Filter and multiplexer
A filter includes: a piezoelectric substrate; input and output pads located on the piezoelectric substrate; a series resonator located in a region sandwiched between the input and output pads and located on the piezoelectric substrate and electrically connected in series between the input and output pads; a parallel resonator located in the region and electrically connected in parallel between the input and output pads; a longitudinally coupled acoustic wave resonator located on the piezoelectric substrate and located at a side, at which one pad of the input and output pads is located, with respect to the region; a first wiring line located on the piezoelectric substrate and connecting the one pad to the longitudinally coupled acoustic wave resonator; a second wiring line located on the piezoelectric substrate and connecting another pad of the input and output pads to the longitudinally coupled acoustic wave resonator; and a separation part located in one of the first and second wiring lines and separating the one of the first and second wiring lines into first and second parts in a planar direction, a distance between the first and second parts being greater than a shortest distance among distances between the first and second wiring lines and the series resonator and the parallel resonator.
1. A filter comprising:
a piezoelectric substrate;
an input pad located on the piezoelectric substrate;
an output pad located on the piezoelectric substrate;
a series resonator located in a region, which is sandwiched between the input pad and the output pad and is located on the piezoelectric substrate, and electrically connected in series with a path between the input pad and the output pad;
a parallel resonator located in the region, a first end of the parallel resonator being electrically connected to the path and a second end of the parallel resonator being electrically connected to a ground;
a longitudinally coupled acoustic wave resonator located on the piezoelectric substrate, the longitudinally coupled acoustic wave resonator being located at a side at which one pad of the input pad and the output pad is located with respect to the region;
a first wiring line located on the piezoelectric substrate and connecting the one pad to the longitudinally coupled acoustic wave resonator, the first wiring line being connected in parallel with the path between the input pad and the output pad;
a second wiring line located on the piezoelectric substrate and connecting the other pad of the input pad and the output pad to the longitudinally coupled acoustic wave resonator, the second wiring line being connected in parallel with the path between the input pad and the output pad; and
a separation part located in one of the first wiring line and the second wiring line, the separation part separating the one of the first wiring line and the second wiring line into a first part and a second part in a planar direction, a shortest distance between the first part and the second part being greater than a shortest distance among a shortest distance between the first wiring line and the series resonator, a shortest distance between the first wiring line and the parallel resonator, a shortest distance between the second wiring line and the series resonator and a shortest distance between the second wiring line and the parallel resonator.
2. The filter according to claim 1 , further comprising:
a capacitor element located in series in the other of the first wiring line and the second wiring line on the piezoelectric substrate.
3. The filter according to claim 2 , wherein
the capacitor element includes a pair of electrodes facing each other in the planar direction at a distance less than the shortest distance.
4. The filter according to claim 3 , wherein
the pair of electrodes facing each other includes a pair of comb-shaped electrodes facing each other.
5. The filter according to claim 1 , wherein
the first wiring line and the second wiring line are most adjacent to a part of the series resonator of the series resonator and the parallel resonator.
6. The filter according to claim 5 , wherein
the series resonator is provided in a plurality, and
the first wiring line and the second wiring line are most adjacent to a series resonator closest to the the other pad among the plurality of the series resonators.
7. The filter according to claim 1 , wherein
the separation part is located in the second wiring line.
8. The filter according to claim 1 , wherein
each of the series resonator and the parallel resonator includes an IDT.
9. The filter according to claim 1 , wherein
the first wiring line, the second wiring line, and the longitudinally coupled acoustic wave resonator generate a signal that cancels a signal in other than a passband of the filter, the signal in other than the passband of the filter passing through the series resonator and the parallel resonator from the input pad to the output pad.
10. A multiplexer comprising:
a filter including:
a piezoelectric substrate;
an input pad located on the piezoelectric substrate;
an output pad located on the piezoelectric substrate;
a series resonator located in a region, which is sandwiched between the input pad and the output pad and is located on the piezoelectric substrate, and electrically connected in series with a path between the input pad and the output pad;
a parallel resonator located in the region a first end of the parallel resonator being electrically connected to the path and a second end of the parallel resonator being electrically connected to a ground;
a longitudinally coupled acoustic wave resonator located on the piezoelectric substrate, the longitudinally coupled acoustic wave resonator being located at a side at which one pad of the input pad and the output pad is located with respect to the region;
a first wiring line located on the piezoelectric substrate and connecting the one pad to the longitudinally coupled acoustic wave resonator, the first wiring line being connected in parallel with the path between the input pad and the output pad;
a second wiring line located on the piezoelectric substrate and connecting the other pad of the input pad and the output pad to the longitudinally coupled acoustic wave resonator, the second wiring line being connected in parallel with the path between the input pad and the output pad; and
a separation part located in one of the first wiring line and the second wiring line, the separation part separating the one of the first wiring line and the second wiring line into a first part and a second part in a planar direction, a shortest distance between the first part and the second part being greater than a shortest distance among a shortest distance between the first wiring line and the series resonator, a shortest distance between the first wiring line and the parallel resonator, a shortest distance between the second wiring line and the series resonator and a shortest distance between the second wiring line and the parallel resonator.