JP5371354B2 - Transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter carrying out nonlinear compensation (linearization) by estimating nonlinearity (distortion) of an amplifier in advance to utilize the estimated nonlinearity (distortion) and positively negating the nonlinearity in an input process to the amplifier. <P>SOLUTION: The transmitter includes: an amplifier (11) for generating a first output signal (y) by amplifying a first input signal (u); a gain setting part (12) for generating a second output signal by providing gain to the first input signal; a comparator (13) for generating a comparison signal by comparing the first output signal with the second output signal; and an adder (15) for generating the first input signal by adding a second input signal and the comparison signal to each other. In the transmitter, the amplifier has a nonlinear amplification characteristic; the first output signal includes a distortion amount (d) from an ideal linear characteristic of the amplifier; the gain of the gain setting part follows the ideal linear characteristic of the amplifier; and the comparison signal includes an estimated distortion amount (d') of the distortion amount of the amplifier. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a transmitter that estimates distortion of an amplifier having nonlinear characteristics and performs nonlinear compensation (linearization), and a signal processing method in the transmitter.

  In wireless communication terminals such as cellular phones, amplifiers having excellent power saving and low distortion are required. However, generally, when an amplifier is operated in a so-called non-linear region (saturation region), power saving is improved, but there is a problem that distortion characteristics deteriorate. FIG. 10 is a diagram illustrating an example of non-linearity in the AM-AM characteristic (output amplitude characteristic with respect to input amplitude) of the amplifier, and FIG. 11 is a non-linearity in the AM-PM characteristic (output phase characteristic with respect to input amplitude) of the amplifier. It is a figure which shows an example.

  Uses LUT (Look Up Table) method such as DPD (Digital Pre Distortion) method and feedback control such as Cartesian loop method to reduce amplifier distortion and linearize amplification characteristics. There is a method.

  FIG. 12 is a diagram showing an outline of nonlinear compensation by the DPD method, and FIG. 13 is a diagram showing a schematic circuit configuration of the DPD method. In the DPD type LUT, for example, a correction coefficient using the amplitude of the input signal or the value of (I, Q) as an index is entered. By correcting the value of the input signal using the LUT, it is possible to generate distortion that cancels distortion generated in the power amplifier. FIG. 14 is a diagram showing a specific circuit configuration according to the DPD method. That is, by using the LUT 110, a signal for canceling the distortion of the power amplifier 118 is applied to the input signal to the transmission apparatus by the mixer 113, so that the output signal of the power amplifier 118 is linear with the input signal to the transmission apparatus. (See, for example, Patent Documents 1 to 4).

  FIG. 15 is a diagram showing an outline of feedback control, and FIG. 16 is a diagram showing a schematic circuit configuration of a feedback system for an IQ input signal. In the Cartesian loop system, amplification characteristics are linearized by demodulating an output signal of an amplifier by a demodulator and inputting it to the input side of the transmitter. FIG. 17 is a diagram showing a specific circuit configuration by the Cartesian loop method. That is, an input signal to the transmission device and an output signal of the power amplifier 119 are taken in via the variable gain attenuator 123, and this signal is compared with a signal demodulated by the quadrature demodulator 117 to minimize an amplitude or phase error. In this way, the control circuit 125 controls the variable gain attenuator 123 (see, for example, Patent Documents 5 and 6).

JP 2007-212245 A JP 2005-151119 A JP 2006-197545 A JP 2006-340181 A JP-A-6-268550 Japanese Patent No. 2811961

  However, the conventional DPD LUT does not consider the difference in characteristics between amplifiers and uses a common LUT for each amplifier. However, since the distortion compensation accuracy differs for each amplifier, a certain distortion is caused. It is difficult to obtain compensation accuracy. In addition, although the distortion characteristics are affected by temperature changes or the like, it is difficult for the conventional DPD method to cope with such changes in distortion characteristics. Also, although an adaptive DPD method for rewriting the LUT at any time has been proposed, it is difficult to find an optimal update algorithm for rewriting the LUT at any time.

  In the Cartesian loop method, for example, if there is nonlinear phase distortion in the AM-PM characteristic, there is a problem that it is difficult to stabilize the operation of the control system.

  The present invention was devised in view of such a problem. The nonlinearity (distortion) of the amplifier is estimated in advance, and the estimated nonlinearity (distortion) is used to positively enter the input process to the amplifier. It is to provide a transmitter and a signal processing method for performing nonlinear compensation (linearization) such as AM-AM and AM-PM characteristics by canceling nonlinearity.

In order to solve the above-described problems, the transmitter of the present invention is
An amplifier that amplifies the IQ signal and has a non-linear amplification characteristic ;
An envelope phase calculation unit for calculating an envelope and a phase of an output signal from the IQ signal amplified by the amplifier;
Means for controlling the power supply voltage of the amplifier from the envelope calculated by the envelope phase calculation unit and the envelope of the IQ signal before amplification;
A phase compensator for compensating the phase of the IQ signal before amplification based on the phase calculated by the envelope phase calculation unit so as to perform nonlinear compensation of the amplifier in response to input of the IQ signal. And

In addition, a low-frequency amplifier for low-frequency amplification of the signal obtained from the envelope calculated by the envelope phase calculation unit and the envelope of the IQ signal before amplification,
It is desirable to control the power supply voltage of the amplifier with a signal output from the low frequency amplifier .

  According to the present invention, the output signal of the amplifier having the nonlinear characteristic is compared with the output signal of the gain setting unit having the ideal characteristic of the amplifier, the estimated distortion amount of the amplifier is calculated, and the estimated distortion amount is supplied to the amplifier. By adding to the input, the non-linearity (distortion) of the amplifier is estimated in advance, and the non-linearity is positively canceled in the input process to the amplifier using the estimated non-linearity (distortion). Nonlinear compensation (linearization) such as AM-PM characteristics can be performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a circuit configuration of a transmitter according to an embodiment of the present invention. The transmitter 10 includes an amplifier 11, a gain setting unit 12, a comparator 13, an adjustment unit 14, and an adder 15. The amplifier 11 amplifies the input signal u and outputs an output signal y. The amplification characteristic such as AM-AM / AM-PM is non-linear, and an ideal linear characteristic (hereinafter referred to as “ideal characteristic”). )) Is generated. The gain setting unit 12 gives the input signal u a gain according to ideal characteristics when the amplifier 11 is not distorted. The comparator 13 compares the output signal y from the amplifier 11 and the output signal from the gain setting unit 12, and estimates the distortion amount d due to the nonlinear characteristic of the amplifier 11 by the comparison, and estimates the distortion amount d. 'Is to calculate. The adjustment unit 14 multiplies the estimated distortion amount d ′ by a predetermined coefficient in order to adjust the level of the estimated distortion amount d ′ calculated by the comparator 13. The adder 15 adds the input signal r and the signal supplied from the adjustment unit 14, and generates the input signal u so as to cancel the distortion amount d due to the nonlinear characteristic of the amplifier 11.

  The control flow in the transmitter 10 will be described with the input signal u from the adder 15 to the amplifier 11 as a starting point. The adder 15 generates an input signal u and supplies the generated input signal u to the amplifier 11. The amplifier 11 amplifies the supplied input signal u and generates an output signal y including a distortion amount d. The adder 15 supplies the generated input signal u to the gain setting unit 12. The gain setting unit 12 gives the input signal u a gain according to ideal characteristics when the amplifier 11 is not distorted, and supplies the generated signal to the comparator 13. The comparator 13 compares the output signal y from the amplifier 11 with the output signal from the gain setting unit 12, estimates the distortion amount d due to the nonlinear characteristic of the amplifier 11, and calculates the estimated distortion amount d '. The comparator 13 supplies the calculated estimated distortion amount d ′ to the adjustment unit 14. The adjustment unit 14 multiplies the estimated distortion amount d ′ by a predetermined coefficient and supplies the generated signal to the adder 15 in order to adjust the level of the estimated distortion amount d ′ calculated by the comparator 13. The adder 15 adds the input signal r and the signal supplied from the adjustment unit 14, and generates the input signal u so as to cancel the distortion amount d due to the nonlinear characteristic of the amplifier 11.

FIG. 2 is a diagram illustrating a circuit configuration representing an example of the nonlinear characteristic of the amplifier. As shown in FIG. 2, the nonlinear characteristic of the amplifier is modeled by y = u ² . FIG. 3A is a diagram showing the amount of distortion in the circuit configuration. Line a represents the ideal characteristic (linear characteristic) of the amplifier, line b represents the nonlinear characteristic (y = u ² ) of the amplifier, and line c represents the difference (distortion amount) between the ideal characteristic and the nonlinear characteristic. FIG. 3B is a diagram showing the amount of distortion after linearizing the characteristics of the amplifier with the circuit configuration of FIG. Line a represents the ideal characteristic (linear characteristic) of the amplifier, line b represents the characteristic of the amplifier after linearization, and line c represents the difference (distortion amount) between the ideal characteristic and the characteristic after linearization. As shown in FIG. 3B, by linearizing the amplifier characteristics, the ideal characteristics and the amplifier characteristics become close to each other, and the amount of distortion can be reduced. FIG. 4 is a diagram showing the distortion amount when the amplifier characteristic is linearized (linearized) in a finer calculation step than in FIG. 3B. Similarly to FIG. 3B, line a represents the ideal characteristic (linear characteristic) of the amplifier, line b represents the characteristic of the amplifier after linearization, and line c represents the difference between the ideal characteristic and the characteristic after linearization. (Distortion amount). As shown in FIG. 4, the distortion amount can be further reduced as the amplifier characteristics are linearized in smaller calculation steps.

  As described above, according to this embodiment, the output signal of the amplifier having nonlinear characteristics is compared with the output signal of the gain setting unit having ideal characteristics of the amplifier, the estimated distortion amount of the amplifier is estimated, and the estimated distortion By adding the quantity to the input to the amplifier, the nonlinearity (distortion) of the amplifier is estimated in advance, and the nonlinearity (distortion) is positively canceled in the input process to the amplifier by using the estimated nonlinearity (distortion). Thus, nonlinear compensation (linearization) such as AM-AM and AM-PM characteristics can be performed.

(Second Embodiment)
FIG. 5 is a diagram illustrating a circuit configuration of a transmitter according to an embodiment of the present invention. The transmitter 20 includes a subtracter 16 in addition to the configuration of FIG. The subtracter 16 subtracts the input signal r and the output signal y of the amplifier 11 and supplies the generated signal to the adder 15. Note that the amplifier 11, the gain setting unit 12, the comparator 13, the adjustment unit 14, and the adder 15 have the same functions as those in the configuration of FIG.

  The control flow in the transmitter 20 will be described with the input signal u from the adder 15 to the amplifier 11 as a starting point. The adder 15 generates an input signal u and supplies the generated input signal u to the amplifier 11. The amplifier 11 amplifies the supplied input signal u and generates an output signal y including a distortion amount d. The adder 15 supplies the generated input signal u to the gain setting unit 12. The gain setting unit 12 gives the input signal u a gain according to ideal characteristics when the amplifier 11 is not distorted, and supplies the generated signal to the comparator 13. The comparator 13 compares the output signal y from the amplifier 11 with the output signal from the gain setting unit 12, estimates the distortion amount d due to the nonlinear characteristic of the amplifier 11, and calculates the estimated distortion amount d '. The comparator 13 supplies the calculated estimated distortion amount d ′ to the adjustment unit 14. The adjustment unit 14 multiplies the estimated distortion amount d ′ by a predetermined coefficient and supplies the generated signal to the adder 15 in order to adjust the level of the estimated distortion amount d ′ calculated by the comparator 13. The subtracter 16 subtracts the input signal r and the output signal y of the amplifier 11 and supplies the generated signal to the adder 15. The adder 15 adds the signal supplied from the subtracter 16 and the signal supplied from the adjustment unit 14, and generates the input signal u so as to cancel the distortion amount d due to the nonlinear characteristic of the amplifier 11.

  As described above, according to the present embodiment, the amplifier output signal is fed back to the input signal, so that the nonlinear compensation (linearization) of the amplifier can be performed with higher accuracy.

(Third embodiment)
FIG. 6 is a diagram illustrating a circuit configuration of a transmitter according to an embodiment of the present invention. The transmitter 30 includes a DPD circuit 17 in addition to the configuration of FIG. The DPD circuit 17 applies a signal for canceling the distortion of the amplifier 11 to the input signal u, and supplies the generated signal to the amplifier 11. The amplifier 11, the gain setting unit 12, the comparator 13, the adjustment unit 14, the adder 15, and the subtractor 16 have functions equivalent to the configurations of FIGS. Description is omitted.

  The control flow in the transmitter 30 will be described with the input signal u from the adder 15 to the amplifier 11 as a starting point. The adder 15 generates an input signal u and supplies the generated input signal u to the DPD circuit 17. The DPD circuit 17 applies a signal for canceling the distortion of the amplifier 11 to the input signal u, and supplies the generated signal to the amplifier 11. The amplifier 11 amplifies the signal supplied from the DPD circuit and generates an output signal y including a distortion amount d. The adder 15 supplies the generated input signal u to the gain setting unit 12. The gain setting unit 12 gives the input signal u a gain according to ideal characteristics when the amplifier 11 is not distorted, and supplies the generated signal to the comparator 13. The comparator 13 compares the output signal y from the amplifier 11 with the output signal from the gain setting unit 12, estimates the distortion amount d due to the nonlinear characteristic of the amplifier 11, and calculates the estimated distortion amount d '. The comparator 13 supplies the calculated estimated distortion amount d ′ to the adjustment unit 14. The adjustment unit 14 multiplies the estimated distortion amount d ′ by a predetermined coefficient and supplies the generated signal to the adder 15 in order to adjust the level of the estimated distortion amount d ′ calculated by the comparator 13. The subtracter 16 subtracts the input signal r and the output signal y of the amplifier 11 and supplies the generated signal to the adder 15. The adder 15 adds the signal supplied from the subtracter 16 and the signal supplied from the adjustment unit 14, and generates the input signal u so as to cancel the distortion amount d due to the nonlinear characteristic of the amplifier 11.

  As described above, according to the present embodiment, the DPD circuit applies a signal that cancels out the nonlinear characteristic of the amplifier to the input signal to the amplifier, thereby performing nonlinear compensation (linearization) of the amplifier with higher accuracy. It can be carried out.

(Fourth embodiment)
FIG. 7 is a diagram illustrating a circuit configuration of a transmitter according to an embodiment of the present invention. The transmitter 40 includes an amplifier 41, an IQ modulator 42, an IQ demodulator 43, a first amplitude phase calculator 44, a second amplitude phase calculator 45, a first comparator 46, and a second comparator. 47, IQ calculation unit 48, first adjustment unit 49, second adjustment unit 50, first adder 51, and second adder 52. The amplifier 41 amplifies the input signal u and outputs the output signal y. However, the amplification characteristic such as AM-AM / AM-PM is non-linear, and a distortion amount d from the ideal characteristic is generated. The IQ modulation unit 42 and the IQ demodulation unit 43 perform predetermined processes necessary for IQ modulation and IQ demodulation, respectively. The first amplitude phase calculation unit 44 and the second amplitude phase calculation unit 45 respectively calculate the amplitude and phase from the input IQ signal. For the I and Q components of the input signal, the amplitude can be calculated by SQRT (I × I + Q × Q) and the phase can be calculated by arctan (Q / I). The first comparator 46 and the second comparator 47 compare the amplitudes G1 and G2 and the phases θ1 and θ2 supplied from the first amplitude phase calculation unit 44 and the second amplitude phase calculation unit 45, respectively. By this comparison, the distortion amount d due to the nonlinear characteristic of the amplifier 11 is estimated, and ΔG and Δθ are calculated. The IQ calculation unit 48 converts ΔG and Δθ calculated by the first comparator 46 and the second comparator 47 into ΔI and ΔQ of the IQ signal as estimated distortion amounts, and ΔI is sent to the first adjustment unit 49 as ΔQ Is supplied to the second adjustment unit 50. For ΔG and Δθ, ΔI can be calculated by ΔG × cos Δθ, and ΔQ can be calculated by ΔG × sin Δθ. The first adjustment unit 49 and the second adjustment unit 50 respectively multiply ΔI and ΔQ by predetermined coefficients in order to adjust the levels of ΔI and ΔQ supplied from the IQ calculation unit 48. The first adder 51 and the second adder 52 add the I and Q components of the input signal and the signals from the first adjustment unit 49 and the second adjustment unit 50, respectively. The input signal u is generated so as to cancel the distortion amount d due to the characteristics.

  The control flow in the transmitter 40 will be described starting from the input signal from the first adder 51 and the second adder 52 to the amplifier 41 through the IQ modulator 42. The IQ modulator 42 performs IQ modulation on the input signal to generate an input signal, and supplies the generated input signal to the amplifier 41. The amplifier 41 amplifies the supplied input signal and generates an output signal including the distortion amount d. The first adder 51 and the second adder 52 supply the input signal to the first amplitude / phase calculation unit 44. The first amplitude phase calculation unit 44 calculates the amplitude and phase when the input signal is given a gain according to ideal characteristics when the amplifier 11 is not distorted with respect to the input signal, and the calculated amplitude and phase are calculated. Are supplied to the first comparator 46 and the second comparator 47, respectively. The IQ demodulator 43 performs IQ demodulation on the output signal y and supplies the demodulated signal to the second amplitude phase calculator. The second amplitude phase calculation unit 45 calculates the amplitude and phase of the input signal from the IQ demodulation unit 43 and supplies the calculated amplitude and phase to the first comparator 46 and the second comparator 47, respectively. The first comparator 46 and the second comparator 47 compare the amplitude and the phase supplied from the first amplitude phase calculation unit 44 and the second amplitude phase calculation unit 45, respectively, and the amount of distortion due to the nonlinear characteristic of the amplifier 41 d is estimated, and ΔG and Δθ are calculated. The first comparator 46 and the second comparator 47 supply the calculated estimated distortion amounts ΔG and Δθ to the IQ calculator 48, respectively. The IQ calculation unit 48 converts the estimated distortion amounts ΔG and Δθ calculated by the first comparator 46 and the second comparator 47 into ΔI and ΔQ of the IQ signal as the estimated distortion amount, and ΔI is converted into the first adjustment unit 49. In addition, ΔQ is supplied to the second adjustment unit 50. In order to adjust the levels of ΔI and ΔQ supplied from the IQ calculation unit 48, the first adjustment unit 49 and the second adjustment unit 50 respectively multiply ΔI and ΔQ by a predetermined coefficient, and first add the generated signals. To the second adder 52 and the second adder 52. The first adder 51 and the second adder 52 add the I and Q components of the input signal and the signals from the first adjustment unit 49 and the second adjustment unit 50, respectively. The input signal u is generated so as to cancel the distortion amount d due to the characteristics.

  Thus, according to the present embodiment, nonlinear compensation (linearization) of the amplifier can be performed in response to the IQ-modulated input signal.

(Fifth embodiment)
FIG. 8 shows a circuit configuration when the present invention is applied to EER (Envelop Elimination and Restoration) polar modulation. Note that EER is one of the methods for improving the efficiency of the amplifier, and always performs the saturation operation of the amplifier. The transmitter 60 includes a first amplifier 61, a second amplifier 62, a detection unit 63, a limiter unit 64, an envelope detection unit 65, a subtractor 66, and an adder 67. The first amplifier 61 amplifies the input signal and outputs the output signal. However, the amplification characteristic such as AM-AM / AM-PM is non-linear, and a distortion amount from the ideal characteristic is generated. The second amplifier 62 is a low-frequency amplifier and supplies a bias signal to be supplied to the first amplifier 61. The detector 63 extracts an envelope (envelope component) of the input signal and supplies the envelope signal to the second amplifier 62. The limiter unit 64 removes the amplitude and fluctuation of the input signal, generates a signal whose phase changes with a constant amplitude, and supplies the signal to the first amplifier 62. The envelope detector 65 extracts the envelope of the output signal of the first amplifier 61 and supplies the signal to the subtractor 66. The subtractor 66 subtracts the bias signal from the second amplifier 62 and the envelope signal from the envelope detector 65 and supplies the generated signal to the adder 67. The adder 67 adds the bias signal from the second amplifier 62 and the signal supplied from the subtractor 66 and supplies the generated signal to the first amplifier 61.

  As described above, according to the present embodiment, it is possible to perform nonlinear compensation (linearization) of the amplifier while corresponding to EER polar modulation and operating the amplifier in a saturated state.

(Sixth embodiment)
FIG. 9 shows a circuit configuration when the present invention is applied to digital EER polar modulation. The transmitter 70 includes a first amplifier 71, a second amplifier 72, a signal processing unit 73, a DA conversion unit 74, an IQ phase compensation unit 75, a digital modulator 76, a frequency synthesizer 77, and an IQ demodulation unit. 78, an envelope phase calculation unit 79, a subtraction unit 80, and an addition unit 81. The first amplifier 71 amplifies the input signal and outputs the output signal. However, the amplification characteristic such as AM-AM / AM-PM is non-linear, and a distortion amount from the ideal characteristic is generated. The second amplifier 72 is a low frequency amplifier and supplies a bias signal to be supplied to the first amplifier 61. The DA converter 74 extracts the envelope (envelope component) of the input signal and supplies the envelope signal to the adder 81. Phase compensation is performed on the signal supplied from the IQ phase compensation unit 73, and the generated signal is supplied to the digital modulator 76. The digital modulator 76 digitally modulates the signal supplied from the IQ phase compensator 75 in accordance with the signal from the frequency synthesizer 77 and supplies the generated signal to the first amplifier 71. The IQ demodulator 78 performs IQ demodulation on the output signal of the first amplifier 71 and supplies the generated signal to the envelope phase calculator 79. The envelope phase calculation unit 79 calculates the envelope and phase of the signal supplied from the IQ demodulation unit, and supplies the calculated value to the subtracter 80. The subtracter 80 subtracts the signal from the DA conversion unit 74 and the envelope calculation value from the envelope phase calculation unit 79 and supplies the generated signal to the adder 81. The adder 81 adds the signal from the DA converter 74 and the signal supplied from the subtractor 80 and supplies the generated signal to the second amplifier 72.

  As described above, according to the present embodiment, non-linear compensation (linearization) of the amplifier is performed corresponding to EER polar modulation, always operating the amplifier in a saturated state, and corresponding to the input of the IQ signal. Can do.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure.

  For example, as a method for performing nonlinear compensation by the DPD method and feedback control, as shown in FIG. 18, the DPD circuit only performs linearization of the phase, and the form in which the amplitude is compensated by a feedback loop is also conceivable. Normally, the system tends to be unstable (is likely to oscillate) when trying to compensate for nonlinear distortion with a linear compensation circuit. However, by performing nonlinear distortion of the phase with a DPD circuit, This is because stable control can be performed even with a linear compensation circuit. According to the present embodiment, since the DPD circuit only needs to perform phase compensation, the configuration becomes simpler and the power saving can be improved as compared with the combination of the conventional DPD method and Cartesian method.

It is a figure which shows the circuit structure of the transmitter which concerns on one Embodiment of this invention. It is a figure which shows the circuit structure showing an example of the nonlinear characteristic of an amplifier. It is a figure which shows an example of the distortion amount of the circuit structure concerning one Embodiment of this invention. It is a figure which shows an example of the distortion amount of the circuit structure concerning one Embodiment of this invention. It is a figure which shows the circuit structure of the transmitter which concerns on one Embodiment of this invention. It is a figure which shows the circuit structure of the transmitter which concerns on one Embodiment of this invention. It is a figure which shows the circuit structure of the transmitter which concerns on one Embodiment of this invention. It is a figure which shows the circuit structure at the time of applying this invention to EER polar modulation. 1 shows a circuit configuration when the present invention is applied to digital EER polar modulation. It is a figure which shows an example of the nonlinear in the AM-AM characteristic of an amplifier. It is a figure which shows an example of the nonlinearity in the AM-PM characteristic of an amplifier. It is a figure which shows the outline | summary of the nonlinear compensation by a DPD system. It is a figure which shows the schematic circuit structure of a DPD system. It is a figure which shows the specific circuit structure by a DPD system. It is a figure which shows the outline | summary of feedback control. It is a figure which shows the schematic circuit structure of the feedback system with respect to IQ input signal. It is a figure which shows the specific circuit structure by a Cartesian loop system. It is a figure which shows an example of the nonlinear compensation by DPD system and feedback control.

Explanation of symbols

10, 20, 30, 40, 60, 70 Transmitter 11, 41 Amplifier 12 Gain setting unit 13 Comparator 14 Adjustment unit 15, 67, 81 Adder 16, 66, 80 Subtractor 17 DPD circuit 44 First amplitude phase calculation Unit 45 second amplitude phase calculation unit 46 first comparator 47 second comparator 49 first adjustment unit 50 second adjustment unit 51 first adder 52 second adder 61, 71 first amplifier 62, 72 second amplifier 65 Envelope detector 79 Envelope phase calculator

Claims (2)

An amplifier that amplifies the IQ signal and has a non-linear amplification characteristic ;
An envelope phase calculation unit for calculating an envelope and a phase of an output signal from the IQ signal amplified by the amplifier;
Means for controlling the power supply voltage of the amplifier from the envelope calculated by the envelope phase calculation unit and the envelope of the IQ signal before amplification;
A phase compensator for compensating the phase of the IQ signal before amplification based on the phase calculated by the envelope phase calculation unit so as to perform nonlinear compensation of the amplifier in response to input of the IQ signal. And transmitter. A low-frequency amplifier for low-frequency amplification of a signal obtained from the envelope calculated by the envelope phase calculation unit and the envelope of the IQ signal before amplification;
2. The transmitter according to claim 1, wherein a power supply voltage of the amplifier is controlled by a signal output from the low frequency amplifier.

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