Patents by Inventor Kazuo Nagatani

Kazuo Nagatani 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).

  • Publication number: 20160261445
    Abstract: A peak suppression device includes a suppression-signal generating unit and a band pass filter (BPF). The suppression-signal generating unit generates a suppression signal that is obtained by adding, to a transmission signal, a frequency component in which components of frequencies from a boundary of a band of the transmission signal to a frequency that is away therefrom toward an out-band of the transmission signal by predetermined frequencies are attenuated, out of frequency components of a signal to suppress a peak of the transmission signal. The BPF attenuates, after the suppression signal is amplified by the amplifier, a frequency component outside the band of the transmission signal in the amplified suppression signal.
    Type: Application
    Filed: February 26, 2016
    Publication date: September 8, 2016
    Inventors: Hiroyoshi ISHIKAWA, Hikaru ISHIKAWA, Kazuo NAGATANI, Takuro NISHIKAWA, Ryo KOIZUMI, Takeshi SUGIYAMA, Yasuharu AMEZAWA
  • Publication number: 20160173147
    Abstract: A distortion compensation device includes: a storage configured to store a distortion compensation coefficient for compensating a distortion of a transmission signal to be amplified and transmitted, by corresponding to a combination of a plurality of addresses; a first generator configured to generate a first address according to a power or an amplitude of an input signal; a second generator configured to generate a second address according to a first vector to interconnect sample points on an IQ plane where the sample points of the input signal are drawn in time series; and a distortion compensation unit configured to acquire the distortion compensation coefficient corresponding to a combination of the first address and the second address from the storage, and to perform a predistortion processing on the input signal, by using the acquired distortion compensation coefficient, so as to generate the transmission signal.
    Type: Application
    Filed: November 19, 2015
    Publication date: June 16, 2016
    Inventors: Hiroyoshi ISHIKAWA, Tomoya OTA, Kazuo NAGATANI
  • Publication number: 20160119172
    Abstract: A peak suppression device includes an acquiring unit that acquires multiple envelopes of carrier signals that are included in a multicarrier signal, an adding unit that adds the envelopes to generate a combined envelope, a detecting unit that detects a peak value and a peak timing of the multicarrier signal by using the combined envelope, and a suppressing unit that suppresses a peak of the multicarrier signal in accordance with the peak value and the peak timing.
    Type: Application
    Filed: September 23, 2015
    Publication date: April 28, 2016
    Inventors: HIROYOSHI ISHIKAWA, TOSHIO KAWASAKI, Hikaru Ishikawa, Kazuo Nagatani
  • Patent number: 9294047
    Abstract: A power amplifier apparatus includes an amplifier configured to amplify an input signal converted into an analog signal, a distortion compensator circuitry configured to perform a pre-distortion process to an input signal at a second sampling rate higher than a first sampling rate at which the input signal is converted into an analog signal, a remover configured to remove a frequency component exceeding a frequency band corresponding to the first sampling rate from the input signal subjected to the pre-distortion process, a first rate converter configured to convert a sampling rate of the input signal from which the frequency component is removed from the second sampling rate to the first sampling rate, and a first signal converter configured to convert the input signal the sampling rate of which is converted into an analog signal at the first sampling rate to supply the input signal converted into the analog signal to the amplifier.
    Type: Grant
    Filed: May 19, 2014
    Date of Patent: March 22, 2016
    Assignee: Fujitsu Limited
    Inventors: Toshio Kawasaki, Hiroyoshi Ishikawa, Kazuo Nagatani, Yuichi Utsunomiya, Alexander Nikolaevich Lozhkin, Hajime Hamada
  • Patent number: 9276799
    Abstract: A wireless transmission apparatus includes an amplifier that amplifies power of a multicarrier signal, a first frequency shift unit that performs a first frequency shift on a first signal fed back from the amplifier on the basis of carrier frequencies of the multicarrier signal to output a second signal after the first frequency shift, a band limiting unit that performs frequency band limitation on the second signal to output a third signal after the frequency band limitation, and a distortion compensation device that compensates nonlinear distortion of the amplifier on the basis of the third signal.
    Type: Grant
    Filed: March 30, 2015
    Date of Patent: March 1, 2016
    Assignee: FUJITSU LIMITED
    Inventors: Yuichi Utsunomiya, Hiroyoshi Ishikawa, Kazuo Nagatani
  • Patent number: 9270231
    Abstract: A distortion compensation apparatus that compensates nonlinear distortion of an amplifier that amplifies power of a multi-carrier signal includes a band limiting unit that places a first frequency band limitation on a first signal fed back from the amplifier to output a second signal after the first frequency band limitation, a decision unit that decides a first cutoff frequency of the first frequency band limitation based on a carrier interval of the multi-carrier signal, and an updating unit that updates a distortion compensation coefficient to be used for compensation of the nonlinear distortion, based on an error between the second signal and the multi-carrier signal.
    Type: Grant
    Filed: January 13, 2015
    Date of Patent: February 23, 2016
    Assignee: FUJITSU LIMITED
    Inventors: Yuichi Utsunomiya, Hiroyoshi Ishikawa, Kazuo Nagatani
  • Patent number: 9263994
    Abstract: An amplifying device including: a first amplifier configured to generate a first output signal by amplifying an input signal, a second amplifier configured to generate a second output signal by amplifying the first output signal, and a processor configured to perform a first compensation by compensating a distortion for the second amplifier in accordance with the first output signal and the second output signal.
    Type: Grant
    Filed: January 15, 2014
    Date of Patent: February 16, 2016
    Assignee: FUJITSU LIMITED
    Inventors: Nobukazu Fudaba, Hiroyoshi Ishikawa, Yuichi Utsunomiya, Toshio Kawasaki, Kazuo Nagatani
  • Patent number: 9236893
    Abstract: A distortion compensation device which compensates for a distortion of an amplifier includes an FIR filter, a calculation unit that calculates an error between a reference signal and a feedback signal from the amplifier, an update unit that updates a coefficient set to the FIR filter on the basis of the error, and a delay unit that, on the basis of a magnitude of the coefficient, delays the feedback signal while controlling a delay of the feedback signal with respect to the reference signal.
    Type: Grant
    Filed: April 9, 2015
    Date of Patent: January 12, 2016
    Assignee: FUJITSU LIMITED
    Inventors: Hiroyoshi Ishikawa, Kazuo Nagatani
  • Patent number: 9225295
    Abstract: A distortion compensation apparatus including: a processor configured to generate a pre-distortion signal by compensating an input signal for a distortion based on a distortion compensation coefficient and a plurality of delayed signals obtained by delaying the input signal by a plurality of amounts of delay, and an amplifier configured to generate an amplified signal by amplifying the pre-distortion signal, wherein the processor calculates the distortion compensation coefficient based on the input signal, the pre-distortion signal, and the amplified signal, and calculates the plurality of amounts of delay based on the amplified signal.
    Type: Grant
    Filed: April 24, 2013
    Date of Patent: December 29, 2015
    Assignee: FUJITSU LIMITED
    Inventors: Hiroyoshi Ishikawa, Satoshi Matsubara, Hideharu Shako, Kazuo Nagatani
  • Publication number: 20150372850
    Abstract: A peak suppression apparatus includes an acquiring unit that acquires a first signal represented by an amplitude waveform of a multicarrier signal, a generator that generates a second signal represented by a waveform sequentially connecting a plurality of peak points adjacent to one another in the first signal as a peak detection signal for the multicarrier signal, a detector that detects a peak value and a peak timing of the multicarrier signal by using the peak detection signal, and a suppressing unit that suppresses a peak of the multicarrier signal based on the peak value and the peak timing.
    Type: Application
    Filed: April 28, 2015
    Publication date: December 24, 2015
    Inventors: Tomoya Ota, HIROYOSHI ISHIKAWA, Kazuo Nagatani
  • Patent number: 9203449
    Abstract: A delay quantity estimation apparatus comprises a first correlation value arithmetic unit to calculate a first correlation value as a correlation value between a first input signal and a feedback signal delayed with a first delay value; a second correlation value arithmetic unit to calculate a second correlation value as a correlation value between the first input signal and a feedback signal delayed with a second delay value; and a delay quantity estimation unit to estimate a delay quantity of the feedback signal with respect to the input signal on the basis of the first difference value as a difference between the first correlation value and the second correlation value, wherein the second delay value is a value given by adding a certain value to the first delay value.
    Type: Grant
    Filed: September 27, 2013
    Date of Patent: December 1, 2015
    Assignee: FUJITSU LIMITED
    Inventors: Satoshi Matsubara, Hideharu Shako, Mitsuharu Hamano, Kazuo Nagatani
  • Publication number: 20150341060
    Abstract: A distortion compensation device which compensates for a distortion of an amplifier includes an FIR filter, a calculation unit that calculates an error between a reference signal and a feedback signal from the amplifier, an update unit that updates a coefficient set to the FIR filter on the basis of the error, and a delay unit that, on the basis of a magnitude of the coefficient, delays the feedback signal while controlling a delay of the feedback signal with respect to the reference signal.
    Type: Application
    Filed: April 9, 2015
    Publication date: November 26, 2015
    Inventors: HIROYOSHI ISHIKAWA, Kazuo Nagatani
  • Patent number: 9190964
    Abstract: A distortion compensation device includes: a distortion compensator configured to output, to a power amplifier, a predistortion signal obtained by performing distortion compensation processing on a transmission signal by using a distortion compensation coefficient, wherein the distortion compensator limits bands of a reference signal and a feedback signal so that the bands fall in a pass band and updates the distortion compensation coefficient based on an error between the reference signal and the feedback signal, the reference signal corresponding to the predistortion signal, the feedback signal corresponding to an output feedback of the power amplifier.
    Type: Grant
    Filed: October 17, 2013
    Date of Patent: November 17, 2015
    Assignee: FUJITSU LIMITED
    Inventors: Yuichi Utsunomiya, Hiroyoshi Ishikawa, Toshio Kawasaki, Alexander Nikolaevich Lozhkin, Kazuo Nagatani
  • Publication number: 20150304154
    Abstract: A wireless transmission apparatus includes an amplifier that amplifies power of a multicarrier signal, a first frequency shift unit that performs a first frequency shift on a first signal fed back from the amplifier on the basis of carrier frequencies of the multicarrier signal to output a second signal after the first frequency shift, a band limiting unit that performs frequency band limitation on the second signal to output a third signal after the frequency band limitation, and a distortion compensation device that compensates nonlinear distortion of the amplifier on the basis of the third signal.
    Type: Application
    Filed: March 30, 2015
    Publication date: October 22, 2015
    Inventors: Yuichi Utsunomiya, HIROYOSHI ISHIKAWA, Kazuo Nagatani
  • Publication number: 20150236656
    Abstract: A distortion compensation apparatus that compensates nonlinear distortion of an amplifier that amplifies power of a multi-carrier signal includes a band limiting unit that places a first frequency band limitation on a first signal fed back from the amplifier to output a second signal after the first frequency band limitation, a decision unit that decides a first cutoff frequency of the first frequency band limitation based on a carrier interval of the multi-carrier signal, and an updating unit that updates a distortion compensation coefficient to be used for compensation of the nonlinear distortion, based on an error between the second signal and the multi-carrier signal.
    Type: Application
    Filed: January 13, 2015
    Publication date: August 20, 2015
    Inventors: Yuichi Utsunomiya, HIROYOSHI ISHIKAWA, Kazuo Nagatani
  • Patent number: 9100263
    Abstract: A distortion compensation apparatus for performing distortion compensation processing by applying the inverse properties of distortion properties of the power amplifier to a transmission signal to be input to a power amplifier, includes a plurality of distortion compensation coefficient storage units configured to store a plurality of distortion compensation coefficients used for the distortion compensation processing, an offset correction processing unit configured to subject the distortion compensation coefficient stored in each of the plurality of distortion compensation coefficient storage units to offset correction processing, and to generate distortion compensation coefficients in the case that the offset correction processing has not been performed, corresponding to plurality of distortion compensation coefficient storage units, in a pseudo manner and a distortion compensation processing unit configured to subject the transmission signal to the distortion compensation processing based on the distortion
    Type: Grant
    Filed: March 15, 2012
    Date of Patent: August 4, 2015
    Assignee: FUJITSU LIMITED
    Inventors: Yuichi Utsunomiya, Hiroyoshi Ishikawa, Nobukazu Fudaba, Kazuo Nagatani
  • Patent number: 8933752
    Abstract: A power amplifier apparatus that includes a processor that performs a first distortion compensation processing on an input signal using a distortion compensation coefficient to obtain a first signal and an amplifier that amplifies the first signal. The processor performs a second distortion compensation processing the amplified signal using the distortion compensation coefficient to obtain a second signal and updates the distortion compensation coefficient to enable convergence between the first signal and the second signal.
    Type: Grant
    Filed: October 20, 2011
    Date of Patent: January 13, 2015
    Assignee: Fujitsu Limited
    Inventors: Kazuo Nagatani, Yuichi Utsunomiya, Nobukazu Fudaba, Hiroyoshi Ishikawa, Hajime Hamada
  • Publication number: 20140347132
    Abstract: A power amplifier apparatus includes an amplifier configured to amplify an input signal converted into an analog signal, a distortion compensator circuitry configured to perform a pre-distortion process to an input signal at a second sampling rate higher than a first sampling rate at which the input signal is converted into an analog signal, a remover configured to remove a frequency component exceeding a frequency band corresponding to the first sampling rate from the input signal subjected to the pre-distortion process, a first rate converter configured to convert a sampling rate of the input signal from which the frequency component is removed from the second sampling rate to the first sampling rate, and a first signal converter configured to convert the input signal the sampling rate of which is converted into an analog signal at the first sampling rate to supply the input signal converted into the analog signal to the amplifier.
    Type: Application
    Filed: May 19, 2014
    Publication date: November 27, 2014
    Applicant: FUJITSU LIMITED
    Inventors: Toshio KAWASAKI, Hiroyoshi Ishikawa, Kazuo Nagatani, Yuichi Utsunomiya, Alexander Nikolaevich Lozhkin, Hajime Hamada
  • Publication number: 20140292405
    Abstract: An amplification device includes: an amplitude adjustment circuit configured to adjust an amplitude level of an input signal so as to keep the amplitude level within a given range; an amplifier configured to amplify the adjusted signal; and a circuitry configured to change an amplitude level of the amplified signal, based on the amplitude level of the input signal and a first distortion compensation corresponding to the amplitude level of the input signal.
    Type: Application
    Filed: March 25, 2014
    Publication date: October 2, 2014
    Applicant: FUJITSU LIMITED
    Inventors: Takeshi TAKANO, Shigekazu KIMURA, Ken TAMANOI, Masakazu KOJIMA, Toru MANIWA, Yasuyuki OISHI, Michiharu NAKAMURA, Kazuo NAGATANI
  • Patent number: 8831135
    Abstract: An address controller includes: a plurality of lookup tables configured to hold values corresponding to a plurality of addresses; a similarity detector configured to detect similarity between the plurality of lookup tables and to group similar lookup tables among the plurality of lookup tables; and a controller configured to read the values out of the plurality of lookup tables grouped by the similarity detector, using address control information common to grouped lookup tables.
    Type: Grant
    Filed: July 1, 2013
    Date of Patent: September 9, 2014
    Assignee: Fujitsu Limited
    Inventors: Yuichi Utsunomiya, Kazuo Nagatani