shifter 20 is subtracted, and only the nonlinear amplification distortion component a is extracted.

This nonlinear amplification distortion component a is input to the multipliers 152 and 153 of the quadrature demodulator 15 after the phase is adjusted by the phase adjuster 22. The carrier g generated by the carrier generator 18 is input to the quadrature demodulation unit 15.
In the quadrature demodulation unit 15, the nonlinear distortion component b output from the phase adjuster 22 is multiplied by the carrier g by the multiplier 152, and is simultaneously multiplied by the carrier m shifted by π / 2 by the π / 2 phase shifter 151. The signals are multiplied and demodulated by the unit 153, and are converted into distortion components e and f in the baseband region via the amplitude adjusters 23 and 24 and the switches 31 and 32, and input to the subtracters 16 and 17.

Therefore, the subtractor 16 preliminarily subtracts the distortion component e generated by the amplifying operation in the high power amplifier 12 from the baseband signal I, so that the baseband signal I on which the inverse distortion component is superimposed is converted to the orthogonal modulation signal. 11 is input. In the subtractor 17, the distortion component f generated by the amplification operation in the high power amplifier 12 is subtracted in advance from the baseband signal Q, so that the baseband signal Q on which the inverse distortion component is superimposed is input to the quadrature modulation unit 11. Is done.

That is, the subtractors 16 and 17 cancel the inverse distortion characteristic in the baseband region generated by orthogonally demodulating the distortion component extracted by the subtractor 14 (a nonlinear distortion component generated at the time of high power amplification). Characteristic)
Can be said to be superimposed on the baseband signal. Therefore, the nonlinear distortion that occurs when the baseband signal on which the inverse distortion component is superimposed is orthogonally modulated by the orthogonal modulator 11 and then nonlinearly and high-power amplified by the high-power amplifier 12 is canceled.

The detector 50 transmits the same quadrature modulated signal as the input terminal of the high power amplifier 12 and a signal having a power level proportional to the power level at the input terminal of the high power amplifier 12. When this signal is detected by the detector 50, a DC voltage proportional to the signal power at the output terminal of the directional coupler or distributor 30, that is, the signal power at the input terminal of the high power amplifier 12, is generated. This DC voltage is input to the control circuit 60.

The control circuit 60 determines that the input power level of the high power amplifier 12 is higher than the input power of the high power amplifier 12 in terms of the ratio of the adjacent channel power to the input power of the high power amplifier 12. The switches 31 and 32 are controlled so that the switches 31 and 32 are turned off when the power is lower than a reference power level which is a power level deteriorated from the state where the control is stopped. As a result, the nonlinear distortion compensation control function is automatically stopped, and the high power amplifier 1
2, the input power to adjacent channel power ratio characteristic is improved.

Therefore, according to the nonlinear distortion compensating circuit according to the present embodiment, when the input power level of the high power amplifier is the characteristic of the adjacent channel power ratio with respect to the input power in the high power amplifier, the characteristic is the nonlinear distortion compensation. When the control is performed at a power level lower than the power level degraded from the control stopped state, the operation of superimposing the distortion component having the opposite phase to the distortion component in the baseband region on the baseband signal is stopped. As a result, good ACPR characteristics can be obtained over the entire range of the input power level of the high power amplifier.

Next, the configuration of a nonlinear distortion compensating circuit according to another embodiment of the present invention is shown in FIG. The nonlinear distortion compensating circuit according to the present embodiment is different in configuration from the nonlinear distortion compensating circuit shown in FIG. 1 in that the output of the quadrature modulator 11 is replaced with the directional coupler or the splitters 19 and 30 in FIG. The signal is converted to a high power amplifier 12, a delay circuit or a phase shifter 2
0, a three-way distributor for distributing to the three directions of the detector 50 is provided, and the other configuration is the same. According to the linear distortion compensation circuit according to the present embodiment, the same effects as those of the linear distortion compensation circuit shown in FIG. 1 can be obtained.

Next, FIG. 6 shows a configuration of a nonlinear distortion compensating circuit according to still another embodiment of the present invention. The non-linear distortion compensating circuit according to the present embodiment differs from the non-linear distortion compensating circuit shown in FIG. 1 in configuration in that the directional couplers or distributors 19 and 30 in FIG. Devices 19 and 80 are provided, and the output signal of the quadrature modulator 11 is branched by the directional coupler or splitter 80 into the directional coupler or splitter 19 and the detector 50.
By arranging the signal input to the directional coupler or the splitter 19 to be branched and input to the high power amplifier 12 and the delay circuit or the phase shifter 20, the output signal of the quadrature modulation unit 11 can be converted to the high power. It is distributed to the amplifier 12, the delay circuit or the phase shifter 20, and the detector 50, and the other configuration is the same. The linear distortion compensation circuit according to the present embodiment also
An effect similar to that of the linear distortion compensation circuit shown in FIG. 1 can be obtained.

In each of the above embodiments, the signal on the input side of the high power amplifier 12 is detected and input to the control circuit 60. However, the present invention is not limited to this. Alternatively, the signal on the output side of 12 may be branched, detected, and input to the control circuit 60. Further, although the detector of FIG. 2 is of a half-wave rectification type, it may be of a full-wave rectification type. Further, the low-pass filter (LPF) constituting the detector of FIG. 2 may have a circuit configuration other than that shown here.

In the nonlinear distortion compensating circuits according to the above embodiments, a switch for passing or blocking an input signal is provided in a feedback loop from a distortion extracting section to a distortion superimposing section, and a quadrature modulated signal is provided. A detector as power detection means for detecting the input power level of the high power amplifier for nonlinearly amplifying the control signal, and a control circuit as control means for controlling the switch, wherein the control circuit captures the output of the detector, In the characteristics of the input power level of the high power amplifier to the adjacent channel power ratio with respect to the input power in the high power amplifier, the power degraded when the characteristic performs nonlinear distortion compensation control is lower than when the control is stopped. Although the switch is controlled so that the switch is turned off when the level is equal to or lower than the level, the present invention is not limited to this.

For example, in the nonlinear distortion compensating circuit according to each of the above embodiments, instead of providing a switch for connecting or disconnecting the feedback loop in a feedback loop for feeding back the nonlinear distortion component generated by the high power amplifier, the high-power amplifier is used. In the characteristics of the ratio of the adjacent channel power to the input power in the high power amplifier, the input power level of the power amplifier deteriorates in the state where the characteristic performs the nonlinear distortion compensation control as compared with the state where the control is stopped. In the following case, the control means is configured to control so as to stop the function of any one of a plurality of functional elements provided in a feedback loop from the distortion extracting unit to the distortion superimposing unit. Also, the same effects as those of the nonlinear distortion compensating circuits according to the above embodiments can be obtained.

[0040]

As described above, according to the first aspect of the present invention, after quadrature modulating a baseband signal,
A transmitter for non-linear high-power amplification by a high-power amplifier, extracting a non-linear distortion component from the non-linear and high-power amplified modulation signal, quadrature demodulating the non-linear distortion component into a baseband region with the phase adjusted, A non-linear distortion compensation method for compensating for non-linear distortion generated when the non-linear high-power amplification is performed by superimposing an anti-phase distortion component of a region distortion component on the baseband signal, wherein the input power level of the high power amplifier is However, in the characteristics of the adjacent channel power ratio with respect to the input power in the high power amplifier, when the characteristic is lower than the power level at which the state in which the nonlinear distortion compensation control is performed is more deteriorated than the state in which the control is stopped. Stopping an operation of superimposing a distortion component having a phase opposite to that of the distortion component in the baseband region on the baseband signal. Since the, it is possible to obtain a good ACPR characteristics over the entire input power level of the high power amplifier.

According to the second aspect of the present invention, after the baseband signal is quadrature-modulated, the transmitter amplifies nonlinearly and high-power by the high-power amplifier, and extracts the nonlinear distortion component from the modulated signal subjected to the nonlinear and high-power amplification. A distortion extracting unit, a quadrature demodulation unit that orthogonally demodulates the nonlinear distortion component into a baseband region with the phase adjusted, and a distortion that superimposes a distortion component having an opposite phase to the distortion component of the baseband region on the baseband signal. And a non-linear distortion compensating circuit for compensating for non-linear distortion generated when the non-linear high-power amplification is performed, wherein the signal is provided in a feedback loop from the distortion extraction unit to the distortion superimposing unit and input. Switch means for passing or blocking the power, power detection means for detecting an input power level of the high power amplifier, and a detection output of the power detection means. In the case where the input power level of the high power amplifier is the characteristic of the adjacent channel power ratio with respect to the input power in the high power amplifier, the state in which the characteristic performs nonlinear distortion compensation control is better than the state in which the control is stopped. Control means for controlling the switch means so that the switch means is turned off when the power level is lower than the deteriorating power level, so that good ACPR characteristics can be obtained over the entire input power level of the high power amplifier. it can.

According to the third aspect of the present invention, a transmitter that quadrature-modulates a baseband signal and then non-linearly and high-power-amplifies with a high-power amplifier extracts a non-linear distortion component from the non-linearly high-power-amplified modulated signal. A distortion extracting unit, a quadrature demodulation unit that orthogonally demodulates the nonlinear distortion component into a baseband region with the phase adjusted, and a distortion that superimposes a distortion component having an opposite phase to the distortion component of the baseband region on the baseband signal. A non-linear distortion compensating circuit for compensating for non-linear distortion generated when performing the non-linear high power amplification, wherein the power detecting means detects an input power level of the high power amplifier; and Capturing the detected output, wherein the input power level of the high power amplifier is characterized by the characteristic of the adjacent channel power to input power ratio in the high power amplifier. When the power is lower than the power level in which the nonlinear distortion compensation control is performed compared to the state in which the control is stopped, a plurality of loops provided in a feedback loop from the distortion extraction unit to the distortion superimposition unit are provided. And control means for controlling the function of any one of the functional elements to stop, so that good ACPR characteristics can be obtained over the entire input power level of the high power amplifier.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a specific configuration of the detector in FIG. 1;

FIG. 3 is a block diagram illustrating an example of a configuration of a control circuit in FIG.

FIG. 4 is a circuit diagram showing another example of the configuration of the control circuit in FIG. 1;

FIG. 5 is a block diagram showing a configuration of a nonlinear distortion compensation circuit according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a nonlinear distortion compensation circuit according to still another embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a nonlinear distortion compensation circuit already proposed by the present inventors.

FIG. 8 is a characteristic diagram showing input power versus ACPR characteristics in a high power amplifier used in a transmitter.

FIG. 9 is a block diagram showing a configuration of an example of a conventional nonlinear distortion compensation circuit.

FIG. 10 is a block diagram showing a configuration of another example of a conventional nonlinear distortion compensation circuit.

[Explanation of symbols]

 1A Nonlinear distortion extraction unit 11 Quadrature modulation unit 12 HPA (high power amplifier) 14, 16, 17 Subtractor 15 Quadrature demodulation unit 18 Carrier generator 19, 21, 40 Directional coupler or distributor 23, 24 Amplitude adjuster 30 Variable voltage attenuator 40 Variable phase shifter 50 Detector 60 Control circuit 114 Adder 111, 151 π / 2 phase shifter 112, 113, 152, 153 Multiplier

Continued on the front page F-term (reference) 5J090 AA01 AA41 CA21 FA17 FA18 GN05 GN06 HA19 HA40 HN03 HN04 HN07 HN08 HN15 KA16 KA17 KA23 KA26 KA42 KA55 MA11 SA14 TA01 5K004 AA05 AA05 AA08 FE00 FF05 H06 FF05 JE00 JF04 KK

Claims (3)

[Claims] 1. After orthogonally modulating a baseband signal,
A transmitter for non-linear high-power amplification by a high-power amplifier, extracting a non-linear distortion component from the non-linear and high-power amplified modulation signal, quadrature demodulating the non-linear distortion component into a baseband region with the phase adjusted, A non-linear distortion compensation method for compensating for non-linear distortion generated when the non-linear high-power amplification is performed by superimposing a distortion component having an opposite phase to a distortion component of a region on the baseband signal, wherein an input power level of the high-power amplifier is provided. However, in the characteristics of the adjacent channel power ratio with respect to the input power in the high power amplifier, when the characteristic is lower than the power level at which the state in which the nonlinear distortion compensation control is performed is more deteriorated than the state in which the control is stopped. Stopping the operation of superimposing a distortion component having an opposite phase to the distortion component in the baseband region on the baseband signal. A nonlinear distortion compensation method characterized by the above-mentioned. 2. A distortion extractor for orthogonally modulating a baseband signal and then performing non-linear high-power amplification by a high-power amplifier, wherein the distortion extraction unit extracts a non-linear distortion component from the non-linear and high-power amplified modulation signal; A quadrature demodulation unit that performs quadrature demodulation on the baseband region in a state where the components are phase-adjusted, and a distortion superimposing unit that superimposes a distortion component having an opposite phase to the distortion component on the baseband region on the baseband signal; What is claimed is: 1. A non-linear distortion compensating circuit for compensating for non-linear distortion generated at the time of high-power amplification, comprising: a switch unit that passes or blocks an input signal provided in a feedback loop from the distortion extraction unit to the distortion superimposition unit. Power detection means for detecting an input power level of the high power amplifier; and a detection output of the power detection means, and an input of the high power amplifier. When the power level is equal to or lower than the power level at which the characteristic in which the nonlinear distortion compensation control is performed is worse than the state in which the control is stopped in the characteristic of the adjacent channel power ratio with respect to the input power in the high power amplifier. And a control means for controlling the switch means so that the switch means is turned off. 3. A transmitter for quadrature-modulating a baseband signal and then performing non-linear high-power amplification by a high-power amplifier, a distortion extracting unit for extracting a non-linear distortion component from the non-linear high-power amplified modulation signal, and the non-linear distortion A quadrature demodulation unit that performs quadrature demodulation on the baseband region in a state where the components are phase-adjusted, and a distortion superimposing unit that superimposes a distortion component having an opposite phase to the distortion component on the baseband region on the baseband signal; What is claimed is: 1. A non-linear distortion compensating circuit for compensating for non-linear distortion generated at the time of high power amplification, comprising: power detection means for detecting an input power level of the high power amplifier; Of the input power level of the high power amplifier, the characteristic performs the nonlinear distortion compensation control in the characteristic of the adjacent channel power ratio with respect to the input power. If the operating state is at or below a power level that deteriorates from the state in which the control is stopped, any one of a plurality of functional elements provided in a feedback loop from the distortion extracting unit to the distortion superimposing unit is provided. And control means for controlling so as to stop the function of the element.