Filter including bulk acoustic wave resonator

1. A filter comprising:

series units, each series unit comprising at least one bulk acoustic wave resonator; and

shunt units, each shunt unit comprising at least one bulk acoustic wave resonator, each of the shunt units being disposed between one of the series units and a ground,

wherein one of the series units or one of the shunt units comprises a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, and a third bulk acoustic wave resonator connected in series,

the second bulk acoustic wave resonator has a polarity different from a polarity of the first bulk acoustic wave resonator and a polarity of the third bulk acoustic wave resonator, and

wherein second harmonic distortion occurring in the first bulk acoustic wave resonator is delayed by an angle Ø when passing through the second bulk acoustic wave resonator and the third bulk acoustic wave resonator, and 0<Ø≤90 or 270<Ø≤360.

2. The filter of claim 1 , wherein the first bulk acoustic resonator, the second bulk acoustic wave resonator, and the third bulk acoustic wave resonator are disposed on a single branch of a circuit constituting the filter.

3. The filter of claim 1 , wherein the second bulk acoustic wave resonator has a length different from a length of the first bulk acoustic wave resonator and a length of the third bulk acoustic wave resonator.

4. The filter of claim 3 , wherein the length of the first bulk acoustic wave resonator is the same as the length of the third bulk acoustic wave resonator.

5. The filter of claim 3 , wherein a ratio of the length of the second bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.5 to 1.

6. The filter of claim 5 , wherein the ratio of the length of the second bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.7 to 0.9.

7. The filter of claim 3 , wherein a ratio of the length of the third bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.5 to 1.

8. The filter of claim 7 , wherein the ratio of the length of the third bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.8 to 1.

9. A bulk acoustic resonator set, comprising:

a first bulk acoustic wave resonator having a first length;

a second bulk acoustic wave resonator having a second length less than the first length; and

a third bulk acoustic wave resonator having a third length greater than the second length and less than or equal to the first length,

wherein the first, second, and third bulk acoustic wave resonators are connected in series between an input terminal and an output terminal, and only two of the first, second, and third bulk acoustic wave resonators have a same polarity.

10. A filer comprising:

series units, each series unit comprising at least one bulk acoustic wave resonator; and

shunt units, each shunt unit comprising at least one bulk acoustic wave resonator, each of the shunt units being disposed between one of the series units and a ground,

wherein one of the series units or one of the shunt units comprises a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, and a third bulk acoustic wave resonator connected in series, and

second harmonic distortion occurring in the first bulk acoustic wave resonator is delayed by an angle Ø when passing through the second bulk acoustic wave resonator and the third bulk acoustic wave resonator, and the angle Ø satisfies 90<Ø≤270.

11. The filter of claim 10 , wherein the second bulk acoustic wave resonator has a length different from a length of the first bulk acoustic wave resonator and a length of the third bulk acoustic wave resonator.

12. The filter of claim 11 , wherein the length of the first bulk acoustic wave resonator is the same as the length of the third bulk acoustic wave resonator.

13. The filter of claim 10 , wherein a ratio of a length of the second bulk acoustic wave resonator to a length of the first bulk acoustic wave resonator is in a range of 0.5 to 1.

14. The filter of claim 13 , wherein the ratio of the length of the second bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.7 to 0.9.

15. The filter of claim 10 , wherein a ratio of a length of the third bulk acoustic wave resonator to a length of the first bulk acoustic wave resonator is in a range of 0.5 to 1.

16. The filter of claim 15 , wherein the ratio of the length of the third bulk acoustic wave resonator to the length of the first bulk acoustic wave resonator is in a range of 0.8 to 1.

17. A bulk acoustic resonator set, comprising:

an input terminal;

an output terminal; and

a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, and a third bulk acoustic wave resonator disposed between the input terminal and the output terminal,

wherein the first bulk acoustic wave resonator has a first polarity, the second bulk acoustic wave resonator has a second polarity that is opposite to the first polarity, and the third bulk acoustic wave resonator has a third polarity that is identical to either the first polarity or the second polarity, and

wherein the first bulk acoustic wave resonator has a first length, the second bulk acoustic wave resonator has a second length less than the first length, and the third bulk acoustic wave resonator has a third length less than or equal to the first length.

18. The bulk acoustic resonator set of claim 17 , wherein the first bulk acoustic wave resonator, the second bulk acoustic wave resonator, and the third bulk acoustic wave resonator are connected in series.

19. The bulk acoustic resonator set of claim 17 , wherein the third length is greater than the second length.