Duplexer
AssigneeNihon Dempa Kogyo Co., Ltd.
InventorsToshihiko Kawamoto, Susumu Yoshimoto
Life of this patent
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Abstract
Disclosed is a miniaturized duplexer having a good isolation characteristic. A duplexer having a high band side filter and a low band side filter that are each formed in a ladder-type filter provided on a common piezoelectric substrate is provided with a first elastic wave resonator to be included in one of these filters, a second elastic wave resonator to be included in the other of the filters, and a first additional grating reflector provided between these resonators to reflect an elastic wave leaked from a grating reflector of the first elastic wave resonator, and in which an additional grating reflector is not provided on a side opposite to the second elastic wave resonator in the first elastic wave resonator.
Claims15
A duplexer provided with a high band side filter and a low band side filter provided on a common piezoelectric substrate, in which these filters are ladder-type filters including elastic wave resonators to be series arms each provided with grating reflectors at both ends of an IDT electrode and elastic wave resonators to be parallel arms each provided with grating reflectors at both ends of an IDT electrode, the duplexer comprising:
- a first elastic wave resonator included in one of the high band side filter and the low band side filter;
- a second elastic wave resonator included in the other of the high band side filter and the low band side filter and being adjacent to said first elastic wave resonator in a main propagation direction of elastic waves;
- and
- a first additional grating reflector provided between said first elastic wave resonator and said second elastic wave resonator and for reflecting an elastic wave leaked from a grating reflector of said first elastic wave resonator, and wherein
- an additional grating reflector is not provided on a side opposite to said second elastic wave resonator in said first elastic wave resonator.
Dependencies are inferred from the claim text.