WO2011102177A1 - 増幅装置とこれを備えた無線送信装置、及び、増幅装置の利得調整方法 - Google Patents
増幅装置とこれを備えた無線送信装置、及び、増幅装置の利得調整方法 Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
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- H—ELECTRICITY
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- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
- H03F1/3247—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits using feedback acting on predistortion circuits
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- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
- H03F1/3258—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits based on polynomial terms
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- H03—ELECTRONIC CIRCUITRY
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- H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
- H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
- H03F3/195—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only in integrated circuits
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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Definitions
- the present invention relates to an amplifying apparatus having a digital pre-distorter (hereinafter, abbreviated as “DPD”) and a wireless transmission apparatus including the amplifying apparatus. More specifically, the present invention relates to a gain adjustment method in the amplification device.
- DPD digital pre-distorter
- the pre-distortion method is a method in which the output signal of the power amplifier is not distorted by adding a characteristic opposite to the distortion characteristic to the input signal in advance with respect to the input signal of the power amplifier. It is obtained in a small state.
- a predistortion type distortion compensation circuit for example, as shown in Non-Patent Document 1, the correction amount is stored in a LUT (Look Up Table), and the difference between the output signal of the amplifier and the target output signal is used.
- a method of sequentially correcting the correction amount (LUT method), a method of approximating the correction amount for the amplifier with a polynomial, and calculating the coefficient value using the output signal and the input signal of the amplifier for adaptive control (polynomial approximation method) There is.
- An amplification apparatus employing the above-mentioned polynomial approximation type digital predistorter (DPD) usually converts a digital transmission signal output from the DPD into an analog signal, and then upconverts and amplifies the signal after the DPD.
- System analog circuit, and an output signal of an amplifier included in the circuit is adjusted to a predetermined amplitude, down-converted, converted to a digital signal, and input to the DPD. (For example, see FIG. 3A).
- the return system analog circuit is disposed between the DPD and the coupler for feeding back the analog output signal of the amplifier extracted by the coupler as a digital signal to the DPD, and an attenuator for adjusting the analog output signal of the amplifier to a predetermined amplitude.
- the main component is a frequency converter for converting the carrier frequency to the baseband, and an A / D converter. Then, the DPD obtains the analog output signal of the power amplifier as a baseband digital signal through the return system analog circuit.
- the gain of the transmission system analog circuit and the return system analog circuit fluctuates due to aging and temperature change, but the gain fluctuation of the transmission system analog circuit can be eliminated by distortion compensation processing by DPD.
- the gain fluctuation of the return system analog circuit cannot be erased only by the distortion compensation processing by the DPD, there is a problem that when the gain fluctuation occurs in the circuit, the distortion compensation processing by the DPD cannot be performed accurately.
- the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an amplifying apparatus and the like that can correct distortion even when the gain of a return analog circuit fluctuates and can accurately perform distortion compensation processing by DPD. To do.
- An amplifying apparatus of the present invention is an amplifying apparatus including an amplifier and a DPD that performs distortion compensation processing of the amplifier, and converts the digital output signal of the DPD into an analog signal, and upconverts the analog signal.
- a transmission system analog circuit including the amplifier, which is input to the amplifier, and an analog output signal of the amplifier is adjusted to a predetermined amplitude, converted to a digital signal by down-converting the analog output signal, and input to the DPD
- the change amount calculation unit calculates the change amount of the gain of the return system analog circuit based on the measurement value of the power measurement circuit, and thus the return system is calculated using the calculated change amount.
- the gain of the analog circuit can be corrected. Therefore, even if the gain of the return analog circuit fluctuates due to aging or temperature change, the distortion compensation processing by DPD can be accurately performed by correcting the gain of the return analog circuit using the calculated change amount.
- the power measurement circuit can be constituted by, for example, a detection circuit (power detector) that detects an analog output signal (RF signal) of an amplifier.
- the DPD considers the gain change amount of the return analog circuit after erasing the gain change amount of the transmission analog circuit by the first distortion compensation processing. It is preferable to correct the gain by a second distortion compensation process. In this case, even if both analog circuits have gain fluctuations, their gains can be corrected by the distortion compensation processing by DPD.
- the change amount calculation unit calculates a change amount of the gain of the return analog circuit using a measurement value of the power measurement circuit corresponding to a known signal pattern. It is preferable. In this way, since the measured value of the power measuring circuit is stabilized, the amount of change in gain of the return analog circuit can be accurately calculated.
- the change amount calculation unit executes the averaging process of the measurement value of the power measurement circuit during the transmission period of the known signal pattern, the measurement for noise is performed. The error is suppressed, and the amount of change in gain of the return analog circuit can be calculated more accurately.
- the change amount calculation unit executes the averaging process over the transmission period of the signal pattern for a plurality of transmission frames, the signal pattern of a single transmission frame As compared with the case where the averaging process is performed during the transmission period, the measurement error with respect to noise can be more reliably suppressed, and the amount of change in the gain of the return analog circuit can be calculated more accurately.
- the change amount calculation unit uses the measurement value of the power measurement circuit corresponding to a capture signal whose maximum amplitude captured in a predetermined sampling period is equal to or greater than a predetermined value.
- the amount of change in the gain of the return analog circuit may be calculated.
- the present invention can also be applied to a transmission device that conforms to a standard that does not include a preamble portion.
- the amplifying apparatus of the present invention further includes a gain correction unit that corrects the gain of the power measurement circuit based on the ambient temperature of the power measurement circuit and / or the use frequency of the transmission signal. It is preferable. In this case, the measured value of the power measurement circuit can be maintained with high accuracy even if the ambient temperature and the operating frequency fluctuate, so that the correction processing of the gain of the return analog circuit can be performed accurately.
- the wireless transmission device of the present invention is a wireless transmission device including the amplification device of the present invention, and has the same effects as the amplification device of the present invention.
- the method of the present invention includes a step of measuring an output power of an amplifier, and a step of calculating a gain change amount of a return analog circuit arranged at a subsequent stage of the DPD based on the measured output power of the amplifier. And a step of correcting the gain of the return analog circuit based on the calculated change amount.
- the amount of change in the gain of the return system analog circuit arranged at the subsequent stage of the DPD is calculated, and on the basis of the calculated amount of change, the return system analog circuit Therefore, even if the gain of the return analog circuit fluctuates due to aging or temperature change, distortion compensation processing by DPD can be performed accurately.
- FIG. 1 is a circuit configuration diagram showing an amplifying device according to a first embodiment of the present invention. It is a functional block diagram of DPD which concerns on 1st Embodiment of this invention.
- (A) is a functional block diagram of the amplifying device for showing power control performed by the DPD, and (b) is a table showing each power in an initial state where there is no fluctuation in gain.
- (A) is a functional block diagram of the amplification device when the gain of the transmission system analog circuit changes, and (b) performs each power and distortion compensation processing once when the gain changes. It is a table
- (A) is a functional block diagram of the amplifying device when the gains of both analog circuits are changed, and (b) is a distortion compensation process performed once for each power when the gain changes. It is a table
- FIG. 1 is a circuit configuration diagram showing an amplifying apparatus 1 according to the first embodiment of the present invention.
- the amplifying apparatus 1 constitutes a transmission part of a base station apparatus that wirelessly communicates with a plurality of terminal apparatuses, for example, and amplifies and outputs a transmission signal for each terminal apparatus.
- the base station apparatus is a base station apparatus of a wide area mobile radio communication system, for example, a so-called WiMAX base station apparatus defined in IEEE 802.16.
- the amplifying apparatus 1 includes a digital processing unit 2 composed of a DSP (Digital Signal Processor), a transmission system analog circuit 3, a return system analog circuit 4, and a coupler 5.
- the transmission analog circuit 3 is disposed between the digital processing unit 2 and the coupler 5, and in order from the processing unit 2 side, a D / A converter (DAC) 8, a low-pass filter (LPF) 9, 1 frequency converter 10 and high power amplifier (HPA: High Power Amplifier; hereinafter simply referred to as “amplifier”) 11.
- DAC D / A converter
- LPF low-pass filter
- HPA High Power Amplifier
- the return system analog circuit 4 is arranged between the coupler 5 and the digital processing unit 2, and in order from the processing unit 2 side, an A / D converter (ADC) 12, a low-pass filter (LPF) 13, a second A frequency converter 14 and an attenuator (ATT) 15 are included.
- ADC A / D converter
- LPF low-pass filter
- ATT attenuator
- the digital processing unit 2 performs predetermined signal processing including processing in a distortion compensation circuit 20 described later on the digital baseband transmission signal, and outputs the digital signal after the processing to the transmission system analog circuit 3.
- the digital output signal of the digital processing unit 2 is converted into an analog signal by the D / A converter 8, up-converted to the carrier frequency by the first frequency conversion unit 10, and then supplied to the amplifier 11.
- the analog output signal of the amplifier 11 is transmitted from the antenna 6 to the outside through the coupler 5.
- the digital processing unit 2 acquires the output waveform of the amplifier 11 via the return analog circuit 4 that converts the analog output signal of the amplifier 11 into a digital signal in order to perform signal processing in the distortion compensation circuit 20 or the like. is doing. That is, the analog output signal of the amplifier 11 is extracted by the coupler 5, adjusted to a predetermined amplitude by the attenuator 15, down-converted to baseband by the second frequency converter 14, and then digitally converted by the A / D converter 12. The signal is converted into a signal and input to the distortion compensation circuit 20 of the digital processing unit 2.
- the amplifying apparatus 1 of the present embodiment extracts the output power of the analog output signal of the amplifier 11 (specifically, extracted by the coupler 5) in order to cope with the gain fluctuation in the return system analog circuit 4.
- a detector circuit 16 is provided as an example of an electronic device that measures the power of the reflected signal.
- the detection circuit 16 includes an integrated circuit 16A for power detection whose input terminal communicates with the coupler 5, and an A / D converter 16B for A / D converting the output signal of the integrated circuit 16A.
- the integrated circuit 16A has a linear characteristic in which when a high-frequency waveform of an arbitrary output level (dBm) is input to an input terminal, a detection voltage having a linear relationship with the input level is output from the output terminal.
- the detection voltage (detection measurement value) of the integrated circuit 16A is converted into a digital value by the A / D converter 16B at the subsequent stage, and then input to the distortion compensation circuit 20 described later.
- the integrated circuit 16A for example, “AD8362” manufactured by ANALOG DEVICES can be used.
- FIG. 2 is a functional block diagram of a distortion compensation circuit (DPD according to the first embodiment of the present invention) 20 functionally included in the digital processing unit 2.
- the distortion compensation circuit 20 of the present embodiment approximates the distortion correction amount for the amplifier 11 by a polynomial, and performs adaptive control by calculating the coefficient value of the polynomial by digital signal processing using an input signal and an output signal for the amplifier 11.
- the digital predistorter (DPD) is a polynomial approximation method.
- the DPD 20 is acquired from the transmission signal buffer 21 that stores the digital transmission signal (input signal y to the amplifier 11) to be sent to the DAC 8 of the transmission system analog circuit 3 and the ADC 12 of the return system analog circuit 4.
- the DPD 20 also performs distortion compensation on the digital transmission signal based on the estimated inverse model and the model estimation unit 24 that estimates the inverse model of the input / output characteristics of the amplifier 11 based on each digital signal after the synchronization processing. And a distortion compensation unit 25.
- the transmission signal buffer 21 accumulates a digital transmission signal (input signal y to the amplifier 11) to the transmission analog circuit 3 for a sampling period set as a period of a predetermined time width, and the accumulated signal y is output to the timing synchronization unit 23.
- the return signal buffer 22 accumulates the return signal (output signal of the amplifier 11) z from the return system analog circuit 4 for a sampling interval of a predetermined time width, and the accumulated signal z is timingd. The data is output to the synchronization unit 23.
- the return signal buffer 22 adjusts the timing for accumulating the output signal z so that the output signal z corresponding to the input signal y accumulated by the transmission signal buffer unit 21 is accumulated.
- the timing synchronization unit 23 acquires the input signal y and the output signal z included in the sampling interval output from both the buffers 21 and 22, and performs a synchronization process for matching the timing between the input signal y and the output signal z. Do.
- the distortion compensation unit 25 performs distortion compensation processing according to the input / output characteristics of the amplifier 11 on the digital transmission signal before distortion compensation, and outputs a distortion-compensated digital transmission signal that becomes the input signal y to the amplifier 11. . Therefore, the amplifier 11 can output an output signal with little or no distortion.
- the input / output characteristics of the amplifier 11 are nonlinear, but the characteristics can be approximated by, for example, a power series polynomial shown in the following equation (1).
- z is an output signal of the amplifier 11 (return signal from the return system analog circuit 4), y is an input signal of the amplifier 11, and ai is a coefficient of each order i.
- the distortion compensator 25 calculates a power series polynomial shown in the following equation (2) to obtain an input signal (a signal output to the transmission system analog circuit 3) y of the amplifier 11. .
- ai ′ is a coefficient at each order i indicating the inverse characteristic of the amplifier 11.
- the distortion compensator 25 converts the inverse characteristic of the distortion characteristic of the amplifier 11 to the digital transmission signal before distortion compensation based on the coefficient ai ′ of each order i indicating the inverse characteristic of the amplifier 11. Distortion compensation is performed by adding to x and canceling distortion caused by the amplifier 11.
- the coefficient ai ′ indicating the inverse characteristic of the amplifier 11 in the above equation (2) is obtained by the model estimation unit 24.
- the model estimation unit 24 reads the data of the input signal y and the output signal z of the amplifier 11 provided from the timing synchronization unit 23, and based on these, estimates a model representing the input / output characteristics of the amplifier 11 and estimates each order i.
- the coefficient ai ′ is obtained.
- the model estimation unit 24 has an inverse model of the amplifier 11 in which the input signal y of the amplifier 11 is represented by a power series polynomial of the output signal z, and the input / output signal given from the timing synchronization unit 23 is the model. And apply the above to estimate the inverse model.
- the model estimation unit 24 outputs the coefficient of each order indicating the estimated inverse model to the distortion compensation unit 25 as a coefficient ai ′ of each order i indicating the inverse characteristic of the amplifier 11.
- the DPD 20 of this embodiment further includes a timing information generation unit 26 and a change amount calculation unit 27.
- the change amount calculation unit 27 acquires the detection voltage (measured value) in the detection circuit 16 only for a predetermined period, calculates the output power (average power) of the amplifier 11 from the measured value, and outputs the calculated output power. Based on the electric power, the change amount ⁇ Grx of the gain Grx of the return system analog circuit 4 is calculated.
- the timing information generation unit 26 acquires a transmission frame timing signal from a signal processing unit (not shown) on the upper layer side, and acquires a measurement value of the detection circuit 16 based on the timing signal. And the change amount calculation unit 27 is instructed. Specifically, the timing information generation unit 26 of the present embodiment obtains a preamble period Tp that is advanced by the time width of the preamble portion from the beginning of the transmission frame, and notifies the change amount calculation unit 27 of this period Tp. Upon receiving this notification, the change amount calculation unit 27 acquires the measurement value of the detection circuit 16 in the notified preamble period Tp.
- the change amount calculation unit 27 calculates the change amount ⁇ Grx of the gain Grx of the return analog circuit 4 using a portion corresponding to the preamble that is a known signal pattern of the transmission frame. It has become.
- the change amount calculation unit 27 notifies the distortion compensation unit 25 of the calculated change amount ⁇ Grx.
- the distortion compensator 25 corrects fluctuations in the gain of the return analog circuit 4 by performing distortion compensation processing based on the notified change amount ⁇ Grx.
- the correction processing will be described later.
- the change amount calculation unit 27 of the present embodiment executes an averaging process of the measurement values of the detection circuit 16 in the preamble period Tp. As a result, the measurement error with respect to noise is suppressed, and the change amount ⁇ Grx of the gain Grx of the return system analog circuit 4 can be accurately calculated.
- the noise is smaller than when the averaging process is performed in the preamble period Tp for a single transmission frame.
- the measurement error for can be more effectively suppressed.
- FIG. 3A is a functional block diagram of the amplifying apparatus 1 for showing power control performed by the DPD 20, and FIG. 3B is a table showing each power in an initial state where there is no gain variation.
- Ptx (dB) is the power (digital transmission power) of the output signal of the DPD
- Prx (dB) is the power of the input signal to the DPD 20 (digital return power)
- Pout (dBm) is , Analog transmission power output from the amplifier 11.
- Gtx (dB) is the gain of the transmission system analog circuit 3 (gain of the amplifier 11)
- Grx (dB) is the gain of the return system analog circuit 4 (gain of the attenuator 15)
- Tout is a target value of the transmission power Pout
- Trx is a target value of the digital return power Prx.
- the DPD 20 matches the transmission power Pout with the target value Tout, so that the digital return power Prx is
- FIG. 4A is a functional block diagram of the amplifying apparatus 1 when the gain Gtx of the transmission system analog circuit 3 changes
- FIG. 4B shows each of the cases where the gain changes. It is a table
- the digital transmission power Ptx and the transmission power Pout after processing are as follows.
- the transmission power Pout can be matched with the target value Tout. That is, the variation ⁇ Gtx of the transmission gain Gtx can be dealt with by the distortion compensation processing of the DPD 20.
- FIG. 5A is a functional block diagram of the amplifying apparatus 1 when the gains Gtx and Grx of both the analog circuits 3 and 4 are changed
- FIG. 5B is a case where the gain is changed.
- 4 is a table showing each power and each power when the distortion compensation processing is performed once.
- the change amount of the gain Gtx of the transmission system analog circuit 3 is ⁇ Gtx and the change amount of the gain Gtx of the return system analog circuit 4 is ⁇ Grx
- the gain of the transmission system analog circuit 3 becomes Gtx ⁇ Gtx + ⁇ Gtx
- the gain of the circuit 4 is Grx ⁇ Grx + ⁇ Grx.
- the digital transmission power Prx and the transmission power Pout after processing are as follows.
- the gain Grx of the return system analog circuit 4 changes, even if only the distortion compensation processing in the DPD 20 is performed, the return ⁇ Grx of the return gain Grx remains in the digital transmission power Prx and the transmission power Pout, and the transmission power Pout is It cannot be matched with the target value Tout. That is, the variation ⁇ Gtx of the transmission gain Gtx can be corrected only by the distortion compensation processing of the DPD 20, but the variation ⁇ Grx of the return gain Grx cannot be corrected only by the distortion compensation processing of the DPD 20.
- the change amount calculation unit 27 calculates the transmission power (average power) Pout of the amplifier 11 from the measurement value of the detection circuit 16, and changes in the return gain Grx calculated based on the output power.
- the transmission power Pout is made to coincide with the target value Tout even if the return gain Grx varies.
- FIG. 6 is a functional block diagram of the amplifying apparatus 1 having the detection circuit 16 when the gains Gtx and Grx of the analog circuits 3 and 4 change.
- FIG. 7 is a table showing each power when the gains Gtx and Grx of both analog circuits 3 and 4 change and each power when the distortion compensation processing is performed twice.
- the procedure of the correction process of the return gain Grx performed by the DPD 20 of the present embodiment will be described.
- the distortion compensation unit 25 of the DPD 20 executes a first distortion compensation process in order to erase the variation ⁇ Gtx of the transmission gain Gtx from the transmission power Pout. To do.
- the transmission power Pout Tout ⁇ Grx
- the change amount ⁇ Grx of the return gain Grx remains in the transmission power Pout.
- the change amount calculation unit 27 of the DPD 20 returns the return gain Grx during the preamble period Tp of the transmission frame based on the transmission power of the amplifier 11 obtained from the measurement value of the detection circuit 16.
- Change amount ⁇ Grx is calculated and sent to the distortion compensation unit 25.
- the distortion compensation unit 25 adds the change amount ⁇ Grx to the target value Trx of the digital return power Prx, and changes the target value Trx from Tout + Grx to Tout + Grx + ⁇ Grx.
- the digital transmission power Ptx and the transmission power Pout after processing are as follows.
- the change amount ⁇ Grx of the return gain Grx is obtained from the measurement value of the detection circuit 16, and the target value Trx of the digital return power Prx is changed by the amount of change ⁇ Grx to perform distortion compensation processing.
- the transmission power Pout can be matched with the target value Tout. For this reason, even when the return gain Grx fluctuates due to aging or temperature change, the distortion compensation processing of the DPD 20 can be performed accurately.
- the return gain Grx is corrected by the second distortion compensation process. Even when there are gain fluctuations in both the analog circuits 3 and 4, those gains can be corrected by the distortion compensation processing of the DPD 20.
- FIG. 8 is a functional block diagram of the DPD 20 according to the second embodiment of the present invention.
- the difference between the DPD 20 of this embodiment (FIG. 8) and that of the first embodiment (FIG. 2) is that the return gain Grx can be corrected using an arbitrary portion of the transmission frame, not the preamble portion of the transmission frame. Therefore, distortion compensation processing is performed using a capture signal having a maximum amplitude equal to or greater than a predetermined value.
- the timing information generation unit 26 of the present embodiment acquires a transmission frame timing signal from a signal processing unit (not shown) on the upper layer side, and periodically performs a sampling period that repeats in synchronization with this timing signal. Has been generated.
- the timing information generation unit 26 acquires the digital transmission signal included in the generated sampling period, and determines whether the transmission signal includes a data pattern with a maximum amplitude or more that makes the amplifier 11 nonlinear. To do.
- the timing information generation unit 26 When the determination result is negative, the timing information generation unit 26 continues to acquire the digital transmission signal in the sampling period after the next time. Conversely, if the determination result is affirmative, the timing information generating unit 26 calculates a sampling period for capturing the data pattern (hereinafter referred to as “capture period Tc”) with each of the buffers 21 and 22. Notification to the unit 27.
- Each of the buffers 21 and 22 accumulates the input signal y and the output signal z in the capture period Tc notified from the timing information generation unit 26, and distortion compensation processing is performed on the capture signal accumulated in the capture period Tc. .
- the change amount calculation unit 27 acquires the measurement value of the detection circuit 16 in the capture period Tc notified from the timing information generation unit 26, and uses the measurement value of the capture signal in the period Tc to return the analog circuit Grx. Change amount ⁇ Grx is calculated, and the calculated change amount ⁇ Grx is notified to the distortion compensation unit 25.
- the return gain Grx can be corrected by executing the distortion compensation processing (the above steps 1) to 3)) in the DPD 20 twice.
- the distortion compensation process is also performed on the capture signal that is transmission data in the capture period Tc determined by the timing information generation unit 26.
- the timing information generation unit 26 determines a capture signal having a maximum amplitude equal to or greater than a predetermined value in a predetermined sampling period, and the change amount calculation unit 27 corresponds to the capture signal. Since the change ⁇ Grx of the gain Grx of the return system analog circuit 4 is calculated using the measurement value of the detection circuit 16, the correction process of the return gain Grx is performed without using a known signal pattern such as a preamble portion. It can be carried out. For this reason, the present invention can also be applied to a base station apparatus that complies with a standard that does not include a preamble portion, such as LTE (Long Term Evolution).
- LTE Long Term Evolution
- FIG. 9 is a circuit configuration diagram showing an amplifying device according to the third embodiment of the present invention.
- the amplifying apparatus 1 of this embodiment (FIG. 9) is different from that of the first embodiment (FIG. 1) in that the digital processing unit 2 has a function of compensating the gain error of the detection circuit 16 due to fluctuations in the ambient temperature and operating frequency. It is in having. That is, in the amplifying apparatus 1 of the present embodiment, the digital processing unit 2 corrects the gain of the detection circuit 16 based on the ambient temperature of the detection circuit 16 and the use frequency of the analog transmission signal (RF signal). 30.
- the gain correction unit 30 always obtains the detection value of the temperature sensor 31 that measures the ambient temperature of the detection circuit 16, and also uses the frequency of the currently used RF signal as a signal processing unit (not shown). Z). Further, the memory of the digital processing unit 2 stores a “temperature gain table” and a “frequency gain table” as shown below, for example, which indicate gain correction amounts for the detection circuit 16 corresponding to temperature and frequency. ing.
- Example of temperature gain table 10 ° C / output -1dB 20 ° C / output 0 dB 30 ° C / output 1 dB
- Example of frequency gain table 2.5GHz / output -1dB 2.6 GHz / output 0 dB 2.7 GHz / output 1 dB
- the gain correction unit 30 corrects the gain of the amplifier of the detection circuit 16 by referring to each gain table according to the detection value acquired from the temperature sensor 31 and the use frequency acquired from the upper layer. That is, when the operating frequency is 2.6 GHz and the output of the detection circuit 16 is X dBm when the ambient temperature is 10 ° C., the gain correction unit 30 outputs (X ⁇ 1) dBm Thus, the gain of the amplifier of the detection circuit 16 is corrected.
- the gain correction unit 30 when the operating frequency is 2.6 GHz and the output of the detection circuit 16 is X dBm when the ambient temperature is 30 ° C., the gain correction unit 30 has an output of (X + 1) dBm. Thus, the gain of the amplifier of the detection circuit 16 is corrected. Further, for example, when the output of the detection circuit 16 is X dBm when the transmission frequency is 2.7 GHz and the ambient temperature is 30 ° C., the gain correction unit 30 sets the output to (X + 2) dBm. In addition, the gain of the amplifier of the detection circuit 16 is corrected.
- the gain correction unit 30 corrects the gain of the amplifier of the detection circuit 16 based on the ambient temperature of the detection circuit 16 and the use frequency of the RF signal. Even if the temperature and the operating frequency fluctuate, the measurement value of the detection circuit 16 can be maintained with high accuracy, and the correction process of the return gain Grx can be performed accurately. Further, according to the amplifying apparatus 1 of the present embodiment, it is only necessary to control the gain of the amplifier of the detection circuit 16, so that there is an advantage that control of temperature compensation and frequency compensation is simplified.
- the analog circuits 3 and 4 are subjected to temperature compensation and frequency compensation without using the detection circuit 16, the power amplifier 11, the attenuator 15, the mixers 10 and 14, the filters 9 and 13, etc.
- the transmission gain Gtx using the measurement value of the detection circuit 16 Since the return gain Grx can be corrected, it is only necessary to compensate for the gain error of the detection circuit 16, and it is sufficient to hold the gain table for the detection circuit 16.
- the gain correction unit 30 corrects the gain of the detection circuit 16 based on both the ambient temperature of the detection circuit 16 and the use frequency of the RF signal. The gain may be corrected based on only one of them.
- the above embodiments are illustrative of the present invention and are not limiting.
- the scope of the present invention is shown not by the above embodiment but by the scope of claims for patent, and includes all modifications equivalent to the scope of claims and their configurations.
- the return gain Grx is corrected by the second distortion compensation process, but the return is made by adjusting the attenuator 15 of the return system analog circuit 4.
- the gain may be corrected.
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Abstract
Description
そこで、電力増幅器の入出力特性の線形性を確保しつつ、電力効率の向上を図るため、非線形領域において生じる歪みを補償する種々の歪補償方式が提案されている。かかる歪補償方式としては、大きく分けて、フィードフォワード方式、フィードバック方式及びプリディストーション方式がある。
かかるプリディストーション方式の歪補償回路としては、例えば非特許文献1に示すように、補正量をLUT(Look Up Table )に記憶させておき、増幅器の出力信号と目標出力信号の差異を用いて、その補正量を逐次修正する方式(LUT方式)や、増幅器に対する補正量を多項式で近似し、その係数値を増幅器の出力信号と入力信号を用いて演算して適応制御する方式(多項式近似方式)とがある。
そして、DPDは、この戻り系アナログ回路を通じて、電力増幅器のアナログ出力信号をベースバンドのデジタル信号として取得する。
しかし、戻り系アナログ回路の利得変動については、DPDによる歪補償処理だけでは消去できないので、当該回路に利得変動が生じた場合には、DPDによる歪補償処理を正確に行えなくなるという問題がある。
このため、経年変化や温度変化によって戻り系アナログ回路の利得が変動しても、算出した変化量を用いて戻り系アナログ回路の利得を補正することにより、DPDによる歪補償処理を正確に行うことができる。
なお、上記電力測定回路は、例えば、増幅器のアナログ出力信号(RF信号)を検波する検波回路(電力検波器)より構成することができる。
この場合、両アナログ回路の双方に利得変動があった場合であっても、DPDによる歪補償処理によってそれらの利得を補正することができる。
このようにすれば、電力測定回路の測定値が安定するので、戻り系アナログ回路の利得の変化量を正確に算出することができる。
この場合、プリアンブル部分のような既知の信号パターンを使用しなくても、戻り利得の補正処理を行えるので、プリアンブル部分を含まない規格に準拠する送信装置にも本発明を適用することができる。
この場合、上記周辺温度や使用周波数が変動しても、電力測定回路の測定値を高精度に維持することができるので、戻り系アナログ回路の利得の補正処理を正確に行うことができる。
〔第1実施形態〕
〔増幅装置の構成〕
図1は、本発明の第1実施形態に係る増幅装置1を示す回路構成図である。この増幅装置1は、例えば複数の端末装置と無線通信する基地局装置の送信部分を構成しており、各端末装置に対する送信信号を増幅して出力する。
本実施形態では、上記基地局装置は、広域移動無線通信システムの基地局となる、例えばIEEE802.16に規定するいわゆるWiMAXの基地局装置よりなる。
このうち、送信系アナログ回路3は、デジタル処理部2とカプラ5の間に配置されており、処理部2側から順に、D/A変換器(DAC)8、ローパスフィルタ(LPF)9、第1周波数変換部10及び高出力増幅器(HPA:High Power Amplifier。以下、単に「増幅器」ということがある。)11を有する。
デジタル処理部2のデジタル出力信号は、D/A変換器8によってアナログ信号に変換され、第1周波数変換部10において搬送周波数にアップコンバートされたあと、増幅器11に与えられる。この増幅器11のアナログ出力信号は、カプラ5を通じてアンテナ6から外部に送出される。
すなわち、増幅器11のアナログ出力信号は、カプラ5で抽出されてアッテネータ15で所定の振幅に調整され、第2周波数変換部14においてベースバンドにダウンコンバートされたあと、A/D変換器12においてデジタル信号に変換され、デジタル処理部2の歪補償回路20に入力される。
この検波回路16は、入力端子がカプラ5に通じる電力検波用の集積回路16Aと、この集積回路16Aの出力信号をA/D変換するA/D変換器16Bとを備えている。集積回路16Aは、任意の出力レベル(dBm)の高周波波形を入力端子に入力すると、その入力レベルと線形関係にある検波電圧を出力端子から出力するリニア特性を有している。
なお、上記集積回路16Aとしては、例えば、ANALOG DEVICES社製の「AD8362」を使用することができる。
図2は、デジタル処理部2が機能的に有する歪補償回路(本発明の第1実施形態に係るDPD)20の機能ブロック図である。
本実施形態の歪補償回路20は、増幅器11に対する歪み補正量を多項式で近似し、その多項式の係数値を、増幅器11に対する入力信号と出力信号を用いてデジタル信号処理によって演算して適応制御する、多項式近似方式のデジタルプリディストータ(DPD)により構成されている。
また、DPD20は、同期処理後の各デジタル信号に基づいて、増幅器11の入出力特性の逆モデルを推定するモデル推定部24と、推定された逆モデルに基づいてデジタル送信信号に歪補償を行う歪補償部25とを備えている。
また同様に、戻り信号バッファ22は、戻り系アナログ回路4からの戻り信号(増幅器11の出力信号)zを、予め定められた時間幅のサンプリング区間分だけ蓄積し、その蓄積した信号zをタイミング同期部23に出力する。
タイミング同期部23は、両バッファ21,22から出力されるサンプリング区間に含まれる入力信号yと出力信号zを取得し、これら入力信号yと出力信号zとの間のタイミングを一致させる同期処理を行う。
ここで、増幅器11の入出力特性は非線形であるが、その特性は、例えば次の式(1)に示す、べき級数多項式で近似することができる。
なお、式(2)において、ai’は、増幅器11の逆特性を示す各次数iでの係数である。
上記式(2)中の増幅器11の逆特性を示す係数ai’は、モデル推定部24により求められる。モデル推定部24は、タイミング同期部23より与えられる増幅器11の入力信号yと出力信号zのデータを読み出し、これらに基づいて、増幅器11の入出力特性を表すモデルを推定して各次数iの係数ai’を求める。
モデル推定部24は、推定した逆モデルを示す各次数の係数を、増幅器11の逆特性を示す各次数iの係数ai’として、歪補償部25に出力する。
このうち、変化量算出部27は、検波回路16での検波電圧(測定値)を所定期間だけ取得しており、この測定値から増幅器11の出力電力(平均電力)を算出するとともに、その出力電力に基づいて、前記戻り系アナログ回路4の利得Grxの変化量ΔGrxを算出するものである。
具体的には、本実施形態のタイミング情報生成部26は、送信フレームの先頭からプリアンブル部分の時間幅だけ進んだプリアンブル期間Tpを求め、この期間Tpを変化量算出部27に通知する。この通知を受けた変化量算出部27は、通知されたプリアンブル期間Tpにおいて検波回路16の測定値を取得する。
変化量算出部27は、上記変化量ΔGrxを算出した場合には、その算出した変化量ΔGrxを歪補償部25に通知する。
また、本実施形態の変化量算出部27は、プリアンブル期間Tpにおいて検波回路16の測定値の平均化処理を実行するようになっている。これにより、雑音に対する測定誤差が抑制され、戻り系アナログ回路4の利得Grxの変化量ΔGrxを正確に算出できる。
図3(a)は、DPD20が行う電力制御を示すための、増幅装置1の機能ブロック図であり、図3(b)は、利得の変動がない初期状態における各電力を示す表である。
図3において、Ptx(dB)は、DPD20の出力信号の電力(デジタル送信電力)であり、Prx(dB)は、DPD20への入力信号の電力(デジタル戻り電力)であり、Pout (dBm)は、増幅器11が出力するアナログ送信電力である。
ここで、DPD20における歪補償処理は、これを電力制御の観点から見ると、デジタル戻り電力Prxがその目標値Trx(=Tout +Grx)となるように、デジタル送信電力Ptxを制御することと等価である。
また、上記各電力Ptx,Prx,Poutと利得Gtx,Grxの間には、次の等式が成立する。
Prx=Pout +Grx=Ptx+Gtx+Grx
Ptx=Prx-(Gtx+Grx)
=(Tout +Grx)-(Gtx+Grx)
=Tout -Gtx
この場合、送信系アナログ回路3の利得Gtxの変化量をΔGtxとすると、送信系アナログ回路3の利得は、Gtx→Gtx+ΔGtxとなる。
すなわち、送信利得がGtx+ΔGtxに変化すると、図4(b)に示すように、デジタル戻り電力Prxと送信電力Pout は、それぞれ次のようになる。
Prx=Tout +ΔGtx+Gtx
Pout =Tout +ΔGtx
Ptx=Prx-(Gtx+ΔGtx+Grx)
=(Tout+Grx)-(Gtx+ΔGtx+Grx)
=Tout -Gtx-ΔGtx
Pout =Ptx+(Gtx+ΔGtx)
=Tout
すなわち、送信利得Gtxの変動ΔGtxについては、DPD20の歪補償処理によって対応することができる。
一方、図5(a)は、両アナログ回路3,4の利得Gtx,Grxが変化した場合の、増幅装置1の機能ブロック図であり、図5(b)は、その利得変化があった場合の各電力と、歪補償処理を1回行った場合の各電力を示す表である。
この場合、送信系アナログ回路3の利得Gtxの変化量をΔGtxとし、戻り系アナログ回路4の利得Gtxの変化量をΔGrxすると、送信系アナログ回路3の利得は、Gtx→Gtx+ΔGtxとなり、戻り系アナログ回路4の利得は、Grx→Grx+ΔGrxとなる。
すなわち、送信利得がGtx+ΔGtxに変化し、戻り利得がGrx+ΔGrxに変化すると、デジタル戻り電力Prxと送信電力Pout は、それぞれ次のようになる。
Prx=Tout +ΔGtx+Gtx+ΔGrx
Pout =Tout +ΔGtx
Ptx=Prx-(Gtx+ΔGtx+Grx+ΔGrx)
=(Tout+Grx)-(Gtx+ΔGtx+Grx+ΔGrx)
=Tout -Gtx-ΔGtx-ΔGrx
Pout =Ptx+(Gtx+ΔGtx)
=Tout-ΔGrx
すなわち、送信利得Gtxの変動ΔGtxについては、DPD20の歪補償処理だけで補正できるが、戻り利得Grxの変動ΔGrxについては、DPD20の歪補償処理だけでは補正することができない。
そこで、本実施形態では、前記変化量算出部27において、検波回路16の測定値から増幅器11の送信電力(平均電力)Pout を算出するとともに、その出力電力に基づいて算出した戻り利得Grxの変化量ΔGrxを用いて、デジタル戻り電力Prxの目標値Trxを更新することにより、戻り利得Grxが変動しても送信電力Pout を目標値Tout に一致させるようにした。
以下、図6及び図7を参照して、本実施形態のDPD20が行う戻り利得Grxの補正処理の手順について説明する。
この場合、前記した通り、送信電力Pout =Tout -ΔGrxとなり、戻り利得Grxの変化量ΔGrxについては送信電力Pout に残っている。
上記変化量ΔGrxを受けた歪補償部25は、その変化量ΔGrxをデジタル戻り電力Prxの目標値Trxに加え、その目標値Trxを、Tout +GrxからTout +Grx+ΔGrxに変更する。
このさい、処理後のデジタル送信電力Ptxと送信電力Pout は、次のようになる。
Ptx=Prx-(Gtx+ΔGtx+Grx+ΔGrx)
=(Tout+Grx+ΔGrx)-(Gtx+ΔGtx+Grx+ΔGrx)
=Tout -Gtx-ΔGtx
Pout =Ptx+(Gtx+ΔGtx)
=Tout
このため、経年変化や温度変化によって戻り利得Grxが変動した場合でも、DPD20の歪補償処理を正確に行うことができる。
図8は、本発明の第2実施形態に係るDPD20の機能ブロック図である。
本実施形態(図8)のDPD20が第1実施形態(図2)のそれと異なる点は、送信フレームのプリアンブル部分ではなく、送信フレームの任意の部分を用いて戻り利得Grxの補正処理を行えるようにするため、最大振幅が所定値以上のキャプチャ信号を用いて歪補償処理を行う点にある。
また、タイミング情報生成部26は、生成したサンプリング期間に含まれるデジタル送信信号を取得するとともに、その送信信号に、増幅器11が非線形になる最大振幅以上のデータパターンが含まれているか否かを判定する。
また、変化量算出部27は、タイミング情報生成部26から通知されたキャプチャ期間Tcに検波回路16の測定値を取得し、その期間Tcのキャプチャ信号についての測定値を用いて戻り系アナログ回路Grxの変化量ΔGrxを算出し、その算出した変化量ΔGrxを歪補償部25に通知する。
なお、本実施形態では、信号パターンが不明な任意の送信データを使用することから、戻り利得Grxを補正する2回目の歪補償処理だけでなく、送信利得Gtxの変化量ΔGtxを消去する1回目の歪補償処理も、タイミング情報生成部26が判定したキャプチャ期間Tcの送信データであるキャプチャ信号に対して行われる。
このため、例えばLTE(Long Term Evolution )のような、プリアンブル部分を含まない規格に準拠する基地局装置の場合にも、本発明を適用することができる。
図9は、本発明の第3実施形態に係る増幅装置を示す回路構成図である。
本実施形態(図9)の増幅装置1が第1実施形態(図1)のそれと異なる点は、デジタル処理部2が、周辺温度や使用周波数の変動による検波回路16の利得誤差の補償機能を有する点にある。
すなわち、本実施形態の増幅装置1では、デジタル処理部2が、検波回路16の周辺温度及びアナログ送信信号(RF信号)の使用周波数に基づいて、当該検波回路16の利得を補正する利得補正部30を備えている。
また、デジタル処理部2のメモリは、温度や周波数に対応する検波回路16に対する利得の補正量を示す、例えば以下に例示するような「温用利得テーブル」と「周波数利得テーブル」とを記憶している。
10°C / 出力-1dB
20°C / 出力 0dB
30°C / 出力 1dB
(周波数利得テーブルの例)
2.5GHz / 出力-1dB
2.6GHz / 出力 0dB
2.7GHz / 出力 1dB
すなわち、利得補正部30は、使用周波数が2.6GHzである場合において、周辺温度が10°Cのときの検波回路16の出力がXdBmである場合には、その出力が(X-1)dBmとなるように、当該検波回路16のアンプの利得を補正する。
更に、利得補正部30は、例えば、送信周波数が2.7GHzでかつ周辺温度が30°Cのときの検波回路16の出力がXdBmである場合には、その出力を(X+2)dBmとなるように、当該検波回路16のアンプの利得を補正する。
また、本実施形態の増幅装置1によれば、検波回路16のアンプの利得を制御するだけで足りるので、温度補償や周波数補償の制御が簡単になるという利点もある。
上記実施形態は本発明の例示であって制限的なものではない。本発明の範囲は、上記実施形態ではなく特許請求の範囲によって示され、特許請求の範囲及びその構成と均等な全ての変更が含まれる。
例えば、上記実施形態では、戻り利得Grxの変化量ΔGrxを算出したあと、2回目の歪補償処理によって戻り利得Grxを補正しているが、戻り系アナログ回路4のアッテネータ15を調整することで戻り利得を補正することにしてもよい。
2 デジタル処理部
3 送信系アナログ回路
4 戻り系アナログ回路
5 カプラ
8 D/A変換器
9 ローパスフィルタ
10 第1周波数変換部
11 高出力増幅器
12 A/D変換器
13 ローパスフィルタ
14 第2周波数変換部
15 アッテネータ
16 検波回路(電力測定回路)
20 歪補償回路(DPD)
27 変化量算出部
Claims (9)
- 増幅器と、この増幅器の歪補償処理を行うデジタルプリディストータ(以下、特許請求の範囲において、「DPD」という。)とを備えた増幅装置であって、
前記DPDのデジタル出力信号をアナログ信号に変換し、これをアップコンバートして前記増幅器に入力する、当該増幅器を含む送信系アナログ回路と、
前記増幅器のアナログ出力信号を所定の振幅に調整し、これをダウンコンバートしてデジタル信号に変換し、前記DPDに入力する戻り系アナログ回路と、
前記増幅器の出力電力を測定する電力測定回路と、
前記電力測定回路の測定値に基づいて、前記戻り系アナログ回路の利得の変化量を算出する変化量算出部と、
を備えていることを特徴とする増幅装置。 - 前記DPDは、1回目の歪補償処理によって前記送信系アナログ回路の利得の変化量を消去してから、前記戻り系アナログ回路の利得の変化量を考慮した2回目の歪補償処理によって当該利得を補正する請求項1に記載の増幅装置。
- 前記変化量算出部は、既知の信号パターンに対応する前記電力測定回路の測定値を用いて、前記戻り系アナログ回路の利得の変化量を算出する請求項1又は2に記載の増幅装置。
- 前記変化量算出部は、既知の前記信号パターンの送信期間において前記電力測定回路の測定値の平均化処理を実行する請求項3に記載の増幅装置。
- 前記変化量算出部は、複数の送信フレームについての前記信号パターンの送信期間に跨って前記平均化処理を実行する請求項4に記載の増幅装置。
- 前記変化量算出部は、予め定めたサンプリング期間にキャプチャされた最大振幅が所定値以上のキャプチャ信号に対応する前記電力測定回路の測定値を用いて、前記戻り系アナログ回路の利得の変化量を算出する請求項1又は2に記載の増幅装置。
- 前記電力測定回路の周辺温度又は送信信号の使用周波数若しくはこれらの双方に基づいて、当該電力測定回路の利得を補正する利得補正部を更に備えている請求項1~6のいずれか1項に記載の増幅装置。
- 請求項1~7のいずれか1項に記載の増幅装置を備えている無線送信装置。
- 増幅器の出力電力を測定するステップと、
測定した前記増幅器の出力電力に基づいて、DPDの後段に配置される戻り系アナログ回路の利得の変化量を算出するステップと、
算出した前記変化量に基づいて、戻り系アナログ回路の利得を補正するステップと、
を含むことを特徴とするDPDを有する増幅装置の利得調整方法。
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KR1020127020197A KR20130008517A (ko) | 2010-02-16 | 2011-01-20 | 증폭 장치와 이것을 구비한 무선 송신 장치, 및 증폭 장치의 이득 조정 방법 |
CN201180009849XA CN102763325A (zh) | 2010-02-16 | 2011-01-20 | 放大器装置、包括放大器装置的无线电发送装置、和调整放大器装置的增益的方法 |
US13/519,196 US8755757B2 (en) | 2010-02-16 | 2011-01-20 | Amplifier apparatus, radio transmitting apparatus including same, and method of adjusting gain of amplifier apparatus |
EP11744466.1A EP2538554A4 (en) | 2010-02-16 | 2011-01-20 | REINFORCING DEVICE AND WIRELESS TRANSMISSION DEVICE THEREFOR AND REINFORCEMENT ADJUSTMENT METHOD FOR THE REINFORCING DEVICE |
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JP2010031630A JP5593724B2 (ja) | 2010-02-16 | 2010-02-16 | 増幅装置とこれを備えた無線送信装置、及び、増幅装置の利得調整方法 |
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EP (1) | EP2538554A4 (ja) |
JP (1) | JP5593724B2 (ja) |
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JP6204222B2 (ja) * | 2014-02-19 | 2017-09-27 | パナソニック株式会社 | 無線通信装置 |
JP2016123095A (ja) * | 2014-12-24 | 2016-07-07 | 日本無線株式会社 | 前置歪み補償装置 |
JP6223388B2 (ja) * | 2015-06-25 | 2017-11-01 | 京セラ株式会社 | 通信装置 |
WO2018176436A1 (zh) * | 2017-04-01 | 2018-10-04 | 华为技术有限公司 | 一种预失真方法、装置和系统 |
CN110543167B (zh) * | 2019-09-20 | 2022-07-08 | 天津津航计算技术研究所 | 一种应用于航空电热控制系统的自检电路 |
WO2021088023A1 (zh) * | 2019-11-08 | 2021-05-14 | 华为技术有限公司 | 一种电子设备及数字芯片 |
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EP2538554A1 (en) | 2012-12-26 |
KR20130008517A (ko) | 2013-01-22 |
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JP2011171840A (ja) | 2011-09-01 |
US20120286867A1 (en) | 2012-11-15 |
US8755757B2 (en) | 2014-06-17 |
CN102763325A (zh) | 2012-10-31 |
JP5593724B2 (ja) | 2014-09-24 |
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