WO2015087494A1 - 等化処理回路、デジタル受信機、信号送受信システム、等化処理方法およびデジタル受信方法 - Google Patents
等化処理回路、デジタル受信機、信号送受信システム、等化処理方法およびデジタル受信方法 Download PDFInfo
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- WO2015087494A1 WO2015087494A1 PCT/JP2014/005801 JP2014005801W WO2015087494A1 WO 2015087494 A1 WO2015087494 A1 WO 2015087494A1 JP 2014005801 W JP2014005801 W JP 2014005801W WO 2015087494 A1 WO2015087494 A1 WO 2015087494A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/04—Control of transmission; Equalising
- H04B3/06—Control of transmission; Equalising by the transmitted signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B1/0475—Circuits with means for limiting noise, interference or distortion
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B2001/0491—Circuits with frequency synthesizers, frequency converters or modulators
Definitions
- the present invention relates to an equalization processing circuit, a digital receiver, a signal transmission / reception system, an equalization processing method, and a digital reception method.
- Patent Document 1 in a coherent receiver, a frequency shift amount between a carrier frequency of an input signal and local light is estimated, and a local oscillator (LO: local oscillator) is reversed in the direction opposite to the estimated value.
- LO local oscillator
- Non-Patent Document 1 discloses a technique for analyzing transfer characteristics from filter coefficients of a time domain equalization filter and compensating for various waveform distortions such as chromatic dispersion and polarization mode dispersion of a received signal based on the analysis result.
- Patent Document 2 discloses a technique for compensating waveform distortion with semi-fixed characteristics that changes due to temperature fluctuations in the previous stage and compensating for waveform distortion that occurs at high speed in the transmission path in the subsequent stage.
- Other related technologies are also disclosed in Patent Documents 3 and 4 and the like.
- Non-Patent Document 1 can compensate for various waveform distortions at high speed, it cannot compensate for waveform distortions with semi-fixed characteristics that change due to temperature fluctuations, for example. Further, the technique of Patent Document 2 performs the waveform distortion with semi-fixed characteristics and the waveform distortion changing at high speed in series, so that the accuracy of individual compensation is lowered.
- the present invention has been made in view of the above-described problems, and an equalization processing circuit, a digital receiver, and a signal capable of highly accurately compensating for waveform distortion with semi-fixed characteristics and waveform distortion that varies at high speed. It is an object to provide a transmission / reception system, an equalization processing method, and a digital reception method.
- an equalization processing circuit uses an input frequency domain equalization coefficient and frequency domain equalization means for frequency domain equalization of an input digital signal.
- Time domain equalization means for equalizing the input digital signal using the time domain equalization coefficient
- waveform distortion detection for detecting dynamic waveform distortion and quasi-static waveform distortion of the equalized digital signal Means
- frequency domain equalization coefficient control means for calculating and outputting a frequency domain equalization coefficient based on the detected quasi-static waveform distortion
- time domain equalization coefficient control means for calculating and outputting the coefficient.
- a digital receiver includes a front-end unit that outputs an input signal by coherent detection using a local signal, and converts the coherently detected signal into a digital signal.
- a / D conversion means for outputting, and the above-described equalization processing circuit to which a digital signal is inputted.
- a signal transmission / reception system includes a digital transmitter that transmits a signal and the above-described digital receiver that receives the transmitted signal.
- the equalization processing method uses the calculated frequency domain equalization coefficient to equalize the input digital signal in the frequency domain and uses the calculated time domain equalization coefficient.
- the digital signal input in the time domain is equalized in the time domain, the dynamic waveform distortion and quasi-static waveform distortion of the equalized digital signal are detected, and the frequency domain equalization coefficient is calculated based on the detected quasi-static waveform distortion.
- the time domain equalization coefficient is calculated based on the detected dynamic waveform distortion.
- a digital reception method outputs an input signal by performing coherent detection using a local oscillation signal, converting the coherent detection signal to a digital signal, and outputting the digital signal.
- the digital signal output using the frequency domain equalization coefficient is equalized in the frequency domain and the digital signal output using the calculated time domain equalization coefficient is equalized in the time domain.
- Detects dynamic waveform distortion and quasi-static waveform distortion calculates frequency domain equalization coefficient based on detected quasi-static waveform distortion and time domain equalization coefficient based on detected dynamic waveform distortion Is calculated.
- waveform distortion with semi-fixed characteristics and waveform distortion that varies at high speed can be compensated with high accuracy.
- FIG. 1 is a block configuration diagram of an equalization processing circuit 10 according to a first embodiment.
- FIG. It is a block block diagram of the waveform distortion detection part 40B which concerns on 1st Embodiment. It is a block block diagram of the waveform distortion detection part 40C which concerns on 1st Embodiment.
- It is a block block diagram of the equalization processing circuit 100 which concerns on 2nd Embodiment.
- It is a block block diagram of the frequency domain equalization part 200 which concerns on 2nd Embodiment.
- 2 is a block configuration diagram of a front end unit 500 of a digital receiver 700.
- FIG. 6 is a diagram for explaining operations of a butterfly FIR filter 310B and a feedback control unit 400 of the digital receiver 700.
- FIG. It is a block block diagram of the digital receiving terminal device 900 which concerns on 2nd Embodiment. It is a block block diagram of the front end part 500B of the digital receiving terminal device 900 which concerns on 2nd Embodiment. It is a block block diagram of another digital receiving terminal device 900B which concerns on 2nd Embodiment. It is a system block diagram of the signal transmission / reception system 1000 which concerns on 2nd Embodiment. It is a block block diagram of the equalization processing circuit 100C which concerns on the modification of 2nd Embodiment.
- the equalization processing circuit 10 includes a frequency domain equalization unit 20, a time domain equalization unit 30, a waveform distortion detection unit 40, a frequency domain equalization coefficient control unit 50, and a time domain equalization coefficient control unit 60.
- the frequency domain equalization unit 20, the time domain equalization unit 30, the waveform distortion detection unit 40, the frequency domain equalization coefficient control unit 50, and the time domain equalization coefficient control unit 60 respectively include the frequency domain equalization means, the time It corresponds to a region equalization means, a waveform distortion detection means, a frequency domain equalization coefficient control means, and a time domain equalization coefficient control means.
- the frequency domain equalization unit 20 performs frequency domain equalization on the digital signal input to the equalization processing circuit 10 based on the control of the frequency domain equalization coefficient control unit 50 and performs frequency domain equalization.
- the digital signal is output to the time domain equalization unit 30.
- the time domain equalization unit 30 performs time domain equalization on the input digital signal based on the control of the time domain equalization coefficient control unit 60, and frequency domain equalization and time domain equalization are performed. Output digital signals.
- the waveform distortion detection unit 40 detects waveform distortion from the digital signal subjected to frequency domain equalization and time domain equalization, and separates it into quasi-static waveform distortion and dynamic waveform distortion.
- the waveform distortion detector 40 outputs the quasi-static waveform distortion to the frequency domain equalization coefficient controller 50 and also outputs the dynamic waveform distortion to the time domain equalization coefficient controller 60.
- the frequency domain equalization coefficient control unit 50 calculates a frequency domain equalization coefficient for compensating for the quasi-static waveform distortion based on the quasi-static waveform distortion input from the waveform distortion detection unit 40 and calculates The frequency domain equalization unit 20 is feedback controlled based on the frequency domain equalization coefficient.
- the time domain equalization coefficient control unit 60 calculates a time domain equalization coefficient for compensating for the dynamic waveform distortion based on the dynamic waveform distortion input from the waveform distortion detection unit 40, and calculates the calculated time domain.
- the time domain equalization unit 30 is feedback-controlled based on the equalization coefficient.
- the waveform distortion detector 40 converts the waveform distortion of a digital signal subjected to frequency domain equalization and time domain equalization into a quasi-static waveform distortion and a dynamic waveform. This is separated into distortion and output to the frequency domain equalization coefficient control unit 50 and the time domain equalization coefficient control unit 60, respectively. Then, the frequency domain equalization coefficient control unit 50 performs feedback control of the frequency domain equalization unit 20 based on the quasi-static waveform distortion, and the time domain equalization coefficient control unit 60 performs time domain etc. based on the dynamic waveform distortion.
- the control unit 30 is feedback-controlled.
- the frequency domain equalization coefficient control unit 50 By performing feedback control of the frequency domain equalization unit 20 based on the quasi-static waveform distortion from which the dynamic waveform distortion is separated, the frequency domain equalization coefficient control unit 50 performs frequency domain equalization over a relatively long time. It can be performed with high accuracy.
- time domain equalization unit 30 is feedback controlled based on the dynamic waveform distortion from which the quasi-static waveform distortion is separated, the processing load on the time domain equalization coefficient control unit 60 that requires high-speed control is reduced. Can do.
- the time domain equalization coefficient control unit 60 outputs the calculated time domain equalization coefficient to the quasi-static waveform distortion extraction unit 41B (dotted arrow), and the quasi-static waveform distortion extraction unit 41B uses the time domain equalization coefficient. It is desirable to extract the quasi-static waveform distortion while referring to FIG. Thereby, the processing load in the quasi-static waveform distortion extraction part 41B can be reduced.
- the 1C includes a low-frequency signal extraction unit 43C, a quasi-static waveform distortion extraction unit 41C, and a dynamic waveform distortion extraction unit 42C.
- the low-frequency signal extracting unit 43C extracts a low-frequency signal from the equalized digital signal, outputs the low-frequency signal to the quasi-static waveform distortion extracting unit 41C, and outputs the rest to the dynamic waveform distortion extracting unit 42C.
- the quasi-static waveform distortion extraction unit 41C extracts quasi-static waveform distortion from the low frequency signal input from the low frequency signal extraction unit 43C.
- the dynamic waveform distortion extraction unit 42C extracts the dynamic waveform distortion from the digital signal from which the low frequency signal has been removed, which is input from the low frequency signal extraction unit 43C.
- a digital signal subjected to equalization processing can be output as it is from the low-frequency signal extraction unit 43C to the dynamic waveform distortion extraction unit 42C.
- the dynamic waveform distortion extraction unit 42C extracts the dynamic waveform distortion from the input digital signal.
- the waveform distortion detectors 40, 40B, and 40C convert the waveform distortion included in the equalized digital signal into a quasi-static waveform distortion and a motion. And are output to the frequency domain equalization coefficient control unit 50 and the time domain equalization coefficient control unit 60, respectively.
- the frequency domain equalization coefficient control unit 50 calculates a frequency domain equalization coefficient based on the separated quasi-static waveform distortion, and the time domain equalization coefficient control unit 60 operates based on the separated dynamic waveform distortion. Calculate the time domain equalization factor.
- the processing in the frequency domain equalization coefficient control unit 50 can be performed with high accuracy over a relatively long time. it can. Further, by calculating the time domain equalization coefficient based on the dynamic waveform distortion from which the quasi-static waveform distortion is separated, the processing load on the time domain equalization coefficient control unit 60 can be reduced.
- the equalization processing circuit 10 compensates for waveform distortion having a semi-fixed characteristic (quasi-static waveform distortion) and waveform distortion (dynamic waveform distortion) that varies at high speed with high accuracy. Can do.
- FIG. 2 shows a block diagram of the equalization processing circuit according to this embodiment.
- the equalization processing circuit 100 includes a frequency domain equalization unit 200, a time domain equalization unit 300, and a feedback control unit 400.
- the frequency domain equalization unit 200 uses the frequency domain equalization coefficient input from the frequency domain equalization coefficient calculation unit 440 to perform frequency domain equalization (FDE: frequency ⁇ ) on the digital signal input to the equalization processing circuit 100. domain equalization) and output to the time domain equalization unit 300.
- FIG. 3 shows a block diagram of the frequency domain equalization unit 200 according to this embodiment.
- the frequency domain equalization unit 200 includes a discrete Fourier transform unit (DFT: discrete Fourier transform) 201, a multiplier 202, and an inverse discrete Fourier transform unit (IDFT: inverse Fourier transform) 203.
- DFT discrete Fourier transform
- IDFT inverse discrete Fourier transform
- the DFT 201 performs a discrete Fourier transform on the digital signal input to the frequency domain equalization unit 200 and outputs N frequency domain signals ⁇ s0 to ⁇ s (N ⁇ 1) to the multiplier 202.
- the converted digital signal has a constant frequency ⁇ s .
- ⁇ s 2 ⁇ f s / N
- FDE applied to OFDM (orthogonal frequency-division multiplexing) modulation system and optical digital coherent communication
- the larger the N the larger the circuit scale and the power consumption to cope with complicated control. Increase.
- the multiplier 202 adds the frequency domain equalization coefficients input from the frequency domain equalization coefficient calculation unit 440 to the N frequency domain signals ⁇ s0 to ⁇ s (N ⁇ 1) input from the DFT 201, respectively.
- the addition result is output to IDFT 203.
- the IDFT 203 performs an inverse discrete Fourier transform on the addition result (N frequency domain equalized signals) input from the multiplier 202, converts the result into a time domain signal, and outputs the time domain signal to the time domain equalization unit 300.
- the general discrete Fourier transform size N is a power of 2 integer.
- a fast Fourier transform FFT
- the frequency domain equalization unit 200 performs frequency domain equalization by performing FFT on the input signal, and performing multiplication by weighting with filter coefficient setting values equal to the FFT size in the multiplier 202. it can.
- the frequency domain equalization unit 200 performs inverse fast Fourier transform (IFFT) on the frequency domain equalized signal to convert it into a time domain signal, and outputs the time domain signal to the time domain equalization unit 300.
- IFFT inverse fast Fourier transform
- the frequency domain equalization unit 200 is an FDE circuit with a smaller circuit scale and lower power consumption than a time domain equalization circuit whose circuit scale is proportional to N.
- the time domain equalization unit 300 uses the frequency domain equalization digital signal input from the frequency domain equalization unit 200 as a time domain using the time domain equalization coefficient input from the time domain equalization coefficient calculation unit 420. Equalize and output.
- the time domain equalization unit 300 can be configured by, for example, a highly controllable FIR (finite impulse response) filter or IIR (infinite impulse response) filter. In this case, the time domain equalization coefficient input from the time domain equalization coefficient calculation unit 420 is applied to the coefficients of the FIR filter and the IIR filter.
- the feedback control unit 400 performs feedback control of the frequency domain equalization unit 200 and the time domain equalization unit 300.
- the feedback control unit 400 includes a waveform distortion detection unit 410, a time domain equalization coefficient calculation unit 420, a quasi-static waveform distortion detection unit 430, and a frequency domain equalization coefficient calculation unit 440. Is provided.
- a part of the digital signal output from the time domain equalization unit 300 is input to the waveform distortion detection unit 410.
- the waveform distortion detector 410 detects the waveform distortion of the input digital signal and outputs the detection result to the time domain equalization coefficient calculator 420 and the quasi-static waveform distortion detector 430.
- the waveform distortion detection unit 410 calculates an error between a reference signal such as a fixed value, a training signal, and a identification determination (DD) signal and a digital signal input from the time domain equalization unit 300.
- the waveform distortion is detected by calculating an error signal corresponding to each waveform equalization (compensation) algorithm.
- the time domain equalization coefficient calculation unit 420 calculates a time domain equalization coefficient based on the waveform distortion input from the waveform distortion detection unit 410 and outputs the calculation result to the time domain equalization unit 300.
- the time domain equalization coefficient calculation unit 420 according to the present embodiment calculates a time domain equalization coefficient using a waveform equalization algorithm selected according to system requirements.
- the waveform equalization algorithm for example, general techniques such as CMA (constant modulus algorithm), LMS (least mean squares) algorithm, RLS (recursive least squares) algorithm can be used.
- the waveform distortion detection unit 410 detects a deviation amount (distortion) from an ideal waveform in which transmission characteristics such as an eye opening ratio and an error rate are suitable as an error signal, and performs time domain
- the equalization coefficient calculation unit 420 can also calculate a time domain equalization coefficient that minimizes the detected error amount.
- the quasi-static waveform distortion detection unit 430 extracts the waveform distortion that slowly changes in time from the waveform distortion input from the waveform distortion detection unit 410 and outputs the waveform distortion to the frequency domain equalization coefficient calculation unit 440.
- the distortion signal with a slow temporal variation is a time domain equalization feedback time constant constituted by the time domain equalization unit 300, the waveform distortion detection unit 410, and the time domain equalization coefficient calculation unit 420.
- This is a waveform distortion signal having a long-term time variation.
- the quasi-static waveform distortion detection unit 430 according to the present embodiment has a deviation amount (error) between the input digital signal and the reference signal, or an ideal waveform of the input digital signal (when the transmission characteristics are suitable). Of the deviation amount from the waveform), a deviation amount with a slow temporal variation is detected as a quasi-static waveform distortion.
- the frequency domain equalization coefficient calculation unit 440 calculates the frequency domain equalization coefficient of the frequency domain equalization unit 200 based on the quasi-static waveform distortion detected by the quasi-static waveform distortion detection unit 430, and uses the calculation result as a frequency.
- the data is output to the area equalization unit 200.
- the frequency domain equalization coefficient calculator 440 according to the present embodiment calculates the frequency domain equalization coefficient using a waveform equalization algorithm selected according to the system requirements.
- the feedback control unit 400 calculates a time domain equalization coefficient based on the waveform distortion of the input digital signal, and performs feedback control of the time domain equalization unit 300.
- a circuit having high circuit efficiency and high controllability such as an FIR filter is applied to the time domain equalization unit 300, and the time domain equalization coefficient input from the feedback control unit 400 is applied to the coefficient of the FIR filter.
- the feedback control unit 400 extracts the quasi-static waveform distortion from the waveform distortion of the input digital signal, and based on the quasi-static waveform distortion, the frequency domain The equalization coefficient is calculated, and the frequency domain equalization unit 200 is feedback controlled.
- the frequency domain equalization unit 200 is applied with FFT / IFFT or the like capable of suppressing an increase in circuit scale, and the frequency domain equalization coefficient input from the feedback control unit 400 is added to the output from the FFT. . Therefore, the frequency domain equalization unit 200 can highly accurately equalize the frequency domain with a slow time fluctuation while suppressing an increase in circuit scale, that is, suppressing an increase in power consumption. .
- the quasi-static waveform distortion detection unit 430 is arranged at the subsequent stage of the waveform distortion detection unit 410, and the quasi-static waveform distortion detection unit 430 detects the waveform distortion output from the waveform distortion detection unit 410.
- waveform distortion that slowly changes with time is extracted, the present invention is not limited to this.
- the quasi-static waveform distortion detection unit 430 can be arranged at a suitable detection location according to an equalization algorithm such as feedforward control or feedback control.
- the waveform distortion that slowly changes in time can be detected by using a signal branched in the previous stage or subsequent stage of the frequency domain equalization unit 200 or the previous stage of the time domain equalization unit 300.
- FIG. 4 shows a block diagram of a digital receiver in which the above equalization processing circuit is arranged.
- a digital receiver 700 includes a front end unit 500, an A / D (Analog to Digital) conversion unit 600, and an equalization processing circuit 100B.
- the equalization processing circuit 100B includes a frequency domain equalization unit 200B, a time domain equalization unit 300B, and a feedback control unit 400.
- the front end unit 500 receives the polarization multiplexed QPSK signal input to the digital receiver 700 and the local light output (local oscillation light) output from a local light source (not shown).
- the front end unit 500 coherently detects the input polarization multiplexed QPSK signal using LO light, and corresponds to the in-phase component (I) and quadrature component (Q) of the two polarizations (X, Y). Two components Ix, Qx, Iy, Qy are output.
- An example of a block diagram of the front end unit 500 is shown in FIG.
- the front end unit 500 includes a polarization diversity 90 ° hybrid 510 and photoelectric conversion units 521, 522, 523, and 524.
- the polarization diversity 90 ° hybrid 510 performs coherent detection on the input polarization multiplexed QPSK signal using LO light, demodulates it into four components Ix, Qx, Iy, and Qy, and photoelectric conversion units 521, 522, and 523. 524, respectively.
- the photoelectric conversion units 521, 522, 523, and 524 each convert the four input components Ix, Qx, Iy, and Qy into electric signals and output them to the A / D conversion unit 600.
- the A / D conversion unit 600 includes four A / D conversion circuits 610, 620, 630, and 640.
- the A / D conversion unit 600 converts the four components Ix, Qx, Iy, Qy input from the front end unit 500 into digital signals, converts the digital signals of Ix and Qx to the FDE 210B, and the digital signals of Iy and Qy Is output to the FDE 220B.
- the frequency domain equalization unit 200B includes an FDE 210B and an FDE 220B.
- the FDE 210B equalizes the input digital signals of Ix and Qx using the frequency domain equalization coefficient input from the frequency domain equalization coefficient calculation unit 440, and outputs the result to the time domain equalization unit 300B.
- the FDE 220B equalizes the input Iy and Qy digital signals using the frequency domain equalization coefficient input from the frequency domain equalization coefficient calculation unit 440 and outputs it to the time domain equalization unit 300B. To do.
- the time domain equalization unit 300B includes a butterfly FIR filter 310B.
- the butterfly FIR filter 310B equalizes and outputs the input frequency domain equalized signal using the time domain equalization coefficient input from the time domain equalization coefficient calculator 420.
- the feedback control unit 400 is the same as the feedback control unit 400 of FIG. That is, the feedback control unit 400 outputs the frequency domain equalization coefficient calculated based on the waveform distortion that varies slowly with time to the frequency domain equalization unit 200B, and calculates based on the waveform distortion whose time variation is fast.
- the time domain equalization coefficient is output to the time domain equalization unit 300B.
- E Xin (t) and E Yin (t) respectively represent input signals to the X polarization port and the Y polarization port that are input to the butterfly FIR filter 310B at time t (t-th sample).
- E Xout (t) and E Yout (t) represent output signals from the X polarization port and the Y polarization port that are output from the butterfly FIR filter 310B at time t, respectively.
- h xx (t), h xy (t), h yx (t), and h yy (t) each represent a filter coefficient of the butterfly FIR filter 310B at time t.
- the number of taps of the butterfly FIR filter 310B is 1 tap will be described.
- the waveform distortion detection unit 410 calculates an error signal expressed by equation (2). ... (2) formula
- the time domain equalization coefficient calculation unit 420 calculates the tap coefficient of the butterfly FIR filter 310B at time t + 1 according to the equation (3), and outputs it to the butterfly FIR filter 310B as the time domain equalization coefficient. ... (3) formula
- ⁇ is a step size parameter
- * represents a complex conjugate
- the feedback control unit 400 sequentially updates the coefficients of the butterfly FIR filter 310B according to the above procedure.
- the butterfly FIR filter 310B performs time domain equalization using sequentially updated coefficients. Thereby, even when the polarization fluctuates with time, the waveform is adaptively compensated.
- the above-described digital receiver 700 of FIG. 4 can also be applied to a digital receiving terminal device that performs wireless communication.
- a block diagram of the digital receiving terminal device in this case is shown in FIG.
- the digital receiving terminal device 900 includes an antenna 800 and a digital receiving unit 700 ′.
- the antenna 800 receives a signal transmitted wirelessly and outputs the received signal to the digital reception unit 700 ′.
- the digital receiving unit 700 'performs coherent detection on the input signal at the front end unit 500B.
- the coherently detected signal is input to the frequency domain equalization unit 200.
- the signal input to the frequency domain equalization unit 200 is based on the frequency domain equalization coefficient and the time domain equalization coefficient calculated by the feedback control unit 400 in the frequency domain equalization unit 200 and the time domain equalization unit 300. Frequency domain equalization and time domain equalization.
- the front end unit 500B of FIG. 7 also has the function of the A / D conversion unit 600 of FIG.
- a block diagram of the front end unit 500B is shown in FIG.
- the front end unit 500B includes a filter 530B, a low noise amplifier 540B, a mixer 550B, a reference signal source 560B, a filter 570B, a variable gain amplifier 580B, and an A / D conversion unit 590B.
- Filter 530B removes a frequency component that becomes noise from the signal received by antenna 800 and outputs an analog signal to low-noise amplifier 540B.
- the low noise amplifier 540B amplifies the input analog signal and outputs it to the mixer 550B.
- the mixer 550B multiplies the analog signal input from the low noise amplifier 540B by the reference signal generated by the reference signal source 560B and outputs the result to the filter 570B.
- the filter 570B removes a frequency component that becomes noise from the input analog signal, and outputs it to the variable gain amplifier 580B.
- the variable gain amplifier 580B amplifies the input analog signal and outputs it to the A / D converter 590B.
- the A / D conversion unit 590B converts the input analog signal into a digital signal and outputs the digital signal.
- the front end unit 500B does not necessarily include the filter 530B, the low noise amplifier 540B, the mixer 550B, the reference signal source 560B, the filter 570B, and the variable gain amplifier 580B.
- the signal received by the antenna 800 can be directly converted into a digital signal and output by the A / D conversion unit 590B of the front end unit 500B.
- the digital reception terminal device 900 described above uses the frequency domain equalization unit 200 that can perform waveform equalization with high circuit efficiency and high accuracy for waveform distortion with low temporal fluctuation among waveform distortions of the input signal.
- the waveform distortion that is equalized in the frequency domain and has a fast time variation is equalized in the time domain using the time domain equalization unit 300 with good controllability.
- a waveform with good controllability can be output with high accuracy and low power consumption.
- the digital receiver 700 of FIG. 4 can be applied to a digital receiving terminal device that performs wireless communication using a MIMO (Multiple Input Multiple Output) method.
- FIG. 9 shows a block diagram of the digital receiving terminal device in this case.
- the digital receiving terminal device 900B includes antennas 810B and 820B and a digital receiving unit 700 ′′.
- the digital receiving unit 700 ′′ includes the front end unit 500 and the A / D conversion of the digital receiver 700 of FIG.
- the part 600 is replaced with front end parts 500C and 500D.
- the antennas 810B and 820B receive signals transmitted wirelessly, and output the received signals to the front end units 500C and 500D of the digital receiving unit 700 ′′, respectively.
- the front end units 500C and 500D respectively receive the antennas 810B and 820B.
- the real component (I n ) and the imaginary component (Q n ) are respectively extracted from the signal input from, and A / D converted to output a digital signal.
- the signal output from the front end units 500C and 500D has a waveform distortion whose time variation is low in the frequency domain, etc. It becomes. Further, the signals output from the FDEs 210B and 220B are subjected to waveform distortion with a fast time variation based on the time domain equalization coefficient input from the time domain equalization coefficient calculation unit 420 in the butterfly FIR filter 310B. It becomes.
- the waveform distortion with slow time fluctuation is equalized in the frequency domain using the FDEs 210B and 220B capable of high-precision waveform equalization with high circuit efficiency.
- the waveform distortion whose time fluctuation is fast is equalized in the time domain using the butterfly FIR filter 310B with good controllability.
- FIG. 10 shows a system configuration diagram of the signal transmission / reception system according to the present embodiment.
- the signal transmission / reception system 1000 includes a transmitter 1100, a transmission medium 1200, and a digital receiver 700B.
- the transmitter 1100 generates a transmission signal and transmits it to the digital receiver 700B.
- the transmission medium 1200 is disposed between the transmitter 1100 and the digital receiver 700B.
- the transmission medium 1200 is, for example, an optical fiber.
- the transmission medium 1200 is, for example, air. Waveform distortion is added to the signal transmitted from the transmitter 1100 by transmitting through the transmission medium 1200.
- the signal transmitted from the transmitter 1100 and added with waveform distortion by transmitting through the transmission medium 1200 is coherently detected by the front end unit 500 of the digital receiver 700B and output to the frequency domain equalization unit 200.
- Equalization of quasi-static waveform distortion out of waveform distortion added by transmitting the transmission medium 1200 to the digital signal input from the front end unit 500 is low power consumption in the frequency domain equalization unit 200.
- the time-domain equalization unit 300 performs equalization of dynamic waveform distortion at high speed.
- the signal transmission / reception system 1000 can maintain a suitable communication state even when it receives waveform distortion that varies with time due to secular change, temperature variation, path switching, and the like.
- the quasi-static waveform distortion detection unit 430 is arranged at the subsequent stage of the waveform distortion detection unit 410, and the quasi-static waveform distortion detection unit 430 takes time from the waveform distortion output from the waveform distortion detection unit 410.
- the waveform distortion that fluctuates slowly is extracted.
- the method of extracting waveform distortion that slowly changes with time is not limited to this.
- FIG. 11 shows a block configuration diagram of the equalization processing circuit according to the present embodiment.
- the equalization processing circuit 100C of FIG. 11 includes a frequency domain equalization unit 200, a time domain equalization unit 300, and a feedback control unit 400B.
- the frequency domain equalization unit 200 and the time domain equalization unit 300 can directly apply the frequency domain equalization unit 200 and the time domain equalization unit 300 of FIG. 2 described in the second embodiment.
- the feedback control unit 400B includes a waveform distortion detection unit 410B, a time domain equalization coefficient calculation unit 420B, a low frequency signal extraction unit 450B, a quasi-static waveform distortion detection unit 430B, and a frequency domain equalization coefficient calculation unit 440B.
- a part of the digital signal subjected to frequency domain equalization and time domain equalization input to the feedback control unit 400B is input to the waveform distortion detection unit 410B and the low frequency signal extraction unit 450B.
- the waveform distortion detector 410B detects the waveform distortion of the input digital signal and outputs the detection result to the time domain equalization coefficient calculator 420B.
- the time-domain equalization coefficient calculation unit 420B calculates a time-domain equalization coefficient based on the waveform distortion whose time variation detected by the waveform distortion detection unit 410B is high, and outputs the time-domain equalization coefficient to the time-domain equalization unit 300.
- the low-frequency signal extraction unit 450B detects only a low-frequency component from the input digital signal and outputs it to the quasi-static waveform distortion detection unit 430B.
- the low-frequency signal extraction unit 450B can be realized by, for example, a low-pass filter or an averaging processing circuit.
- the quasi-static waveform distortion detection unit 430B extracts a waveform distortion that slowly changes in time from the input low-frequency component signal, and outputs the waveform distortion to the frequency domain equalization coefficient calculation unit 440B.
- the frequency domain equalization coefficient calculation unit 440B calculates a frequency domain equalization coefficient based on the input waveform distortion and outputs it to the frequency domain equalization unit 200.
- the quasi-static waveform distortion detection is directly performed on the digital signal output from the time domain equalization unit 300. It can also branch to the part 430B.
- the quasi-static waveform distortion detection unit 430B detects the waveform distortion of the low frequency signal from the input digital signal, further extracts the waveform distortion that slowly changes in time, and calculates the frequency domain equalization coefficient To the unit 440B.
- FIG. 12 shows a block configuration diagram of the equalization processing circuit according to the present embodiment.
- the equalization processing circuit 100D of FIG. 12 includes a frequency domain equalization unit 200, a time domain equalization unit 300, and a feedback control unit 400C.
- the frequency domain equalization unit 200 and the time domain equalization unit 300 can directly apply the frequency domain equalization unit 200 and the time domain equalization unit 300 of FIG. 2 described in the second embodiment.
- the feedback control unit 400C includes a waveform distortion detection unit 410C, a time domain equalization coefficient calculation unit 420C, an equalization transfer characteristic extraction unit 460C, a quasi-static waveform distortion detection unit 430C, a frequency domain equalization coefficient calculation unit 440C, semi-fixed, etc.
- a quantization coefficient setting unit 470C and a multiplier 480C are provided.
- the waveform distortion detection unit 410C detects the waveform distortion of the digital signal subjected to frequency domain equalization and time domain equalization, and outputs the detected waveform distortion to the time domain equalization coefficient calculation unit 420C.
- the time domain equalization coefficient calculation unit 420C calculates a time domain equalization coefficient based on the input waveform distortion and outputs it to the time domain equalization unit 300 and the equalization transfer characteristic extraction unit 460C.
- the equalization transfer characteristic extraction unit 460C uses the input time domain equalization coefficient to transfer the waveform equalization performed by the time domain equalization unit 300 (hereinafter referred to as equalization transfer characteristic information). Is output to the quasi-static waveform distortion detector 430C.
- an equalization transfer characteristic extraction unit 460C calculates equalization transfer characteristic information H FIR (z) by the equation (4). ... (4) formula
- m is the number of taps of the FIR filter
- h 0 , h 1 ,..., H m ⁇ 1 are tap coefficients (time domain equalization coefficients) calculated by the time domain equalization coefficient calculation unit 420C. It is.
- the quasi-static waveform distortion detection unit 430C extracts quasi-static waveform distortion from the input equalization transfer characteristic information H FIR (z) and outputs the quasi-static waveform distortion detection unit 430C to the frequency domain equalization coefficient calculation unit 440C.
- the quasi-static waveform distortion detection unit 430C uses the input equalization transfer characteristic information H FIR (z) and the waveform distortion H FIR (z included in the digital signal output from the frequency domain equalization unit 200. calculating the inverse function H -1 FIR (z) of) extracting a quasi-static waveform distortion based on the calculation result.
- H FIR (z) is the output result of the time domain equalization coefficient calculation unit 420C, it varies adaptively with time.
- the quasi-static waveform distortion detection unit 430C performs averaging or filtering processing on H FIR (z) to H ⁇ 1 FIR (z) to extract a low-speed fluctuation component, thereby quasi-static waveform distortion. To detect.
- the frequency domain equalization coefficient calculation unit 440C performs frequency domain equalization based on the quasi-static waveform distortion extracted by the quasi-static waveform distortion detection unit 430C using a waveform equalization algorithm selected according to the system requirements. Calculate and output the coefficient error.
- the semi-fixed equalization coefficient setting unit 470C holds the reference value of the frequency domain equalization coefficient of the frequency domain equalization unit 200.
- the multiplier 480C adds the error of the frequency domain equalization coefficient calculated in the frequency domain equalization coefficient calculation unit 440C to the reference value of the frequency domain equalization coefficient held in the semi-fixed equalization coefficient setting unit 470C. The addition result is output to the frequency domain equalization unit 200 as a frequency domain equalization coefficient.
- the equalization processing circuit 100D configured as described above operates as follows. That is, the feedback control unit 400C calculates a time domain equalization coefficient based on the waveform distortion detected from the digital signal subjected to frequency domain equalization and time domain equalization, and outputs the time domain equalization coefficient to the time domain equalization unit 300.
- the feedback control unit 400C calculates a waveform equalization transfer characteristic (equalization transfer characteristic information H FIR (z)) from the calculated time domain equalization coefficient, and quasi-statically from the calculated waveform equalization transfer characteristic. Waveform distortion is extracted, and an error of the frequency domain equalization coefficient is calculated based on the extracted quasi-static waveform distortion.
- the feedback control unit 400C calculates a new frequency domain equalization coefficient by adding an error of the calculated frequency domain equalization coefficient to a reference value of the frequency domain equalization coefficient that is held in advance, thereby performing frequency domain equalization. Output to the unit 200.
- the frequency domain equalization unit 200 performs frequency domain equalization on the digital signal input to the equalization processing circuit 100D based on the frequency domain equalization coefficient input from the feedback control unit 400C. Output. Further, the time domain equalization unit 300 performs dynamic waveform distortion on the digital signal input from the frequency domain equalization unit 200 based on the time domain equalization coefficient input from the feedback control unit 400C. And output.
- the equalization processing circuits 100 ⁇ / b> C and 100 ⁇ / b> D separate the quasi-static waveform distortion and the dynamic waveform distortion and perform equalization processing to generate a waveform with good controllability. It is possible to output with high accuracy and low power consumption.
- Factors that cause quasi-static waveform distortion include, for example, fluctuations in chromatic dispersion, fluctuations in polarization mode dispersion, temperature dependence of band characteristics of the front-end device, etc., in addition to fluctuations in frequency.
- quasi-static waveform distortion caused by fluctuations in chromatic dispersion is subjected to chromatic dispersion compensation (CDC) in the frequency domain equalization unit, and dynamic waveform distortion is also subjected to time domain equalization unit 300. Is equalized.
- CDC chromatic dispersion compensation
- FIG. 13 shows a block configuration diagram of the equalization processing circuit according to the present embodiment.
- the equalization processing circuit 100E includes a frequency domain equalization unit 200C, a time domain equalization unit 300, and a feedback control unit 400D.
- the time domain equalization unit 300 can apply the time domain equalization unit 300 of FIG. 2 described in the second embodiment as it is.
- the frequency domain equalization unit 200C performs residual chromatic dispersion compensation on the digital signal input to the equalization processing circuit 100E based on the chromatic dispersion compensation coefficient input from the multiplier 480D.
- the feedback control unit 400D includes a waveform distortion detection unit 410D, a time domain equalization coefficient calculation unit 420D, an equalization transfer characteristic extraction unit 460D, a residual chromatic dispersion estimation unit 490D, a control unit 4100D, a chromatic dispersion compensation coefficient calculation unit 4110D, and semi-fixed.
- a chromatic dispersion compensation coefficient setting unit 4120D and a multiplier 480D are provided.
- the waveform distortion detection unit 410D detects the waveform distortion of the digital signal subjected to frequency domain equalization and time domain equalization, and outputs the detection result to the time domain equalization coefficient calculation unit 420D.
- Time domain equalization coefficient calculation section 420D calculates a time domain equalization coefficient based on the input waveform distortion, and outputs it to time domain equalization section 300 and equalization transfer characteristic extraction section 460D.
- the equalization transfer characteristic extraction unit 460D extracts the equalization transfer characteristic information of the time domain equalization unit 300 from the input time domain equalization coefficient and outputs it to the residual chromatic dispersion estimation unit 490D.
- the residual chromatic dispersion estimation unit 490D estimates the residual dispersion compensation amount in the time domain equalization unit 300 from the input equalization transfer characteristic information.
- the control unit 4100D stores the estimated value D of the residual chromatic dispersion amount at time T of the residual chromatic dispersion estimation unit 490D in a read register or the like, and at the same time, sets a value corresponding to the residual chromatic dispersion amount D as a set value as a chromatic dispersion compensation coefficient. The result is output to the calculation unit 4110D.
- the chromatic dispersion compensation coefficient calculation unit 4110D calculates an error of the chromatic dispersion compensation coefficient based on the input set value D and outputs the calculated error to the multiplier 480D.
- the wavelength dispersion compensation coefficient calculating unit 4110D using equation (5), set value at time T 0 which is input from the control unit 4100D (residual chromatic compensation quantity) D
- the filter coefficient of the frequency domain equalization unit 200C is calculated from 0 . ... (5)
- f is the baseband frequency of the signal
- ⁇ is the wavelength of the input optical signal
- c is the speed of light
- ⁇ 0 is the amount of phase rotation caused by chromatic dispersion.
- the semi-fixed chromatic dispersion compensation coefficient setting unit 4120D holds the reference value of the chromatic dispersion compensation coefficient.
- the reference value of the chromatic dispersion compensation coefficient held in the semi-fixed chromatic dispersion compensation coefficient setting unit 4120D is a fixed chromatic dispersion amount estimated in advance from the transmission path length or the like using the above equation (5).
- the compensation coefficient corresponding to is calculated.
- the multiplier 480D adds the error of the chromatic dispersion compensation coefficient calculated by the chromatic dispersion compensation coefficient calculation unit 4110D to the reference value of the chromatic dispersion compensation coefficient acquired from the semi-fixed chromatic dispersion compensation coefficient setting unit 4120D, and creates a new The chromatic dispersion compensation coefficient is output to the frequency domain equalization unit 200C.
- FIG. 14 is a plot of the equalization transfer characteristics H FIR (solid line) of the time domain equalization unit 300 (FIR filter) and the residual chromatic dispersion H CD (dotted line) of the input digital signal.
- H FIR solid line
- H CD residual chromatic dispersion
- the amount of phase rotation caused by residual chromatic dispersion is proportional to the square of the frequency f. Accordingly, the residual chromatic dispersion estimation unit 490D performs quadratic function fitting or the like on the phase rotation amount ⁇ FIR by the equalization transfer characteristic H FIR of the FIR filter shown in FIG. 14, and extracts a component proportional to f 2. As a result, the residual chromatic dispersion D 0 can be estimated.
- the residual chromatic dispersion compensation amount generally fluctuates very slowly due to temperature fluctuation, aging, and path switching. For this reason, even if the quadratic function fitting is not performed on ⁇ FIR , a transfer characteristic shift caused by quasi-static waveform distortion other than residual chromatic dispersion compensation is obtained by averaging or filtering the H FIR. It is also possible to calculate an equalization coefficient that is detected and compensates for the deviation in the transfer characteristic.
- Control unit 4100D operates as follows when the residual dispersion compensation amount estimated by residual chromatic dispersion estimation unit 490D changes quasi-statically from D 0 at time T 0 to D 1 at time T 1. .
- FIG. 15 shows an operation flow of the control unit 4100D and the residual chromatic dispersion estimation unit 490D at this time.
- the residual chromatic dispersion estimation unit 490D estimates the residual dispersion compensation amount D 0 and outputs it to the control unit 4100D (S101).
- Control unit 4100D may store the residual dispersion compensation amount D 0 to the register, and outputs to the wavelength dispersion compensation coefficient calculating unit 4110D a value corresponding to a residual chromatic dispersion amount D 0 as the setting value (S102).
- Frequency domain equalization section 200C is, by performing the residual chromatic dispersion compensation based on the wavelength dispersion compensation coefficient computed from the residual dispersion amount estimation value D 0 at time T 0, at time T 1, the residual chromatic dispersion estimator 490D is outputted to the control unit 4100D to estimate the residual dispersion compensation amount D 1 (S103).
- the residual dispersion compensation amount D 1 estimated by the residual chromatic dispersion estimation unit 490D at time T 1 is different from the original residual chromatic dispersion amount of the output signal from the frequency domain equalization unit 200C, and the frequency domain and the like.
- the difference from D 0 compensated for residual chromatic dispersion in the conversion unit 200C.
- control unit 4100D adds the estimated value D 1 at time T 1 to the wavelength dispersion compensation amount D 0 which are stored in the register to update the register value as described above, set to the wavelength dispersion compensation coefficient calculating unit 4110D D 0 + D 1 is output as a value (S104).
- the residual chromatic dispersion estimation unit 490D is unable to compensate for the chromatic dispersion of the input digital signal with the fixed chromatic dispersion compensation coefficient held by the semi-fixed chromatic dispersion compensation coefficient setting unit 4120D.
- the chromatic dispersion is estimated as a residual dispersion compensation amount. Therefore, the following can also be performed. That is, the control unit 4100D acquires the reference value D 0 of the wavelength dispersion compensation coefficient held in the semi-fixed wavelength dispersion compensation coefficient setting unit 4120D directly. Then, the control unit 4100D, adds the reference value D 0 obtained in the estimate D 1 of the residual chromatic dispersion at the time T 1 which is input from the residual variance estimator unit 490 d.
- the control unit 4100D outputs (D 0 + D 1 ) as a new set value D 1 ′ to the chromatic dispersion compensation coefficient calculation unit 4110D.
- the setting value D 1 ′ is not necessarily held in the register in the control unit 4100D.
- the frequency domain equalization unit 200C performs residual chromatic dispersion compensation as quasi-static waveform distortion compensation, but by applying a similar configuration, polarization mode dispersion and It is also possible to compensate for waveform distortion caused by an analog front-end device.
- Non-Patent Document 1 described in Background Art discloses a technique for detecting various waveform distortions such as polarization mode dispersion and polarization dependent loss by digital signal processing in addition to chromatic dispersion estimation. . By applying these methods in the equalization processing circuit 100E according to the present embodiment, quasi-static waveform distortion can be compensated with high accuracy and low power consumption.
- FIG. 16 shows a block configuration diagram of the digital receiver according to the present embodiment.
- a digital receiver 700C includes a front end unit 500, a frequency domain equalization unit 200D, a phase adjustment unit 300 ′, and a feedback control unit 400E.
- the front end unit 500 synthesizes the reception signal input to the digital receiver 700C and a local oscillation signal (LO) and outputs the synthesized signal as a baseband signal to the frequency domain equalization unit 200D. At this time, a deviation (deviation) occurs between the carrier frequency of the received signal and the LO frequency.
- LO local oscillation signal
- the frequency domain equalization unit 200D compensates the frequency deviation of the input baseband signal based on the control from the frequency shift amount control unit 4170E, and outputs it to the phase adjustment unit 300 '.
- the frequency domain equalization unit 200D compensates the frequency deviation by uniformly shifting the frequency of the input baseband signal to the high frequency side or the low frequency side.
- the phase adjustment unit 300 ′ compensates for the frequency deviation that cannot be removed by the frequency domain equalization unit 200 ⁇ / b> D by performing frequency deviation compensation with higher accuracy on the input baseband signal with compensated frequency deviation.
- the phase adjustment unit 300 ′ according to the present embodiment adjusts the phase of the input baseband signal based on the control from the phase compensation amount calculation unit 4140 E. Since the phase adjustment unit 300 ′ is required to have a fast time response, the phase adjustment unit 300 ′ generally performs time-domain signal processing capable of high-speed control. The phase adjustment unit 300 ′ adjusts the phase at high speed by performing signal processing in the time domain.
- the feedback control unit 400E performs feedback control of the frequency domain equalization unit 200D and the phase adjustment unit 300 '.
- the feedback control unit 400E includes a phase deviation estimation unit 4130E, a phase compensation amount calculation unit 4140E, a frequency deviation estimation unit 4150E, a control unit 4160E, and a frequency shift amount control unit 4170E.
- the baseband signal input from the frequency domain equalization unit 200D is branched to the phase deviation estimation unit 4130E and the frequency deviation estimation unit 4150E.
- the phase deviation estimation unit 4130E receives the baseband signal from the frequency domain equalization unit 200D and the baseband signal from the phase adjustment unit 300 ′, and the phase deviation estimation unit 4130E receives the two input baseband signals. The phase deviation is estimated and output to the phase compensation amount calculation unit 4140E.
- the phase deviation estimation unit 4130E estimates the phase deviation by a method disclosed in Patent Document 1 of the background art and its cited document, a method based on m-th power estimation, or the like.
- the phase compensation amount calculation unit 4140E determines the phase compensation amount based on the input phase deviation estimation result, and controls the phase compensation amount of the phase adjustment unit 300 '. For example, when the phase deviation estimated by the phase deviation estimation unit 4130E is ⁇ , the phase compensation amount calculation unit 4140E calculates exp ( ⁇ j ⁇ ) as the phase compensation amount, and the phase adjustment unit 300 ′ and the main signal exp Multiply by ( ⁇ j ⁇ ).
- the frequency deviation estimation unit 4150E roughly estimates the frequency deviation amount from the baseband signal input from the frequency domain equalization unit 200D and outputs it to the control unit 4160E.
- the frequency deviation estimation unit 4150E estimates the amount of frequency deviation by the method disclosed in Patent Document 1 of the background art, the estimation method using a pilot tone / training signal, or the like.
- the control unit 4160E reads out the frequency deviation estimation value F at time T of the frequency deviation estimation unit 4150E in a read register or the like, and at the same time, sets a value corresponding to the frequency deviation estimation value F as a set value as a frequency shift amount control unit 4170E. Output to.
- the frequency shift amount control unit 4170E determines a frequency deviation compensation amount (frequency shift amount) based on the set value input from the control unit 4160E, and controls the frequency shift amount of the frequency domain equalization unit 200D.
- the control unit 4160E sets the set value ⁇ f 0 in the frequency shift amount control unit 4170E and stores the set initial value ⁇ f 0 in a register or the like.
- the frequency deviation estimation unit 4150E installed in the subsequent stage estimates the value ⁇ f 1 in which the frequency is compensated by ⁇ f 0 from the original frequency deviation. Detected as a value.
- the control unit 4160E reads the estimated value ⁇ f 1 of the frequency deviation of the frequency deviation estimation unit 4150E.
- the control unit 4160E updates the register value with ⁇ f 0 + ⁇ f 1 as a new set value, and at the same time updates the set value of the frequency shift amount control unit 4170E to ⁇ f 0 + ⁇ f 1 .
- the digital receiver 700C can always perform suitable frequency deviation compensation.
- the digital receiver 700C shifts the frequency of the quasi-static relatively slow frequency deviation in the frequency domain equalization unit 200D based on the control from the frequency shift amount control unit 4170E. .
- high-precision frequency control by frequency domain equalization can be realized without performing complicated control such as PLL (phase-locked loop).
- the digital receiver 700C can output a waveform with good controllability with high accuracy and low power consumption.
- the output signal from the frequency domain equalization unit 200D is branched to the phase deviation estimation unit 4130E and the frequency deviation estimation unit 4150E, but the output signal from the phase adjustment unit 300 ′ is branched. It can also be made.
- the phase deviation estimation unit 4130E performs feedback phase adjustment by a DD-PLL (decisionisdirected phase-locked loop) algorithm.
- the equalization processing circuit according to the present invention is applied to an optical communication system that handles an optical polarization multiplexed phase modulated signal such as a polarization multiplexed QPSK (Quadrature Shift Keying) signal or a polarization multiplexed 16QAM (Quadrature Amplitude Modulation) signal. can do.
- an optical polarization multiplexed phase modulated signal such as a polarization multiplexed QPSK (Quadrature Shift Keying) signal or a polarization multiplexed 16QAM (Quadrature Amplitude Modulation) signal.
- Equalization processing circuit 20 Frequency domain equalization part 30 Time domain equalization part 40, 40B, 40C Waveform distortion detection part 41B, 41C Quasi-static waveform distortion extraction part 42B, 42C Dynamic waveform distortion extraction part 43C Low-frequency signal extraction Unit 50 frequency domain equalization coefficient control unit 60 time domain equalization coefficient control unit 100, 100B, 100C, 100D, 100E equalization processing circuit 200, 200B, 200C, 200D frequency domain equalization unit 201 DFT 202 Multiplier 203 IDFT 300, 300B Time domain equalization unit 310B Butterfly FIR filter 300 'Phase adjustment unit 400, 400B, 400C, 400D, 400E Feedback control unit 410, 410B, 410C, 410D Waveform distortion detection unit 420, 420B, 420C, 420D Time domain, etc.
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Abstract
Description
本発明の第1の実施形態について説明する。本実施形態に係る等化処理回路のブロック構成図を図1Aに示す。図1Aにおいて、等化処理回路10は、周波数領域等化部20、時間領域等化部30、波形歪検出部40、周波数領域等化係数制御部50および時間領域等化係数制御部60を備える。周波数領域等化部20、時間領域等化部30、波形歪検出部40、周波数領域等化係数制御部50および時間領域等化係数制御部60がそれぞれ、請求項の周波数領域等化手段、時間領域等化手段、波形歪検出手段、周波数領域等化係数制御手段および時間領域等化係数制御手段に相当する。
第2の実施形態について説明する。本実施形態に係る等化処理回路のブロック構成図を図2に示す。図2において、等化処理回路100は、周波数領域等化部200、時間領域等化部300およびフィードバック制御部400を備える。
…(3)式
第2の実施形態の変形例について説明する。第2の実施形態では、準静的波形歪み検出部430を波形歪み検出部410の後段に配置し、準静的波形歪み検出部430において、波形歪み検出部410から出力された波形歪から時間的に緩慢に変動する波形歪みを抽出した。しかし、時間的に緩慢に変動する波形歪みの抽出方法はこれに限定されない。
…(4)式
第3の実施形態について説明する。準静的な波形歪みが発生する要因としては、周波数の変動の他にも、例えば、波長分散の変動、偏波モード分散の変動、フロントエンドデバイスの帯域特性の温度依存性等が挙げられる。本実施形態では、波長分散の変動に起因する準静的な波形歪みを周波数領域等化部において波長分散補償(CDC:chromatic dispersion compensation)すると共に、動的な波形歪みを時間領域等化部300において等化する。
…(5)式
第4の実施形態について説明する。本実施形態に係るデジタル受信機のブロック構成図を図16に示す。図16において、デジタル受信機700Cは、フロントエンド部500、周波数領域等化部200D、位相調整部300’およびフィードバック制御部400Eを備える。
20 周波数領域等化部
30 時間領域等化部
40、40B、40C 波形歪検出部
41B、41C 準静的波形歪抽出部
42B、42C 動的波形歪抽出部
43C 低域信号抽出部
50 周波数領域等化係数制御部
60 時間領域等化係数制御部
100、100B、100C、100D、100E 等化処理回路
200、200B、200C、200D 周波数領域等化部
201 DFT
202 乗算器
203 IDFT
300、300B 時間領域等化部
310B バタフライFIRフィルタ
300’ 位相調整部
400、400B、400C、400D、400E フィードバック制御部
410、410B、410C、410D 波形歪み検出部
420、420B、420C、420D 時間領域等化係数演算部
430、430B、430C 準静的波形歪み検出部
440、440B、440C 周波数領域等化係数演算部
450B 低域信号抽出部
460C、460D 等化伝達特性抽出部
470C 半固定等化係数設定部
480C、480D 乗算器
490D 残留波長分散推定部
4100D 制御部
4110D 波長分散補償係数演算部
4120D 半固定波長分散補償係数設定部
4130E 位相偏差推定部
4140E 位相補償量演算部
4150E 周波数偏差推定部
4160E 制御部
4170E 周波数シフト量制御部
500、500B、500C、500D フロントエンド部
510 偏波ダイバーシティ90°ハイブリッド
521、522、523、524 光電変換部
530B フィルタ
540B ローノイズアンプ
550B ミキサー
560B 基準信号源
570B フィルタ
580B 可変利得アンプ
590B A/D変換部
600 A/D変換部
610、620、630、640 A/D変換回路
700、700B、700C デジタル受信機
700’、700” デジタル受信部
800、810B、820B アンテナ
900、900B デジタル受信端末装置
1000 信号送受信システム
1100 送信機
1200 伝送媒質
Claims (10)
- 入力された周波数領域等化係数を用いて、入力されたデジタル信号を周波数領域等化する周波数領域等化手段と、
入力された時間領域等化係数を用いて、前記入力されたデジタル信号を時間領域等化する時間領域等化手段と、
前記等化されたデジタル信号の動的波形歪および準静的波形歪を検出する波形歪検出手段と、
前記検出された準静的波形歪に基づいて、前記周波数領域等化係数を演算して出力する周波数領域等化係数制御手段と、
前記検出された動的波形歪に基づいて、前記時間領域等化係数を演算して出力する時間領域等化係数制御手段と、
を備える等化処理回路。 - 前記波形歪検出手段は、
前記等化されたデジタル信号から動的波形歪を抽出する動的波形歪抽出手段と、
前記等化されたデジタル信号から低域信号を抽出する低域信号抽出手段と、
前記抽出された低域信号から準静的波形歪を抽出する準静的波形歪抽出手段と、
を備える、請求項1記載の等化処理回路。 - 前記波形歪検出手段は、
前記等化されたデジタル信号から動的波形歪を抽出する動的波形歪抽出手段と、
前記抽出された動的波形歪に基づいて演算された時間領域等化係数を用いて、前記等化されたデジタル信号から準静的波形歪を抽出する準静的波形歪抽出手段と、
を備える、請求項1記載の等化処理回路。 - 前記周波数領域等化手段は、周波数領域等化として残留波長分散補償を行い、
前記波形歪検出手段は、前記準静的波形歪として前記等化されたデジタル信号の残留波長分散を検出し、
前記周波数領域等化係数制御手段は、周波数領域等化係数として前記検出された残留波長分散を補償する波長分散補償係数を演算する、
請求項1乃至3のいずれか1項に記載の等化処理回路。 - 入力された信号を局発信号を用いてコヒーレント検波して出力するフロントエンド手段と、
前記コヒーレント検波された信号をデジタル信号に変換して出力するA/D変換手段と、
前記デジタル信号が入力される請求項1乃至4のいずれか1項に記載の等化処理回路と、
を備えるデジタル受信機。 - 前記波形歪検出手段は、前記入力されたデジタル信号と前記局発信号との位相偏差を取得する位相偏差取得手段および前記入力されたデジタル信号と前記局発信号との周波数偏差を取得する周波数偏差取得手段を備え、
前記周波数領域等化係数制御手段は、前記取得された周波数偏差を補償する周波数シフト量を演算し、周波数領域等化係数として出力し、
前記時間領域等化係数制御手段は、前記取得された位相偏差を補償する位相補償量を演算し、時間領域等化係数として出力し、
前記周波数領域等化手段は、周波数領域等化として周波数シフトを行い、
前記時間領域等化手段は、時間領域等化として位相調整を行う、
請求項5記載のデジタル受信機。 - 信号を受信するアンテナをさらに備え、
前記フロントエンド手段は、前記受信した信号をコヒーレント検波する、
請求項5または6記載のデジタル受信機。 - 信号を送信するデジタル送信機と、
前記送信された信号が入力される請求項5乃至7のいずれか1項に記載のデジタル受信機と、
を備える信号送受信システム。 - 演算された周波数領域等化係数を用いて入力されたデジタル信号を周波数領域等化すると共に演算された時間領域等化係数を用いて入力されたデジタル信号を時間領域等化し、
前記等化されたデジタル信号の動的波形歪および準静的波形歪を検出し、
前記検出された準静的波形歪に基づいて周波数領域等化係数を演算すると共に前記検出された動的波形歪に基づいて時間領域等化係数を演算する、
等化処理方法。 - 入力された信号を局発信号を用いてコヒーレント検波して出力し、
前記コヒーレント検波された信号をデジタル信号に変換して出力し、
演算された周波数領域等化係数を用いて前記出力されたデジタル信号を周波数領域等化すると共に演算された時間領域等化係数を用いて前記出力されたデジタル信号を時間領域等化し、
前記等化されたデジタル信号の動的波形歪および準静的波形歪を検出し、
前記検出された準静的波形歪に基づいて周波数領域等化係数を演算すると共に前記検出された動的波形歪に基づいて時間領域等化係数を演算する、
デジタル受信方法。
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