RADIO FREQUENCY (RF) FILTER WITH INCREASED SHUNT RESONATOR COUPLING COEFFICIENT
Certain aspects of the present disclosure generally relate to a filter, such as an acoustic resonator filter. An example filter generally includes a first series resonator coupled between a first port of the filter and a second port of the filter, the first series resonator including a first piezoelectric layer disposed between a first electrode and a second electrode of the first series resonator. The filter also includes a first shunt resonator coupled between a first node of the filter and a reference potential node of the filter, the first shunt resonator including a second piezoelectric layer disposed between a third electrode and a fourth electrode of the first shunt resonator. The first node is coupled between the two ports, and the second piezoelectric layer's thickness is greater than the first piezoelectric layer's thickness.
1 . A filter comprising:
a first series resonator coupled between a first port of the filter and a second port of the filter, the first series resonator comprising a first piezoelectric layer disposed between a first electrode and a second electrode of the first series resonator; and
a first shunt resonator coupled between a first node of the filter and a reference potential node of the filter, the first shunt resonator comprising a second piezoelectric layer disposed between a third electrode and a fourth electrode of the first shunt resonator, wherein:
the first node is coupled between the first port and the second port of the filter; and
a thickness of the second piezoelectric layer is greater than a thickness of the first piezoelectric layer.
2 . The filter of claim 1 , wherein the first series resonator has a first coupling coefficient, and wherein the first shunt resonator has a second coupling coefficient that is greater than the first coupling coefficient.
3 . The filter of claim 1 , wherein the first electrode, the second electrode, the third electrode, and the fourth electrode have same thickness.
4 . The filter of claim 1 , wherein the third electrode and the fourth electrode have same thickness.
5 . The filter of claim 1 , wherein a thickness of the third electrode is different from a thickness of the fourth electrode.
6 . The filter of claim 1 , wherein the first node is connected to the first port of the filter.
7 . The filter of claim 1 , wherein each of the first piezoelectric layer and the second piezoelectric layer comprises scandium (Sc)-doped aluminum nitride (AlN).
8 . The filter of claim 1 , wherein each of the first electrode, the second electrode, the third electrode, and the fourth electrode comprises molybdenum (Mo), tungsten (W), aluminum (Al)-copper (Cu) alloy, AlN, titanium (Ti), titanium tungsten (TiW), titanium nitride (TiN), or a combination thereof.
9 . The filter of claim 1 , further comprising:
a second series resonator coupled between the first series resonator and the second port of the filter, the second series resonator comprising a third piezoelectric layer disposed between a fifth electrode and a sixth electrode of the second series resonator; and
a second shunt resonator coupled between a second node of the filter and the reference potential node of the filter, the second shunt resonator comprising a fourth piezoelectric layer disposed between a seventh electrode and an eighth electrode of the second shunt resonator, wherein the second node is coupled between the first port and the second port of the filter and wherein a thickness of the fourth piezoelectric layer is greater than a thickness of the third piezoelectric layer.
10 . The filter of claim 9 , wherein the second node is coupled between the first series resonator and the second series resonator.
11 . The filter of claim 9 , wherein the second node is connected to the second port of the filter.
12 . The filter of claim 9 , wherein the second series resonator has a third coupling coefficient and wherein the second shunt resonator has a fourth coupling coefficient that is greater than the third coupling coefficient.
13 . The filter of claim 9 , wherein the thickness of the fourth piezoelectric layer is different from the thickness of the second piezoelectric layer.
14 . The filter of claim 9 , wherein a thickness of the seventh electrode is different from a thickness of the eighth electrode.
15 . The filter of claim 9 , wherein the fifth electrode, the sixth electrode, the seventh electrode, and the eighth electrode have same thickness.
16 . The filter of claim 9 , wherein each of the third piezoelectric layer and the fourth piezoelectric layer comprises scandium (Sc)-doped aluminum nitride (AlN).
17 . The filter of claim 9 , wherein each of the fifth electrode, the sixth electrode, the seventh electrode, and the eighth electrode comprises molybdenum (Mo).
18 . A method for filtering an input signal, comprising:
receiving the input signal at a first port of a filter; and
generating a filtered version of the input signal at a second port of the filter, the filter comprising:
a first series resonator coupled between the first port and the second port of the filter, the first series resonator comprising a first piezoelectric layer disposed between a first electrode and a second electrode of the first series resonator; and
a first shunt resonator coupled between a first node of the filter and a reference potential node of the filter, the first shunt resonator comprising a second piezoelectric layer disposed between a third electrode and a fourth electrode of the first shunt resonator, wherein:
the first node is coupled between the first port and the second port of the filter; and
a thickness of the second piezoelectric layer is greater than a thickness of the first piezoelectric layer.
19 . The method of claim 18 , wherein the first series resonator has a first coupling coefficient, and wherein the first shunt resonator has a second coupling coefficient that is greater than the first coupling coefficient.
20 . The method of claim 18 , wherein the first electrode, the second electrode, the third electrode, and the fourth electrode have same thickness.
21 . The method of claim 18 , wherein the third electrode and the fourth electrode have same thickness.
22 . The method of claim 18 , wherein a thickness of the third electrode is different from a thickness of the fourth electrode.
23 . The method of claim 18 , wherein the first node is connected to the first port of the filter.
24 . The method of claim 18 , wherein each of the first piezoelectric layer and the second piezoelectric layer comprises scandium (Sc)-doped aluminum nitride (AlN).
25 . The method of claim 18 , wherein each of the first electrode, the second electrode, the third electrode, and the fourth electrode comprises molybdenum (Mo), tungsten (W), aluminum (Al)-copper (Cu) alloy, AlN, titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), or a combination thereof.
26 . The method of claim 18 , wherein the filter further comprises:
a second series resonator coupled between the first series resonator and the second port of the filter, the second series resonator comprising a third piezoelectric layer disposed between a fifth electrode and a sixth electrode of the second series resonator; and
a second shunt resonator coupled between a second node of the filter and the reference potential node of the filter, the second shunt resonator comprising a fourth piezoelectric layer disposed between a seventh electrode and an eighth electrode of the second shunt resonator, wherein the second node is coupled between the first port and the second port of the filter and wherein a thickness of the fourth piezoelectric layer is greater than a thickness of the third piezoelectric layer.
27 . The method of claim 26 , wherein the second node is coupled between the first series resonator and the second series resonator.
28 . The method of claim 26 , wherein the second node is connected to the second port of the filter.
29 . The method of claim 26 , wherein the second series resonator has a third coupling coefficient and wherein the second shunt resonator has a fourth coupling coefficient that is greater than the third coupling coefficient.
30 . The method of claim 26 , wherein the thickness of the fourth piezoelectric layer is different from the thickness of the second piezoelectric layer.