US5717367A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surface acoustic wave (SAW) filter with improved spacing between input and output interdigital transducers
Assignee: Mitsubishi Electric Corp
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Filing: 1996-02-02
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Granted: 1998-02-10
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Expires: 2016-02-02
Abstract
Abstract A SAW filter is disclosed which includes two reflectors and a group of interdigital transducers (IDTs) located therebetween on a piezoelectric substrate, wherein the IDTs comprises at least four input IDTs and output IDTs alternatively aligned on the substrate in a SAW propagation direction to increase an transducer efficiency between an electronic signal and SAWs. Further, a distance between the center lines of the end electrode fingers of the adjacent input and output IDTs are set to be in a range from 0.625 λ to 1.25 λ (λ: wave length of SAW) to establish input and output impedances of the SAW filter.
Inventors
- 👤 Koji Murai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 08:26
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6423; H03H9/6433; H03H9/6436; H03H9/25; H03H9/6489; H03H9/6493
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
103 words
A surface acoustic wave (SAW) filter comprising: a piezoelectric substrate; at least four input and output interdigital transducers (IDTs) alternately aligned on said substrate in a SAW propagation direction and being respectively connected to input and output terminals of said SAW filter; and two reflectors positioned at the opposite sides of said IDTs on said substrate, wherein a distance between center lines of electrode fingers at the inner ends of the adjacent input and output IDTs is set to be within a range from 0.625 λ to 1.25 λ, where λ denotes a wave length of a resonant frequency of said SAW filter.
Claim 2
Dependent Claim
103 words
A surface acoustic wave (SAW) filter comprising: a piezoelectric substrate; at least four input and output interdigital transducers (IDTs) alternately aligned on said substrate in a SAW propagation direction and being respectively connected to input and output terminals of said SAW filter; and two reflectors positioned at the opposite sides of said IDTs on said substrate, wherein a distance between center lines of electrode fingers at the inner ends of the adjacent input and output IDTs is set to be within a range from 0.625 λ to 1.25 λ, where λ denotes a wave length of a resonant frequency of said SAW filter.
Claim 3
Dependent Claim
26 words
A SAW filter according to claim 1, wherein the number of said input and output IDTs is an odd number equal to or more than five.
Claim 4
Dependent Claim
36 words
A SAW filter according to claim 1, further comprising at least a resonator having a pair of terminals respectively connected to said input or output terminal of said SAW filter and said input or output IDTs.
Claim 5
Dependent Claim
44 words
A SAW filter according to claim 3, an anti-resonant frequency of said resonator is set to substantially the same as a frequency of a primary upper sidelobe of a main filter part comprising said IDTs and reflectors, whereby the primary upper sidelobe is suppressed.
Claim 6
Dependent Claim
30 words
A SAW filter according to claim 3, wherein said resonator is situated on said substrate and consists of an IDT and two reflectors at the opposite sides of the IDT.
Claim 7
Dependent Claim
32 words
A SAW filter according to claim 1, further comprising at least a resonator having a pair of terminals respectively connected to said input or output terminal of said SAW filter and ground.
Claim 8
Dependent Claim
45 words
A SAW filter according to claim 6, a resonant frequency of said resonator is set to be substantially the same as a frequency of a primary lower sidelobe of a main filter part comprising said IDTs and reflectors, whereby the primary lower sidelobe is suppressed.
Claim 9
Dependent Claim
29 words
A SAW filter according to claim 6, wherein said resonator is situated on said substrate and consists of an IDT and two reflectors at the opposite of the IDT.
Claim 10
Dependent Claim
52 words
A SAW filter according to claim 1, further comprising: a first resonator having a pair of terminals respectively connected to said input terminal of said SAW filter and said input IDTs; and a second resonator having a pair of terminals respectively connected to said output terminal of said SAW filter and ground.
Claim 11
Dependent Claim
77 words
A SAW filter according to claim 9, wherein an anti-resonant frequency of said first resonator is set to be substantially the same as a frequency of a primary upper sidelobe of a main filter part comprising said IDTs and reflectors, and a resonant frequency of said second resonator is set to be substantially the same as a frequency of a primary lower sidelobe of said main filter part, whereby the primary upper and lower sidelobes are suppressed.
Claim 12
Dependent Claim
35 words
A SAW filter according to claim 10, wherein each of said first and second resonators is constituted on said substrate and consists of an IDT and two reflectors at the opposite sides of the IDT.
Claim 13
Dependent Claim
52 words
A SAW filter according to claim 1, further comprising: a first resonator having a pair of terminals respectively connected to said output terminal of said SAW filter and said output IDTs; and a second resonator having a pair of terminals respectively connected to said input terminal of said SAW filter and ground.
Claim 14
Dependent Claim
75 words
A SAW filter according to claim 12, wherein an anti-resonant frequency of said first resonator is set to substantially the same as a frequency of a primary upper sidelobe of a main filter part comprising said IDTs and reflectors, and a resonant frequency of said second resonator is set to substantially the same as a frequency of a primary lower sidelobe of said main filter part, whereby the primary upper and lower sidelobes are suppressed.
Claim 15
Dependent Claim
35 words
A SAW filter according to claim 12, wherein each of said first and second resonators is situated on said substrate and consists of an IDT and two reflectors at the opposite sides of the IDT.
Claim 16
Dependent Claim
25 words
A SAW filter according to claim 1, wherein said substrate is made by LiTaO 3 having 36° Y cut and X axis SAW propagation characteristic.
References Cited (Backward Citations)
US4166258A
Cited
US4159435A
Cited
US5087901A
Cited
US5179310A
Cited
US5300902A
Cited
JPH05267990A
Cited
US5309126A
Cited
US5463361A
Cited
US5485052A
Cited
US5392013A
Cited
US5396199A
Cited
EP0600705A1
Cited
US5521453A
Cited
JPH0738369A
Cited
US5426339A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-02-09 | 2001-08-11 | 2002-02-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-02-09 | 2005-08-11 | 2006-02-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-02-09 | 2009-08-11 | 2010-02-10 | $7700.00 | Window Closed / Lapsed |