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Ladder-type acoustic wave filter

An elastic wave filter and filter technology, applied in impedance networks, electrical components, etc., can solve the problems of insufficient reduction of passband loss and deterioration of frequency band loss, so as to reduce loss, reduce loss, and realize broadband the effect of

Active Publication Date: 2012-01-25
MURATA MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] However, when the resonance frequencies of the plurality of series arm resonators are different, the loss in the passband cannot be sufficiently reduced.
In particular, there is a problem that the loss in the frequency band on the high frequency side within the passband becomes worse

Method used

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Examples

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Embodiment Construction

[0029] Hereinafter, in order to clearly understand the present invention, specific embodiments of the present invention will be described with reference to the drawings.

[0030] figure 1 It is a diagram showing a circuit configuration of a ladder-type elastic wave filter according to an embodiment of the present invention.

[0031] Ladder elastic wave filter 1 has a series arm connecting input terminal 2 and output terminal 3 . In this series arm, a plurality of series arm resonators S1 to S4 are connected in series with each other. Here, from the input terminal 2 side to the output terminal 3 side, these series arm resonators S1- S4.

[0032] In addition, a first parallel arm is formed to connect the connection point between the output terminal 3 and the first series arm resonator S1 to the ground potential, and the first parallel arm has the first parallel arm resonator P1.

[0033] Similarly, the second parallel arm connecting the connection point between the resonator...

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Abstract

Provided is a ladder-type acoustic wave filter which can not only widen the bandwidth and increase attenuation but also sufficiently reduce loss in the passing band. A ladder-type acoustic wave filter (1) is equipped with a series arm connecting the input end and the output end, and a parallel arm connecting the series arm and the ground potential, wherein at least three series arm resonators (S1-S3) are connected in series with each other in the series arm, the at least three series arm resonators (S1-S3) have different resonance frequencies, and when the ratio of the cross width of an electrode finger to the logarithm of electrode finger in each series arm resonator is assumed as the aspect ratio, the aspect ratio (T1) of a series arm resonator (S1) having a lowest resonance frequency is set larger than the average (T0) of aspect ratios of all series arm resonators (S1-S3).

Description

technical field [0001] The present invention relates to an elastic wave filter used in a bandpass filter of a mobile phone, and more specifically, to an elastic wave filter having a ladder circuit structure. Background technique [0002] Conventionally, surface acoustic wave filters have been widely used as bandpass filters in the RF band of mobile phones. For example, Patent Document 1 below discloses a ladder-type surface acoustic wave filter as an example of such a bandpass filter. In the SAW ladder filter, the resonant frequency fr of the series arm resonator S and the antiresonant frequency fa of the parallel arm resonator P Set near the center frequency of the passband. On the other hand, let the antiresonant frequency fa of the series arm resonator be S An attenuation pole located near the high frequency side of the passband; make the resonant frequency fr of the parallel arm resonator P An attenuation pole located near the low frequency side of the passband. Th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H9/64H03H9/145H03H9/72
CPCH03H9/0222H03H9/1452H03H9/725H03H9/6483
Inventor 藤田茂幸
Owner MURATA MFG CO LTD
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