Patents by Inventor Hiroyoshi Ishikawa

Hiroyoshi Ishikawa 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: 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
  • Publication number: 20150077179
    Abstract: A distortion compensation apparatus including: a memory configured to store a plurality of distortion compensation coefficients for compensating distortion to an input signal amplified by an amplifier, each of the plurality of distortion compensation coefficients being associated with a different combination of two addresses, and a processor configured to receive temperature information associated with a temperature of the amplifier, generate a first address based on the input signal at a first time, generate a second address based on an average of the input signal during a previous period preceding the first time, the average being calculated based on the temperature information, select a distortion compensation coefficient from the plurality of distortion compensation coefficients based on the first address and the second address, and compensate distortion to the input signal based on the selected distortion compensation coefficient.
    Type: Application
    Filed: September 11, 2014
    Publication date: March 19, 2015
    Inventors: Satoshi MATSUBARA, Hiroyoshi ISHIKAWA
  • 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
  • Patent number: 8787487
    Abstract: A distortion compensation device which reduces a distortion of an amplifier which is added to an output signal of the amplifier, the distortion compensation device including: a plurality of distortion compensation coefficient storage circuits which stores a plurality of distortion compensation coefficients and outputs the distortion compensation coefficients according to an amplitude of an input signal of the amplifier, a distortion compensating processing circuit which adds the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to the input signal of the amplifier, and a distortion compensation coefficient updating circuit which performs weighting processing on the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to reduce the distortion compensation coefficient and which calculates an update value of the distortion compensation coefficient by using the disto
    Type: Grant
    Filed: May 2, 2012
    Date of Patent: July 22, 2014
    Assignee: Fujitsu Limited
    Inventors: Kazuo Nagatani, Hiroyoshi Ishikawa, Nobukazu Fudaba, Yuichi Utsunomiya
  • Publication number: 20140197885
    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: Application
    Filed: January 15, 2014
    Publication date: July 17, 2014
    Applicant: FUJITSU LIMITED
    Inventors: Nobukazu FUDABA, Hiroyoshi ISHIKAWA, Yuichi UTSUNOMIYA, Toshio KAWASAKI, Kazuo NAGATANI
  • Publication number: 20140167844
    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: Application
    Filed: October 17, 2013
    Publication date: June 19, 2014
    Applicant: FUJITSU LIMITED
    Inventors: Yuichi UTSUNOMIYA, Hiroyoshi ISHIKAWA, Toshio KAWASAKI, Alexander Nikolaevich LOZHKIN, Kazuo NAGATANI
  • Patent number: 8737937
    Abstract: A distortion compensation apparatus includes an amplifying unit, a plurality of distortion compensation coefficient storage units, a first address generating unit, a second address generating unit, and a distortion compensating unit. The amplifying unit amplifies an input signal. A plurality of distortion compensation coefficient storage units store the distortion compensation coefficients for compensating for the distortion of the amplifying unit by being associated with two different addresses. The first address generating unit generates a first address based on the current input signal. The second address generating unit generates a second address different from the first address based on the previous input signal.
    Type: Grant
    Filed: July 5, 2012
    Date of Patent: May 27, 2014
    Assignee: Fujitsu Limited
    Inventors: Hiroyoshi Ishikawa, Kazuo Nagatani, Nobukazu Fudaba
  • Patent number: 8712345
    Abstract: A distortion compensation device includes: a frequency-characteristic adding unit configured to add a frequency characteristic to an error signal to generate an added error signal, the error signal being a difference between an input signal input to an amplifier and an output signal output from the amplifier; a distortion-compensation-coefficient updating unit configured to update a distortion compensation coefficient for compensating for a distortion characteristic of the amplifier based on the added error signal; and a distortion compensation unit configured to perform distortion compensation on the input signal using the updated distortion compensation coefficient.
    Type: Grant
    Filed: July 26, 2012
    Date of Patent: April 29, 2014
    Assignee: Fujitsu Limited
    Inventors: Hiroyoshi Ishikawa, Kazuo Nagatani, Nobukazu Fudaba, Yuichi Utsunomiya
  • Patent number: 8655289
    Abstract: A distortion compensation device includes a distortion compensator that predistorts an input signal based on delay signals and distortion compensation coefficients corresponding to the respective delay signals obtained by applying different amounts of delay to the input signal, a calculator that calculates an error signal based on the predistorted input signal and an output signal from an amplifier that amplifies the predistorted input signal, a calculator that calculates prospective distortion compensation coefficients for updating the distortion compensation coefficients, based on the error signal, a saturation processor that performs saturation processing for bringing, when the prospective distortion compensation coefficients do not fall into a preset range, the prospective distortion compensation coefficients into the preset range, and a controller that controls the updating of the distortion compensation coefficients based on pieces of coefficient saturation information indicating whether the saturation
    Type: Grant
    Filed: February 7, 2012
    Date of Patent: February 18, 2014
    Assignee: Fujitsu Limited
    Inventors: Nobukazu Fudaba, Hiroyoshi Ishikawa, Yuichi Utsunomiya, Kazuo Nagatani
  • Patent number: 8619905
    Abstract: A predistorter includes a distortion compensating unit which gives, in advance, a reverse characteristic of a characteristic of input to output of a power amplifier to a transmission signal which is to be input to the power amplifier; a distortion compensation signal generating unit which generates a distortion compensation signal indicating the reverse characteristic based on transmission data that is sample data of the transmission signal and the delayed transmission data; and a delay amount control unit which controls a delay amount of the transmission data according to an output signal of the power amplifier.
    Type: Grant
    Filed: January 26, 2010
    Date of Patent: December 31, 2013
    Assignee: Fujitsu Limited
    Inventors: Hiroyoshi Ishikawa, Nobukazu Fudaba, Yuichi Utsunomiya, Kazuo Nagatani
  • Patent number: 8605815
    Abstract: A delay amount estimating apparatus includes a delay value search section that searches for a first delay value smaller than a delay setting value at which a given correlation value between an input signal and a feedback signal is provided, and also for a second delay value greater than the delay setting value, the feedback signal coming from a signal processing apparatus that applies signal processing on the input signal, wherein respective correlation values of the first delay value and the second delay value satisfy a given condition; and a delay estimating section that estimates a delay amount of the feedback signal relative to the input signal based on the first delay value and the second delay value.
    Type: Grant
    Filed: July 8, 2009
    Date of Patent: December 10, 2013
    Assignee: Fujitsu Limited
    Inventors: Yuichi Utsunomiya, Hiroyoshi Ishikawa, Nobukazu Fudaba, Hajime Hamada, Kazuo Nagatani
  • Publication number: 20130321078
    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: Application
    Filed: April 24, 2013
    Publication date: December 5, 2013
    Applicant: Fujitsu Limited
    Inventors: Hiroyoshi ISHIKAWA, Satoshi Matsubara, Hideharu Shako, Kazuo Nagatani
  • Patent number: 8588711
    Abstract: A transmission apparatus includes an analog digital converter that performs sampling on a demodulated signal obtained by demodulating a part of an output signal, which is produced by amplifying a modulated signal of a baseband signal including a plurality of signals having frequencies separated from each other, at a sampling frequency lower than a frequency of a given intermodulation distortion component and converting the demodulated signal into a digital signal, a detection section that detects an aliasing component of the given intermodulation distortion component produced by the conversion of the analog digital converter, and a distortion compensation section that compensates an input signal to be modulated for the given intermodulation distortion component in accordance with the detected aliasing component.
    Type: Grant
    Filed: September 16, 2011
    Date of Patent: November 19, 2013
    Assignee: Fujitsu Limited
    Inventors: Hiroyoshi Ishikawa, Nobukazu Fudaba, Kazuo Nagatani, Yasuyuki Oishi
  • Patent number: 8571495
    Abstract: A distortion compensation apparatus includes a distortion compensation signal generation unit that performs, on a transmission signal, distortion compensation processing using a series operation; a coefficient updating unit that updates series operation coefficients used for the series operation based on a feedback signal of a power amplification output which is output through power amplification processing of a distortion compensation signal output from the distortion compensation signal generation unit, and based on the distortion compensation signal; a memory that stores the distortion compensation signal corresponding to a transmission signal having a given power value and the feedback signal of the power amplification output as restraint information; and a control unit that performs control so that, in accordance with the power value of the transmission signal, restraint information corresponding to a power value different from the power value of the transmission signal is read and used for updating the
    Type: Grant
    Filed: February 8, 2010
    Date of Patent: October 29, 2013
    Assignee: Fujitsu Limited
    Inventors: Kazuo Nagatani, Yuichi Utsunomiya, Hajime Hamada, Hiroyoshi Ishikawa, Nobukazu Fudaba, Shohei Ishikawa
  • Patent number: 8532223
    Abstract: A power amplifying device includes an amplifier that amplifies a signal which is input in accordance with a voltage signal which is supplied to the amplifier, a voltage control section that controls the voltage signal in accordance with a transmission signal, a distortion compensating section that executes a distortion compensating process on the transmission signal by giving a value indicative of a reverse characteristic of the amplifier to the transmission signal in advance and inputs an output signal obtained by executing the distortion compensating process into the amplifier, an amplitude detecting section that detects an amplitude of the transmission signal, and a timing adjusting section that adjusts timings of the output signal and the voltage signal so that a value relating to the distortion compensating process meets a given condition when a detected value of the amplitude of the transmission signal is less than a given value.
    Type: Grant
    Filed: March 9, 2010
    Date of Patent: September 10, 2013
    Assignee: Fujitsu Limited
    Inventors: Kazuo Nagatani, Hiroyoshi Ishikawa