Elastic wave filter
An elastic wave filter and filter technology, applied in electrical components, impedance networks, etc., can solve the problems of increasing the number of stages, increasing the number of inductors, miniaturization and low price of π-shaped ladder filters, etc. Filter characteristics, the effect of realizing miniaturization
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no. 1 approach
[0043] In this embodiment, an elastic wave filter is described as a notch filter in which the terrestrial digital broadcasting reception band (470 to 770 MHz) is used as the pass band and the RF transmission band (near 800 MHz and 900 MHz) is used as the pass band. near) as the blocking band.
[0044] figure 1 It is a schematic diagram of the elastic wave filter of the first embodiment. Such as figure 1 As shown, the elastic wave filter 1 includes a plurality of series arm resonators S1 and S2 connected in series to each other in the series arm 12 connecting the input terminal 10 and the output terminal 11 . Specifically, in the present embodiment, a first series arm resonator S1 and a second series arm resonator S2 are provided in the series arm 12 . In this embodiment, the antiresonance frequency of the first series arm resonator S1 is set to be equal to or lower than the resonance frequency of the second series arm resonator S2.
[0045] Furthermore, an inductor 13 a ...
no. 2 approach
[0093] Figure 10 It is a schematic diagram of an elastic wave filter 2 according to the second embodiment. Such as Figure 10 As shown, the elastic wave filter 2 of the present embodiment further has a π-shaped ladder filter unit connected to the subsequent stage of the elastic wave filter of the first embodiment. Specifically, elastic wave filter 2 includes first to third series arm resonators S1 to S3 connected in series to each other in series arm 12 . Between the connection point 14 between the first series arm resonator S1 and the input terminal 10 and the connection point 15 between the second series arm resonator S2 and the third series arm resonator S3, an inductor 13a is connected. Furthermore, an inductor 13 b is connected between the connection point 15 and the connection point 18 between the third series arm resonator S2 and the output terminal 11 . The connection points 14, 17, 15, and 18 are connected to the ground potential through the first to fourth parall...
no. 3 approach
[0133] Figure 13 It is a schematic diagram of the elastic wave filter 4 of the third embodiment. Such as Figure 13 As shown, the elastic wave filter 4 of the present embodiment is obtained by connecting the elastic wave filter 1 of the above-mentioned first embodiment in two stages. Specifically, in elastic wave filter 4 , first to fourth series arm resonators S1 to S4 connected in series to each other are arranged in series arm 12 . Between the connection point 14 between the first series arm resonator S1 and the input terminal 10 and the connection point 15 between the second series arm resonator S2 and the third series arm resonator S3, an inductor 13a is connected. Furthermore, an inductor 13 c is connected between the connection point 15 and the connection point 8 between the fourth series arm resonator S4 and the output terminal 11 . Between the aforementioned connection points 14, 15, 8 and ground potential, between the connection point 17 between the first series ...
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