JP2017208753A - Amplifier circuit and radio communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform distortion compensation in consideration of a frequency difference between bands in a multiband.SOLUTION: An amplifier circuit includes: an arithmetic unit 110; a plurality of distortion compensators 210a, 210b which distortion-compensate a plurality of input signals x, xwhich are frequency converted into a plurality of different frequency bands f, f; a plurality of converters 250a, 250b which frequency-convert a plurality of distortion compensation signals, which are output from the plurality of distortion compensators 210a, 210b, into a plurality of different frequency bands; and an amplifier 130 which amplifies a composite signal obtained by composing the outputs of the plurality of converters 250a, 250b. The arithmetic unit 110 calculates an estimated envelope P of the composite signal from the plurality of input signals, using a frequency difference Δf among the plurality of frequency bands. The plurality of distortion compensators 210a, 210b respectively perform distortion compensation on the basis of the estimated envelope P.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an amplifier circuit and a wireless communication device.

  As disclosed in Patent Document 1, there is an increasing demand for making a wireless communication device compatible with multiband. A multiband wireless communication apparatus amplifies and transmits signals in a plurality of frequency bands using a common amplifier.

  Since the amplifier has non-linear characteristics, it generates signal distortion. Such distortion is compensated by predistortion. Patent Document 1 discloses a plurality of distortion compensation calculation units that perform distortion compensation on signals in a plurality of frequency bands.

  In Patent Document 1, each of the distortion compensation signals output from a plurality of distortion compensation calculation units is modulated by separate orthogonal modulation units. The signals output from the quadrature modulation unit are combined, and the combined signal is amplified by an amplifier.

International Publication No. 2013/118367

  Since distortion due to the amplifier changes depending on the magnitude of power input to the amplifier, in order to obtain sufficient distortion compensation performance, distortion compensation considering the magnitude of power input to the amplifier is desired. From this viewpoint, the distortion compensation disclosed in Patent Document 1 may not provide sufficient distortion compensation performance. In Patent Document 1, only a signal for each frequency band is input to each of the plurality of distortion compensators. For this reason, distortion compensation in each distortion compensator can only consider input power for each frequency band.

  However, in a multiband amplifier circuit, the power input to the amplifier is a combined power of signals in a plurality of bands. The combined power of signals in a plurality of bands varies depending on the frequency difference between the bands. For this reason, in order to accurately consider the magnitude of the power input to the amplifier, it is desirable to consider the frequency difference between the bands.

  One embodiment of the present invention is an amplifier circuit including an amplifier. In the embodiment, the amplifier circuit includes a plurality of distortion compensators that perform distortion compensation on a plurality of input signals that are frequency-converted to a plurality of different frequency bands, and a plurality of distortion compensation signals that are output from the plurality of distortion compensators. And a plurality of converters that perform frequency conversion to the frequency band. The amplifier amplifies a combined signal obtained by combining the outputs of the plurality of converters.

  The computing unit computes an estimated envelope of the synthesized signal from a plurality of the input signals using frequency differences between the plurality of frequency bands. The plurality of distortion compensators each perform distortion compensation based on the estimated envelope.

  Another aspect of the present invention is a communication device including the signal processing device.

  According to the present invention, distortion compensation can be performed in consideration of a frequency difference between bands.

It is a block diagram of the radio | wireless communication apparatus provided with the amplifier circuit. It is a block diagram of the synthetic | combination power calculator for 2 input signals. It is explanatory drawing of two frequency bands. It is a block diagram of the synthetic | combination power calculator for 3 input signals. It is explanatory drawing of three frequency bands. It is explanatory drawing of the modification of an estimation envelope calculation. It is explanatory drawing of two frequency bands.

[1. Outline of Embodiment]
(1) The amplifier circuit according to the embodiment is output from an arithmetic unit, a plurality of distortion compensators for compensating distortion of a plurality of input signals that are frequency-converted into a plurality of different frequency bands, and a plurality of the distortion compensators. A plurality of converters for frequency-converting a plurality of distortion compensation signals to a plurality of different frequency bands; and an amplifier for amplifying a combined signal obtained by combining the outputs of the plurality of converters. The computing unit computes an estimated envelope of the synthesized signal from a plurality of the input signals using frequency differences between the plurality of frequency bands. The plurality of distortion compensators each perform distortion compensation based on the estimated envelope. In this case, each of the plurality of distortion compensators performs distortion compensation based on the calculation of the estimated envelope calculated using the frequency difference between the plurality of frequency bands. Distortion compensation is performed.

(2) It is preferable that the computing unit computes the estimated envelope by further using phase differences in the output signals of the plurality of converters. Considering the phase difference, distortion compensation is more appropriate.

(3) The estimated envelope is preferably a signal having a sampling frequency lower than a sampling frequency corresponding to a frequency difference between a plurality of frequency bands. In this case, an increase in sampling frequency can be suppressed.

(4) The estimated envelope calculated by the calculator is preferably a signal having the same sampling frequency as the highest sampling frequency among the sampling frequencies of the plurality of input signals input to the plurality of distortion compensators. . In this case, the sampling frequency is optimized.

(5) The plurality of input signals include a first input signal having a first sampling frequency which is the highest sampling frequency among sampling frequencies of the plurality of input signals input to the plurality of distortion compensators, and a first sampling frequency. A second signal having a lower second sampling frequency, and the computing unit computes the estimated envelope from a plurality of the input signals including the second signal up-sampled to the first sampling frequency. Is preferred. In this case, the estimated envelope can be calculated even if the sampling frequency of the input signal is different.

(6) A wireless communication device according to the embodiment includes the amplifier circuit according to any one of (1) to (5).

[2. Details of Embodiment]
FIG. 1 shows a wireless communication device 10. The radio communication device 10 is, for example, a mobile base station that communicates with a radio base station or a radio base station. The wireless communication device 10 includes an amplifier circuit 100. The signal amplified by the amplifier circuit 100 is wirelessly transmitted from the antenna 300.

The amplifier circuit 100 is multiband compatible and receives a plurality of input signals x ₁ and x ₂ . The input signals x ₁ and x ₂ are digital baseband signals, for example, and are generated by a baseband processor (not shown). The plurality of input signals x ₁ and x ₂ are signals for different frequency bands, respectively.

In the embodiment, the input signal x ₁ is a complex baseband signal that is frequency-converted into a radio communication signal in the frequency band f ₁ , and the input signal x ₂ is a radio communication in a frequency band f ₂ different from the frequency band f _1. It is a complex baseband signal that is frequency converted to a signal. Frequency frequency band _{f 1} is, for example, a 1GHz band, the frequency band _{f 2} is, for example, a 1.5GHz band. The input signals x ₁ and x _{2 in the} embodiment are digital signals. In this case, both frequency bands f ₁ and f ₂ have a frequency difference of 0.5 GHz.

Input signal _{x 1} is applied to the circuit 200a by the signal processing of the input signal _{x 1} is performed, the input signal _{x 2,} the signal processing for the input signal _{x 2} is applied to the circuit 200b to be performed. Circuit 200a includes a distortion compensator 210a and a frequency converter 250a to perform a predistortion compensation for the input signal _{x 1,} circuit 200b includes a distortion compensator 210b and a frequency converter that performs predistortion compensation before against the input signal _{x 2} 250b is provided.

Distortion compensator 210a embodiments, the digital pre-distortion compensation (Digital Pre-Distortion (DPD) ) for the input signals x _1, and outputs a distortion compensation signal y _1. Distortion compensation signal y ₁ is a digital complex signal. Distortion compensation signal _{y 1} via the digital-to-analog converter (DAC) 230a, is provided to the frequency converter 250a. The frequency converter 250a of the embodiment is a quadrature modulator. Quadrature modulator 250a is to the orthogonal modulation with respect to the distortion compensation signal y _1, and outputs the quadrature-modulated signal of a frequency band f _1.

The distortion compensator 210b and the frequency converter 250b have the same configuration as the distortion compensator 210a and the frequency converter 250a. In other words, the distortion compensator 210b is the digital predistortion compensation on the input signal _{x 2,} and outputs a distortion compensation signal _{y 2.} Compensation signal y ₂ is a digital complex signal. Compensation signal _{y 2} is digital-to-analog converter (DAC) via 230b, is provided to the frequency converter 250b. The frequency converter 250b is a quadrature modulator. Quadrature modulator 250b is to the orthogonal modulation with respect to the distortion compensation signal y _2, and outputs a quadrature modulation signal of the frequency band f _2.

The quadrature modulators 250 a and 250 b obtain a local signal for quadrature modulation from the frequency synthesizer 500. The frequency synthesizer 500 generates a local signal (frequency f _L1 ) for the quadrature modulator 250a and a local signal (frequency f _L2 ) for the quadrature modulator 250b. The frequency of the local signal generated by the frequency synthesizer 500 is controlled by the controller 400.

  The frequency synthesizer 500 generates a plurality of local signals using a common reference oscillator 510. For this reason, the temporal change of the phase difference between the plurality of local signals is prevented. As a result, the temporal change of the phase difference between the plurality of orthogonal modulation signals is also prevented.

  The plurality of quadrature modulation signals are synthesized by the synthesizer 120. The combined signal output from the combiner 120 is amplified by the amplifier 130.

Of formula (1-1) below, shows an example of a generation equation of the distortion compensation signal _{y 1} by the distortion compensator 210a, formula (1-2), the distortion compensation signal _{y 2} by the distortion compensator 210b for generating formula An example is shown.

Here, * [n] represents a digital signal at time n × T when the sampling interval is T (seconds). x ₁ [n] and x ₂ [n] are digital signal representations of the input signals x ₁ and x ₂ , and y ₁ [n] and y ₂ [n] are digital signals of the distortion compensation signals y ₁ and y ₂ . Signal representation.

In Expression (1-1) and Expression (1-2), Δf is a frequency band f ₂ (f ₂ is a center frequency of the band) and a frequency band f ₁ (f ₁ is a center frequency of the band). The difference (f ₂ −f ₁ ) is shown. Δθ represents the phase theta ₂ of the frequency band _{f 2} of the signal, the phase theta ₁ of the frequency band _{f 1} of the signal, the difference a (θ ₂ -θ _1).

The meanings of symbols in formula (1-1) are as follows.
M _1,1 : Maximum value of relative number of preceding samples M _1,2 : Maximum value of relative number of delayed samples K _{1, m} : Maximum order of characteristics of amplifier 130 h _{1, k, m} : Distortion compensation coefficient

The meanings of symbols in formula (1-2) are as follows.
M _2,1 : Maximum value of relative number of preceding samples M _2,2 : Maximum value of relative number of delayed samples K _{2, m} : Maximum order of characteristics of amplifier 130 h _{2, k, m} : Distortion compensation coefficient

As shown in Expression (1-1), the distortion compensator 210a performs distortion compensation on the input signal x ₁ [n−m] using the distortion compensation coefficients h _{1, k, m,} and performs the distortion compensation signal. Generate y ₁ [n]. As shown in Expression (1-2), the distortion compensator 210b performs distortion compensation on the input signal x ₂ [n−m] using the distortion compensation coefficients h _{2, k, and m} to obtain a distortion compensation signal. Generate y ₂ [n].

In Expression (1-1) and Expression (1-2), a portion P of “x ₁ [nm] + x ₂ [nm] · e− ^{j (2πΔf · n + Δθ)} ” is input to the amplifier 130. Is an estimated envelope of the synthesized signal. The estimated envelope P indicates the magnitude of power input to the amplifier 130. The way the signal is distorted by the amplifier 130 is determined by the amount of power input to the amplifier 130. As is clear from the equations (1-1) and (1-2), the distortion compensators 210a and 210b of this embodiment perform distortion compensation based on the estimated envelope P. For this reason, at the time of distortion compensation, the amplifier input power indicated by the estimated envelope P is considered, and the distortion compensation performance is improved.

Based on the estimated envelope P, the distortion compensators 210a and 210b are h _{1, k, m} | x ₁ [n−m] + x ₂ [n−m] · e− ^{j (2πΔf · n + Δθ)} | ^k−1 and _{h 2, k, m | x} 1 [n-m] + x 2 [n-m] · e -j (2πΔf · n + Δθ) | computes the ^k-1 in real time. Distortion compensator 210a, 210b refers to the lookup _{table, h 1, k, m |} x 1 [n-m] + x 2 [n-m] · e -j (2πΔf · n + Δθ) | k-1 and _{h 2, k, m | x} 1 [n-m] + x 2 [n-m] · e -j (2πΔf · n + Δθ) | k-1 may be obtained. Lookup table, the estimated envelope _{P, h 1, k, m} | x 1 [n-m] + x 2 [n-m] · e -j (2πΔf · n + Δθ) | k-1 and _{h 2, k,} ^Assume that the values _m | x ₁ [n−m] + x ₂ [n−m] · e− ^{j (2πΔf · n + Δθ)} | ^k−1 are associated with each other. Distortion compensator 210a, 210b, based on the estimated envelope P, by referring to the look-up _{table, h 1, k, m |} x 1 [n-m] + x 2 [n-m] · e -j ( ^{2πΔf · n + Δθ)} | ^k−1 and h _{2, k, m} | x ₁ [n−m] + x ₂ [n−m] · e− ^{j (2πΔf · n + Δθ)} | ^k−1 .

The estimated envelope P is calculated by the calculator 110. The computing unit 110 estimates the estimated envelope of the combined signal input to the amplifier 130 from the plurality of input signals x ₁ [nm], x ₂ [nm]. As illustrated in FIG. 2A, the arithmetic unit 110 includes an adder 112 and a multiplier 114. The multiplier 114 multiplies the input signal x ₂ [n−m] by e ^{−j (2πΔf · n + Δθ)} . The adder 112 adds the output x ₂ [n−m] · e− ^{j (2πΔf · n + Δθ)} of the multiplier 114 to the input signal x ₁ [n−m]. The output of the adder 112 is an estimated envelope.

In the embodiment, the estimated envelope P is not generated by simply adding the input signals x ₁ [n−m] and x ₂ [n−m], but the input signals x ₁ [n−m], x ₂ [nm] is generated so as to reflect the frequency difference Δf (see FIG. 2B) when the frequency is converted. The power of the frequency-converted composite signal changes depending on the frequency difference Δf, but the estimated envelope in which the frequency difference Δf is reflected by the operation of multiplying the input signal x ₂ [n−m] by e ^{−j (2πΔf · n).} P is generated. The calculator 110 acquires the frequency difference Δf from the controller 400. ^{Incidentally,} calculation of multiplying a ^{e -j (2πΔf · n)} is the input signal _x 2 [n-m] rather, may be performed on the input signal _x 1 [n-m].

In the embodiment, the estimated envelope P is generated also using the phase difference Δθ of the quadrature modulation signals output from the quadrature modulators 250a and 250b. That is, the multiplier 114 multiplies the input signal x ₂ [n−m] by e ^{−j (2πΔf · n + Δθ)} . Since the phase difference Δθ also affects the magnitude of power input to the amplifier 130, the distortion compensation performance can be further improved by taking the phase difference Δθ into consideration.

The phase difference Δθ between the plurality of orthogonal modulation signals is, for example, when the phase of one orthogonal modulation signal is fixed to the first phase θ ₁ and the phase θ ₂ of the other orthogonal modulation signal is rotated 360 °, It can be obtained as θ ₂ −θ ₁ when the distortion due to the amplifier 130 is minimized. The calculation for obtaining the phase difference Δθ is performed by the controller 400, for example. In this case, the arithmetic unit 110 acquires the phase difference Δθ from the controller 400.

  In the present embodiment, the adoption of the common reference oscillator 510 prevents the temporal change in the phase difference Δθ between a plurality of quadrature modulation signals, so the phase difference Δθ may be an initial phase difference.

[3. Modified example]

[3.1 Distortion compensation signal generation formula]
The following formula (2-1) shows a modification of formula (1-1), and formula (2-2) shows a modification of formula (1-2). Expressions (2-1) and (2-2) are expressions suitable when the amplifier 130 is an envelope tracking amplifier (ET amplifier). Using the equations (2-1) and (2-2), not only the memory effect that occurs in the path from the amplifier input port to the output port, but also the memory effect that occurs in the path from the power supply port of the amplifier to the output port. Can be compensated.

The meanings of symbols in the formula (2-1) are as follows.
M _1,1 : Maximum value of the relative number of preceding samples for considering the memory effect generated in the path from the amplifier input port to the output port M _1,2 : Path from the amplifier input port to the output port Maximum value of relative delay samples for taking into account the memory effect occurring in L _{1, m, 1} : Relative for taking into account the memory effect occurring in the path from the power supply port of the amplifier to the output port Maximum number of preceding samples L _{1, m, 2} : Maximum relative number of delayed samples K _{1, m, l} to take into account the memory effect occurring in the path from the power supply port to the output port of the amplifier : Maximum order of characteristics of amplifier 130 h _{1, k, l, m} : Distortion compensation coefficient

The meanings of the symbols in the formula (2-2) are as follows.
M _2,1 : Maximum value of the relative number of preceding samples for considering the memory effect generated in the path from the input port to the output port of the amplifier M _2,2 : Path from the input port to the output port of the amplifier Relative maximum number of delay samples for considering the memory effect occurring in L _{2, m, 1} : Relative for considering the memory effect occurring in the path from the power supply port of the amplifier to the output port Maximum number of preceding samples L _{2, m, 2} : Maximum relative number of delayed samples K _{2, m, l} to take into account the memory effect that occurs in the path from the power supply port to the output port of the amplifier : Maximum order of characteristics of amplifier 130 h _{2, k, l, m} : Distortion compensation coefficient

[3.2 Three frequency bands]
₁ and ₂ correspond to the _two frequency bands f ₁ and f ₂ , but the number of frequency bands that can be supported is not limited to two, and may be three or three or more. FIG. 3A shows an arithmetic unit 110 corresponding to _three frequency bands f ₁ , f ₂ , and f ₃ (see FIG. 3B). 3A includes an adder 116 and a multiplier 118 in addition to the adder 112 and the multiplier 114 shown in FIG. 2A.

The multiplier 114 multiplies the input signal x ₂ [n−m] by e ^{−j (2πΔfa · n + Δθa)} . As shown in FIG. 3B, Δf _a is a frequency difference between the frequency band f ₂ and the frequency band f ₁ . [Delta] [theta] _a is a phase theta ₂ of the frequency band _{f 2} of the signal, the phase theta ₁ of the frequency band _{f 1} of the signal, which is the difference (θ ₂ -θ _1). The adder 112 adds the output x ₂ [n−m] · e− ^{j (2πΔfa · n + Δθa)} of the multiplier 114 to the input signal x ₁ [n−m].

The multiplier 118 multiplies the input signal x ₃ [n−m] by e ^{−j (2πΔfb · n + Δθb)} . As shown in FIG. 3B, Δf _b is a frequency difference between the frequency band f ₃ and the frequency band f ₁ . [Delta] [theta] _b is the phase theta ₃ of the signal of the frequency band _{f 3,} the phase theta ₁ of the frequency band _{f 1} of the signal, which is the difference between (θ ₃ -θ _1). The adder 116 adds the output of the multiplier 118 to the output of the adder 112. The output of the adder 116 is an estimated envelope P.

Incidentally, in order to correspond to three frequency bands, in the amplifier circuit 100, a circuit signal processing for the input signal x ₃ frequency bands f ₃ (distortion compensation and frequency conversion) is performed is provided. The synthesizer 120 also synthesizes the output signal (orthogonal modulation signal in the frequency band f ₃ ) from the circuit that performs signal processing for the input signal x ₃ .

[3.3 Sampling frequency conversion]
The bandwidths of the plurality of frequency bands f ₁ and f ₂ may be different. FIG. 4A shows (a part of) an amplifier circuit 100 suitable for cases where the bandwidths of the plurality of frequency bands f ₁ and f ₂ are different. Here, as an example, as shown in FIG. 4B, the bandwidth BW1 of the frequency band _{f 1} is 20 MHz, it is assumed the bandwidth BW2 of the frequency band _{f 2} is 10 MHz. In this case, the bandwidth BW1 of the input signals _{x 1} to be frequency-converted into a frequency band _{f 1} is 20 MHz, the bandwidth BW2 of the input signal _{x 2} that is frequency-converted to a frequency band _{f 2} is 10 MHz.

The distortion compensators 210a and 210b perform processing with a bandwidth several times the bandwidths BW1 and BW2 of the input signals x ₁ and x _{2 in} order to appropriately perform distortion compensation. Here, it is assumed that the distortion compensators 210a and 210b operate with a bandwidth five times the bandwidths BW1 and BW2 of the input signals x ₁ and x ₂ . In this case, the distortion compensator 210a operates at 20 MHz × 5 = 100 MHz, and the distortion compensator 210b operates at 10 MHz × 5 = 50 MHz. Thus, the sampling frequency of the input signal _{x 1} that is input to the distortion compensator 210a is the sampling frequency of the input signal _{x 2} input 100MHz, and the distortion compensation unit 210b becomes 50 MHz.

Calculator 110, to handle input signals _x 1, _{x 2} of different sampling frequencies, the input signal x2 is up-sampled to 100MHz by upsampler 150. By the upsampling, the sampling frequencies of the plurality of input signals x ₁ and x ₂ are aligned.

  The calculator 110 outputs the estimated envelope P as a 100 MHz signal. The estimated envelope P of 100 MHz is appropriate for the distortion compensator 210a operating at 100 MHz, but not appropriate for the distortion compensator 210b operating at 50 MHz. Therefore, the estimated envelope P is downsampled to 50 MHz by the downsampler 160 before being input to the distortion compensator 210b. Since the estimated envelope P is downsampled, the distortion compensator 210b can operate at a low sampling frequency. Since the distortion compensator 210b can operate at a low sampling frequency, the DAC 230b in the subsequent stage of the distortion compensator 210b can be low in speed and can reduce the cost.

In FIG. 4A, the estimated envelope P output from the computing unit 110 is the same sampling frequency as the highest sampling frequency among the sampling frequencies of the plurality of input signals x ₁ and x ₂ input to the plurality of distortion compensators 210a and 210b. Although it is a (100 MHz) signal, it is not restricted to this. For example, the estimated envelope P may be a signal having a sampling frequency lower than the sampling frequency corresponding to the frequency difference Δf (for example, 500 MHz) between the plurality of frequency bands f ₁ and f ₂ . When the estimated envelope P is a signal having a sampling frequency higher than the sampling frequency corresponding to the frequency difference Δf, the operation speeds of the distortion compensators 210a and 210b and the subsequent DACs 230a and 230b operate at a high speed accordingly. It is necessary and incurs high cost. In particular, when the DACs 230a and 230b are operated at a sampling frequency higher than the sampling frequency corresponding to the frequency difference Δf, the merit divided into the plurality of circuits 200a and 200b is easily lost, so the sampling frequency is as low as possible. Is preferred.

[4. Addendum]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Radio | wireless communication apparatus 100 Amplifier circuit 110 Operation unit 112 Adder 114 Multiplier 116 Adder 118 Multiplier 120 Synthesizer 130 Amplifier 150 Upsampler 160 Downsampler 200a Circuit 200b Circuit 210a Distortion compensator 210b Distortion compensator 230a DAC
230b DAC
250a Quadrature modulator (frequency converter)
250b Quadrature modulator (frequency converter)
300 Antenna 400 Controller 500 Frequency Synthesizer 510 Reference Oscillator

Claims (6)

An arithmetic unit;
A plurality of distortion compensators for compensating distortion of a plurality of input signals that are frequency-converted into different frequency bands;
A plurality of converters for frequency-converting a plurality of distortion compensation signals output from the plurality of distortion compensators into different frequency bands;
An amplifier for amplifying a combined signal obtained by combining the outputs of the plurality of converters;
With
The computing unit computes an estimated envelope of the synthesized signal from a plurality of the input signals using a frequency difference between the plurality of frequency bands,
The plurality of distortion compensators each perform distortion compensation based on the estimated envelope. The amplifying circuit according to claim 1, wherein the computing unit computes the estimated envelope by further using phase differences in output signals of the plurality of converters. The amplifier circuit according to claim 1, wherein the estimated envelope is a signal having a sampling frequency lower than a sampling frequency corresponding to a frequency difference between a plurality of frequency bands. The estimated envelope calculated by the calculator is a signal having the same sampling frequency as the highest sampling frequency among the sampling frequencies of the plurality of input signals input to the plurality of distortion compensators. The amplifier circuit according to any one of the above. The plurality of input signals are lower than the first input signal having the first sampling frequency which is the highest sampling frequency among the sampling frequencies of the plurality of input signals input to the plurality of distortion compensators, and the first sampling frequency. A second signal of a second sampling frequency,
The amplifier circuit according to claim 4, wherein the computing unit computes the estimated envelope from a plurality of the input signals including the second signal upsampled to the first sampling frequency.   A wireless communication device comprising the amplifier circuit according to claim 1.