PURPOSE: To secure a desired input/output impedance matching degree even if an electrode against capacitance in a one terminal against surface acoustic wave resonator is set low on a surface acoustic wave filter constituted by connecting unit filters where the one terminal against surface acoustic wave resonators are connected to the parallel arms and the serial arms of ladders for more than one stage in a ladder type.
CONSTITUTION: In the surface acoustic wave filter which consists of a first resonator 10 connected to the parallel arm of the ladder type and a second resonator 20 connected to the serial arm and which makes a wave to pass through the band of prescribed width, in which a filter center frequency f0(MHz) is set to be a center, the relation of the first resonator 10 and the second resonator 20 with the electrode against capacitance Cop(pF) and Cos(pF) is decided within the range of a band where a primary expression Cop=-0.28Cos+3448/f0 is set to be the center, and a numerical value obtained by dividing a constant decided in accordance with a permissible filter reflectance by the filter center frequency f0 is set to be the upper limit/lower limit of the range in the band.
| WO/2019/081232 | RF FILTER AND METHOD OF DESIGNING AN RF FILTER |
| JP2000315933 | MULTI-STAGE COUPLING TYPE SURFACE ACOUSTIC WAVE FILTER |
| JP6421899 | SAW filter device |
IGATA OSAMU
MIYASHITA TSUTOMU
TAKAMATSU MITSUO
| JPS5619765A | 1981-02-24 | |||
| JPS581850A | 1983-01-07 |