ELASTIC-WAVE FILTER DEVICE
First Claim
1. An elastic-wave filter device having a pass band and a stop band at frequencies higher than the pass band, the elastic-wave filter device comprising:
- an input terminal;
an output terminal;
a band-pass filter connected in series between the input terminal and the output terminal; and
a first band-eliminate filter connected in series between the input terminal and the output terminal;
whereinthe first band-eliminate filter includes a series arm connected in series between the input terminal and the output terminal, at least one inductor connected in series in the series arm, a plurality of parallel arms connected between the series arm and a ground potential, and a plurality of parallel-arm resonators in the respective plurality of parallel arms;
the plurality of parallel-arm resonators include a first parallel-arm resonator having a first resonance frequency in the stop band and a second parallel-arm resonator having a second resonance frequency in the stop band, the second resonance frequency being higher than the first resonance frequency; and
an impedance value of the first parallel-arm resonator is larger than an impedance value of the second parallel-arm resonator.
1 Assignment
0 Petitions
Accused Products
Abstract
In an elastic-wave filter device that includes a band-pass filter and a band-eliminate filter connected to the band-pass filter, insertion loss in a pass band is significantly reduced and attenuation in a stop band is significantly increased. The elastic-wave filter device has a pass band and a stop band at frequencies higher than the pass band. The band-pass filter and the first band-eliminate filter are connected in series between an input terminal and an output terminal. A first parallel-arm resonator of the first band-eliminate filter includes a first resonance frequency in the stop band. A second parallel-arm resonator includes a second resonance frequency in the stop band, the second resonance frequency being higher than the first resonance frequency. An impedance value of the first parallel-arm resonator is larger than an impedance value of the second parallel-arm resonator.
13 Citations
7 Claims
-
1. An elastic-wave filter device having a pass band and a stop band at frequencies higher than the pass band, the elastic-wave filter device comprising:
-
an input terminal; an output terminal; a band-pass filter connected in series between the input terminal and the output terminal; and a first band-eliminate filter connected in series between the input terminal and the output terminal;
whereinthe first band-eliminate filter includes a series arm connected in series between the input terminal and the output terminal, at least one inductor connected in series in the series arm, a plurality of parallel arms connected between the series arm and a ground potential, and a plurality of parallel-arm resonators in the respective plurality of parallel arms; the plurality of parallel-arm resonators include a first parallel-arm resonator having a first resonance frequency in the stop band and a second parallel-arm resonator having a second resonance frequency in the stop band, the second resonance frequency being higher than the first resonance frequency; and an impedance value of the first parallel-arm resonator is larger than an impedance value of the second parallel-arm resonator. - View Dependent Claims (3, 4, 5, 6, 7)
-
-
2. An elastic-wave filter device having a pass band and a stop band at frequencies lower than the pass band, the elastic-wave filter device comprising:
-
an input terminal; an output terminal; a band-pass filter connected in series between the input terminal and the output terminal; and a first band-eliminate filter connected in series between the input terminal and the output terminal;
wherein the first band-eliminate filter includes a series arm connected in series between the input terminal and the output terminal, at least one inductor connected in series in the series arm, a plurality of parallel arms connected between the series arm and a ground potential, and a plurality of parallel-arm resonators in the respective plurality of parallel arms;the plurality of parallel-arm resonators include a first parallel-arm resonator having a first resonance frequency in the stop band and a second parallel-arm resonator having a second resonance frequency in the stop band, the second resonance frequency being higher than the first resonance frequency; and an impedance value of the second parallel-arm resonator is larger than an impedance value of the first parallel-arm resonator.
-
Specification