Patents by Inventor Manabu Yamazaki
Manabu Yamazaki has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20210257982Abstract: A receiving device, includes a memory; and a processor coupled to the memory and configured to: when amplifying a multi-valued signal of a multi-valued modulation technique according to a control signal, acquire a first multi-valued signal before amplifying the multi-valued signal and a second multi-valued signal after amplifying the multi-valued signal, detect a first peak voltage of the first multi-valued signal, detect a second peak voltage of the second multi-valued signal, and control the control signal based on the first peak voltage and the second peak voltage such that a maximum amplitude of the second multi-valued signal and linearity of the second multi-valued signal are maintained.Type: ApplicationFiled: January 7, 2021Publication date: August 19, 2021Applicant: FUJITSU LIMITEDInventors: DAISUKE USUI, MANABU YAMAZAKI, Hirotomo Izumi
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Patent number: 11070352Abstract: A clock data recovery circuit includes a circuit that receives a data signal for which each of a plurality of potential levels is associated with a value of 2 bits or more, based on a result of a first comparison that compares the 3 or more first thresholds with the data signal at timing synchronized with a clock signal; a circuit that outputs a result of a second comparison that compares the data signal with a second threshold at the timing; a circuit that generates a phase difference signal indicating whether to advance or delay a phase of the clock signal, based on the result of the determination and the result of the second comparison; a filter that generates a phase adjusted value indicating an adjustment amount of the phase, based on the phase difference signal; and a circuit that adjusts the phase based on the phase adjusted value.Type: GrantFiled: August 27, 2020Date of Patent: July 20, 2021Assignee: FUJITSU LIMITEDInventors: Nobuaki Kawasoe, Yoshiharu Yoshizawa, Manabu Yamazaki
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Patent number: 10944601Abstract: A reception circuit includes: a first equalizer configured to equalize a reception waveform; a second equalizer configured to equalize an input waveform from the first equalizer; a monitor configured to monitor magnitude of the input waveform; and a controller configured to generate a gain control code used for setting a gain of the first equalizer and a threshold voltage control code used for setting a threshold voltage to be compared with the input waveform in the second equalizer, in accordance with a monitoring result of the magnitude obtained by the monitor.Type: GrantFiled: April 21, 2020Date of Patent: March 9, 2021Assignee: FUJITSU LIMITEDInventor: Manabu Yamazaki
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Publication number: 20210067312Abstract: A clock data recovery circuit includes a circuit that receives a data signal for which each of a plurality of potential levels is associated with a value of 2 bits or more, based on a result of a first comparison that compares the 3 or more first thresholds with the data signal at timing synchronized with a clock signal; a circuit that outputs a result of a second comparison that compares the data signal with a second threshold at the timing; a circuit that generates a phase difference signal indicating whether to advance or delay a phase of the clock signal, based on the result of the determination and the result of the second comparison; a filter that generates a phase adjusted value indicating an adjustment amount of the phase, based on the phase difference signal; and a circuit that adjusts the phase based on the phase adjusted value.Type: ApplicationFiled: August 27, 2020Publication date: March 4, 2021Applicant: FUJITSU LIMITEDInventors: Nobuaki Kawasoe, Yoshiharu YOSHIZAWA, MANABU YAMAZAKI
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Patent number: 10890822Abstract: A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.Type: GrantFiled: July 31, 2019Date of Patent: January 12, 2021Assignee: FUJITSU LIMITEDInventors: Shigeki Kawaai, Hirotomo Izumi, Manabu Yamazaki
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Publication number: 20200358639Abstract: A reception circuit includes: a first equalizer configured to equalize a reception waveform; a second equalizer configured to equalize an input waveform from the first equalizer; a monitor configured to monitor magnitude of the input waveform; and a controller configured to generate a gain control code used for setting a gain of the first equalizer and a threshold voltage control code used for setting a threshold voltage to be compared with the input waveform in the second equalizer, in accordance with a monitoring result of the magnitude obtained by the monitor.Type: ApplicationFiled: April 21, 2020Publication date: November 12, 2020Applicant: FUJITSU LIMITEDInventor: MANABU YAMAZAKI
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Publication number: 20200089075Abstract: A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.Type: ApplicationFiled: July 31, 2019Publication date: March 19, 2020Applicant: FUJITSU LIMITEDInventors: Shigeki Kawaai, Hirotomo Izumi, MANABU YAMAZAKI
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Patent number: 10284302Abstract: An optical transmitter includes an optical modulator that includes a first phase shifter for a most significant bit, a second phase shifter for a least significant bit, and a third phase shifter for fine adjustment, the first phase shifter, the second phase shifter, and the third phase shifter are disposed along an optical waveguide, and a drive circuit that includes a first driver that drives the first phase shifter, a second driver that drives the second phase shifter, and a third driver that drives the third phase shifter, wherein a drive polarity of the third driver is adjustable in a positive direction and a negative direction, and the third phase shifter adjusts an amount of phase change of the optical modulator in a positive direction or a negative direction based on a drive voltage inputted from the third driver.Type: GrantFiled: May 23, 2018Date of Patent: May 7, 2019Assignee: FUJITSU LIMITEDInventors: Shigeki Kawaai, Yoshiharu Yoshizawa, Manabu Yamazaki, Daisuke Usui
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Publication number: 20180343064Abstract: An optical transmitter includes an optical modulator that includes a first phase shifter for a most significant bit, a second phase shifter for a least significant bit, and a third phase shifter for fine adjustment, the first phase shifter, the second phase shifter, and the third phase shifter are disposed along an optical waveguide, and a drive circuit that includes a first driver that drives the first phase shifter, a second driver that drives the second phase shifter, and a third driver that drives the third phase shifter, wherein a drive polarity of the third driver is adjustable in a positive direction and a negative direction, and the third phase shifter adjusts an amount of phase change of the optical modulator in a positive direction or a negative direction based on a drive voltage inputted from the third driver.Type: ApplicationFiled: May 23, 2018Publication date: November 29, 2018Applicant: FUJITSU LIMITEDInventors: Shigeki Kawaai, Yoshiharu Yoshizawa, Manabu Yamazaki, Daisuke Usui
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Patent number: 9680667Abstract: A circuit includes a calculation circuit configured to calculate a noise power of a predetermined-training-sequence pattern repeatedly included in a first signal input into an adaptive equalizer, based on a second signal obtained by compensating the first signal by a compensation circuit, a channel-estimation value based on the second signal, and the predetermined-training-sequence pattern; and an average circuit configured to obtain an average value of estimation values of frequency offsets based on the predetermined-training-sequence pattern having the noise power equal to or smaller than a predetermined power, among estimation values of frequency offsets based on the predetermined-training-sequence pattern, wherein the compensation circuit is configured to compensate a frequency offset of the predetermined-training sequence pattern based on the average value and thereby obtain the second signal, and the adaptive equalizer is configured to perform adaptive-equalization processing of the first signal with aType: GrantFiled: July 6, 2016Date of Patent: June 13, 2017Assignee: FUJITSU LIMITEDInventors: Daisuke Sasaki, Kazuhiko Hatae, Tomoki Katou, Nobukazu Koizumi, Masato Oota, Yasuo Ohtomo, Manabu Yamazaki, Masashi Sato
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Patent number: 9660733Abstract: A signal processing apparatus includes: a filter; and a filter control circuit, wherein the filter control circuit is configured to: detect a power of signals output from the filter; determine one of a plurality of numerical ranges to which the power belongs; update a filter coefficient of the filter according to a determination result; count a number of the signals having the power of a first value or more; set an invalid area which becomes a target not to be determined for each of one or more boundaries between the plurality of numerical ranges when the number of the signals becomes a second value or more; and control a width of the invalid area based on the number of signals.Type: GrantFiled: September 1, 2015Date of Patent: May 23, 2017Assignee: FUJITSU LIMITEDInventors: Masashi Sato, Kazuhiko Hatae, Tomoki Katou, Nobukazu Koizumi, Masato Oota, Yasuo Ohtomo, Manabu Yamazaki, Daisuke Sasaki
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Publication number: 20170012803Abstract: A circuit includes a calculation circuit configured to calculate a noise power of a predetermined-training-sequence pattern repeatedly included in a first signal input into an adaptive equalizer, based on a second signal obtained by compensating the first signal by a compensation circuit, a channel-estimation value based on the second signal, and the predetermined-training-sequence pattern; and an average circuit configured to obtain an average value of estimation values of frequency offsets based on the predetermined-training-sequence pattern having the noise power equal to or smaller than a predetermined power, among estimation values of frequency offsets based on the predetermined-training-sequence pattern, wherein the compensation circuit is configured to compensate a frequency offset of the predetermined-training sequence pattern based on the average value and thereby obtain the second signal, and the adaptive equalizer is configured to perform adaptive-equalization processing of the first signal with aType: ApplicationFiled: July 6, 2016Publication date: January 12, 2017Applicant: FUJITSU LIMITEDInventors: Daisuke SASAKI, KAZUHIKO HATAE, TOMOKI KATOU, Nobukazu KOIZUMI, Masato OOTA, Yasuo OHTOMO, MANABU YAMAZAKI, Masashi Sato
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Patent number: 9496966Abstract: A receiving device that converts, to a digital signal, a signal in which signal light from an optical transmission path and local oscillation light are mixed, so as to perform digital signal processing, the optical communication receiving device comprising: a frequency offset compensation unit configured to calculate a frequency offset of the digital signal and to, based on the frequency offset, compensate for a phase of the digital signal; a carrier phase recovery unit configured to calculate a carrier phase of the digital signal whose phase is compensated for in the frequency offset compensation unit; and a residual frequency offset detection unit configured to calculate an average of differences in the carrier phase, and to output the average as a residual frequency offset, wherein the frequency offset compensation unit is configured to correct the frequency offset using the residual frequency offset output by the residual frequency offset detection unit.Type: GrantFiled: September 24, 2014Date of Patent: November 15, 2016Assignee: FUJITSU LIMITEDInventors: Kazuhiko Hatae, Nobukazu Koizumi, Koji Nakamuta, Manabu Yamazaki, Tomoki Katou, Masashi Sato, Hisao Nakashima
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Patent number: 9401765Abstract: A frequency offset estimation circuit estimates a frequency offset that indicates a difference between a carrier frequency of a received optical signal and a frequency of a local oscillation light used to recover a transmission signal from the received optical signal. The frequency offset estimation circuit includes: a phase difference detector configured to detect a phase difference due to the frequency offset between a first symbol and a second symbol that is transmitted after the first symbol by a specified symbol interval based on a phase of the first symbol and a phase of the second symbol; an estimator configured to estimate the frequency offset based on the phase difference detected by the phase difference detector; and a symbol interval controller configured to specify the symbol interval based on the frequency offset estimated by the estimator.Type: GrantFiled: October 13, 2014Date of Patent: July 26, 2016Assignee: FUJITSU LIMITEDInventors: Nobuaki Kawasoe, Manabu Yamazaki, Kazuhiko Hatae
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Patent number: 9374170Abstract: An optical receiving device includes: an adaptive equalizer that includes a position estimation unit configured to estimate, based on a first signal component and a second signal component of a reception signal generated by reception of a training sequence pattern transmitted from an optical transmitter, a symbol position of the reception signal, and generates an estimated symbol position, a delay unit configured to provide a delay difference between the first signal component and the second signal component, a control unit configured to set a plurality of symbol displacement amount candidates of displacement amounts for the estimated symbol position, causes the delay unit to generate a plurality of delay differences, and generates a channel estimation symbol position used for channel estimation, and an error rate calculation unit configured to calculate an error rate of the signal restored by an adaptive equalization unit.Type: GrantFiled: December 4, 2014Date of Patent: June 21, 2016Assignee: FUJITSU LIMITEDInventors: Masato Oota, Tomoki Katou, Kazuhiko Hatae, Hisao Nakashima, Manabu Yamazaki
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Publication number: 20160134261Abstract: A signal processing apparatus includes: a filter; and a filter control circuit, wherein the filter control circuit is configured to: detect a power of signals output from the filter; determine one of a plurality of numerical ranges to which the power belongs; update a filter coefficient of the filter according to a determination result; count a number of the signals having the power of a first value or more; set an invalid area which becomes a target not to be determined for each of one or more boundaries between the plurality of numerical ranges when the number of the signals becomes a second value or more; and control a width of the invalid area based on the number of signals.Type: ApplicationFiled: September 1, 2015Publication date: May 12, 2016Inventors: Masashi Sato, KAZUHIKO HATAE, TOMOKI KATOU, Nobukazu KOIZUMI, Masato OOTA, Yasuo OHTOMO, MANABU YAMAZAKI, Daisuke SASAKI
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Patent number: 9143239Abstract: A signal processing device includes: a plurality of multipliers configured to obtain a first multiplication result by multiplying a tap coefficient by 1/?2; a plurality of mappers configured to output a mapping result based on a first mapping coefficient and a digital input signal; and a plurality of first selectors configured to select the first multiplication result based on the mapping result.Type: GrantFiled: October 4, 2013Date of Patent: September 22, 2015Assignee: FUJITSU LIMITEDInventor: Manabu Yamazaki
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Publication number: 20150180586Abstract: An optical receiving device includes: an adaptive equalizer that includes a position estimation unit configured to estimate, based on a first signal component and a second signal component of a reception signal generated by reception of a training sequence pattern transmitted from an optical transmitter, a symbol position of the reception signal, and generates an estimated symbol position, a delay unit configured to provide a delay difference between the first signal component and the second signal component, a control unit configured to set a plurality of symbol displacement amount candidates of displacement amounts for the estimated symbol position, causes the delay unit to generate a plurality of delay differences, and generates a channel estimation symbol position used for channel estimation, and an error rate calculation unit configured to calculate an error rate of the signal restored by an adaptive equalization unit.Type: ApplicationFiled: December 4, 2014Publication date: June 25, 2015Inventors: Masato OOTA, Tomoki KATOU, Kazuhiko HATAE, Hisao NAKASHIMA, Manabu YAMAZAKI
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Publication number: 20150147071Abstract: A frequency offset estimation circuit estimates a frequency offset that indicates a difference between a carrier frequency of a received optical signal and a frequency of a local oscillation light used to recover a transmission signal from the received optical signal. The frequency offset estimation circuit includes: a phase difference detector configured to detect a phase difference due to the frequency offset between a first symbol and a second symbol that is transmitted after the first symbol by a specified symbol interval based on a phase of the first symbol and a phase of the second symbol; an estimator configured to estimate the frequency offset based on the phase difference detected by the phase difference detector; and a symbol interval controller configured to specify the symbol interval based on the frequency offset estimated by the estimator.Type: ApplicationFiled: October 13, 2014Publication date: May 28, 2015Inventors: Nobuaki Kawasoe, MANABU YAMAZAKI, KAZUHIKO HATAE
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Publication number: 20150098714Abstract: A receiving device that converts, to a digital signal, a signal in which signal light from an optical transmission path and local oscillation light are mixed, so as to perform digital signal processing, the optical communication receiving device comprising: a frequency offset compensation unit configured to calculate a frequency offset of the digital signal and to, based on the frequency offset, compensate for a phase of the digital signal; a carrier phase recovery unit configured to calculate a carrier phase of the digital signal whose phase is compensated for in the frequency offset compensation unit; and a residual frequency offset detection unit configured to calculate an average of differences in the carrier phase, and to output the average as a residual frequency offset, wherein the frequency offset compensation unit is configured to correct the frequency offset using the residual frequency offset output by the residual frequency offset detection unit.Type: ApplicationFiled: September 24, 2014Publication date: April 9, 2015Applicant: Fujitsu LimitedInventors: Kazuhiko HATAE, Nobukazu KOIZUMI, Koji NAKAMUTA, Manabu YAMAZAKI, Tomoki KATOU, Masashi SATO, Hisao NAKASHIMA