Patents by Inventor Kazumi Shiikuma

Kazumi Shiikuma 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).

  • Patent number: 10361693
    Abstract: A power source supply circuit includes: a plurality of power sources (11-1, 11-2) that generate power source voltages different from each other; a switch circuit (14) that switches and outputs the power source voltages generated in the plurality of power sources (11-1, 11-2); a voltage output terminal (16) that outputs outside the power source voltages output from the switch circuit (14); an RF choke circuit (15) provided between the switch circuit (14) and the voltage output terminal (16), the RF choke circuit (15) including a first capacitor; and a second capacitor (12-1, 12-2) provided between the plurality of power sources (11-1, 11-2) and the switch circuit (14), the second capacitor (12-1, 12-2) having a larger capacitance than the first capacitor.
    Type: Grant
    Filed: January 5, 2016
    Date of Patent: July 23, 2019
    Assignee: NEC CORPORATION
    Inventors: Yoji Murao, Kazumi Shiikuma
  • Publication number: 20180026619
    Abstract: A power source supply circuit includes: a plurality of power sources (11-1, 11-2) that generate power source voltages different from each other; a switch circuit (14) that switches and outputs the power source voltages generated in the plurality of power sources (11-1, 11-2); a voltage output terminal (16) that outputs outside the power source voltages output from the switch circuit (14); an RF choke circuit (15) provided between the switch circuit (14) and the voltage output terminal (16), the RF choke circuit (15) including a first capacitor; and a second capacitor (12-1, 12-2) provided between the plurality of power sources (11-1, 11-2) and the switch circuit (14), the second capacitor (12-1, 12-2) having a larger capacitance than the first capacitor.
    Type: Application
    Filed: January 5, 2016
    Publication date: January 25, 2018
    Applicant: NEC Corporation
    Inventors: Yoji MURAO, Kazumi SHIIKUMA
  • Patent number: 9853605
    Abstract: A transistor package according to one exemplary embodiment includes main transistors and a sub-transistor placed in the same package as the main transistors and having a smaller size than the main transistors. It is thereby possible to provide a transistor package with more versatility capable of forming various types of Doherty amplification circuits such as a Doherty amplification circuit with auto-biasing function and an extended Doherty amplification circuit with desired operating characteristics, an amplification circuit including the same, and a method of forming a transistor.
    Type: Grant
    Filed: October 10, 2014
    Date of Patent: December 26, 2017
    Assignee: NEC Corporation
    Inventor: Kazumi Shiikuma
  • Patent number: 9793862
    Abstract: A transmitter according to an exemplary aspect of the present invention includes: a modulation circuit configured to modulate a baseband signal into a multi-bit digital signal including a component in a radio-frequency band; a plurality of switch-mode power amplifiers corresponding to each bit of the multi-bit digital signal output from the modulation circuit; and a signal synthesis circuit including a band limiting unit configured to perform a band limitation on output signals from the plurality of switch-mode power amplifiers, and a plurality of voltage-to-current converting units configured to perform a voltage-to-current conversion on respective output signals from the plurality of switch-mode power amplifiers, the signal synthesis circuit configured to makes a synthesized signal connecting the band limiting unit and the plurality of voltage-to-current converting units, wherein, depending on an output power at a synthesis point where the synthesized signal is made, a switch-mode power amplifier is selecte
    Type: Grant
    Filed: October 29, 2014
    Date of Patent: October 17, 2017
    Assignee: NEC Corporation
    Inventors: Keiichi Motoi, Kazumi Shiikuma, Shinichi Hori
  • Publication number: 20170201302
    Abstract: A wireless transmission device (1) is provided with: a signal conversion unit (20) which converts a baseband signal to a high frequency signal; multiple quadrature modulators (11_1-11_n) which modulate the high frequency signal to multiple high-frequency transmission signals (RFb1-RFbn) based on multiple control voltages (CNT1-CNTn); and multiple antenna elements (12_1-12_n) which emit the multiple transmission signals (RFb1-RFbn) into air.
    Type: Application
    Filed: June 9, 2015
    Publication date: July 13, 2017
    Applicant: NEC Corporation
    Inventors: Tomoya KANEKO, Kazumi SHIIKUMA
  • Publication number: 20170104456
    Abstract: A transmitter according to an exemplary aspect of the present invention includes: a modulation circuit configured to modulate a baseband signal into a multi-bit digital signal including a component in a radio-frequency band; a plurality of switch-mode power amplifiers corresponding to each bit of the multi-bit digital signal output from the modulation circuit; and a signal synthesis circuit including a band limiting unit configured to perform a band limitation on output signals from the plurality of switch-mode power amplifiers, and a plurality of voltage-to-current converting units configured to perform a voltage-to-current conversion on respective output signals from the plurality of switch-mode power amplifiers, the signal synthesis circuit configured to makes a synthesized signal connecting the band limiting unit and the plurality of voltage-to-current converting units, wherein, depending on an output power at a synthesis point where the synthesized signal is made, a switch-mode power amplifier is selecte
    Type: Application
    Filed: October 29, 2014
    Publication date: April 13, 2017
    Applicant: NEC Corporation
    Inventors: Keiichi MOTOI, Kazumi SHIIKUMA, Shinichi HORI
  • Publication number: 20160344349
    Abstract: A transistor package according to one exemplary embodiment includes main transistors and a sub-transistor placed in the same package as the main transistors and having a smaller size than the main transistors. It is thereby possible to provide a transistor package with more versatility capable of forming various types of Doherty amplification circuits such as a Doherty amplification circuit with auto-biasing function and an extended Doherty amplification circuit with desired operating characteristics, an amplification circuit including the same, and a method of forming a transistor.
    Type: Application
    Filed: October 10, 2014
    Publication date: November 24, 2016
    Applicant: NEC Corporation
    Inventor: Kazumi SHIIKUMA
  • Patent number: 9503029
    Abstract: The present invention is applied to a transmitting amplifier including one of a carrier amplifier and a peak amplifier as a first amplifier and the other as a second amplifier. A transmitting amplifier according to the present invention includes a transmission line transformer with a ¼ wavelength, dual-coaxial structure such that a center conductor, an inner conductor, and an outer conductor are formed in that order from the center toward the outside. The center conductor and the inner conductor constitute a first coaxial line, and the inner conductor and the outer conductor constitute a second coaxial line. The output of the first amplifier is connected to one end of the first and the second coaxial lines, and an output terminal is connected to the other end of the first and second coaxial lines. The other end of the first coaxial line, the output of the second amplifier, and the other end of the second coaxial line are connected.
    Type: Grant
    Filed: April 9, 2013
    Date of Patent: November 22, 2016
    Assignee: NEC Corporation
    Inventor: Kazumi Shiikuma
  • Patent number: 9319255
    Abstract: A transmitter includes: a modulation circuit for modulating a baseband signal into a multi-bit digital signal containing a radio frequency band component; a plurality of switch mode amplifiers each provided corresponding to a respective bit of the multi-bit digital signal supplied from the modulation circuit; and a signal-synthesizing circuit. The signal-synthesizing circuit connects a band-restricting unit that restricts the band of the output signals of the plurality of switch mode amplifiers and a voltage-current conversion unit that converts output signals of the switch mode amplifiers from voltage into current to perform signal synthesizing.
    Type: Grant
    Filed: September 12, 2013
    Date of Patent: April 19, 2016
    Assignee: NEC Corporation
    Inventors: Keiichi Motoi, Shinichi Hori, Kazumi Shiikuma
  • Publication number: 20150263768
    Abstract: A transmitter includes: multiple digital transmitters which perform delta-sigma modulation on the same baseband signal; a combiner that combines the output signals from the plural digital transmitters and outputs the combined result; a control unit that generates an external signal different for every digital transmitter, to be supplied to each of the digital transmitters; and, an input means that supplies the different external signal for every digital transmitter, to the input terminal or the internal node of a delta-sigma modulator that performs the delta-sigma modulation, the delta-sigma modulator being provided for every digital transmitter.
    Type: Application
    Filed: September 17, 2013
    Publication date: September 17, 2015
    Applicant: NEC CORPORATION
    Inventors: Shinichi Hori, Kazuaki Kunihiro, Kazumi Shiikuma
  • Publication number: 20150229276
    Abstract: The present invention is applied to a transmitting amplifier including one of a carrier amplifier and a peak amplifier as a first amplifier and the other as a second amplifier. A transmitting amplifier according to the present invention includes a transmission line transformer with a ¼ wavelength, dual-coaxial structure such that a center conductor, an inner conductor, and an outer conductor are formed in that order from the center toward the outside. The center conductor and the inner conductor constitute a first coaxial line, and the inner conductor and the outer conductor constitute a second coaxial line. The output of the first amplifier is connected to one end of the first and the second coaxial lines, and an output terminal is connected to the other end of the first and second coaxial lines. The other end of the first coaxial line, the output of the second amplifier, and the other end of the second coaxial line are connected.
    Type: Application
    Filed: April 9, 2013
    Publication date: August 13, 2015
    Applicant: NEC Corporation
    Inventor: Kazumi Shiikuma
  • Publication number: 20150222461
    Abstract: A transmitter includes: a modulation circuit for modulating a baseband signal into a multi-bit digital signal containing a radio frequency band component; a plurality of switch mode amplifiers each provided corresponding to a respective bit of the multi-bit digital signal supplied from the modulation circuit; and a signal-synthesizing circuit. The signal-synthesizing circuit connects a band-restricting unit that restricts the band of the output signals of the plurality of switch mode amplifiers and a voltage-current conversion unit that converts output signals of the switch mode amplifiers from voltage into current to perform signal synthesizing.
    Type: Application
    Filed: September 12, 2013
    Publication date: August 6, 2015
    Applicant: NEC CORPORATION
    Inventors: Keiichi Motoi, Shinichi Hori, Kazumi Shiikuma
  • Patent number: 9054647
    Abstract: A Doherty amplifier includes an impedance transformer located between a load and a signal combining point of a carrier amplifier and a peak amplifier. The impedance transformer subjects, at frequencies including a fundamental frequency and at least a second harmonic frequency thereof, an impedance Zo of the load to impedance transformation into a value lower than Zo, for example, (½)×Zo, over a wide band or a plurality of frequency bands.
    Type: Grant
    Filed: June 22, 2011
    Date of Patent: June 9, 2015
    Assignee: NEC CORPORATION
    Inventors: Kazumi Shiikuma, Makoto Hayakawa
  • Patent number: 8736364
    Abstract: A power amplifier is provided which is capable of performing efficient amplification in a wider transmission signal power range than conventional power amplifiers. The power amplifier for amplifying and outputting an input signal includes first to N-th amplifiers (N is an integer of two or more) which are cascaded. A Doherty amplifier is used in circuit configuration of each of the first to N-th amplifiers. At least one of the first to (N?1)-th amplifiers has a different power ratio from that of the N-th amplifier.
    Type: Grant
    Filed: September 27, 2010
    Date of Patent: May 27, 2014
    Assignee: NEC Corporation
    Inventors: Makoto Hayakawa, Kazumi Shiikuma
  • Patent number: 8693578
    Abstract: A transmission device includes a pulse modulated signal generator that generates a pulse-modulated signal by changing the width of a pulse or the density of a pulse according to the magnitude of the amplitude component of an input signal while discretely changing the pulse height according to the magnitude of the amplitude, a modulated-signal generator that generates a modulated signal by integrating the pulse-modulated signal and the phase component of the input signal, a power amplifier that includes at least as many amplifiers as the number of the discrete amplitude levels of the modulated signal, changes the number of amplifies that amplify the modulated signal on the basis of the value of the amplitude level of the modulated signal, combines outputs of the amplifiers, and outputs a combined output, and an output filter that eliminates a square-wave component from the output of the power amplifier.
    Type: Grant
    Filed: December 1, 2010
    Date of Patent: April 8, 2014
    Assignee: NEC Corporation
    Inventors: Kazuaki Kunihiro, Shinichi Hori, Kazumi Shiikuma
  • Patent number: 8620240
    Abstract: An aspect of a power amplifier according to the present invention is a power amplifier that amplifies a modulated signal including amplitude modulated components and phase modulated components, the power amplifier including a first voltage source 21 that amplifies low-frequency components of the amplitude modulated components of the modulated signal to output a first voltage VC_L, a second voltage source 22 that amplifies high-frequency components of the amplitude modulated components of the modulated signal to output a second voltage VC_H, a current source 24 that amplifies amplitude components of the modulated signal to output a current, a combiner circuit 23 that combines the first voltage VC_L, the second voltage VC_H, and a current IM to generate a modulated power supply signal VOUT, and an RF amplifier 30 that amplifies a signal obtained by up-converting the modulated signal to a carrier frequency and outputs the amplified signal after modulating amplitude of the amplified signal by the modulated power
    Type: Grant
    Filed: January 27, 2010
    Date of Patent: December 31, 2013
    Assignee: NEC Corporation
    Inventors: Shingo Yamanouchi, Kazuaki Kunihiro, Kazumi Shiikuma
  • Patent number: 8451054
    Abstract: A radio frequency amplifier amplifies a modulation signal or its phase modulation component and outputs the resultant signal. A linear amplifier adds an output voltage to a power supply voltage supplied to the radio frequency amplifier, amplifies a difference between the output voltage and the amplitude modulation component, and outputs the resultant difference. A control signal generation section detects a direction in which an output current of the linear amplifying section flows and generates a pulse modulation signal according to the direction of the current. A switching amplifying section controls connection and disconnection of a DC current based on the pulse modulation signal as a control signal so as to perform switching amplification for an output signal of the linear amplifying section, add the resultant signal to a predetermined DC voltage, and supply the resultant signal as the power supply voltage to the radio frequency amplifier.
    Type: Grant
    Filed: December 16, 2009
    Date of Patent: May 28, 2013
    Assignee: NEC Corporation
    Inventors: Kazuaki Kunihiro, Shingo Yamanouchi, Kazumi Shiikuma
  • Publication number: 20130099860
    Abstract: A Doherty amplifier includes an impedance transformer located between a load and a signal combining point of a carrier amplifier and a peak amplifier. The impedance transformer subjects, at frequencies including a fundamental frequency and at least a second harmonic frequency thereof, an impedance Zo of the load to impedance transformation into a value lower than Zo, for example, (½)×Zo, over a wide band or a plurality of frequency bands.
    Type: Application
    Filed: June 22, 2011
    Publication date: April 25, 2013
    Applicant: NEC CORPORATION
    Inventors: Kazumi Shiikuma, Makoto Hayakawa
  • Publication number: 20130016795
    Abstract: A transmission device includes a pulse modulated signal generator that generates a pulse-modulated signal by changing the width of a pulse or the density of a pulse according to the magnitude of the amplitude component of an input signal while discretely changing the pulse height according to the magnitude of the amplitude, a modulated-signal generator that generates a modulated signal by integrating the pulse-modulated signal and the phase component of the input signal, a power amplifier that includes at least as many amplifiers as the number of the discrete amplitude levels of the modulated signal, changes the number of amplifies that amplify the modulated signal on the basis of the value of the amplitude level of the modulated signal, combines outputs of the amplifiers, and outputs a combined output, and an output filter that eliminates a square-wave component from the output of the power amplifier.
    Type: Application
    Filed: December 1, 2010
    Publication date: January 17, 2013
    Applicant: NEC CORPORATION
    Inventors: Kazuaki Kunihiro, Shinichi Hori, Kazumi Shiikuma
  • Publication number: 20120200353
    Abstract: A power amplifier is provided which is capable of performing efficient amplification in a wider transmission signal power range than conventional power amplifiers. The power amplifier for amplifying and outputting an input signal includes first to N-th amplifiers (N is an integer of two or more) which are cascaded. A Doherty amplifier is used in circuit configuration of each of the first to N-th amplifiers. At least one of the first to (N?1)-th amplifiers has a different power ratio from that of the N-th amplifier.
    Type: Application
    Filed: September 27, 2010
    Publication date: August 9, 2012
    Applicant: NEC CORPORATION
    Inventors: Makoto Hayakawa, Kazumi Shiikuma