JP2016119601A - Distortion compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distortion compensation circuit capable of precisely compensating nonlinear distortion which is generated by a power amplifier without being mounted with any digital circuit of a large calculation scale with a simple feedback circuit configuration requiring no quadrature demodulator.SOLUTION: The distortion compensation circuit has a deviation calculation section 12 that analyzes the frequency of a feedback signal Mix2(t) output from an A/D converter 11; based on the analysis result of the frequency, identifies magnitude value Magand phase value θ of an analog signal after down-conversion by a mixer 10; based on the identified magnitude value Magand phase value θ and magnitude value Aand phase value θof a known signal, calculates a gain deviation ΔGain(n) and a phase deviation ΔPhase(n) on a power amplifier 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a distortion compensation circuit that compensates for nonlinear distortion generated in a power amplifier.

A distortion compensation circuit disclosed in the following Non-Patent Document 1 includes a modulation wave generation unit that generates a modulation wave signal, and a D / A converter that converts the modulation wave signal generated by the modulation wave generation unit into an analog signal And using the local signal source that generates the local oscillation signal, the local oscillation signal generated by the local signal source, and upconverting the frequency of the analog modulated wave signal converted by the D / A converter. A first mixer that outputs a high-frequency signal that is a subsequent modulated wave signal, and a power amplifier that amplifies the high-frequency signal output from the first mixer and outputs the amplified high-frequency signal to the antenna.
In addition, the distortion compensation circuit includes a feedback circuit for a high-frequency signal amplified by the power amplifier in order to compensate for nonlinear distortion generated in the power amplifier.

The feedback circuit includes a quadrature demodulator that demodulates the I baseband signal and the Q baseband signal of the modulated wave signal from the high frequency signal amplified by the power amplifier using the local oscillation signal generated by the local signal source, A first A / D converter that converts the I baseband signal demodulated by the demodulator into a digital signal, and a second A / D converter that converts the Q baseband signal demodulated by the quadrature demodulator into a digital signal And an amplifier specific estimator that calculates inverse characteristics of the power amplifier from the two digital signals converted by the first and second A / D converters.
The DPD processing unit of the distortion compensation circuit performs distortion compensation processing on the modulation wave signal generated by the modulation wave generation unit using the inverse characteristic of the power amplifier calculated by the amplifier specific estimation unit, and performs distortion compensation processing after the distortion compensation processing. The modulated wave signal is output to the D / A converter.

  Further, in the distortion compensation circuit disclosed in Patent Document 1 below, the modulation wave signal generated by the modulation wave generation unit is used to improve the accuracy of the inverse characteristic of the power amplifier calculated by the amplifier specific estimation unit. And digital signal processing for matching the timing of the feedback signal output from the feedback circuit.

JP2013-132009A (paragraph number [0011], FIG. 1)

“Development of high-efficiency amplifiers for mobile phone base stations,” SEI Technical Review, January 2010

Since the conventional distortion compensation circuit is configured as described above, in the case of Non-Patent Document 1, in order to calculate the reverse characteristic of the power amplifier, the I baseband of the modulated wave signal from the high-frequency signal amplified by the power amplifier. The quadrature demodulator that demodulates the signal and the Q baseband signal and the two A / D converters need to be mounted, and there is a problem that the circuit scale of the feedback circuit becomes large.
In the case of Patent Document 1, it is possible to improve the accuracy of the reverse characteristic of the power amplifier. However, in order to perform digital signal processing for matching the timing of the modulated wave signal and the feedback signal, a digital circuit having a large operation scale is required. There was a problem that it was necessary to implement.

  The present invention has been made to solve the above-described problems, and can simplify the configuration of the feedback circuit by eliminating the need for a quadrature demodulator or the like, and without mounting a digital circuit having a large calculation scale. An object of the present invention is to obtain a distortion compensation circuit capable of highly accurately compensating for nonlinear distortion generated in a power amplifier.

  The distortion compensation circuit according to the present invention includes a known signal generation unit that sequentially outputs a plurality of known signals having different amplitude values, a first conversion that converts the known signal into an analog signal, and converts the frequency of the analog signal. A power amplifier for amplifying the analog signal whose frequency is converted, an attenuator for attenuating the analog signal amplified by the power amplifier, and a frequency of the analog signal attenuated by the attenuator, A second conversion unit that converts an analog signal into a digital signal, and an amplitude value and a phase value of the analog signal after frequency conversion by the second conversion unit are identified by analyzing the frequency of the digital signal, and the identification is performed Deviation calculation that calculates the gain deviation and phase deviation of the power amplifier corresponding to the amplitude value of the known signal from the amplitude value and phase value and the amplitude value and phase value of the known signal The distortion compensator specifies the gain deviation and the phase deviation corresponding to the amplitude value of the modulated wave signal from the gain deviation and the phase deviation corresponding to each amplitude value calculated by the deviation calculating unit. The distortion compensation process is performed on the modulated wave signal using the specified gain deviation and phase deviation, and the modulated wave signal after the distortion compensation process is output to the first conversion unit.

  According to the present invention, by analyzing the frequency of the digital signal, the amplitude value and phase value of the analog signal after frequency conversion by the second conversion unit are specified, and the specified amplitude value and phase value and the known signal A deviation calculating unit that calculates a gain deviation and a phase deviation of the power amplifier corresponding to the amplitude value of the known signal from the amplitude value and the phase value is provided, and each distortion value is calculated by the deviation calculating unit. The gain deviation and the phase deviation corresponding to the amplitude value of the modulated wave signal are identified from the gain deviation and the phase deviation corresponding to, and distortion compensation for the modulated wave signal is performed using the identified gain deviation and phase deviation. Since it is configured to output the modulated wave signal after distortion compensation processing to the first conversion unit, power amplification is achieved without mounting a large-scale digital circuit or quadrature demodulator. In an effect that can compensate for nonlinear distortion generated with high accuracy.

It is a block diagram which shows the distortion compensation circuit by Embodiment 1 of this invention. It is a hardware block diagram in case the digital circuit part of a distortion compensation circuit is comprised with a computer. It is explanatory drawing which shows the spectrum of the signal of the frequency domain obtained by the Fourier-transform by the Fourier-transform part. It is explanatory drawing which shows the example of preparation of the compensation table by the compensation table preparation part 15. FIG. It is explanatory drawing which shows the example of a change of the frequency of known signal s (t). In explanatory diagram showing an example of a stored by the compensation table creation unit 15 (M × N) number of gain deviation ΔGain corresponding to the amplitude value _{A n (n, f m)} and the phase deviation ΔPhase (n, _{f m)} is there. It is explanatory drawing which shows the example of preparation of the compensation table by the compensation table preparation part 15. FIG.

Hereinafter, in order to describe the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a distortion compensation circuit according to Embodiment 1 of the present invention.
In this distortion compensation circuit, the calibration mode is executed in advance at the stage of creating a compensation table to be referred to when compensating nonlinear distortion generated in the power amplifier, and the calibration mode is completed at the stage of completing the creation of the compensation table. With reference to the compensation table created in step 1, an operation mode for performing distortion compensation processing on the modulated wave signal is performed.

In FIG. 1, a known signal generator 1 operates in a calibration mode, generates a signal of frequency f ₀ (hereinafter referred to as “known signal”) whose amplitude value _An and phase value θ ₀ are known, and Output a known signal.
Here, the phase value θ is identical, the N amplitude values A _n are different (n = 1, ···, N : N is an integer of 2 or more) to generate a known signal, the order of N known signal Shall be output.
The modulated wave generator 2 operates in the operation mode, generates a modulated wave signal, and outputs the modulated wave signal to the distortion compensator 16.
The switch 3 outputs the known signal output from the known signal generator 1 to the D / A converter 5 in the calibration mode, and D / A converts the modulated wave signal after distortion compensation processing by the distortion compensator 16 in the operation mode. Output to the device 5.
Note that a mode notification to the known signal generation unit 1, the modulated wave generation unit 2, and the switch 3 is given from the control unit 20. The control unit 20 may be mounted inside the distortion compensation circuit or may be mounted outside the distortion compensation circuit.
Alternatively, the known signal generation unit 1 and the modulated wave generation unit 2 may be configured to always generate signals without being notified of the mode.

The local signal source 4 generates a local oscillation signal and outputs the local oscillation signal to the mixers 6 and 10.
The D / A converter 5 converts the known signal or modulated wave signal output from the switch 3 into an analog signal.
The mixer 6 upconverts the frequency of the analog signal converted by the D / A converter 5 using the local oscillation signal output from the local signal source 4 and converts the frequency of the analog signal after the frequency conversion into a high frequency signal. The signal is output to the power amplifier 7.
The D / A converter 5 and the mixer 6 constitute a first conversion unit.

The power amplifier 7 amplifies the high frequency signal output from the mixer 6 and outputs the amplified high frequency signal to the output terminal 8 and the attenuator 9.
The output terminal 8 is a terminal that outputs a high-frequency signal amplified by the power amplifier 7, and is connected to an antenna, for example.
The attenuator 9 attenuates the high frequency signal amplified by the power amplifier.
In the first embodiment, an attenuation factor is set in the attenuator 9 so that the amplitude value of the high-frequency signal attenuated by the attenuator 9 matches the amplitude value of the high-frequency signal before being amplified by the power amplifier 7. It shall be.

The mixer 10 uses the local oscillation signal output from the local signal source 4 to down-convert the frequency of the high-frequency signal attenuated by the attenuator 9 and converts the feedback signal, which is an analog signal after frequency conversion, to A / D converter 11 to output.
The A / D converter 11 converts the feedback signal output from the mixer 10 into a digital signal, and outputs the digital feedback signal to the deviation calculation unit 12.
The mixer 10 and the A / D converter 11 constitute a second conversion unit.

The deviation calculation unit 12 includes a Fourier transform unit 13, an amplitude phase identification unit 14, and a compensation table creation unit 15. The deviation calculation unit 12 analyzes the frequency of the feedback signal output from the A / D converter 11, and analyzes the frequency. From this, the amplitude value Mag _n and phase value θ of the analog signal (feedback signal) after down-conversion by the mixer 10 are specified, the specified amplitude value Mag _n and phase value θ, and the amplitude value _An and phase of the known signal. the value theta ₀ Prefecture, carries out a process of calculating a gain deviation of the power amplifier 7 corresponding to the amplitude value _{a n} of the known signal ΔGain (n) and the phase deviation ΔPhase (n).
The Fourier transform unit 13 performs a Fourier transform on the feedback signal output from the A / D converter 11 and performs a process of converting the feedback signal into a frequency domain signal.
The amplitude phase specifying unit 14 searches for the peak value of the signal in the frequency domain converted by the Fourier transform unit 13, and from the peak value, the amplitude value Mag _n and the phase value θ at the frequency f ₀ (analog after frequency conversion by the mixer 10). Processing for specifying the amplitude value Mag _n and the phase value θ) of the signal is performed.
Compensation table creation unit 15 from the amplitude values Mag _n and a phase value theta specified by the amplitude phase identification unit 14, an amplitude value of the known signal A _n and phase value theta ₀ Prefecture, corresponds to the amplitude value A _n of known signals calculating a gain deviation ΔGain of the power amplifier 7 (n) and the phase deviation ΔPhase (n), compensating showing a gain deviation ΔGain of the power amplifier 7 corresponding to each of the amplitude values _{a n} (n) and the phase deviation ΔPhase (n) Implement the process to create a table.

  The distortion compensator 16 detects the amplitude value B of the modulated wave signal generated by the modulated wave generator 2 and corresponds to the amplitude value B from the compensation table created by the compensation table creator 15 of the deviation calculator 12. The gain deviation ΔGain (n) and the phase deviation ΔPhase (n) are read out, and the distortion compensation processing is performed on the modulated wave signal by using the read gain deviation ΔGain (n) and the phase deviation ΔPhase (n). The modulated wave signal after processing is output to the switch 3.

In the example of FIG. 1, each of the known signal generation unit 1, the modulation wave generation unit 2, the deviation calculation unit 12, and the distortion compensation unit 16 that is a component of the digital circuit unit of the distortion compensation circuit is dedicated hardware (for example, CPU However, the digital circuit portion may be configured by a computer.
FIG. 2 is a hardware configuration diagram when the digital circuit portion of the distortion compensation circuit is configured by a computer.
When the digital circuit unit of the distortion compensation circuit is configured by a computer, the processing contents of the known signal generation unit 1, the modulation wave generation unit 2, the deviation calculation unit 12, and the distortion compensation unit 16 are described as shown in FIG. May be stored in the memory 51 of the computer, and the processor 52 of the computer may execute the program stored in the memory 51.

Next, the operation will be described.
In the first embodiment, the distortion compensation circuit includes a calibration mode for creating a compensation table and an operation mode for performing distortion compensation processing on a modulated wave signal.
First, the operation in the calibration mode will be described.
The control unit 20 notifies the known signal generation unit 1 and the switch 3 that the operation mode is the calibration mode.

式（１）において、ｔは時間を表す変数である。 When the known signal generation unit 1 receives a notification from the control unit 20 that the operation mode is the calibration mode, the known signal generation unit 1 outputs a known signal s (t) having a frequency f ₀ at which the amplitude value _An and the phase value θ ₀ are known. The known signal is output to the switch 3 and the compensation table creating unit 15.
At this time, the phase value of the known signal s (t) is identical with theta _0, N pieces of amplitude _{A n} are different: known signal (n = 1, ···, N N is an integer of 2 or more) s (t) is generated, and N known signals s (t) are output in order.
The known signal s (t) generated by the known signal generation unit 1 is expressed as the following formula (1).

In Expression (1), t is a variable representing time.

Since the switch 3 receives the notification that the operation mode is the calibration mode from the control unit 20, when the switch 3 receives the known signal s (t) from the known signal generation unit 1, the switch 3 converts the known signal s (t) to D. / A converter 5 to output.
When receiving the known signal s (t) from the switch 3, the D / A converter 5 converts the known signal s (t) into an analog signal and outputs the analog signal to the mixer 6.
When receiving an analog signal from the D / A converter 5, the mixer 6 uses the local oscillation signal output from the local signal source 4 to up-convert the frequency of the analog signal, and is an analog signal after the up-conversion. The high frequency signal Mix1 (t) is output to the power amplifier 7.
Here, when the frequency of the local oscillation signal output from the local signal source 4 is assumed to be f _RF, high-frequency signal Mix1 (t) output from the mixer 6 is expressed by the following equation (2) .

式（３）において、Ｇ_０は電力増幅器７の線形利得、ΔＧ_ｎは振幅値Ａ_ｎの信号を増幅する場合の電力増幅器７の利得偏差、Δφ_ｎは振幅値Ａ_ｎの信号を増幅する場合の電力増幅器７の位相偏差である。 When receiving the high frequency signal Mix1 (t) from the mixer 6, the power amplifier 7 amplifies the high frequency signal Mix1 (t) and outputs the amplified high frequency signal P _out (t) to the output terminal 8 and the attenuator 9. .
Since the high frequency signal P _out (t) amplified by the power amplifier 7 includes nonlinear distortion generated in the power amplifier 7, the high frequency signal P _out (t) is expressed by the following equation (3). expressed.

In the formula (3), G ₀ is linear gain of the power amplifier 7, .DELTA.G _n if the gain deviation of the power amplifier 7 in the case of amplifying a signal amplitude A _n, the [Delta] [phi _n for amplifying a signal of amplitude A _n The phase deviation of the power amplifier 7 of FIG.

Attenuator 9 receives the RF signal _{P out} (t) after amplification from the power amplifier 7, attenuates the high-frequency signal _{P out} (t), and outputs the high frequency signal ATT after attenuation (t) to the mixer 10 .
In the first embodiment, as described above, the amplitude value of the high-frequency signal ATT (t) attenuated by the attenuator 9 matches the amplitude value of the high-frequency signal Mix1 (t) before being amplified by the power amplifier 7. Since the attenuation factor is set in the attenuator 9, the amplitude value becomes 1 / G ₀ by the attenuator 9, as shown in the following equation (4).

Ａ／Ｄ変換器１１は、ミクサ１０から帰還信号Ｍｉｘ２（ｔ）を受けると、その帰還信号Ｍｉｘ２（ｔ）をディジタル信号に変換し、ディジタルの帰還信号Ｍｉｘ２（ｔ）を偏差算出部１２に出力する。 When the mixer 10 receives the attenuated high-frequency signal ATT (t) from the attenuator 9, it uses the local oscillation signal output from the local signal source 4 to down-convert the frequency of the high-frequency signal ATT (t), A feedback signal Mix2 (t), which is an analog signal after down-conversion, is output to the A / D converter 11.
Here, when the frequency of the local oscillation signal output from the local signal source 4 is assumed to be f _RF, the feedback signal output from the mixer 10 Mix2 (t) is expressed by the following formula (5) .

When the A / D converter 11 receives the feedback signal Mix2 (t) from the mixer 10, the A / D converter 11 converts the feedback signal Mix2 (t) into a digital signal and outputs the digital feedback signal Mix2 (t) to the deviation calculation unit 12. To do.

Upon receiving the digital feedback signal Mix2 (t) from the A / D converter 11, the Fourier transform unit 13 of the deviation calculation unit 12 performs Fourier transform on the digital feedback signal Mix2 (t), and the feedback signal Mix2 (T) is converted into a signal in the frequency domain.
FIG. 3 is an explanatory diagram showing a spectrum of a frequency domain signal obtained by Fourier transform by the Fourier transform unit 13.
As shown in FIG. 3, the peak value of the signal in the frequency domain appears at the frequency f ₀ of the feedback signal Mix2 (t), and the peak value is expressed by a complex number indicating the amplitude value Mag _n and the phase value θ at the frequency f ₀ . Is done.

When the Fourier transform unit 13 converts the digital feedback signal Mix2 (t) into a frequency domain signal, the amplitude phase specifying unit 14 of the deviation calculating unit 12 searches for the peak value of the frequency domain signal, and from the peak value, The amplitude value Mag _n and the phase value θ at the frequency f ₀ are specified.
Amplitude Mag _n at frequency f ₀ which is specified by the amplitude phase identification unit 14 corresponds to the amplitude value Mag _n of the analog signal down-converted by mixer 10, at a frequency f ₀ which is specified by the amplitude phase identification unit 14 The phase value θ corresponds to the phase value θ of the analog signal after down-conversion by the mixer 10.
The amplitude value Mag _n and the phase value θ are expressed by the following equations (6) and (7).

Compensation table creation unit 15 of the deviation calculator 12, the amplitude-phase identifying unit identifies the amplitude values Mag _n and a phase value θ at the frequency f _0, as shown in the following equation (8), an amplitude value at a frequency f ₀ The gain deviation ΔGain (n) and phase deviation ΔPhase (n) of the power amplifier 7 are calculated from Mag _n and the phase value θ, and the amplitude value _An and the phase value θ _{0 of} the known signal.

The equation (6) above, since it is Mag _n = ΔG _n A _n, gain deviation ΔGain of the power amplifier 7 shown in equation (8) (n), as shown in the following equation (10), the amplitude value consistent with gain deviation .DELTA.G _n of power amplifier 7 in the case of amplifying a signal of the a _n.
Further, from the above equation (7), since it is theta = [Delta] [phi _n, if the phase value theta ₀ known signal s (t) _(known phase value) is for example "0", shown in the formula (9) phase deviation ΔPhase power amplifier 7 (n), as shown in the following equation (11), coincides with the phase deviation [Delta] [phi _n of power amplifier 7 in the case of amplifying a signal amplitude value a _n.

The compensation table creation unit 15 calculates the gain deviation ΔGain (n) and the phase deviation ΔPhase (n) of the power amplifier 7 every time the known signal generation unit 1 outputs the known signal s (t). (N) and the phase deviation ΔPhase (n) are stored.
In the first embodiment, a known signal generator 1, since it is assumed that the amplitude value A _n outputs the N different known signal s (t), the gain corresponding to the N amplitude values A _n deviation ΔGain (N) and the phase deviation ΔPhase (n) are stored.
Thus, compensation table creation unit 15 creates a compensation table indicating the gain deviation ΔGain of the power amplifier 7 corresponding to each of the amplitude values _{A n} of the known signal s (t) (n) and the phase deviation ΔPhase (n) .

FIG. 4 is an explanatory diagram showing an example of creating a compensation table by the compensation table creating unit 15.
In the example of FIG. 4 shows the case where the amplitude value A _n of the known signal s (t) outputted from the known-signal generating unit 1 is represented by 3 bits, the amplitude values A _n of the known signal s (t) Varies from 0 to 7.
The gain deviation ΔGain (n) and phase deviation ΔPhase (n) of the power amplifier 7 shown in FIG. 4 are normalized values by rounding off the actual calculated values.

式（１２）において、Ｂは変調波信号ｍ（ｔ）の振幅値である。 Next, the operation in the operation mode will be described.
When the creation of the compensation table is completed, the control unit 20 notifies the modulated wave generation unit 2 and the switch 3 that the operation mode is operation.
When receiving a notification from the control unit 20 that the operation mode is the operation mode, the modulation wave generation unit 2 generates a modulation wave signal m (t) and uses the modulation wave signal m (t) as the distortion compensation unit 16. Output to.
The modulated wave signal m (t) generated by the modulated wave generator 2 is expressed as the following equation (12).

In Expression (12), B is the amplitude value of the modulated wave signal m (t).

When the distortion compensator 16 receives the modulated wave signal m (t) from the modulated wave generator 2, the distortion compensator 16 detects the amplitude value B of the modulated wave signal m (t).
Since the detection process of the amplitude value B itself is a known technique, a detailed description thereof is omitted, but the amplitude value B of the modulated wave signal m (t) may be notified from the modulated wave generation unit 2.
When the distortion compensator 16 detects the amplitude value B of the modulated wave signal m (t), the gain deviation ΔGain (corresponding to the amplitude value B is obtained from the compensation table created by the compensation table creator 15 of the deviation calculator 12. n) and phase deviation ΔPhase (n) are read out.

When compensation table of FIG. 4 has been created, the amplitude value B of the modulated wave signal m (t) is, for example, if it matches the amplitude value A _3, as the gain deviation ΔGain (n) corresponding to the amplitude value B “1” is specified, and “2” is specified as the phase deviation ΔPhase (n) corresponding to the amplitude value B.
Further, when the amplitude value B of the modulated wave signal m (t) is, for example, a value between the amplitude value A ₃ and the amplitude value A ₄ , the amplitude value B is greater than the amplitude value A ₄ by the amplitude value A ₃ . the closer towards the phase difference thereof as the amplitude value B to the corresponding gain deviation ΔGain (n) "1" which identifies the (gain deviation corresponds to the amplitude value _{a 3} ΔGain (n)), corresponding to the amplitude value B as ΔPhase (n) "2" specifying the (phase deviation corresponds to the amplitude value _{a 3} ΔPhase (n)). On the other hand, the if the amplitude value B is close than the amplitude value _{A 3} towards the amplitude _{A 4,} gain deviation corresponds to the gain deviation ΔGain (n) as the "2" (amplitude value _{A 4} corresponding to the amplitude value B DerutaGain (n)) to identify, for specifying the phase deviation DerutaPhase corresponding to the amplitude value B (as n) "2" (phase deviation corresponds to the amplitude value _{a 4} ΔPhase (n)).
Here, an example is shown in which the gain deviation ΔGain (n) and the phase deviation ΔPhase (n) corresponding to the closer amplitude value of the amplitude value A ₃ or the amplitude value A ₄ are specified, but the amplitude value A ₃ the interpolation value of the corresponding gain deviation DerutaGain (n) and the gain deviation DerutaGain (n) corresponding to the amplitude value _{a 4} and gain deviation DerutaGain (n) corresponding to the amplitude value B, the phase corresponding to the amplitude value _{a 3} interpolated value of the phase deviation DerutaPhase (n) the deviation DerutaPhase and (n) corresponding to the amplitude value _{a 4} may be the phase deviation DerutaPhase (n) corresponding to the amplitude value B of.

When the distortion compensator 16 reads the gain deviation ΔGain (n) and the phase deviation ΔPhase (n) corresponding to the amplitude value B of the modulated wave signal m (t), the gain deviation ΔGain (n) and the phase deviation ΔPhase (n) ) Is used to perform distortion compensation processing on the modulated wave signal m (t), and m _c (t), which is the modulated wave signal after the distortion compensation processing, is output to the switch 3.
Specifically, (see Equation (3)) is the amplitude value of the amplified RF signal _{P out} (t) by the power amplifier _{7 (G 0 × ΔG n)} × A n is the _{G 0} × _{A n} In order to achieve this, the amplitude value B of the modulated wave signal m (t) is divided by the gain deviation ΔGain (n).
Further, modulation is performed so that 2π × (f _RF + f ₀ ) t + Δφ _n that is the phase value of the high-frequency signal P _out (t) amplified by the power amplifier 7 becomes 2π × (f _RF + f ₀ ) t. The phase deviation ΔPhase (n) is subtracted from the phase value of the wave signal m (t).
Thereby, m _c (t), which is the modulated wave signal after the distortion compensation processing, is expressed as the following equation (13).

Since the switch 3 receives notification from the control unit 20 that the operation mode is the operation mode, when receiving the modulated wave signal m _c (t) after distortion compensation processing from the distortion compensating unit 16, the modulated wave signal m _c (t) is output to the D / A converter 5.
When receiving the modulation wave signal m _c (t) from the switch 3, the D / A converter 5 converts the modulation wave signal m _c (t) into an analog signal and outputs the analog signal to the mixer 6.
When receiving an analog signal from the D / A converter 5, the mixer 6 uses the local oscillation signal output from the local signal source 4 to up-convert the frequency of the analog signal, and is an analog signal after the up-conversion. The high frequency signal Mix1 (t) is output to the power amplifier 7.
Here, when the frequency of the local oscillation signal output from the local signal source 4 is assumed to be f _RF, high-frequency signal Mix1 output from the mixer 6 (t) is represented as the following equation (14) .

When receiving the high frequency signal Mix1 (t) from the mixer 6, the power amplifier 7 amplifies the high frequency signal Mix1 (t) and outputs the amplified high frequency signal P _out (t) to the output terminal 8.
Since distortion compensation processing is performed on the modulated wave signal m (t) by the distortion compensator 16, the high-frequency signal P _out (t) amplified by the power amplifier 7 is expressed as the following equation (15). The

As apparent from the above, according to the first embodiment, the frequency of the feedback signal Mix2 (t) output from the A / D converter 11 is analyzed, and the down-conversion by the mixer 10 is performed based on the analysis result of the frequency. The amplitude value Mag _n and phase value θ of the subsequent analog signal are specified, and the amplitude value of the known signal is determined from the specified amplitude value Mag _n and phase value θ and the amplitude value _An and phase value θ ₀ of the known signal. the deviation calculating section 12 for calculating a gain deviation ΔGain of the power amplifier 7 corresponding to a _n (n) and the phase deviation ΔPhase (n) is provided, the distortion compensation section 16, the amplitude value a calculated by the deviation calculating section 12 from the corresponding gain deviation ΔGain (n) and the phase deviation ΔPhase (n) for _n, the gain deviation DerutaGain corresponding to the amplitude value B of the modulated wave signal m (t) (n) and the phase deviation ΔPhase (n And the distortion compensation processing for the modulated wave signal m (t) is performed using the specified gain deviation ΔGain (n) and phase deviation ΔPhase (n). There is an effect that nonlinear distortion generated in the power amplifier 7 can be compensated with high accuracy without mounting a circuit, a quadrature demodulator, or the like.

That is, when calculating the gain deviation ΔGain (n) and phase deviation ΔPhase (n) of the power amplifier 7 used for the distortion compensation processing for the modulated wave signal m (t), the modulated wave signal is calculated from the high frequency signal amplified by the power amplifier. There is no need to mount a quadrature demodulator for demodulating the I baseband signal and the Q baseband signal in the feedback circuit. Further, it is sufficient to mount one A / D converter 11 in the feedback circuit. Therefore, the configuration of the feedback circuit can be simplified as compared with the distortion compensation circuit disclosed in Non-Patent Document 1.
Further, when calculating the gain deviation ΔGain (n) and phase deviation ΔPhase (n) of the power amplifier 7 used for the distortion compensation processing for the modulated wave signal m (t), the modulated wave signal m (t) and the feedback signal Mix2 (t ), The gain deviation ΔGain (n) and the phase deviation ΔPhase (n) can be calculated with high accuracy without performing the digital signal processing for matching the timings), so that it is necessary to mount a digital circuit having a large computation scale. Absent. Therefore, the nonlinear distortion generated in the power amplifier 7 can be compensated with high accuracy without incurring a large computation scale.

式（１６）において、ｍ＝０，・・・Ｍである。 Embodiment 2. FIG.
In the first embodiment, an example in which the frequency of the known signal s (t) is constant at f ₀ has been described. However, in the second embodiment, a case where the frequency of the known signal s (t) is changed will be described. To do.
FIG. 5 is an explanatory diagram showing an example of changing the frequency of the known signal s (t).
In the example of FIG. 5, the frequency of the known signal s (t) is changed as f ₀ → f ₁ as time passes, and the amplitude value is changed when the frequency of the known signal s (t) is f _0. A ₀ → A ₁ → A ₂ ... And when the frequency of the known signal s (t) is f ₁ , the amplitude value is changed as A ₀ → A ₁ → A _2. Yes.
Because with the passage of time the frequency f _n and the amplitude values A _n of the known signal s (t) is changed, a known signal s generated by the known signal generator unit 1 (t), the following equation (16) It is expressed as

In equation (16), m = 0,...

The configuration of the distortion compensation circuit is the same as that of the first embodiment.
Hereinafter, the operation of the distortion compensation circuit will be described.
First, the operation in the calibration mode will be described.
The control unit 20 notifies the known signal generation unit 1 and the switch 3 that the operation mode is the calibration mode.

When the known signal generation unit 1 receives a notification from the control unit 20 that the operation mode is the calibration mode, the known signal generation unit 1 generates a known signal s (t) represented by Expression (16), and the known signal is converted to the switch 3 and the compensation. The data is output to the table creation unit 15.
FIG. 5 is an example of M = 1, and since the frequency of the known signal s (t) is changed as f ₀ → f ₁ , first, the phase value is θ ₀ , the frequency is f ₀ , and the amplitude N known signals s (t) having different values _An are generated, and N known signals s (t) are output in order.
Next, N known signals s (t) having a phase value of θ ₀ , a frequency of f ₁ and different amplitude values _An are generated, and the N known signals s (t) are sequentially output.

Since the switch 3 receives the notification that the operation mode is the calibration mode from the control unit 20, when the known signal s (t) is received from the known signal generation unit 1, the switch 3 is similar to the first embodiment. The known signal s (t) is output to the D / A converter 5.
When the D / A converter 5 receives the known signal s (t) from the switch 3, the D / A converter 5 converts the known signal s (t) into an analog signal as in the first embodiment, and converts the analog signal into the mixer 6. Output to.
When the mixer 6 receives the analog signal from the D / A converter 5, the mixer 6 up-converts the frequency of the analog signal using the local oscillation signal output from the local signal source 4 as in the first embodiment. The high-frequency signal Mix1 (t), which is an analog signal after up-conversion, is output to the power amplifier 7.
Here, assuming that the frequency of the local oscillation signal output from the local signal source 4 is f _RF , the high-frequency signal Mix1 (t) output from the mixer 6 is expressed by the following equation (17). .

When receiving the high frequency signal Mix1 (t) from the mixer 6, the power amplifier 7 amplifies the high frequency signal Mix1 (t) and outputs the amplified high frequency signal P _out (t), as in the first embodiment. Output to terminal 8 and attenuator 9.
Since the high frequency signal P _out (t) amplified by the power amplifier 7 includes nonlinear distortion generated in the power amplifier 7, the high frequency signal P _out (t) is expressed by the following equation (18). expressed.

When receiving the amplified high-frequency signal P _out (t) from the power amplifier 7, the attenuator 9 attenuates the high-frequency signal P _out (t) and attenuates the high-frequency signal ATT as in the first embodiment. (T) is output to the mixer 10.
The high frequency signal ATT (t) attenuated by the attenuator 9 is expressed as the following equation (19).

Ａ／Ｄ変換器１１は、ミクサ１０から帰還信号Ｍｉｘ２（ｔ）を受けると、上記実施の形態１と同様に、その帰還信号Ｍｉｘ２（ｔ）をディジタル信号に変換し、ディジタルの帰還信号Ｍｉｘ２（ｔ）を偏差算出部１２に出力する。 When receiving the attenuated high-frequency signal ATT (t) from the attenuator 9, the mixer 10 uses the local oscillation signal output from the local signal source 4 and uses the high-frequency signal ATT ( The frequency of t) is down-converted, and the feedback signal Mix2 (t), which is an analog signal after down-conversion, is output to the A / D converter 11.
The feedback signal Mix2 (t) output from the mixer 10 is represented by the following equation (20).

When the A / D converter 11 receives the feedback signal Mix2 (t) from the mixer 10, the A / D converter 11 converts the feedback signal Mix2 (t) into a digital signal as in the first embodiment, and the digital feedback signal Mix2 ( t) is output to the deviation calculator 12.

Upon receiving the digital feedback signal Mix2 (t) from the A / D converter 11, the Fourier transform unit 13 of the deviation calculating unit 12 performs a Fourier transform on the digital feedback signal Mix2 (t) as in the first embodiment. To convert the feedback signal into a frequency domain signal.
When the Fourier transform unit 13 converts the digital feedback signal Mix2 (t) into a frequency domain signal, the amplitude / phase specifying unit 14 of the deviation calculating unit 12 peaks the signal in the frequency domain as in the first embodiment. searching a value to identify the amplitude values Mag _n and a phase value θ at the frequency f _m from its peak value.
Since the frequency f _m of the known signal s (t) is changed over time, from the known signal generator 1, for example, when a known signal s frequency f ₀ (t) is being output, the frequency domain The amplitude value Mag _n and the phase value θ at the frequency f ₀ are specified from the peak value of the signal of, for example, and when the known signal s (t) of the frequency f ₁ is output, the frequency The amplitude value Mag _n and the phase value θ at f ₁ are specified.
Amplitude Mag _n at the frequency f _m which is specified by the amplitude phase identification unit 14 corresponds to the amplitude value Mag _n of the analog signal down-converted by mixer 10, at a frequency f _m which is specified by the amplitude phase identification unit 14 The phase value θ corresponds to the phase value θ of the analog signal after down-conversion by the mixer 10.
The amplitude value Mag _n and the phase value θ are expressed as in the above equations (6) and (7).

Compensation table creation unit 15 of the deviation calculator 12, the amplitude-phase identifying unit identifies the amplitude values Mag _n and a phase value θ at the frequency f _m, as shown in the following equation (21), the amplitude value at a frequency f _m The gain deviation ΔGain (n, f _m ) and the phase deviation ΔPhase (n, f _m ) of the power amplifier 7 are calculated from Mag _n and the phase value θ and the amplitude value _An and the phase value θ _{0 of} the known signal.

From the above equation (6), since Mag _n = _An , the gain deviation ΔGain (n, f _m ) of the power amplifier 7 shown in equation (21) has an amplitude as shown in the following equation (23). consistent with gain deviation .DELTA.G _n of power amplifier 7 in the case of amplifying a signal having a value a _n.
Further, from the above equation (7), since θ = Δφn, _if the phase value θ ₀ (known phase value) of the known signal s (t) is, for example, “0”, the equation (22) is obtained. phase deviation ΔPhase power amplifier 7 (n), as shown in the following equation (24), coincides with the phase deviation [Delta] [phi _n of power amplifier 7 in the case of amplifying a signal amplitude value a _n.

Compensation table creation unit 15 calculates, for each of the known signal generating unit 1 outputs a known signal s (t), the gain deviation ΔGain (n, _{f m)} of the power amplifier 7 and phase deviation ΔPhase (n, _{f m)} a Then, store the gain deviation ΔGain (n, _{f m)} and the phase deviation ΔPhase (n, _{f m)} a.
In the second embodiment, the known signal generator 1, while changing the frequency f _m, since it is assumed that the amplitude value A _n outputs the N different known signal s (t), (M × N) storing pieces of gain deviation ΔGain (n, _{f m)} corresponding to the amplitude value _{a n} and phase deviation ΔPhase (n, _{f m)} a.

Figure 6 shows an example of compensation are stored by the table creating unit 15 (M × N) number of gain deviation ΔGain corresponding to the amplitude value _{A n (n, f m)} and the phase deviation ΔPhase (n, _{f m)} It is explanatory drawing.
In the example of FIG. 6 shows the case where the amplitude value A _n of the known signal s (t) outputted from the known-signal generating unit 1 is represented by 3 bits, the amplitude values A _n of the known signal s (t) Varies from 0 to 7.
Gain deviation ΔGain of the power amplifier 7 that are shown in FIG. 6 (n, _{f m)} and the phase deviation ΔPhase (n, _{f m)} is adapted to the value normalized by rounding or the like of the actual calculated value .

Compensation table creation unit 15, for example, the case of FIG. 6, the gain deviation ΔGain (n, _{f 0)} corresponding to the eight amplitude values _{A n} of the known signal s (t) of frequency _{f 0} and phase deviation ΔPhase (n stores the _{f 0),} 8 pieces of gain deviation ΔGain (n corresponding to the amplitude value _{a n} of the frequency _{f 1} of the known signal s (t), _{f 1)} and the phase deviation ΔPhase (n, the _{f 1)} and since it has two gain deviation DerutaGain corresponding to the frequency _{f 0, f 1 (n,} f 0), ΔGain (n, f 1) with integrating two phase deviation corresponding to the frequency _f 0, _{f 1 ΔPhase (n, f 0),} ΔPhase (n, f 1) by integrating compensation illustrating a gain deviation ΔGain of the power amplifier 7 corresponding to each of the amplitude values _{a n} (n) and the phase deviation ΔPhase (n) Create a table.
FIG. 7 is an explanatory diagram showing an example of creating a compensation table by the compensation table creating unit 15.
In the example of FIG. 7, the gain deviations ΔGain (n, f ₀ ) and ΔGain (n, f ₁ ) corresponding to the two frequencies f ₀ and f ₁ are integrated by averaging, and the two frequencies f ₀ and f are integrated. _The phase deviations ΔPhase (n, f ₀ ) and ΔPhase (n, f ₁ ) corresponding to ₁ are integrated by averaging.
For example, paying attention to the amplitude value _{A 6} before integration in FIG 6, the gain deviation ΔGain (6, _{f 0)} is 4, the gain deviation ΔGain (6, _{f 1)} is 3, the phase deviation ΔPhase (6, _{f 0)} is 4. Since the phase deviation ΔPhase (6, f ₁ ) is 2, as shown in FIG. 7, the gain deviation ΔGain (6) and the phase deviation ΔPhase (6) after integration are as follows.
Gain deviation after integration ΔGain (6) = (4 + 3) /2=3.5
Phase deviation after integration ΔPhase (6) = (4 + 2) / 2 = 3

Since the operation in the operation mode is the same as that in the first embodiment, description thereof is omitted.
As the second embodiment, a plurality compensation table creation unit 15, while integrating the plurality of gain deviation corresponding to the same amplitude values A _n of different frequencies, corresponding to the same amplitude values A _n of different frequencies of by integrating the phase difference, since it is configured to create a compensation table indicating the gain deviation corresponding to each of the amplitude values a _n ΔGain _(n) and the phase deviation ΔPhase (n), a known signal s (t) even if the change with a frequency f _m to the passage of time, as in the first embodiment, without the computational complexity to implement, such as large digital circuits and quadrature demodulator, nonlinear distortion generated by the power amplifier 7 Can be compensated with high accuracy.
Further, by changing the frequency f _m of the known signal s (t), it is possible to create a compensation table in consideration of the frequency characteristic of the power amplifier 7, a power amplifier to a higher accuracy than the first embodiment 7 can compensate for the non-linear distortion that occurs in 7.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Known signal production | generation part, 2 Modulation wave production | generation part, 3 Switch, 4 Local signal source, 5 D / A converter (1st conversion part), 6 Mixer (1st conversion part), 7 Power amplifier, 8 outputs Terminal, 9 Attenuator, 10 Mixer (second conversion unit), 11 A / D converter (second conversion unit), 12 Deviation calculation unit, 13 Fourier transform unit, 14 Amplitude phase identification unit, 15 Compensation table creation Unit, 16 distortion compensation unit, 20 control unit, 51 memory, 52 processor.

Claims (5)

A known signal generator for sequentially outputting a plurality of known signals having different amplitude values;
A first converter that converts the known signal into an analog signal and converts the frequency of the analog signal;
A power amplifier for amplifying the analog signal having the converted frequency;
An attenuator for attenuating the analog signal amplified by the power amplifier;
A second converter that converts the frequency of the analog signal attenuated by the attenuator and converts the analog signal after the frequency conversion into a digital signal;
By analyzing the frequency of the digital signal, the amplitude value and phase value of the analog signal after frequency conversion by the second conversion unit are specified, and the specified amplitude value and phase value and the amplitude value of the known signal and A deviation calculating unit for calculating a gain deviation and a phase deviation of the power amplifier corresponding to the amplitude value of the known signal from the phase value;
From the gain deviation and the phase deviation corresponding to each amplitude value calculated by the deviation calculating unit, the gain deviation and the phase deviation corresponding to the amplitude value of the modulated wave signal are specified, and the specified gain deviation and A distortion compensation circuit comprising: a distortion compensation unit that performs a distortion compensation process on the modulated wave signal using a phase deviation and outputs the modulated wave signal after the distortion compensation process to the first conversion unit. The deviation calculator is
A Fourier transform unit that performs a Fourier transform on the digital signal converted by the second conversion unit, and converts the digital signal into a frequency domain signal;
An amplitude phase specifying unit for specifying an amplitude value and a phase value of an analog signal after frequency conversion by the second conversion unit, from the frequency domain signal converted by the Fourier transform unit;
The gain deviation of the power amplifier corresponding to the amplitude value of the known signal is calculated from the amplitude value of the analog signal specified by the amplitude phase specifying unit and the amplitude value of the known signal, and specified by the amplitude phase specifying unit The phase deviation of the power amplifier corresponding to the amplitude value of the known signal is calculated from the phase value of the analog signal and the phase value of the known signal, and the gain deviation and phase of the power amplifier corresponding to each amplitude value are calculated. The distortion compensation circuit according to claim 1, further comprising a compensation table creation unit that creates a compensation table indicating a deviation.   The distortion compensation unit reads the gain deviation and the phase deviation corresponding to the amplitude value of the modulated wave signal from the compensation table created by the compensation table creation unit, and uses the read gain deviation and phase deviation, 3. The distortion compensation circuit according to claim 2, wherein a distortion compensation process is performed on the modulated wave signal.   In the step of creating the compensation table by the compensation table creation unit, the known signal output from the known signal generation unit is given to the first conversion unit, and the creation of the compensation table by the compensation table creation unit is completed. 4. The distortion compensation circuit according to claim 2, further comprising a switch that applies a modulated wave signal after distortion compensation processing by the distortion compensation unit to the first conversion unit. When the known signal generation unit sequentially outputs a plurality of known signals having different amplitude values, the frequency of the plurality of known signals is changed, and then the process of outputting the plurality of known signals in order is repeatedly performed.
The compensation table creation unit integrates a plurality of gain deviations corresponding to a plurality of known signals having different frequencies but having the same amplitude value, and a plurality of known signals having different frequencies but the same amplitude value. The compensation table which shows the gain deviation and phase deviation of the power amplifier corresponding to each amplitude value is created by integrating the phase deviation corresponding to the signal. The distortion compensation circuit according to claim 1.

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