WO2011018874A1 - 電圧制御発振器を用いた二点変調装置及び較正処理方法 - Google Patents
電圧制御発振器を用いた二点変調装置及び較正処理方法 Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03C—MODULATION
- H03C3/00—Angle modulation
- H03C3/02—Details
- H03C3/09—Modifications of modulator for regulating the mean frequency
- H03C3/0908—Modifications of modulator for regulating the mean frequency using a phase locked loop
- H03C3/0941—Modifications of modulator for regulating the mean frequency using a phase locked loop applying frequency modulation at more than one point in the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03C—MODULATION
- H03C3/00—Angle modulation
- H03C3/02—Details
- H03C3/09—Modifications of modulator for regulating the mean frequency
- H03C3/0908—Modifications of modulator for regulating the mean frequency using a phase locked loop
- H03C3/095—Modifications of modulator for regulating the mean frequency using a phase locked loop applying frequency modulation to the loop in front of the voltage controlled oscillator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03C—MODULATION
- H03C3/00—Angle modulation
- H03C3/02—Details
- H03C3/09—Modifications of modulator for regulating the mean frequency
- H03C3/0908—Modifications of modulator for regulating the mean frequency using a phase locked loop
- H03C3/0966—Modifications of modulator for regulating the mean frequency using a phase locked loop modulating the reference clock
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/083—Details of the phase-locked loop the reference signal being additionally directly applied to the generator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L2207/00—Indexing scheme relating to automatic control of frequency or phase and to synchronisation
- H03L2207/05—Compensating for non-linear characteristics of the controlled oscillator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L2207/00—Indexing scheme relating to automatic control of frequency or phase and to synchronisation
- H03L2207/06—Phase locked loops with a controlled oscillator having at least two frequency control terminals
Definitions
- the present invention relates to a two-point modulation apparatus using a voltage-controlled oscillator and a calibration processing method, and more specifically, a two-point modulation apparatus that calibrates the gain and nonlinearity of a voltage-controlled oscillator and a calibration performed by the two-point modulation apparatus. It relates to the processing method.
- a voltage-controlled oscillator (hereinafter referred to as VCO) is widely used as a device for generating a local oscillation signal in a modulation device of a wireless communication device.
- VCO voltage-controlled oscillator
- a frequency modulation signal and a phase modulation signal can be generated.
- a modulation signal having a constant envelope generated by such a VCO is input to a power amplifier, while a power supply voltage of the power amplifier is controlled, whereby a modulation signal having a modulation component in an amplitude component (phase shift keying; PSK, code division multiple access; CDMA, orthogonal frequency division multiplexing; OFDM, etc.) can be generated.
- PSK phase shift keying
- CDMA orthogonal frequency division multiplexing
- OFDM orthogonal frequency division multiplexing
- FIG. 11 is a diagram illustrating a configuration example of a modulation device using a conventional two-point modulation method.
- the conventional two-point modulation device 501 includes a calculation unit 521, a frequency error calculation unit 522, a loop filter 523, an addition unit 525, a VCO 526, a frequency detection unit 527, and a buffer 528.
- the modulation signal is converted into a signal corresponding to a desired frequency channel in the calculation unit 521 and output as a low-pass response signal via the frequency error calculation unit 522 and the loop filter 523.
- the modulated signal is adjusted to a necessary signal by the buffer 528 and output as a high-pass response signal.
- Adder 525 adds the low-pass response signal and the high-pass response signal, and inputs the result to VCO 526.
- the signal output from the VCO 526 is fed back to the frequency error calculator 522 via the frequency detector 527.
- the frequency error calculation unit 522 detects and outputs a frequency error between the modulation signal output from the computing unit 521 and the signal output from the frequency detection unit 527. By this feedback processing, the frequency of the signal output from the VCO 526 is stabilized.
- FIG. 14 is a diagram illustrating a configuration example of a conventional direct modulation device 511 described in Patent Document 1.
- FIG. 14 is a diagram illustrating a configuration example of a conventional direct modulation device 511 described in Patent Document 1.
- a conventional direct modulation device 511 has a PLL circuit including a VCO 1506, an N-frequency divider (N counter) 1508, a phase comparator, a charge pump (CP), and an RC coupling filter. is doing.
- a phase signal corresponding to a desired channel is converted into a digital modulation signal by a ⁇ modulator and supplied to an N-frequency divider 1508 and a phase comparator.
- the step signal ⁇ fPM is converted into an analog signal by the D / A converter 1510 and then input to the auxiliary terminal 1504 of the VCO 1506 through a low-pass filter (hereinafter referred to as LPF) 1512.
- LPF low-pass filter
- the PLL circuit is operated in a closed loop state.
- the step signal ⁇ fPM is input, and the frequency division ratio of the N-frequency divider 1508 is shifted by ⁇ N.
- the conventional direct modulation device 511 calibrates the gain and nonlinearity of the VCO 1506.
- the adder 525 included in the conventional two-point modulator 501 shown in FIG. 11 is substantially equivalent to a high-pass filter (hereinafter referred to as HPF) (FIG. 15), and therefore passes through the feedforward circuit.
- HPF high-pass filter
- the DC component in the signal that becomes a high-pass response is attenuated.
- a feedforward circuit is used to suppress an increase in circuit scale. It is desirable to use both.
- the reference signal passes through the feedforward circuit, the DC component is attenuated, and the reference signal input to the VCO may be distorted. For this reason, there is a problem that the VCO calibration process cannot be performed with high accuracy.
- the object of the present invention is to calibrate the gain and nonlinearity of the VCO with the feedback circuit in an open loop state while suppressing the signal distortion due to the HPF of the feedforward circuit, and can calibrate optimally in a short time. It is to provide a two-point modulation device and a calibration processing method.
- the present invention is directed to a two-point modulator using a voltage controlled oscillator.
- the two-point modulator of the present invention includes a feedback circuit that feedback-controls an output signal from a voltage-controlled oscillator based on an input modulation signal, and a voltage obtained by calibrating the modulation signal.
- a voltage including a modulation unit including a feedforward circuit that outputs to the controlled oscillator, a signal output unit that outputs a predetermined reference signal to the modulation unit instead of the modulation signal, and a feedback circuit in an open loop during the calibration process
- a gain correction unit that calculates a frequency transition amount of the reference signal output from the controlled oscillator and corrects a gain used for calibration of the modulation signal in the feedforward circuit based on the calculated frequency transition amount; This gain correction unit corrects the gain to reflect the effect of signal distortion caused by the high-pass filter included in the feedforward circuit.
- the reference signal is a signal having a pattern in which positive and negative rectangular pulses representing the frequency f are alternately generated with a pulse width T.
- the reference signal includes at least a pulse having a pulse value of 0 having no frequency information, a positive and negative rectangular pulse expressing the frequency f1, and a positive and negative rectangular pulse expressing the frequency f2 different from the frequency f1.
- the reference signal is preferably a signal having a pattern that changes in ascending order from a rectangular pulse having the lowest frequency transition amount to a rectangular pulse having the highest frequency transition amount.
- the modulation unit fixes the output voltage to the voltage controlled oscillator to the lock-up voltage.
- the feedback circuit can be easily brought into an open loop state.
- the gain correction unit calculates a frequency transition amount for each of a plurality of rectangular pulses constituting the reference signal.
- the gain correction unit calculates the frequency transition amount after waiting for the output of the voltage controlled oscillator to stabilize after rising of a plurality of rectangular pulses.
- the calibration processing method performed in the two-point modulation device using the voltage controlled oscillator includes a step of locking up a feedback circuit that feedback-controls an output signal from the voltage controlled oscillator based on the input modulation signal. Applying a voltage to the voltage controlled oscillator to cause the feedback circuit to be in an open loop state, outputting a predetermined reference signal to the voltage controlled oscillator through a feed forward circuit for calibrating the modulation signal, and This is realized by calculating the frequency transition amount of the reference signal output from the voltage controlled oscillator and correcting the gain used for calibration of the modulation signal in the feedforward circuit based on the calculated frequency transition amount.
- the VCO gain and nonlinearity can be appropriately calibrated in a short time.
- FIG. 1 is a diagram illustrating a configuration example of a two-point modulation device 1 according to an embodiment of the present invention.
- FIG. 2 is a flowchart showing the procedure of the calibration operation performed by the two-point modulation device 1.
- FIG. 3 is a diagram illustrating an example of a pulse pattern of a reference signal used in the first embodiment.
- FIG. 4 is a diagram illustrating an example in which distortion due to HPF attenuation occurs in the pulse pattern of FIG.
- FIG. 5 is a diagram illustrating a detailed configuration example of the correction gain calculation unit 31 used in the first embodiment.
- FIG. 6 is a diagram illustrating an example of a table included in the correction gain holding unit 32 in the first embodiment.
- FIG. 7 is a diagram illustrating an example of a pulse pattern of a reference signal used in the second embodiment.
- FIG. 8 is a diagram illustrating an example in which distortion due to HPF attenuation occurs in the pulse pattern of FIG.
- FIG. 9 is a diagram illustrating an example of a table included in the correction gain holding unit 32 in the second embodiment.
- FIG. 10 is a diagram illustrating an example of a pulse pattern of a reference signal used in the third embodiment.
- FIG. 11 is a diagram illustrating a configuration example of a conventional two-point modulation device 501.
- FIG. 12 is a diagram for explaining that a wide band can be realized by a modulation device of a two-point modulation method.
- FIG. 13 is a diagram for explaining the frequency characteristics of a non-linear VCO.
- FIG. 14 is a diagram illustrating a configuration example of a conventional direct modulation device 511.
- FIG. 15 is a diagram illustrating an equivalent circuit of addition unit 525 shown in FIG.
- FIG. 1 is a diagram illustrating a configuration example of a two-point modulation device 1 according to an embodiment of the present invention.
- the two-point modulation device 1 includes a signal output unit 10, a modulation unit 20, and a gain correction unit 30.
- the signal output unit 10 includes a signal selection unit 11 and a reference signal generation unit 12.
- the modulation unit 20 includes a calculation unit 21, a frequency error calculation unit 22, a loop filter 23, a voltage holding unit 24, an addition unit 25, a VCO 26, a frequency detection unit 27, and a gain calibration unit 28.
- the gain correction unit 30 includes a correction gain calculation unit 31 and a correction gain holding unit 32.
- the reference signal generation unit 12 generates a reference signal used during a calibration operation described later.
- the signal selection unit 11 receives the modulation signal and the reference signal, selects and outputs the modulation signal during normal modulation processing, and selectively outputs the reference signal during calibration processing.
- a multiplexer is used for the signal selection unit 11.
- the signal output from the signal selection unit 11 is input to the calculation unit 21 and the gain calibration unit 28 of the modulation unit 20.
- the calculation unit 21 receives the signal output from the signal selection unit 11 and a desired frequency channel signal, and controls the center frequency of the signal output from the signal selection unit 11 to a desired value.
- the signal output from the calculation unit 21 is compared with the frequency signal detected by the frequency detection unit 27 in the frequency error calculation unit 22, and an error signal indicating the frequency error between the two signals is calculated.
- the error signal is output to the adding unit 25 via the voltage holding unit 24 after the high frequency side component is suppressed by the loop filter 23.
- This loop filter 23 for example, a low-pass filter is used.
- the voltage holding unit 24 holds the output signal of the loop filter 23 as necessary.
- the VCO 26 outputs a signal having a frequency corresponding to the signal (control voltage) output from the adder 25.
- the frequency detector 27 detects the frequency of the signal output from the VCO 26 and outputs the detected frequency to the frequency error calculator 22.
- a frequency digital converter (FDC) is used for the frequency detection unit 27.
- the frequency error calculation unit 22, the loop filter 23, the voltage holding unit 24, the addition unit 25, the VCO 26, and the frequency detection unit 27 form a low-pass response feedback circuit.
- the error signal calculated by the frequency error calculation unit 22 is finally a value corresponding to zero and the control voltage is stabilized, and the VCO 26 outputs a signal having a frequency corresponding to a desired channel signal. , The VCO 26 is locked up.
- the gain calibration unit 28 receives the signal output from the signal selection unit 11 and calibrates the gain of the signal output from the signal selection unit 11 according to the correction gain value held by the correction gain holding unit 32.
- the adding unit 25 combines the signal output from the voltage holding unit 24 and the signal output from the gain calibration unit 28 and outputs the resultant signal to the VCO 26.
- the gain calibration unit 28, the addition unit 25, and the VCO 26 form a high-pass response feedforward circuit.
- the correction gain calculator 31 calculates the correction gain of the VCO 26 from the frequency detected by the frequency detector 27 during the calibration operation.
- the correction gain holding unit 32 holds the correction gain calculated by the correction gain calculation unit 31 for each frequency for which the calibration operation has been performed.
- the gain calibration unit 28 calibrates the modulation signal passing through the feedforward circuit using the correction gain held in the correction gain holding unit 32 during the modulation process.
- FIG. 2 is a flowchart showing the procedure of the first embodiment of the calibration operation performed by the two-point modulator 1 of the present invention. This first embodiment describes a method for calibrating the gain of the VCO 26.
- the signal selection unit 11 selects a state in which no signal is input.
- a frequency channel signal having a desired frequency fc is input to the frequency error calculation unit 22 to place the feedback circuit in a closed loop state (step S201).
- Measurement is performed (step S202).
- the lockup voltage is held by the voltage holding unit 24 (step S203).
- the loop filter 23 is stopped, and the lockup voltage held by the voltage holding unit 24 is fixedly supplied as a voltage to be output to the adding unit 25, and the feedback circuit is set in an open loop state (step S204).
- the signal selection unit 11 switches the output of the reference signal generation unit 12 to the selected state (step S205).
- the gain calibration unit 28 sets the correction gain value of the VCO 26 to an initial value (step S205).
- the reference signal generation unit 12 generates a reference signal having the pulse pattern shown in FIG. 3 and outputs the reference signal to the correction gain holding unit 32 and the gain calibration unit 28.
- FIG. 3 is a diagram for explaining the reference signal used in the first embodiment in order to measure the correction gain value of the VCO 26.
- the reference signal shown in FIG. 3 includes a first pulse having a positive pulse value + A expressing the frequency f, a second pulse having a negative pulse value ⁇ A expressing the frequency f, and a positive pulse value + A.
- the third pulse having The pulse widths of the first to third pulses are time T, respectively.
- the pulse value A and the pulse width T of the reference signal are set to values that allow the correction gain calculation unit 31 to calculate the correction gain with sufficient accuracy. For example, if the pulse value A is too small, the amount of transition of the output frequency of the VCO 26 becomes smaller than the resolution of the frequency detector 27.
- the correction gain calculation unit 31 cannot calculate an accurate correction gain.
- the correction gain calculation unit 31 cannot calculate an accurate correction gain due to the influence of the non-linearity of the VCO 26. If the pulse width T is too small, the correction gain calculation unit 31 cannot sufficiently average the output signal of the frequency detection unit 27 and cannot calculate an accurate correction gain due to the influence of noise. On the other hand, if the pulse width T is too large, the correction gain calculation unit 31 needs useless time to calculate the correction gain.
- FIG. 5 is a diagram illustrating a detailed configuration example of the correction gain calculation unit 31.
- the frequency transition amount measuring unit 311 For each of the first to third pulses, the frequency transition amount measuring unit 311 has a period from a time when a predetermined time t0 has elapsed from the pulse rising point to a pulse falling point at which the time t1 has elapsed from the time t0. The frequency is measured and the average frequency transition amount of each pulse is obtained.
- the predetermined time t0 is a time required for the output of the VCO 26 to follow and stabilize with respect to the pulse change, and the length of the time can be arbitrarily set.
- HPF output HPF out (t) is expressed by the following equation [1].
- CR is a time constant of HPF.
- the frequency at the time when the predetermined time t0 has elapsed from the rising point of the pulse is + A ⁇ D
- the frequency at the falling point T of the pulse is + AD.
- ⁇ t0 / (t0 + t1). Therefore, the frequency transition amount fmeas1 of the first pulse is expressed by the following equation [4].
- the frequency transition amount fmeas2 of the second pulse is expressed by the following equation [5].
- the frequency transition amount fmeas3 of the third pulse is the same as that of the first pulse and is given by the following equation [6].
- the frequency transition amount correction unit 312 calculates the frequency transition amount fcomp of the reference signal that has been distorted by HPF from the frequency transition amounts fmeas1 to fmeas3 of the first to third pulses measured by the frequency transition amount measurement unit 311. It calculates
- the calculation unit 313 corrects the gain of the VCO 26 in consideration of signal distortion due to HPF based on the frequency transition amount fref and the frequency transition amount fcomp of the reference signal output from the reference signal generation unit 12.
- the gain value G is obtained by the following equation [8].
- the obtained correction gain value G of the VCO 26 is held in the correction gain holding unit 32 (step S207).
- the correction gain value G of the VCO 26 is obtained for each of the plurality of channel frequencies.
- FIG. 6 is a diagram illustrating an example of a table included in the correction gain holding unit 32 according to the first embodiment.
- the table may hold correction gain values G for a plurality of channel frequencies as shown in FIG. 6, or only one correction gain value G may be held and locked to each channel frequency.
- the correction gain value G may be calibrated. In the latter case, the circuit scale can be reduced compared to the former.
- the signal selection unit 11 switches to the state in which the modulation signal is selected, and the feedback circuit changes the output of the voltage holding unit 24 to the output from the loop filter 23 and returns to the closed loop state (step) S208).
- the correction gain holding unit 32 determines the frequency of the modulation signal and outputs the correction gain value G of the VCO 26 associated with the determined frequency to the gain calibration unit 28.
- the average value of the frequency transition amount of each pulse constituting the reference signal is reflected in the correction gain value.
- the reference signal in which the first pulse having the pulse value + A, the second pulse having the pulse value ⁇ A, and the third pulse having the pulse value + A are generated for each period T has been described.
- the reference signal is not limited to the pulse pattern described in the first embodiment. If the pulse pattern is such that a pulse with a pulse value + A and a pulse with a pulse value ⁇ A are alternately generated with a pulse width T, The order and number can be freely set.
- This second embodiment describes a method for calibrating the gain and nonlinearity of the VCO 26.
- the procedure of the second embodiment of the calibration operation performed by the two-point modulation device 1 of the present invention is basically the same as the procedure shown in FIG. 2, but the process of step S206 is different.
- the second embodiment will be described focusing on the processing in step S206.
- the reference signal generation unit 12 When the initial correction gain value is set in the gain calibration unit 28 (step S205), the reference signal generation unit 12 generates a reference signal of the pulse pattern shown in FIG. 7, and the correction gain holding unit 32 and the gain calibration unit To 28.
- FIG. 7 is a diagram for explaining a reference signal used in the second embodiment in order to measure the correction gain value of the VCO 26.
- the reference signal shown in FIG. 7 includes a zeroth pulse of no signal for which no frequency information is output, a first pulse having a negative pulse value ⁇ A1 expressing the frequency f1, and a positive pulse value expressing the frequency f1.
- the pulse widths of the 0th to 9th pulses are each time T.
- the attenuation by HPF in the feedforward circuit causes each pulse value ⁇ A of the 0th to 9th pulses of the reference signal observed by the frequency detector 27 as shown by the solid line in FIG.
- the frequency ⁇ A2 is attenuated (drift) by the frequency D2, the frequency ⁇ A3 by the frequency D3, and the frequency ⁇ A4 by the frequency D4. Therefore, in the second embodiment, the correction gain calculation unit 31 performs the calculation by the following method (step S206).
- the frequency transition amount measuring unit 311 determines, for each of the 0th to 9th pulses, the time ⁇ when the predetermined time t0 has elapsed from the rising point of the pulse and the time t1 from the time ⁇ .
- the frequency of two points with the falling point of the elapsed pulse is measured, and the frequency transition amount of each pulse is obtained.
- the frequency transition amounts fmeas0 to fmeas9 of the 0th to 9th pulses are expressed by the following equations [9] to [18], respectively.
- the frequency transition amount correction unit 312 uses the frequency transition amounts fmeas1 to fmeas3 of the first to ninth pulses measured by the frequency transition amount measurement unit 311 to each frequency transition amount of the reference signal subjected to distortion.
- fcomp is obtained by the following equation [29].
- the calculation unit 313 corrects for each frequency for calibrating the gain and nonlinearity of the VCO 26 based on the frequency transition amount fref of the reference signal output from the reference signal generation unit 12 and each frequency transition amount fcomp.
- the gain value G is obtained by equation [30].
- the frequency transition amounts fcomp1 to fcomp3 of the first to third pulses are used to calibrate the gain of the VCO 26, and the frequency transition amounts fcomp2 to fcomp9 of the second to ninth pulses are nonlinearities of the VCO 26. Is used to calibrate
- the obtained correction gain value G of the VCO 26 is held in the correction gain holding unit 32 (step S207).
- the correction gain value G of the VCO 26 is obtained for each of the plurality of channel frequencies.
- FIG. 9 is a diagram illustrating an example of a table included in the correction gain holding unit 32 according to the second embodiment.
- the correction gain value G is not limited to holding all values corresponding to all of the pulse values ⁇ A1, ⁇ A2, ⁇ A3, and ⁇ A4 shown in FIG. You may hold
- the frequency transition amount of each pulse constituting the reference signal is reflected in the correction gain value.
- a reference signal having four rectangular pulses with pulse values ⁇ A1, ⁇ A2, ⁇ A3, and ⁇ A4 is used to calibrate the nonlinearity of the VCO 26.
- the non-linearity calibration of the VCO 26 is performed by correcting the correction gain value for at least two frequencies in the frequency band of the modulation signal (in the second embodiment, the pulse values ⁇ A4 to + A4 correspond to the frequency bandwidth of the modulation signal). This is possible by calculating.
- the frequency spectrum of a modulation signal is observed, many components are often included in the vicinity of DC (in the vicinity of the channel frequency when observed in the RF band).
- the correction gain value is calculated with respect to the both-end frequencies of the modulation signal bandwidth (pulse values -A4 and + A4 in the second embodiment) and a frequency in the middle (pulse values ⁇ A1 in the second embodiment).
- the pulse value ⁇ A1 may be a frequency transition amount equal to or higher than the minimum resolution of the frequency detection unit 27.
- the nonlinearity can be calibrated with higher accuracy.
- one point of correction gain value was obtained by calibration, and in the second embodiment, plural points of correction gain values were obtained.
- the number of correction gain values to be determined is determined by the bandwidth of the modulation signal and the non-linearity of the VCO 26. In FIG. 13, when the linear region of the VCO 26 is larger than the bandwidth of the modulation signal, the number of correction gain values may be one point. Conversely, when the linear region of the VCO 26 is smaller than the bandwidth of the modulation signal, a plurality of correction gain values are required.
- the plurality of pulses constituting the reference signal are rectangular pulses having a frequency with the smallest frequency transition amount (in this example, pulse value ⁇ A1) as shown in FIG. It is desirable that the pattern be configured in a pattern that changes in ascending order up to a rectangular pulse having a frequency transition amount (pulse value ⁇ A4 in this example) having the largest frequency transition amount.
- the pulse width T is constant for all reference signals.
- the pulse width T may be changed according to the pulse value.
- ⁇ Third embodiment> a method (predistortion) in which the frequency transition amount fcomp obtained by the frequency transition amount correction unit 312 in the second embodiment is reflected in the reference signal in advance will be described.
- FIG. 10 is a diagram for explaining a reference signal used in the third embodiment.
- the frequency transition amount fcomp that the frequency transition amount correction unit 312 will obtain is reflected in the reference signal in advance.
- the configuration of the frequency transition amount correction unit 312 can be omitted, and the processing load performed by the frequency transition amount correction unit 312 can be eliminated, and the calibration process can be executed at high speed.
- the present invention can be used for a wireless communication device equipped with a two-point modulation device using a VCO, and is particularly useful when calibrating the gain and nonlinearity of a VCO considering signal distortion caused by the HPF of the feedforward circuit. It is.
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Abstract
Description
図1は、本発明の一実施形態に係る二点変調装置1の構成例を示す図である。この二点変調装置1は、信号出力部10と、変調部20と、利得補正部30とを備える。信号出力部10は、信号選択部11及び参照信号生成部12を含む。変調部20は、演算部21、周波数誤差算出部22、ループフィルタ23、電圧保持部24、加算部25、VCO26、周波数検出部27、及び利得較正部28を含む。利得補正部30は、補正利得算出部31及び補正利得保持部32を含む。
図2は、本発明の二点変調装置1が行う較正動作の第1実施例の手順を示すフローチャートである。この第1実施例は、VCO26の利得を較正する方法を説明する。
この第2実施例は、VCO26の利得及び非線形性を較正する方法を説明する。本発明の二点変調装置1が行う較正動作の第2実施例の手順は、基本的に図2に示す手順と同様であるが、ステップS206の処理が異なる。以下、ステップS206の処理を中心に第2実施例を説明する。
この第3実施例は、上記第2実施例において周波数遷移量補正部312が求めた周波数遷移量fcompを、予め参照信号に反映させておく手法(プリディストーション)を説明する。
10 信号出力部
11 信号選択部
12 参照信号生成部
20 変調部
21、313、521 演算部
22、522 周波数誤差算出部
23、523 ループフィルタ
24 電圧保持部
25、525 加算部
26、526 VCO
27、527 周波数検出部
28 利得較正部
30 利得補正部
31 補正利得算出部
32 補正利得保持部
311 周波数遷移量測定部
312 周波数遷移量補正部
Claims (12)
- 電圧制御発振器を用いた二点変調装置であって、
入力される変調信号に基づいた前記電圧制御発振器からの出力信号をフィードバック制御するフィードバック回路、及び当該変調信号を較正して前記電圧制御発振器へ出力するフィードフォワード回路、を含む変調部と、
較正処理時に、前記変調信号に代えて所定の参照信号を前記変調部へ出力する信号出力部と、
前記フィードバック回路をオープンループにした状態で、前記電圧制御発振器が出力する前記参照信号の周波数遷移量を算出し、当該算出した周波数遷移量に基づいて前記フィードフォワード回路で変調信号の較正に用いられる利得を補正する利得補正部とを備える、二点変調装置。 - 前記参照信号は、周波数fを表現する正極性の矩形パルスと、周波数fを表現する負極性の矩形パルスとが、パルス幅Tで交互に発生するパターンの信号である、請求項1に記載の二点変調装置。
- 前記参照信号は、少なくとも、周波数情報がないパルス値0のパルス、周波数f1を表現する正極性の矩形パルス、周波数f1を表現する負極性の矩形パルス、周波数f1とは異なる周波数f2を表現する正極性の矩形パルス、及び周波数f2を表現する負極性の矩形パルスを、パルス幅Tで発生するパターンの信号である、請求項1に記載の二点変調装置。
- 前記周波数f1が、チャネル周波数が取り得る帯域幅の最小周波数であり、前記周波数f2が、チャネル周波数が取り得る帯域幅の最大周波数である、請求項3に記載の二点変調装置。
- 前記参照信号は、周波数遷移量が最も少ない周波数の矩形パルスから周波数遷移量が最も多い周波数の矩形パルスまで昇順で変化するパターンの信号である、請求項3に記載の二点変調装置。
- 前記フィードバック回路をクローズループにした状態における前記電圧制御発振器のロックアップ電圧を保持する電圧保持部をさらに備え、
前記変調部は、前記電圧制御発振器への出力電圧を前記ロックアップ電圧に固定することで、前記フィードバック回路をオープンループ状態にする、請求項1に記載の二点変調装置。 - 前記利得補正部は、前記参照信号を構成する複数の矩形パルス毎に周波数遷移量を算出する、請求項2に記載の二点変調装置。
- 前記利得補正部は、前記参照信号を構成する複数の矩形パルス毎に周波数遷移量を算出する、請求項3に記載の二点変調装置。
- 前記利得補正部は、前記複数の矩形パルスの立ち上がり後前記電圧制御発振器の出力が安定するまで待って周波数遷移量を算出する、請求項7に記載の二点変調装置。
- 前記利得補正部は、前記複数の矩形パルスの立ち上がり後前記電圧制御発振器の出力が安定するまで待って周波数遷移量を算出する、請求項8に記載の二点変調装置。
- 前記利得補正部は、前記フィードフォワード回路に含まれるハイパスフィルタによる信号歪みの影響を反映させた利得に補正する、請求項1に記載の二点変調装置。
- 電圧制御発振器を用いた二点変調装置で行われる較正処理方法であって、
入力される変調信号に基づいた前記電圧制御発振器からの出力信号をフィードバック制御するフィードバック回路をロックアップさせるステップ、
前記ロックアップさせた時の電圧を前記電圧制御発振器に印加して、前記フィードバック回路をオープンループ状態にさせるステップ、
変調信号の較正を行うフィードフォワード回路を通って、所定の参照信号を前記電圧制御発振器へ出力させるステップ、及び
前記電圧制御発振器が出力する前記参照信号の周波数遷移量を算出し、当該算出した周波数遷移量に基づいて前記フィードフォワード回路で変調信号の較正に用いられる利得を補正するステップを備える、二点変調方法。
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US9350296B1 (en) | 2015-01-23 | 2016-05-24 | Freescale Semiconductor, Inc. | Systems and methods for calibrating a dual port phase locked loop |
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