Acoustic wave filter
A technology of acoustic wave filters and resonators, applied in electrical components, impedance networks, etc., can solve problems such as increased resonant frequency variability, increased film thickness dependence, and difficulty in obtaining wide bandwidth filters
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no. 1 approach
[0046] Figure 7 A to C among them are schematic diagrams illustrating the structure of the piezoelectric thin film resonator in the acoustic wave filter according to the first embodiment, and are respectively compared with those of the comparative example. Figure 2A to Figure 2C Corresponding. The structure of the piezoelectric thin film resonator according to the first embodiment is substantially the same as that in the comparative example, except that a frequency control channel is formed in the resonance region 40 between the upper electrode 18 and the frequency adjustment film 20 . The mass-loading membrane (hereinafter referred to as the second mass-loading membrane 24 ). The second mass load film 24 is used to make the resonance frequencies of the respective resonators constituting the acoustic wave filter have different values (as described below). In the acoustic wave filters (filters A, B, and G) according to the comparative example, the second mass load film 24...
no. 2 approach
[0059] The second embodiment is an embodiment in which the structure of the ladder-type filter is changed.
[0060] Figure 11 is a circuit diagram illustrating the configuration of the acoustic wave filter (filter D) according to the second embodiment. The circuit configuration of the acoustic wave filter according to the second embodiment is the same as that of the acoustic wave filter according to the first embodiment ( figure 1 ), except for the inductors L1 and L2, an inductor L3 with one end grounded is connected between the input terminal In and the series resonator S4. The structure of the piezoelectric thin film resonator constituting the ladder filter is the same as that of the first embodiment ( Figure 7 and 16 f03788-b70c-4a96-9767-2538e897fa32). The resonant frequency of the resonator is at Figure 5 The Filter D column is shown.
[0061] Figure 12A to Figure 12C is a graph illustrating a comparison of band pass characteristics between the acoustic wave f...
no. 3 approach
[0066] The third embodiment is an embodiment using a piezoelectric thin film resonator with improved piezoelectricity of the piezoelectric film.
[0067] The circuit configuration of the acoustic wave filter (filters E, F) according to the third embodiment is the same as that of the acoustic wave filter ( Figure 11 ) The circuit configuration is the same, and the structure of the piezoelectric thin film resonator constituting the ladder filter is the same as that of the first and second embodiments ( Figure 7 , Figure 8A to Figure 8C ) of the same. The difference from the first and second embodiments is that, to the piezoelectric films (the first piezoelectric film 14 a and the second piezoelectric film 14 b ) of the piezoelectric thin film resonator is added to increase the piezoelectric constant ( e33 ). element. For example, alkaline earth metals (scandium (Sc) and the like), rare earth metals (erbium (Er) and the like) can be used as elements for increasing the piezo...
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