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US4733207A Expired / Lapsed US ⏱️ 0.0 years remaining

Surface acoustic wave filters

Assignee: The General Electric Company PLC
•
Filing: 1987-06-12
•
Granted: 1988-03-22
•
Expires: 2007-06-12
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Abstract

Abstract A surface acoustic wave filter comprising; a first bidirectional ID transducer (5) of symmetrical form; a second ID transducer (1) acoustically coupled with the first transducer and comprising two parts (1A, 1B) each of which parts is in the form of one half of a respective bidirectional ID transducer (9 or 11) of symmetrical form, the two parts being positioned with respect to one another and the first transducer so that when respectively excited by corresponding signals of different phases they co-operate to produce a unidirectional acoustic signal propagating towards the first transducer from one side thereof; and a third transducer (3) acoustically coupled with the first transducer and comprising two parts (3A, 3B ), each of which parts is electrically connected in parallel with a respective one of the two parts of said second transducer, and each of which parts of the third transducer is effectively in the form of the mirror image about the center line (7) of the first transducer of the other half of the bidirectional transducer whose one half constitutes the part of the second transducer with which it is connected. The invention provides a filter of intrinsically low insertion loss without the use of a cross-over structure as it required in known forms of low loss filter using undirectional multiphase ID transducers.

Inventors

  • 👤 Robert C. Peach

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-07 14:50
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/02; H03H9/125; H03H9/145; H03H9/14502; H03H9/14505

Claims Analysis

Total Claims: 10
Claim 1
Independent Claim 165 words
A SAW filter comprising: a first bidirectional ID transducer of symmetrical form; a second ID transducer comprising two parts each of which parts is in the form of one half of a respective bidirectional ID transducer of symmetrical form, the two parts being positioned with respect to one another and the first transducer so that when respectively excited by corresponding signals of different phases they co-operate to produce a unidirectional acoustic signal propagating towards the first transducer from one side thereof; and a third transducer acoustically coupled with the first transducer and comprising two parts, each of which parts is electrically connected in parallel with a respective one of the two parts of said second transducer, and each of which parts of the third transducer is effectively in the form of the mirror image about the centre line of the first transducer of the other half of the bidirectional transducer whose one half constitutes the part of the second transducer with which it is connected.
Claim 2
Dependent Claim 165 words
A SAW filter comprising: a first bidirectional ID transducer of symmetrical form; a second ID transducer comprising two parts each of which parts is in the form of one half of a respective bidirectional ID transducer of symmetrical form, the two parts being positioned with respect to one another and the first transducer so that when respectively excited by corresponding signals of different phases they co-operate to produce a unidirectional acoustic signal propagating towards the first transducer from one side thereof; and a third transducer acoustically coupled with the first transducer and comprising two parts, each of which parts is electrically connected in parallel with a respective one of the two parts of said second transducer, and each of which parts of the third transducer is effectively in the form of the mirror image about the centre line of the first transducer of the other half of the bidirectional transducer whose one half constitutes the part of the second transducer with which it is connected.
Claim 3
Dependent Claim 39 words
A filter according to claim 1 wherein said two parts of said second transducer are spaced apart by an amount such that they co-operate to produce said unidirectional acoustic signal when respectively excited by signals in quadrature phase relationship.
Claim 4
Dependent Claim 15 words
A filter according to claim 1 wherein said transducers are of the split finger type.
Claim 5
Dependent Claim 15 words
A filter according to claim 3 wherein said transducers have four fingers per acoustic wavelength.
Claim 6
Dependent Claim 32 words
A filter according to claim 4 wherein said transducers each comprise a plurality of units each comprising a pair of driven fingers between two fingers maintained at a fixed potential in operation.
Claim 7
Dependent Claim 34 words
A filter according to claim 4 wherein said transducers each comprise a plurality of units each comprising a pair of driven fingers alongside a pair of fingers maintained at a fixed potential in operation.
Claim 8
Dependent Claim 50 words
A filter according to claim 1 further including a tuning network comprising: an impedance matching first sub network connected with said first transducer; an impedance matching second sub network connected with said second and third transducers and a phase shifting third sub network connected with said second and third transducers.
Claim 9
Dependent Claim 15 words
A filter according to claim 7 wherein each said sub network includes only one inductor.
Claim 10
Dependent Claim 16 words
A filter according to claim 8 wherein each said sub network further includes only one capacitor.

References Cited (Backward Citations)

US4575696A Cited
US3727155A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1991-03-22 1991-09-21 1992-03-22 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1995-03-22 1995-09-21 1996-03-22 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1999-03-22 1999-09-21 2000-03-22 $7700.00 Window Closed / Lapsed

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