US4602228A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surface acoustic wave filter
Assignee: Hitachi Ltd
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Filing: 1984-11-16
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Granted: 1986-07-22
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Expires: 2004-11-16
Abstract
Abstract A surface acoustic wave filter comprising unidirectional interdigital input and output transducers at least one of which has imperfect unidirectivity and includes two interdigital electrodes arranged to provide a geometrical phase difference φ M therebetween and interconnected through a phase shifter which provides an electrical phase difference φ E therebetween, the sum of the phase differences φ M and φ E being unequal to π radians to provide the imperfectness of unidirectivity. The selection range of conductance of an external load or radiation conductance of the unidirectional transducer necessary for suppressing the undesired triple transit echo level can thus be extended while keeping the insertion loss relatively low.
Inventors
- 👤 Jun Yamada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 01:54
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/02; H03H9/02535; H03H9/02818; H03H9/02842; H03H9/0285; H03H9/125; H03H9/145; H03H9/14502; H03H9/14505
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
183 words
A surface acoustic wave filter comprising: a substance for propagating surface acoustic waves; at least one interdigital input transducer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigital sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians when said acoustic surface wave travels a predetermined distance between respective centers of said sending and reflection electrode parts and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, the sum (φ M +φ E ) of said phase differences being a value within a range from 0 to 2π radians other than a value of π radians.
Claim 2
Dependent Claim
183 words
A surface acoustic wave filter comprising: a substance for propagating surface acoustic waves; at least one interdigital input transducer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigital sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians when said acoustic surface wave travels a predetermined distance between respective centers of said sending and reflection electrode parts and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, the sum (φ M +φ E ) of said phase differences being a value within a range from 0 to 2π radians other than a value of π radians.
Claim 3
Dependent Claim
57 words
A surface acoustic wave filter according to claim 1 wherein when degree a defined by ##EQU13## falls within a range 0<a≦9/11, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU14##
Claim 4
Dependent Claim
57 words
A surface acoustic wave filter according to claim 1 wherein when degree a defined by ##EQU15## falls within a range 9/11≦a≦1, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU16##
Claim 5
Dependent Claim
184 words
A surface acoustic wave filter comprising: a substrate for propagating surface acoustic waves; at least one interdigital input transudcer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigial sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians therebetween and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, wherein when degree a defined by ##EQU17## falls within a range 0<a≦9/11, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU18##
Claim 6
Dependent Claim
184 words
A surface acoustic wave filter comprising: a substrate for propagating surface acoustic waves; at least one interdigital input transudcer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigial sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians therebetween and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, wherein when degree a defined by ##EQU17## falls within a range 0<a≦9/11, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU18##
Claim 7
Dependent Claim
184 words
A surface acoustic wave filter comprising: a substrate for propagating surface acoustic waves; at least one interdigital input transducer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigital sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians therebetween and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, wherein when degree a defined by ##EQU19## falls within a range 9/11≦a≦1, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU20##
Claim 8
Dependent Claim
184 words
A surface acoustic wave filter comprising: a substrate for propagating surface acoustic waves; at least one interdigital input transducer, formed on said substrate, which is adapted for connection to a signal source and for conversion of an electrical signal from said signal source into a surface acoustic wave; at least one interdigital output transducer, formed on said substrate, which is adapted for connection to a load and for conversion of said acoustic surface wave into said electric signal; and at least one of said interdigital input and output transducers including an interdigital sending electrode part and an interdigital reflection electrode part, said interdigital sending and reflection electrode parts being arranged to provide a geometrical phase difference φ M radians therebetween and interconnected through phase shifter means which provides an electrical phase difference φ E radians therebetween, wherein when degree a defined by ##EQU19## falls within a range 9/11≦a≦1, the ratio of at least one of conductances G l of said signal source or load to a radiation conductance G a of said interdigital transducer is so set as to satisfy the following condition: ##EQU20##
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-07-21 | 1990-01-20 | 1990-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-07-21 | 1994-01-20 | 1994-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-07-21 | 1998-01-20 | 1998-07-22 | $7700.00 | Window Closed / Lapsed |