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Surface acoustic wave filter

A surface acoustic wave and filter technology, applied in the direction of electrical components, impedance networks, etc., can solve the problems of unobtainable, unsatisfactory, attenuation, etc., and achieve the effect of small size

Inactive Publication Date: 2002-07-24
SANYO ELECTRIC CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, in general, regarding the passband characteristics, the sharpness around the cutoff frequency on the high frequency side (such as Figure 3A shown) is unsatisfactory, therefore, it has the problem of not being able to obtain sufficient attenuation
However, this structure introduces a large amount of insertion loss (difference between attenuation when the filter is inserted and when it is not inserted)

Method used

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Embodiment Construction

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings of the embodiments.

[0035] Figure 7It is a structural schematic diagram of the substantial part of the embodiment of the surface acoustic wave filter (SAW filter) of the present invention, and the SAW filter is formed by connecting the vertically connected dual-mode resonator filter 1 and the single-port resonator 2 in series on the piezoelectric substrate 8 above.

[0036] In the longitudinally connected dual-mode resonator filter 1, three intermediate digital transducers 4, 3, 4 (IDTs) for exciting and receiving surface acoustic waves are arranged along the propagation direction of the surface acoustic waves. Two reflectors 5 for reflecting surface acoustic waves are arranged on both sides of the above three middle digital sensors 4, 3, 4 and arranged along the propagation direction of surface acoustic waves.

[0037] In each middle digital sensor 3 or 4, there a...

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Abstract

In the surface acoustic wave filter, a longitudinally-coupled double-mode resonator filter formed by arranging a plurality of inter-digital transducers for exciting and receiving a surface acoustic wave adjacent each other in the direction of propagation of the surface acoustic wave is connected in series to a resonator having one or a plurality of inter-digital transducers for exciting and receiving a surface acoustic wave. A cutoff frequency on the high-frequency side of the pass band of the longitudinally-coupled double-mode resonator filter and the antiresonant frequency of the resonator are substantially equal. In the surface acoustic wave filter, the sharpness in the vicinity of the cutoff frequency on the high-frequency side of the pass band is high, sufficient attenuation can be obtained, and the input and output impedance matching state is good.

Description

technical field [0001] The present invention relates to a surface acoustic wave filter (SAW filter) used as a high frequency device in mobile communication equipment. Background technique [0002] Surface acoustic wave (SAW) is a wave generated by the accumulation of energy near the surface of an elastic body such as a piezoelectric substrate. Electronic devices using surface acoustic waves have been put into use, such as filters, resonators, delay lines, and oscillators. [0003] figure 1 is a longitudinally connected dual-mode resonator filter structure as one of SAW filters, in which longitudinally connected dual-mode resonator filter 1, three intermediate digital sensors 4, 3 for exciting and receiving surface acoustic waves , 4 (IDTs) are arranged on the piezoelectric substrate 10 along the propagation direction of the surface acoustic wave, and two reflectors 5 for reflecting the surface acoustic wave are arranged on the above-mentioned three middle digital sensors 4,...

Claims

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Application Information

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IPC IPC(8): H03H9/145H03H9/64
CPCH03H9/6436H03H9/6473
Inventor 田中直树臼杵辰朗
Owner SANYO ELECTRIC CO LTD
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