Title:
ELASTIC SURFACE WAVE FILTER
Document Type and Number:
Japanese Patent JPH01194603
Kind Code:
A
Abstract:
PURPOSE:To increase the attenuation quantity on the low frequency side of a blocking band and to enhance the sharpness of rise characteristics by electrically and serially connecting plural elastic surface wave transducers successively arranged from lower resonance frequencies in the propagating direction of the elastic surface wave of more than one elastic surface wave resonator or connecting them in a serial-parallel way. CONSTITUTION:An upper side transducer area formed by a common electrode 9-1 and an intermediate electrode 18 and a lower side transducer area formed by the intermediate electrode 18 and a common electrode 9-2 are alternately arranged. An electrode width (l) of a part to cross the propagation path of the elastic surface wave is set at lambda/4+lambda/2+nlambda (lambda: the wavelength of the surface wave, n: an integer) so that the exciting waves of the input side and the output side transducers may be a standing wave at the same phase. At such a time, the impedance of the resonator is high, and the attenuation quantity increase. In addition, capacity Cp slightly decreases the impedance, whereas, it makes resonant frequencies (fr) approach to anti-resonant frequencies (fa). As this result, the rise characteristics between the bands of the title filter are made sharper.
Inventors:
TABUCHI TOYOJI
HIKITA MITSUTAKA
KUROSAWA KAZUHITO
SUMIOKA JUNJI
KINOSHITA TSUNEO
HIKITA MITSUTAKA
KUROSAWA KAZUHITO
SUMIOKA JUNJI
KINOSHITA TSUNEO
Application Number:
JP1708988A
Publication Date:
August 04, 1989
Filing Date:
January 29, 1988
Export Citation:
Assignee:
HITACHI LTD
HITACHI ELECTRONICS
HITACHI COMMUNICATION SYSTEM
HITACHI ELECTRONICS
HITACHI COMMUNICATION SYSTEM
International Classes:
H03H9/25; H03H3/08; H03H9/64; (IPC1-7): H03H9/25; H03H9/64
Attorney, Agent or Firm:
Katsuo Ogawa (1 person outside)