JP2013207575A - Transmitter, signal generation apparatus, and signal generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter capable of improving accuracy of IQ calibration.SOLUTION: The transmitter comprises: a test signal generation unit 101; an IQ imbalance correction unit 104 for correcting the IQ imbalance of a test signal; a modulator 105; an envelope detection unit 106; and an operation unit 107. The test signal generation unit 101 generates a first test signal S1 and a second test signal S2 on the basis of the detectable range D of the envelope detection unit 106. The operation unit 107 calculates a correction coefficient on the basis of a reference phase θand a measurement phase θ.

Description

  The present invention relates to a transmitter, a signal generation device, and a signal generation method. In particular, the present invention relates to a technique for IQ signal calibration in a transmitter.

  A conventional transmitter modulates and outputs a signal to be transmitted using, for example, an I signal and a Q signal (hereinafter also referred to as an IQ signal). When the I signal and the Q signal are set to the same digital value, if the phase difference between the I signal and the Q signal is 90 degrees and the I signal and the Q signal have the same amplitude, it can be said that the modulation accuracy is high. However, in practice, the transmitter includes an analog circuit, so that the amplitudes of the I signal and the Q signal are different, and the phase difference may deviate from 90 degrees. The transmitter calibrates (calibrates) the IQ signal in the digital domain in order to bring the IQ signal closer to a desired state.

  Conventional transmitters include the following transmitters. The transmitter uses a sinusoidal single sideband signal as a test signal, analyzes the frequency of the envelope-detected signal, and obtains the phase of the frequency-analyzed signal. And a transmitter calculates | requires the directionality of a gain error and a phase error from the calculated | required phase, and calibrates (for example, refer patent document 1).

US Patent No. 7881402

  In order to calibrate the IQ signal, an envelope detector that detects the envelope of the signal is used. The envelope detector is configured using, for example, a detection diode. In the transmitter, an AD converter (Analog to Digital Converter) that receives the output of the envelope detector is disposed after the envelope detector.

In the conventional transmitter, it is desirable to obtain the reference phase in order to improve the calibration accuracy of the IQ signal, but it is unclear how to obtain it. For example, as a simple test signal example for obtaining a 0 ° reference phase, a test signal (I = cos ω _mt , Q = 0) with an extremely large gain error can be considered. Since the test signal has a large dynamic range, a large dynamic range is required for the detection system. That is, a wide detection range is required for the detection diode, or a large number of bits is required for the AD converter.

  When a signal in a relatively narrow frequency band (for example, 1 GHz band) is handled, the modulation frequency of the AD converter can be lowered, and the number of bits (dynamic range, vertical resolution) that can be handled by the AD converter can be increased. In the AD converter, since the frequency band of the input signal and the number of bits are in a trade-off relationship, the number of bits that can be handled can be increased as the frequency band is narrower. Therefore, there is a high possibility that a signal having a relatively narrow frequency band can be detected accurately.

  On the other hand, when a signal in a relatively wide frequency band (for example, 60 GHz band) is handled, it is necessary to increase the modulation frequency of the AD converter. Therefore, since the detection accuracy of the test signal having a large dynamic range is deteriorated, it is difficult to obtain an accurate reference phase, and the accuracy of IQ calibration is insufficient.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a transmitter, a signal generation device, and a signal generation method capable of improving the accuracy of IQ calibration.

  The transmitter of the present invention includes a test signal generation unit that generates a first test signal and a second test signal, a signal correction unit that corrects IQ imbalance of the test signal generated by the test signal generation unit, A modulation unit that modulates the correction signal corrected by the signal correction unit, an envelope detection unit that detects an envelope of the modulation signal modulated by the modulation unit, and an envelope detected by the envelope detection unit A correction coefficient processing unit that calculates a correction coefficient for correcting the IQ imbalance by the signal correction unit, and the test signal generation unit is based on a detectable range of the envelope detection unit. The first test signal and the second test signal are generated, and the correction coefficient processing unit calculates a reference phase of the test signal based on a first envelope based on the first test signal , Based on the second envelope curve based on the second test signal, it calculates the measured phase of the test signal, and calculates the correction factor based on the measured phase and the reference phase.

  With this configuration, the detection accuracy of the envelope detector is improved, and the reference phase can be obtained with high accuracy. Therefore, the accuracy of IQ calibration can be improved.

  In addition, the signal generation device of the present invention includes a test signal generation unit that generates the first test signal and the second test signal, and a signal correction that corrects IQ imbalance of the test signal generated by the test signal generation unit. And a correction coefficient processing unit that calculates a correction coefficient for correcting the IQ imbalance by the signal correction unit based on an envelope of a modulation signal obtained by modulating the correction signal corrected by the signal correction unit. The test signal generation unit generates the first test signal and the second test signal based on a detectable range of an envelope detection unit that detects the envelope, and the correction coefficient processing unit Calculates a reference phase of the test signal based on the first envelope based on the first test signal, and measures the test signal based on the second envelope based on the second test signal. Calculating a phase, and calculates the correction factor based on the measured phase and the reference phase.

  With this configuration, the detection accuracy of the envelope detector is improved, and the reference phase can be obtained with high accuracy. Therefore, the accuracy of IQ calibration can be improved.

  The signal generation method of the present invention includes a test signal generation step for generating a first test signal and a second test signal, a correction step for correcting IQ imbalance of the generated test signal, and the correction. And a calculation step for calculating a correction coefficient for correcting the IQ imbalance based on an envelope of the modulation signal obtained by modulating the correction signal. In the test signal generation step, the envelope is detected. The first test signal and the second test signal are generated based on a detectable range of an envelope detector, and in the calculation step, based on the first envelope based on the first test signal, A reference phase of the test signal is calculated, a measurement phase of the test signal is calculated based on a second envelope based on the second test signal, and the measurement phase and the reference position are calculated. And calculates the correction coefficient based on.

  By this method, the detection accuracy of the envelope detection unit is improved, and the reference phase can be obtained with high accuracy. Therefore, the accuracy of IQ calibration can be improved.

  According to the present invention, the accuracy of IQ calibration can be improved.

Block diagram of a transmitter in an embodiment of the present invention The block diagram which shows the detailed structural example of the IQ imbalance correction part in embodiment of this invention The block diagram which shows the detailed structural example of the modulator in embodiment of this invention (A), (B) The figure which shows an example of the 1st test signal in the IQ plane in the embodiment of the present invention, and the 2nd test signal The figure which shows an example of the input-output characteristic of the envelope detector in embodiment of this invention The flowchart which shows the operation example of the calculating part in embodiment of this invention The figure which shows an example of the relationship between the detection phase and direction of IQ imbalance in embodiment of this invention The block diagram which shows the 1st structural example of the radio | wireless apparatus in embodiment of this invention. The block diagram which shows the 2nd structural example of the radio | wireless apparatus in embodiment of this invention.

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

  FIG. 1 is a block diagram illustrating a configuration example of a transmitter 100 according to an embodiment of the present invention. The transmitter 100 includes a test signal generation unit 101, a baseband signal generation unit 102, a MUX (Multiplexer) 103, an IQ imbalance correction unit 104, a modulator 105, an envelope detection unit 106, a calculation unit 107, and a memory 108. .

  The test signal generation unit 101 generates a test signal for measuring IQ imbalance and outputs the test signal to the MUX 103. The test signal generation unit 101 generates a test signal based on the detectable range of the envelope detection unit 106. Details of the test signal generation method will be described later.

  The baseband signal generation unit 102 generates a baseband signal used for communication and outputs it to the MUX 103.

  The MUX 103 selects either the test signal or the baseband signal and outputs it to the IQ imbalance correction unit. The MUX 103 selects an output from the test signal generation unit 101 in the calibration mode, that is, when the IQ signal is calibrated. In addition, the MUX 103 selects an output from the baseband signal generation unit 102 in the data transmission mode, that is, when transmitting a burst band signal.

  The IQ imbalance correction unit 104 corrects the input IQ signal using a parameter (correction coefficient) stored in a LUT (Look Up Table) held by the memory 108, and outputs the correction signal to the modulator 105. . In the correction by the IQ imbalance correction unit 104, the IQ imbalance is corrected. IQ imbalance includes amplitude error and phase error.

  The modulator 105 modulates the correction signal from the IQ imbalance correction unit 104 and outputs a modulation signal (high frequency signal).

  The envelope detector 106 includes an envelope detector 106A and an AD converter 106B connected in series at the subsequent stage of the envelope detector. The envelope detector 106 </ b> A is configured using a detection diode, and detects the envelope of the high-frequency signal output from the modulator 105. The AD converter 106 </ b> B converts an analog signal as a detection result of the envelope into a digital signal, and outputs the digital signal (envelope signal) to the calculation unit 107.

  The computing unit 107 detects the IQ imbalance by analyzing the envelope signal. In addition, the calculation unit 107 obtains a correction coefficient for correcting the IQ imbalance, and updates the LUT held by the memory 108. That is, the calculation unit 107 has a function as a correction coefficient processing unit that calculates a correction coefficient based on the envelope detected by the envelope detection unit 106.

  The arithmetic unit 107 implements each function by executing a program stored in a memory (not shown). Details of the operation of the arithmetic unit 107 will be described later.

  The memory 108 has an LUT and stores various data and various parameters. Various parameters include a matrix c including correction coefficients.

  Note that the test signal generation unit 101, the baseband signal generation unit 102, the MUX 103, the IQ imbalance correction unit 104, the calculation unit 107, and the memory 108 are configured in the first integrated circuit, and the modulator 105 and the envelope detection unit 106 may be configured in the second integrated circuit. Moreover, all the components in the transmitter 100 may be configured by one integrated circuit.

Next, the IQ imbalance correction unit 104 will be described.
The matrix c used for IQ imbalance correction is described by, for example, the following (Equation 1) using the value g _c and the value θ _c . The value g _c is a contributing value for the correction of the amplitude error g _e, the value theta _c that contribute value to correct the phase error theta _e.

If the amplitude error g _e and the phase error theta _e is sufficiently small, also becomes small enough value g _c and the value theta _c, the matrix c can be approximated by the following equation (2).

FIG. 2 is a block diagram illustrating a detailed configuration example of the IQ imbalance correction unit 104.
The IQ imbalance correction unit 104 includes, for example, multipliers 201, 202, 203, and 204 and adders 205 and 206.

  The multiplier 201 receives the I signal (pre-correction I signal) from the MUX 103 and the correction coefficient c (1, 1) stored in the LUT and multiplies them. The multiplier 202 receives the I signal (pre-correction I signal) from the MUX 103 and the correction coefficient c (2, 1) stored in the LUT and multiplies them. The multiplier 203 receives the Q signal (Q signal before correction) from the MUX 103 and the correction coefficient c (1, 2) stored in the LUT and multiplies them. The multiplier 204 receives the Q signal (Q signal before correction) from the MUX 103 and the correction coefficient c (2, 2) stored in the LUT and multiplies them.

  Adder 205 inputs and multiplies the output of multiplier 201 and the output of multiplier 203, and outputs a corrected I signal (corrected I signal). Adder 206 inputs and multiplies the output of multiplier 202 and the output of multiplier 204, and outputs a corrected Q signal (corrected Q signal).

Next, the modulator 105 will be described.
FIG. 3 is a block diagram illustrating a detailed configuration example of the modulator 105.
The modulator 105 includes multipliers 301 and 302, an oscillator 303, and an adder 304.

  Multiplier 301 receives and multiplies the I signal (corrected I signal) corrected by IQ imbalance correction unit 104 and the output of oscillator 303. Multiplier 302 receives and multiplies the Q signal (corrected Q signal) corrected by IQ imbalance correction unit 104 and the output of oscillator 303.

  The oscillator 303 generates a continuous wave signal, adds a 90 ° phase difference between the two continuous wave signals, and supplies the signal to the multiplier 301 and the multiplier 302. The adder 304 inputs the output of the multiplier 301 and the output of the multiplier 302 and adds them.

The output of the adder 304 becomes a modulated signal and becomes an output signal of the transmitter 100. The transmitter 100 may be provided with an amplifier after the modulator 105. The output signal of the transmitter 100 is represented by the following (Equation 3) using the amplitude error g _e and the phase error θ _e .

Next, the test signal generation unit 101 will be described.
The test signal includes a first test signal S1 and a second test signal S2. The first test signal S1 is a signal for measuring the reference phase of the signal generated by the transmitter 100. The second test signal S2 is a signal for measuring the measurement phase of the signal generated by the transmitter 100.

  First, the first test signal S1 will be described.

The test signal generation unit 101 outputs, for example, a first test signal S11 expressed by the following (Equation 4) as the first test signal S1. The first test signal S11 represented by (Expression 4) is a signal for obtaining a 0 ° reference phase.

In (Formula 4), A and α are constants. ω _m is an angular frequency of a second test signal (single sideband signal) described later. α is determined by the magnitude of the IQ imbalance of the transmitter 100 and the residual IQ imbalance allowed after the IQ imbalance correction. The same applies to the following equations.

  The first test signal S11 represented by (Equation 4) is expressed as (I, Q) = (A (1 + α), 0) (point A in FIG. 4A) at t = 0 on the IQ plane. Vibration is started with an amplitude Aα in the negative direction of the axis. That is, the distance A is offset as compared with simple test signal vibration centered at the origin (0, 0). Therefore, if the amplitude A ± Aα of the first test signal S11 input to the envelope detector 106A is within the detectable range D shown in FIG. 5, the first test signal S11 can be suitably detected.

Further, the test signal generation unit 101 may output, for example, a first test signal S12 represented by the following (Equation 5) as the first test signal S1. The first test signal S12 represented by (Equation 5) can obtain a 90 ° reference phase.

  On the IQ plane, the first test signal S12 is negative on the Q axis from the point of (I, Q) = (0, A (1 + α)) (point B in FIG. 4A) at t = 0. Vibration is started with an amplitude Aα in the direction. That is, the distance A is offset in the Q-axis direction compared to simple test signal vibration centered on the origin. Therefore, if the amplitude A ± Aα of the first test signal S12 input to the envelope detector 106A is within the detectable range D shown in FIG. 5, the first test signal S12 can be suitably detected.

Further, the test signal generation unit 101 outputs, for example, a first test signal S13 represented by the following (Equation 6) as the first test signal S1. The first test signal S13 represented by (Expression 6) is a signal for obtaining a reference phase of 180 °.

  The first test signal S13 expressed by (Equation 6) is (I, Q) = (A (1-α), 0) (point A in FIG. 4A) at t = 0 on the IQ plane. From this point, vibration is started with an amplitude Aα in the positive direction of the I axis. That is, the distance A is offset in the I-axis direction as compared with the simple test signal vibration centered at the origin (0, 0). Therefore, if the amplitude A ± Aα of the first test signal S13 input to the envelope detector 106A is within the detectable range D shown in FIG. 5, the first test signal S13 can be suitably detected.

  In (Expression 4) to (Expression 6), the first test signals S11, S12, and S13 are IQ signals for amplitude modulation (AM) signals, for example.

Next, the second test signal S2 will be described.
The test signal generation unit 101 outputs a second test signal S2 represented by the following (Equation 7), for example.

In (Expression 7), the second test signal S2 is an IQ signal for a single sideband signal that rotates around the origin (0, 0) on the IQ plane, for example. Further, the angular frequency ω _m of the second test signal S2 is half of the angular frequency 2ω _m of the first test signals S11 to S13.

Here, the reason why the angular frequency ω _{m of} the second test signal S2 is half of the angular frequency 2ω _m of the first test signals S11 to S13 will be described.

  FIG. 4A is a diagram illustrating an example of the first test signal S11 and the ideal second test signal S2 in the IQ plane. FIG. 4B is a diagram illustrating an example of the second test signal S2 in which the I signal is larger than the ideal state and the Q signal is smaller than the ideal state in the IQ plane. Here, the first test signal S11 represented by (Equation 4) is exemplified as the first test signal S1.

  In FIG. 4A, the first test signal S11 repeats linear vibration in the IQ plane. The second test signal S2 rotates to draw a circle in the IQ plane. For example, in FIG. 4B, when the second test signal S2 has a distortion, the amplitude becomes large → small → large → small → large during one cycle on the IQ plane, and the angular frequency is 2 Will change times. Therefore, spurious appears in a half cycle of the second test signal S2.

  On the other hand, for the first test signal S11, the amplitude changes from large to small to large during one cycle, and the angular frequency changes once. Therefore, when the envelope is detected, spurious appears in the same cycle as that of the first test signal S11.

Accordingly, the test signal generator 101, the angular frequency 2 [omega _m of the first test signal S11, so that twice the angular frequency omega _m of the second test signal S2, and generates a test signal. That is, the frequency of the first test signal S1 is twice the frequency of the second test signal S2.

  Next, the envelope detector 106 will be described.

  FIG. 5 is a diagram illustrating an example of input / output characteristics of the envelope detector 106A. The horizontal axis of FIG. 5 indicates the input magnitude of the envelope detector 106A, and the vertical axis indicates the output of the envelope detector 106A, that is, the input magnitude of the AD converter 106B. Referring to FIG. 5, it can be understood that the output of the envelope detector 106A sharply increases in the detectable range D.

In FIG. 4A, the first test signal S11 is offset from the zero point on the I axis on the IQ plane to the A point. Therefore, when a test signal that passes through the origin 0 point on the I axis on the IQ plane is used, the test signal does not preferably fit within the detectable range D, but the first test signal S11 is within the detectable range. D fits well.
Therefore, the entire number of bits of the AD converter 106B can be used, and the detection accuracy of the envelope detector 106A is improved. Therefore, the reference phase can be detected with high accuracy.

  The test signal generation unit 101 adjusts the constant A in (Expression 4) to (Expression 6) indicating the first test signal S1. Specifically, the test signal generation unit 101 determines that the center of vibration A (A, 0) (see FIG. 4A) of the first test signal S1 is in accordance with the characteristics of the envelope detector 106A. It is set to be near the center Dm of the detectable range D of the line detector 106A.

  Further, the test signal generation unit 101 adjusts the constant A in (Expression 7) indicating the second test signal S2. Specifically, the test signal generation unit 101 determines that the center of vibration of the second test signal S2 is in the vicinity of the center Dm of the detectable range D of the envelope detector 106A in accordance with the characteristics of the envelope detector 106A. Set to be. Note that the constant A in the second test signal S2 may be the same value as the constant A in the first test signal S1.

  The magnitude of the signal detected by the envelope detector 106A corresponds to the absolute value of the combined vector of the I signal and the Q signal. When the transmitter 100 does not have IQ imbalance, the size of the envelope of the second test signal S2 detected by the envelope detector 106A is constant. On the other hand, when the transmitter 100 has IQ imbalance, the size of the envelope detected by the envelope detector 106A varies.

  Accordingly, the envelope detector 106A detects a waveform oscillating around the center Dm of the detectable range D regardless of whether the first test signal S1 or the second test signal S2. Further, by setting α so that the magnitudes of the envelope signals of the first test signal S1 and the second test signal S2 are approximately the same, the amplitude can be approximately the same. Therefore, even if the envelope detector 106A or the AD converter 106B having a narrow dynamic range is used, the signal can be detected with high accuracy.

Next, the operation of the calculation unit 107 will be described.
FIG. 6 is a flowchart showing an operation example of the calculation unit 107.

  First, the calculation unit 107 inputs an envelope signal (first envelope) corresponding to the first test signal S1 from the envelope detection unit 106 (step S101).

When the first test signal S1 is input, the arithmetic unit 107 performs frequency analysis by, for example, Fast Fourier Transform (FFT) to obtain the phase θ _ref of the angular frequency component of ω _m (step S102). The phase θ _ref is a reference phase when the second test signal S2 is used.

  Subsequently, the calculation unit 107 inputs an envelope signal (second envelope) corresponding to the second test signal S2 from the envelope detection unit 106 (step S103).

Subsequently, the operating unit 107 inputs the second test signal S2, for example, a frequency analysis by fast Fourier transform, obtaining the phase theta _meas angular frequency components of 2 [omega _m (step S104). The phase θ _meas is the measurement phase of the second test signal S2.

Subsequently, the calculation unit 107 obtains the phase θ = θ _meas −θ _ref (step S105). The phase theta, a phase of the angular frequency components of 2 [omega _m due to IQ imbalance. The transmitter 100 has a phase rotation of the phase θ _ref mainly due to the delay of the MUX 103, the IQ imbalance correction unit 104, and the modulator 105. Therefore, the phase θ can be used to remove the influence of the delay of the system itself and extract the phase component resulting from IQ imbalance.

Subsequently, the computing unit 107 obtains the directions of the amplitude error g _e and the phase error θ _e based on the value of the phase θ (step S106).

  FIG. 7 is a diagram illustrating an example of the relationship between the phase θ and the IQ imbalance direction. Information indicating the relationship of FIG. 7 is stored in, for example, an LUT held by the memory 108.

7, the -45 ° ≦ θ <45 °, the arithmetic unit 107 determines the orientation of the amplitude error _{g e} is negative. That is, the I signal component of the output V is larger than the ideal state. Also, the 45 ° ≦ θ <135 °, the arithmetic unit 107 determines the orientation of the phase error theta _e is to be negative. Further, in the -135 ° ≦ θ <180 ° or -180 ° ≦ θ <135 °, the arithmetic unit 107 determines the orientation of the amplitude error _{g e} is positive. Further, in the -135 ° ≦ θ <-45 °, computing unit 107 determines that the orientation of the phase error theta _e is positive.

Subsequently, the calculation unit 107 updates the value of the matrix c stored in the LUT based on the direction of the amplitude error g _e and the phase error θ _e (step S107). Note that the initial value of the matrix c is set to a unit matrix. By updating the matrix c, the accuracy of the correction coefficient can be improved.

For example, the arithmetic unit 107, the orientation of the amplitude error g _e is in the negative, the value gc of each element of the matrix c and Δg subtracted, it does not change the value .theta.c. That is, in the negative direction of the amplitude error g _e, since components of the I signal is greater than the ideal state, the arithmetic unit 107 updates the value of the matrix c as component of the I signal becomes small.

The arithmetic unit 107, the orientation of the phase error theta _e is in the negative, the value θc of each element of the matrix c and Δθ is subtracted and does not change the value gc. In addition, when the direction of the phase error θ _e is positive, the calculation unit 107 adds Δθ to the value θ _c in each element of the matrix c and does not change the value g _c . The arithmetic unit 107, the orientation of the amplitude error g _e is the positive, the value g _c for each element of the matrix c and Δg subtracted, does not change the value .theta.c.

Incidentally, Delta] g and Δθ are the adjustment parameters of the amplitude error g _e and phase errors theta _e in the case of carrying out the IQ calibration, convergence time is determined from the required convergence accuracy. Further, the IQ imbalance correction unit 104 performs correction using the updated matrix c.

The calculation unit 107 repeats the above processing (step S103 to step S107) using the second test signal S2. Calculation unit 107, the amplitude of the angular frequency component 2 [omega _m to determine whether is smaller than the amplitude of the previous angular frequency component 2 [omega _m (step S108). If the amplitude of the angular frequency component 2 [omega _m is smaller than the amplitude of the previous angular frequency component 2 [omega _m, the process proceeds to step S103.

Accordingly, by repeatedly executing the test using a second test signal S2, the amplitude of the angular frequency component 2 [omega _m is gradually reduced, IQ imbalance of the second test signal S2 is reduced.

On the other hand, if the amplitude of the angular frequency component 2 [omega _m is not smaller than the amplitude of the previous angular frequency component 2 [omega _m, it ends the processing of FIG. That is, at the time when the amplitude of the angular frequency components 2 [omega _m of the second test signal S2 detected by the envelope detector 106A is no longer become smaller, the calibration end.

The computing unit 107 calculates the reference phase θ _ref of the second test signal S2 based on the first envelope based on the first test signal S1. In addition, the arithmetic unit 107 calculates the measurement phase θ _meas of the second test signal S2 based on the second envelope based on the second test signal S2. In addition, the calculation unit 107 calculates a correction coefficient based on the measurement phase θ _meas and the reference phase θ _ref . The correction coefficient is, for example, each element of the matrix c.

Specifically, it is preferable that the calculation unit 107 subtracts the reference phase θ _ref from the measurement phase θ _meas to obtain the phase θ, and calculates a correction coefficient based on the phase θ. More specifically, the arithmetic unit 107, based on the phase theta, to estimate the direction of the amplitude error g _e or phase error theta _e included in the IQ imbalance, based on the orientation of the amplitude error g _e or phase error theta _e It is preferable to calculate the correction coefficient.

According to the operation of the calculation unit 107, the phase θ due to IQ imbalance can be accurately estimated using the reference phase θ _ref . Therefore, the accuracy of IQ calibration can be improved.

In addition, it is preferable that the calculation unit 107 calculates the measurement phase θ _meas a plurality of times from the second test signal S2, and repeats calculation of the correction coefficient based on the calculated measurement phase θ _meas and the reference phase θ _{ref a} plurality of times. Thereby, IQ imbalance can be gradually reduced and converged.

  Next, the operation of the transmitter after completion of calibration will be described.

  When the calibration is completed, the transmitter 100 ends the calibration mode. When the calibration mode ends, the transmitter 100 switches to the data transmission mode. Specifically, the MUX 103 in FIG. 1 selects the output of the baseband signal generation unit 102.

  Subsequently, the IQ imbalance correction unit 104 corrects the IQ signal output from the baseband signal generation unit 102 with reference to the LUT in which the parameter including the matrix c updated by the calculation unit 107 is stored. Subsequently, the modulator 105 modulates the correction signal and transmits the modulated signal.

  According to the transmitter 100, even the envelope detector 106 with a narrow dynamic range can perform highly accurate IQ imbalance calibration, and can reduce distortion of the transmission signal. Note that the IQ calibration may be performed, for example, when the transmitter 100 is turned on, when starting from the sleep mode, and before starting data transmission.

Next, the wireless device 600 including the transmitter 100 will be described.
FIG. 8 is a block diagram illustrating a configuration example of the wireless device 600. Wireless device 600 includes transmitter 100, receiver 602, duplexer 603, and antenna 604.

  The transmitter 100 corrects IQ imbalance, modulates desired data, and transmits a modulated signal. The receiver 602 receives data from other communication devices. The duplexer 603 separates the transmission signal and the reception signal and shares the antenna 604 during transmission and reception.

  The wireless device 600 can transmit data with less distortion.

  Further, as in the wireless device 700 illustrated in FIG. 9, a configuration may be employed in which a transmitting antenna 703 and a receiving antenna 704 are separately provided.

  The present invention is not limited to the configuration of the above embodiment, and any configuration can be used as long as it can achieve the functions shown in the claims or the functions of the configuration of the present embodiment. Applicable.

  In the above embodiment, the case where the present invention is configured by hardware has been described as an example, but the present invention can also be realized by software in cooperation with hardware.

  Each functional block used in the description of the above embodiment is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Here, it may be an LSI, or may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. For example, a Field Programmable Gate Array (FPGA) that can be programmed after manufacturing the LSI, connection of circuit cells in the LSI, or a reconfigurable processor whose settings can be reconfigured may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The present invention is useful for a transmitter, a signal generation apparatus, a signal generation method, and the like that can improve the accuracy of IQ calibration.

100 transmitter 101 test signal generator 102 baseband signal generator 103 MUX
104 IQ imbalance correction unit 105 Modulator 106 Envelope detector 106A Envelope detector 106B AD converter 107 Operation unit 108 Memory 201, 202, 203, 204 Multiplier 205, 206 Adder 301, 302 Multiplier 303 Oscillator 304 Addition Device 600 wireless device 601 transmitter 602 receiver 603 duplexer 604 antenna 700 wireless device 701 transmitter 702 receiver 703, 704 antenna

Claims (9)

A test signal generator for generating a first test signal and a second test signal;
A signal correction unit that corrects IQ imbalance of the test signal generated by the test signal generation unit;
A modulation unit that modulates the correction signal corrected by the signal correction unit;
An envelope detector for detecting an envelope of the modulated signal modulated by the modulator;
A correction coefficient processing unit that calculates a correction coefficient for correcting the IQ imbalance by the signal correction unit, based on the envelope detected by the envelope detection unit;
With
The test signal generation unit generates the first test signal and the second test signal based on a detectable range of the envelope detection unit,
The correction coefficient processing unit calculates a reference phase of the test signal based on a first envelope based on the first test signal, and based on a second envelope based on the second test signal A transmitter that calculates a measurement phase of the test signal and calculates the correction coefficient based on the measurement phase and the reference phase. The transmitter of claim 1, comprising:
The transmitter, wherein the correction coefficient processing unit calculates the phase of the second test signal by subtracting the reference phase from the measurement phase, and calculates the correction coefficient based on the phase. The transmitter according to claim 2, wherein
The correction coefficient processing unit estimates an amplitude error or phase error direction included in the IQ imbalance based on the phase of the second test signal, and calculates a correction coefficient based on the amplitude error or phase error direction. Transmitter. The transmitter according to any one of claims 1 to 3,
The first test signal is an IQ signal for an amplitude modulation signal,
The second test signal is an IQ signal for a single sideband signal that rotates about the origin in the IQ plane,
The transmitter wherein the frequency of the first test signal is twice the frequency of the second test signal. The transmitter according to any one of claims 1 to 4, further comprising:
A storage unit for storing the correction coefficient information;
The said correction coefficient process part is a transmitter which updates the information of the correction coefficient memorize | stored in the said memory | storage part with the calculated correction coefficient. The transmitter according to claim 5, wherein
The correction coefficient processing unit is a transmitter that calculates the measurement phase of the generated signal a plurality of times and repeats the calculation of the correction coefficient based on the calculated measurement phase and the reference phase a plurality of times. The transmitter according to any one of claims 1 to 6, further comprising:
A baseband signal generator for generating a baseband signal;
A transmitter for transmitting the modulated signal;
With
The transmitter, wherein the signal correction unit corrects the baseband signal based on the correction coefficient calculated by the correction coefficient processing unit and generates the correction signal. A test signal generator for generating a first test signal and a second test signal;
A signal correction unit that corrects IQ imbalance of the test signal generated by the test signal generation unit;
A correction coefficient processing unit that calculates a correction coefficient for correcting the IQ imbalance by the signal correction unit based on an envelope of a modulation signal obtained by modulating the correction signal corrected by the signal correction unit;
With
The test signal generation unit generates the first test signal and the second test signal based on a detectable range of an envelope detection unit that detects the envelope.
The correction coefficient processing unit calculates a reference phase of the test signal based on a first envelope based on a first test signal, and based on a second envelope based on a second test signal, A signal generation device that calculates a measurement phase of a test signal and calculates the correction coefficient based on the measurement phase and the reference phase. A test signal generating step for generating a first test signal and a second test signal;
A correction step of correcting IQ imbalance of the generated test signal;
A calculation step of calculating a correction coefficient for correcting the IQ imbalance based on an envelope of a modulation signal obtained by modulating the corrected correction signal;
With
In the test signal generation step, the first test signal and the second test signal are generated based on a detectable range of an envelope detector that detects the envelope.
In the calculation step, a reference phase of the test signal is calculated based on a first envelope based on a first test signal, and the test signal is calculated based on a second envelope based on a second test signal. A signal generation method for calculating the correction coefficient based on the measurement phase and the reference phase.

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