JP2012222369A - Radio transmitter device and orthogonal modulation error compensation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio transmitter device and an orthogonal modulation error compensation method thereof, capable of contributing downsizing and cost reduction.SOLUTION: A signal processing part 30 transmits one of baseband signal of monitoring channel from a monitoring I channel baseband signal or a monitoring Q channel baseband signal which are separated by a mixer 23 from a modulated output signal of an orthogonal modulator 15, maximizes the baseband signal amplitude of the one of the monitoring channels by controlling a phase shifter 21, then transmits the baseband signal of the other monitoring channel, and minimizes the baseband signal of the other monitoring channel to compensate an orthogonal phase error.

Description

  The present invention includes a quadrature modulator that directly modulates a carrier wave with an I-channel baseband signal and a Q-channel baseband signal, and by monitoring the output of the quadrature modulator, the quadrature phase error and amplitude of the quadrature modulator are monitored. The present invention relates to a radio transmission apparatus and a quadrature modulation error correction method for correcting a balance error.

  Conventionally, a radio transmission apparatus that performs quadrature modulation generates a modulation wave by generating a modulation signal by signal processing and converting it to an analog signal by a DAC (Digital to Analog Converter). The DAC has a limit on the frequency of a modulated wave that can be extracted, and the modulated wave has an intermediate frequency (IF) that is relatively close to the baseband. For this reason, a mechanism for up-conversion to high frequency (RF) is necessary. In order to perform this up-conversion, a large number of components such as a band limit filter (BPF: Band Pass Filter) and a filter that suppresses the leakage of the local oscillator are required, resulting in an increase in cost.

Therefore, in order to reduce the cost and the number of parts, there is a tendency to adopt a mechanism based on direct conversion, particularly in a radio station such as a terminal radio station that is required to be small in size and low in cost. According to direct conversion, an I-channel baseband signal and a Q-channel baseband signal, which are modulated waves, are input to a quadrature modulator together with the carrier wave. It can be modulated with the baseband signal of the channel. Therefore, a filter or the like for suppressing unnecessary components is not required without having unnecessary frequency components, and it is possible to reduce the size and cost.
By the way, in the direct conversion, for example, as disclosed in Patent Document 1, a modulated wave is generated by analog arithmetic processing using a quadrature modulator. Specifically, the quadrature modulator includes two mixers and a π / 2 phase shifter. Then, when the carrier wave and the carrier wave whose phase is shifted by π / 2 by the π / 2 phase shifter are input to the local terminals of the respective mixers, and the I signal and the Q signal are input to the respective mixers, the carrier wave phases are orthogonal to each other. Two modulated waves are generated, and an orthogonal modulated wave can be obtained by combining them.

  At this time, if the phase shift amount of the π / 2 phase shifter is shifted or the conversion gains of the two mixers are different, the quadrature phase error and the baseband signal of the I channel and the baseband signal of the Q channel The amplitude balance error is reflected on the modulated wave as it is, which causes the EVM (Error Vector Magnitude) degradation. In order to correct these quadrature modulation errors, for example, as disclosed in Patent Documents 2 and 3, for example, a part of a quadrature modulated wave is taken out and an I channel baseband signal and a Q channel are obtained by a quadrature demodulator. There is known a method of correcting an amplitude balance error and a quadrature phase error of an I-channel baseband signal and a Q-channel baseband signal separately from each other.

JP-A-6-303265 JP 7-177188 A JP-A-9-186729

However, according to the methods disclosed in Patent Documents 2 and 3 described above, since the error component of the quadrature demodulator is included in the output modulated wave, the amplitude balance between the I-channel baseband signal and the Q-channel baseband signal. It was difficult to accurately correct errors and phase errors. For this reason, there is also known an IF sampling method in which a signal once down-converted into an IF signal is directly taken into an ADC (Analog to Digital Converter) without using a quadrature demodulator, and quadrature demodulation is performed by digital calculation. However, this method also requires a local oscillator for demodulation in addition to a local oscillator for quadrature modulation, which complicates the configuration and is difficult to apply to a radio station that requires a reduction in size and cost. It is.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a radio transmission apparatus and a quadrature modulation error correction method in the apparatus that can contribute to downsizing and cost reduction. .

  In order to solve the above-described problems, the present invention includes a quadrature modulator that directly modulates a carrier wave using an I-channel baseband signal and a Q-channel baseband signal, and monitors the output of the quadrature modulator. A radio transmission apparatus that performs quadrature modulation error correction, a phase shifter that controls a phase of an output signal of a local oscillator that generates the carrier wave, and an I-channel baseband signal for monitoring the output of the quadrature modulator And a mixer for converting to a Q-band baseband signal for monitoring, and an I-channel baseband signal for monitoring and a baseband signal for monitoring Q-channel converted by the mixer during error correction of the quadrature modulator Only the baseband signal of one monitoring channel is transmitted, and the amplitude of the baseband signal of the one monitoring channel is maximized. After controlling the phase shifter, only the baseband signal of the other monitoring channel is transmitted, and the baseband signal of the other monitoring channel is minimized so that the baseband signal of the other monitoring channel is minimized. A signal processing unit that calculates a baseband signal corresponding to the band signal and generates the I-channel baseband signal or the Q-channel baseband signal in which the quadrature phase error is corrected.

  According to the present invention, the signal processing unit includes a monitoring channel base of one of the monitoring I-channel baseband signal and the Q-channel baseband signal converted by the mixer from the modulated output wave of the quadrature modulator. Only the band signal is transmitted and the phase shifter is controlled so that the amplitude of the baseband signal of one of the monitoring channels is maximized. Thereafter, the signal processing unit transmits only the baseband signal of the other monitoring channel, calculates the baseband signal corresponding to the baseband signal of the other monitoring channel, and determines the baseband signal of the other monitoring channel. Minimizing the quadrature modulation error of the output modulated wave of the quadrature modulator by generating an I-channel baseband signal or a Q-channel baseband signal with the quadrature phase error corrected by controlling to be minimized. be able to. For this reason, it is possible to correct the quadrature phase error using only the baseband signal of one channel, which is scalar information, without using the quadrature demodulated signal, which is vector information. Therefore, the configuration is simplified and the cost is reduced. A wireless transmission device that contributes to downsizing as well as suppression can be provided.

  In the present invention, the signal processing unit stores the amplitude when the amplitude of the baseband signal of the one monitoring channel is maximized, and then transmits the baseband signal of the other monitoring channel. The phase shifter is controlled so that the amplitude of the baseband signal of the other monitoring channel is maximized, and the amplitude of the baseband signal of the other monitoring channel and the baseband of the stored one channel are controlled. The amplitude balance error of the output of the quadrature modulator is minimized by correcting the amplitude of the baseband signal of the I channel or the baseband signal of the Q channel so that the amplitude of the signal is the same. And According to the present invention, it is possible to correct not only the quadrature phase error but also the amplitude balance error with only the baseband signal of one channel which is scalar information, without using the quadrature modulation signal which is vector information. For this reason, EVM can be improved.

  The present invention relates to a quadrature modulator that directly modulates a carrier wave using an I-channel baseband signal and a Q-channel baseband signal, and a phase shifter that controls the phase of an output signal of a local oscillator that generates the carrier wave. A signal processing unit, wherein the signal processing unit monitors the output of the quadrature modulator and performs error correction in a radio transmission apparatus, wherein the quadrature modulator corrects the error. Converting the quadrature modulator output into an I-channel baseband signal for monitoring and a Q-band baseband signal for monitoring, and the converted I-channel baseband signal for monitoring and monitoring Of the Q channel baseband signals, only the baseband signal of one monitoring channel is transmitted, and the baseband signal of the one monitoring channel is transmitted. Controlling the phase shifter to maximize the amplitude of the signal, followed by transmitting only the baseband signal of the other monitoring channel and minimizing the baseband signal of the other monitoring channel. Calculating a baseband signal corresponding to the baseband signal of the other monitoring channel to generate a baseband signal of the I channel or a baseband signal of the Q channel corrected for quadrature phase error, It is characterized by having.

  According to the present invention, the wireless transmission device transmits only the baseband signal of one monitoring channel among the baseband signals of the I channel and the Q channel, and the amplitude of the baseband signal of one monitoring channel is After controlling to be maximized, only the baseband signal of the other monitoring channel is transmitted, and the baseband signal of the other monitoring channel is controlled to be minimized to correct the quadrature phase error. Baseband signal or Q channel baseband signal. For this reason, the quadrature modulation error of the output modulated wave of the quadrature modulator can be minimized, and the quadrature phase error can be obtained only with the baseband signal of one channel that is scalar information without using the quadrature demodulation signal that is vector information Can be corrected. Therefore, the configuration is simplified, and it is possible to contribute to the miniaturization of the apparatus as well as cost reduction.

  In the present invention, the step of storing the amplitude when the amplitude of the baseband signal of the one monitoring channel is maximized, and then transmitting the baseband signal of the other monitoring channel, the amplitude of which is The phase shifter is controlled so as to be maximized, and the amplitude of the baseband signal of the other monitoring channel is the same as the amplitude of the stored baseband signal of the one monitoring channel. And correcting the amplitude of the baseband signal of the Q channel or the baseband signal of the Q channel to minimize the amplitude balance error of the output of the quadrature modulator. According to the present invention, it is possible to correct not only the quadrature phase error but also the amplitude balance error with only the baseband signal of one channel that is scalar information without using the quadrature modulation signal that is vector information. For this reason, the EVM can be improved.

  According to the present invention, it is possible to provide a radio transmission apparatus and a quadrature modulation error correction method in the apparatus that can contribute to miniaturization and cost reduction.

It is a block diagram which shows the structure of the radio | wireless transmitter which concerns on embodiment of this invention. It is a flowchart which shows schematic operation | movement of the radio | wireless transmitter which concerns on embodiment of this invention. It is a flowchart which shows the detailed process sequence of the quadrature phase error correction of the radio | wireless transmitter which concerns on embodiment of this invention. It is a flowchart which shows the detailed operation | movement procedure of the amplitude balance error correction | amendment of the radio | wireless transmitter which concerns on embodiment of this invention. It is the figure which showed typically operation | movement of the radio | wireless transmitter which concerns on embodiment of this invention using IQ constellation. It is the figure which showed typically operation | movement of the radio | wireless transmitter which concerns on embodiment of this invention using IQ constellation.

Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as the present embodiment) will be described in detail with reference to the accompanying drawings.
(Configuration of the embodiment)
FIG. 1 is a block diagram illustrating a configuration of a wireless transmission device according to the present embodiment. As shown in FIG. 1, the wireless transmission device 1 according to the present embodiment includes a transmission system circuit unit 10, an error correction circuit unit 20 added by the present invention, and a signal processing unit 30.

  The transmission system circuit unit 10 is configured by a direct conversion system transmission system circuit including DACs 11 and 12, LPFs 13 and 14, quadrature modulator 15, amplifier (PA 16), BPF 17, and local oscillator 18. . In the transmission system circuit unit 10, the baseband signals of the I and Q channels before orthogonal modulation generated by the signal processing unit 30 are converted into analog signals by the DACs 11 and 12, and the converted analog signals are converted here. Are input to the quadrature modulator 15 through the LPFs 13 and 14, respectively. At this time, the carrier wave generated by the local oscillator 18 is also input to the quadrature modulator 15, and therefore the quadrature modulator 15 directly converts the carrier wave into an I-channel baseband signal (hereinafter simply referred to as an I signal). , And Q channel baseband signals (hereinafter simply referred to as Q signals). The output modulated wave generated by the quadrature modulator 15 is amplified by the amplifier 16 and transmitted via the BPF 17.

  The error correction circuit unit 20 includes a phase shifter 21, a BPF 22, a mixer 23, an LPF 24, and an ADC 25. In the error correction circuit unit 20, the mixer 23 acquires the output modulated wave of the quadrature modulator 15 via the BPF 22 and converts it into a monitoring I signal and a monitoring Q signal. The monitoring I signal and Q signal output from the mixer 23 are converted into digital signals by the ADC 25 via the LPF 24 and output to the signal processing unit 30. The phase shifter 21 controls the phase of the output signal of the local oscillator 18 that generates a carrier wave under the control of the signal processing unit 30. For example, when the phase shifter 21 is configured by an infinite phase shifter using the quadrature modulator 15, the phase from 0 to 2π × n [rad] (n is a natural number) is continuously controlled by the control of the signal processing unit 30. Can be changed.

  That is, the error correction circuit unit 20 takes out a part of the orthogonally modulated signal, converts it to an I signal and a Q signal for monitoring by the mixer 23, supplies them to the signal processing unit 30, and shifts the phase by the signal processing unit 30. Under the phase shift amount control of the device 21, the amplitude balance error and the quadrature phase error of the I signal and the Q signal are corrected.

  The signal processing unit 30 is configured by, for example, a DSP (Digital Signal Processor), and here, by controlling the error correction circuit unit 20 based on the contents programmed in advance, the quadrature phase error and the amplitude balance error of the quadrature converter 15 are controlled. Orthogonal modulation error correction control is performed to minimize.

  Specifically, the signal processing unit 30 performs the monitoring I signal and Q signal converted from the output modulated wave by the mixer 23 at the orthogonal modulation error correction (calibration) timing of the orthogonal modulator 15 at the time of signal reception or the like. Among them, only one monitoring signal (for example, monitoring I signal) is output to the transmission system circuit unit 10, and the phase shifter 21 is controlled so that the amplitude of the one monitoring signal is maximized. Thereafter, the signal processing unit 30 transmits only the other monitoring signal (for example, the monitoring Q signal), and the base corresponding to the baseband signal of the other monitoring channel so that the other monitoring signal is minimized. The band signal is calculated to generate a signal (for example, Q signal) of the other channel in which the quadrature phase error is corrected. By controlling in this way, the quadrature phase error of the modulated wave output from the quadrature modulator 15 can be minimized. A detailed processing procedure of this quadrature phase error correction will be described later with reference to the flowchart of FIG.

Further, the signal processing unit 30 stores the amplitude when the amplitude of one of the monitoring baseband signals becomes maximum in a built-in memory. Then, the other monitoring signal is transmitted to control the phase shifter 21 so that the amplitude of the other monitoring signal is maximized. Then, the amplitude of the I signal or the Q signal is corrected so that the amplitude of the other monitoring signal is the same as the amplitude of the stored one monitoring signal. The signal processing unit 30 performs control to minimize the amplitude balance error between the I signal and the Q signal due to the output modulated wave of the quadrature modulator 15 by controlling in this way. A detailed procedure of the IQ amplitude balance error correction will be described later with reference to the flowchart of FIG.
(Operation of the embodiment)
FIG. 2 is a flowchart showing a schematic operation of the wireless transmission device according to the present embodiment. The schematic operation of the wireless transmission device 1 shown in FIG. 1 will be described below with reference to the flowchart of FIG.

  In the wireless transmission device 1, the signal processing unit 30 monitors the arrival of the timing of orthogonal modulation error correction (hereinafter referred to as calibration) that does not affect the transmission processing by the wireless transmission device 1 (step S11). At a timing when calibration cannot be performed, such as during wireless transmission (step S11 “NO”), the signal processing unit 30 transmits and outputs the modulated wave generated by the quadrature modulator 15 of the transmission system circuit unit 10 to the outside. (Step S12).

  On the other hand, for example, at the time of reception or the like that does not affect wireless transmission (step S11 “YES”), the signal processing unit 30 monitors the output modulation wave of the quadrature modulator 15 of the transmission circuit unit 10. The monitoring I signal and the monitoring Q signal separated by the mixer 23 of the error correction circuit unit 20 (step S13) and converted into a digital signal by the ADC 25 (step S14) are captured (step S15).

  Next, the signal processing unit 30 outputs only one monitoring signal (for example, an I signal) out of the captured monitoring I signal and monitoring Q signal to the transmission system circuit unit 10. The signal processing unit 30 controls the phase shifter 21 of the error correction circuit unit 20 so that the amplitude of one of the monitoring signals is maximized. Subsequently, the signal processing unit 30 outputs only the other monitoring signal (for example, Q signal) to the transmission system circuit unit 10. Then, the signal processing unit 30 calculates the baseband signal corresponding to the baseband signal of the other monitoring channel so that the other monitoring signal is minimized, and the quadrature phase shift error is corrected, for example, A Q signal is generated (step S16).

  Further, the signal processing unit 30 stores the amplitude when the amplitude of one of the monitoring signals (for example, the I signal) at the time of correcting the quadrature phase error becomes maximum in a built-in memory. Then, the other monitoring signal (for example, Q signal) is transmitted, and the phase shifter 21 is controlled so that the amplitude thereof is maximized. Subsequently, the amplitude of the other monitoring signal is corrected so that the amplitude of the other monitoring signal is the same as the amplitude of the one monitoring signal previously stored in the built-in memory. For example, by controlling the amplitude of the Q signal to the amplitude of the I signal, IQ amplitude balance error correction of the output modulated wave of the quadrature modulator 15 is performed (step S17).

  Next, a detailed processing procedure of the quadrature phase error correction process (step S16) shown in FIG. 2 will be described with reference to the flowchart shown in FIG. In the following description, the baseband signal of each channel generated by the signal processing unit 30 and transmitted by the transmission system circuit unit 10 (orthogonal modulator 15) is defined as an I signal and a Q signal, and error correction is performed from the output modulation wave. The baseband signal of the monitoring channel that is taken in by the circuit unit 20 and input to the signal processing unit 30 is distinguished and expressed as an I "signal and a Q" signal.

  First, when the signal processing unit 30 detects the start timing of calibration, such as at the time of reception, the I signal output via the DAC 11 constituting the transmission system circuit unit 10 is externally transmitted via the LPF 13 and the quadrature modulator 15. (Step S161). At this time, transmission of the Q signal is stopped. Subsequently, the signal processing unit 30 continuously changes the phase shift amount by the phase shifter 21 of the error correction circuit unit 20 from, for example, 0 to π (step S162), and the amplitude of the I ″ signal at that time is changed. (Step S163) The signal processing unit 30 controls the phase shifter 21 as described above until the amplitude of the I "signal is maximized (Step S164" YES "), and the phase shift by the phase shifter 21 is performed. The amount control is continued, and the amplitude of the I ″ signal at that time is stored in the built-in memory (step S165).

  Subsequently, the signal processing unit 30 transmits the Q signal output via the DAC 12 to the outside via the LPF 14 and the quadrature modulator 15 (step S166). At this time, the transmission of the I signal is stopped, and the Q signal has the same amplitude as the previously transmitted I signal. Next, the signal processing unit 30 monitors the amplitude of the Q ″ signal at that time (step S167). The signal processing unit 30 performs the quadrature phase error until the Q ″ signal is minimized (“YES” in step S168). A Q signal is generated by correcting (step S169).

  Next, a detailed processing procedure of the IQ amplitude balance error correction process (step S17) shown in FIG. 2 will be described with reference to the flowchart shown in FIG.

  The signal processing unit 30 transmits and outputs the Q signal output via the DAC 12 to the outside via the LPF 14 and the quadrature modulator 15 (step S170 in FIG. 4). At this time, the I signal is not transmitted.

  Next, the signal processing unit 30 continuously changes the amount of phase shift by the phase shifter 21 (step S171), and monitors the amplitude of the Q ″ signal at that time (step S173). When the amplitude of the Q ″ signal is maximized by controlling the phase shifter 21 as described above (“YES” in step S173), the amplitude of the Q ″ signal at that time is stored in the built-in memory first. The amplitude of the I ″ signal is compared (step S174). As a result of the comparison, if a mismatch determination is made (step S174 “NO”), the signal processing unit 30 performs amplitude error correction to make the amplitude of the Q signal the same as the I ″ signal previously stored in the built-in memory. (Step S175), the process returns to the “Q signal transmission process” in step S170. When a coincidence determination is finally made (step S174 “YES”), a series of calibration processes for the quadrature modulation error correction (quadrature phase error correction and IQ amplitude balance error correction) is completed.

  Here, with reference to the IQ constellation shown in FIGS. 5 and 6, supplementary explanation about the orthogonal modulation error correction described in the flowcharts of FIGS. 3 and 4 will be given. Here, the IQ constellation represents the output modulated wave of the quadrature converter 15 on the phase plane by symbol points, the in-phase component is shown on the x axis, and the quadrature component is shown on the y axis. Here, a case where QPSK (Quadrature Phase Shift Keying) modulation is performed will be described as an example.

Specifically, during ideal transmission with no quadrature phase shift error and amplitude error, the in-phase component and quadrature component are accurate from the QPSK modulated wave, which is the transmission output of the quadrature modulator 15, as shown in FIG. A quadratic constellation orthogonal to is observed. On the other hand, in the wireless transmission device 1 according to the present embodiment, when correcting the quadrature modulation phase error, the quadrature modulation is performed by transmitting only the I signal under the control of the signal processing unit 30. The output modulated wave becomes a QPSK modulated wave of only the I axis.
Then, when the demodulation side uses the output signal of the local oscillator 18 via the phase shifter 21 as a carrier wave and performs quadrature demodulation, as shown in FIG. 5B, the phase shift between the transmission side and the demodulation side carrier waves. Thus, a rhombus constellation in which the in-phase component and the quadrature component are not exactly orthogonal is observed. At this time, as shown as the DAC observation signal of the transmission system circuit unit 10, the mixer 23 of the error correction circuit unit 20 performs mixing with the same carrier wave as that during transmission, thereby obtaining an I "signal in the baseband.
Next, the signal processing unit 30 continuously changes the amount of phase shift by the phase shifter 21 so that the amplitude of the I ″ signal is maximized. The constellation on the demodulation side at this time is shown in FIG. That is, the signal processing unit 30 performs control to rotate the diamond-shaped constellation clockwise so that the I ″ signal is maximized. Subsequently, when the signal processing unit 30 transmits only the Q signal and performs quadrature modulation, the Q "signal is obtained in the same baseband as described above. Here, if the quadrature modulation is accurately performed, As shown in FIG. 6A as a DAC observation signal, the amplitude of the Q ″ signal becomes zero.

However, if there is a quadrature phase error in the quadrature modulator 15, an amplitude appears in the Q ″ signal as shown in FIG. 6B. By generating the signal, the quadrature phase error of the output modulated wave is eliminated. When the signal processing unit 30 generates the I and Q signals so that the I ″ signal and the Q ″ signal are equal, the quadrature modulator 15. The amplitude error between the I signal and the Q signal of the output modulation wave is eliminated, so that the EVM can be improved by controlling both of the signal processing unit 30.
(Effect of embodiment)
As described above, according to the wireless transmission device 1 according to the present embodiment, the signal processing unit 30 transmits only the monitoring I signal converted by the mixer 23 from the output modulated wave of the quadrature modulator 15 and shifts the signal. After controlling the phaser 21 to maximize the amplitude of the I signal, only the monitoring Q signal is transmitted, and the signal processor 30 generates a signal so that the Q signal is minimized. Thus, the quadrature modulation error of the output modulated wave of the quadrature modulator 15 can be minimized. For this reason, it is possible to correct the quadrature phase error with only one signal that is scalar information without using the quadrature demodulated signal that is vector information. Accordingly, it is possible to provide the wireless transmission device 1 that has a simplified configuration and contributes to miniaturization as well as cost reduction.

  Further, the signal processing unit 30 stores the amplitude when the amplitude of the monitoring Q signal becomes maximum, transmits the monitoring Q signal, and the amplitude of the monitoring I signal becomes maximum. By controlling the phase shifter 21 and controlling the amplitude of the monitoring I signal to be the same as the amplitude of the stored Q signal, the IQ amplitude balance error can also be corrected. For this reason, EVM can be improved.

  In the wireless transmission device 1 according to this embodiment described above, the baseband signal of one monitoring channel is described as I, and the baseband signal of the other monitoring channel is described as Q. The same effect can be obtained when Q is the baseband signal of I and I is the baseband signal of the other monitoring channel.

In addition, in a TDD (Time Division Duplex) system such as PHS (Personal handy-Phone System), if the orthogonal modulation error correction method according to this embodiment is applied to the reception timing, the degradation of EVM is minimized while operating the system. It becomes possible to suppress. Also, if applied to a feedback system that adapts to changes in the response of PA (Power Amp) such as digital predistortion, the feedback system can be used as it is as a circuit for orthogonal modulation error correction. The cost for correcting the modulation error becomes unnecessary.
(Quadrature modulation error correction method in wireless transmitter)
Note that the quadrature modulation error correction method in the radio apparatus according to the present embodiment includes, for example, a quadrature modulator 15 that directly modulates a carrier wave using an I-channel baseband signal and a Q-channel baseband signal in FIG. A phase shifter 21 that controls the phase of the output signal of the local oscillator 18 that generates the carrier wave, and a signal processing unit 30. The signal processing unit 30 monitors the output of the quadrature modulator 15 and performs quadrature. This is a quadrature modulation error correction method in the wireless transmission device 1 that performs modulation error correction. For example, in the flowcharts shown in FIGS. 2 to 4, when the error of the quadrature modulator is corrected, the output of the quadrature modulator is converted into a monitoring I channel baseband signal and a monitoring Q channel baseband signal. Step of conversion (S11 to S15 in FIG. 2), and the baseband signal of one of the converted monitoring I channel baseband signal and the monitoring Q channel baseband signal Only the step of controlling the phase shifter so that the amplitude of the baseband signal of the one monitoring channel is maximized (S16 in FIG. 2 and S160 to S163 in FIG. 3), Only the baseband signal of the other monitoring channel is transmitted and the other monitoring channel baseband signal is minimized. Calculating a baseband signal corresponding to the baseband signal of the monitoring channel of the first channel and generating the baseband signal of the I channel or the baseband signal of the Q channel corrected for quadrature error (S165 to S168); It is characterized by having.

  In the present invention, the step of storing the amplitude when the amplitude of the baseband signal of the one monitoring channel becomes maximum (S165 in FIG. 3), and then the baseband of the other monitoring channel Transmitting the signal and controlling the phase shifter so that the amplitude is maximized, and the amplitude of the baseband signal of the other monitoring channel and the amplitude of the stored baseband signal of the one monitoring channel are The method further includes a step of correcting the amplitude of the baseband signal of the other monitoring channel so as to be the same (S17 in FIG. 2 and S170 to S175 in FIG. 4).

  According to the quadrature modulation error correction method in the radio transmission apparatus according to the present embodiment, the quadrature modulation error of the output modulated wave of the quadrature modulator 15 can be minimized. For this reason, it is possible to correct the quadrature phase error using only the baseband signal of one channel, which is scalar information, without using the quadrature demodulated signal, which is vector information. Therefore, the configuration is simplified and the cost is reduced. A wireless transmission device that contributes to downsizing as well as suppression can be provided. In addition, the amplitude error can be corrected, and therefore, EVM can be improved.

  As mentioned above, although preferred embodiment of this invention was explained in full detail, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

1 .... Radio transmitter 10 ... Transmission system circuit unit 11,12 ... DAC, 13,14 ... LPF, 15 .... Quadrature modulator, 16 .... Amplifier, 17 .... BPF, 18 .... Local part Oscillator, 20 ... Error correction circuit, 21 ... Phase shifter, 22 ... BPF, 23 ... Mixer, 24 ... LPF, 25 ... ADC, 30 ... Signal processor

Claims (4)

A wireless transmission device that includes a quadrature modulator that directly modulates a carrier wave using an I-channel baseband signal and a Q-channel baseband signal, and that performs quadrature modulation error correction by monitoring the output of the quadrature modulator. And
A phase shifter for controlling the phase of the output signal of the local oscillator that generates the carrier wave;
A mixer for converting the output of the quadrature modulator into a monitoring I-channel baseband signal and a monitoring Q-channel baseband signal;
At the time of error correction of the quadrature modulator, only the baseband signal of one monitoring channel is transmitted from the monitoring I channel baseband signal and the monitoring Q channel baseband signal converted by the mixer. After controlling the phase shifter so that the amplitude of the baseband signal of the one monitoring channel is maximized, only the baseband signal of the other monitoring channel is transmitted, The baseband signal corresponding to the baseband signal of the other monitoring channel is calculated so as to minimize the baseband signal and the quadrature phase error is corrected, and the baseband signal of the I channel or the baseband of the Q channel A signal processing unit for generating a signal;
A wireless transmission device comprising: The signal processing unit
The amplitude when the amplitude of the baseband signal of the one monitoring channel becomes maximum is stored, then the baseband signal of the other monitoring channel is transmitted, and the base of the other monitoring channel is transmitted. The phase shifter is controlled so that the amplitude of the band signal is maximized so that the amplitude of the baseband signal of the other monitoring channel is the same as the amplitude of the stored baseband signal of the one channel. The radio transmission apparatus according to claim 1, wherein the amplitude of the baseband signal of the I channel or the baseband signal of the Q channel is corrected to minimize an amplitude balance error of the output of the quadrature modulator. A quadrature modulator that directly modulates a carrier wave using an I-channel baseband signal and a Q-channel baseband signal, a phase shifter that controls the phase of an output signal of a local oscillator that generates the carrier wave, and a signal processing unit A quadrature modulation error correction method in a wireless transmission device that performs quadrature modulation error correction by monitoring the output of the quadrature modulator,
Converting the quadrature modulator output into an I-channel baseband signal for monitoring and a Q-band baseband signal for monitoring when error correction of the quadrature modulator is performed;
Of the converted I channel baseband signal for monitoring and Q channel baseband signal for monitoring, only the baseband signal of one monitoring channel is transmitted, and the baseband signal of the one monitoring channel is transmitted. Controlling the phase shifter to maximize the amplitude of
Subsequently, only the baseband signal of the other monitoring channel is transmitted, and the baseband signal corresponding to the baseband signal of the other monitoring channel is minimized so that the baseband signal of the other monitoring channel is minimized. Calculating the I-channel baseband signal or the Q-channel baseband signal corrected for quadrature phase error; and
A quadrature modulation error correction method in a wireless transmission device comprising: Storing the amplitude when the amplitude of the baseband signal of the one monitoring channel becomes maximum;
Subsequently, the baseband signal of the other monitoring channel is transmitted, the phase shifter is controlled so that the amplitude is maximized, and the amplitude of the baseband signal of the other monitoring channel and the stored one The amplitude of the output of the quadrature modulator is corrected by correcting the amplitude of the baseband signal of the I channel or the baseband signal of the Q channel so that the amplitude of the baseband signal of the monitoring channel is the same. Steps to minimize,
The quadrature modulation error correction method in the radio transmission apparatus according to claim 3, further comprising:

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