Patents by Inventor Tadasu Ishikawa

Tadasu 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).

  • Electric field sensor
    Patent number: 5574805
    Abstract: An electric field sensor comprises an electric field sensor head (3) for varying an intensity of a propagating light beam in response to an electric field intensity of an input signal received by a reception antenna (1). The electric field sensor head (3) comprises an incident optical waveguide (9), two phase-shift optical waveguides (10) having a variable refractive index which varies in response to the electric field intensity, an outgoing optical waveguide (11) and, at least one modulation electrode (12) formed in the vicinity of at least one of the two phase-shift optical waveguides (19). The electric field sensor further comprises a circuit element (2) connected between the modulation electrode (12) and the reception antenna (1). The modulation electrode (12) has a thickness not smaller than 1 .mu.m. The modulation electrode (12) may comprise a plurality of split electrodes which are split in a light propagating direction and which are capacitively coupled.
    Type: Grant
    Filed: May 11, 1995
    Date of Patent: November 12, 1996
    Assignees: Tokin Corporation, Nippon Hoso Kyokai
    Inventors: Yoshikazu Toba, Michikazu Kondo, Yoshiro Sato, Kazuhisa Hayeiwa, Hisashi Naka, Tadasu Ishikawa
  • Optical transmission and reception module having coupled optical waveguide chips
    Patent number: 5497438
    Abstract: A first optical waveguide chip has a ceramic substrate and a cover, and the ceramic substrate has a V groove and guide grooves with an optical fiber being fixed in the V groove. A second optical waveguide chip has a ceramic substrate and a cover, and the ceramic substrate has a V groove and guide grooves with an optical fiber being fixed in the V groove. The first and second optical waveguide chips have respective end faces inclined 62.degree. to the direction in which light is propagated through the optical fibers. The first and second optical waveguide chips are positioned by guide pins intimately fitted in the guide grooves.
    Type: Grant
    Filed: September 30, 1994
    Date of Patent: March 5, 1996
    Assignees: Nippon Hoso Kyokai, NGK Insulators, Ltd.
    Inventors: Tadasu Ishikawa, Yoshinari Kozuka, Yukihisa Osugi
  • Bidirectional light transmission system and optical device therefor
    Patent number: 5361157
    Abstract: A bidirectional light transmission system comprises a transmitting station having a light source for intensity-modulating a transmission signal, a first light branching portion for branching intensity-modulated light of the light source in a predetermined ratio and a first light receiving portion, and a receiving station having a second light branching portion, a light phase-modulating portion, a light reflecting portion and a second light receiving portion.
    Type: Grant
    Filed: August 25, 1992
    Date of Patent: November 1, 1994
    Assignee: Nippon Hoso Kyokai
    Inventors: Tadasu Ishikawa, Mikio Maeda, Kimiyuki Oyamada, Shuichi Fujisawa, Yozo Utsumi, Kunihara Takizawa