Claims
- 1. A transducer comprising:base cells each having a length λ, where λ is a wavelength corresponding to a center frequency of the transducer, the base cells being arranged in a direction of propagation of a surface acoustic wave, the base cells including exciting base cells, the base cells including an excitation portion and a reflection portion, the excitation portion being non-zero for exciting base cells, the reflection portion of each base cell having a strength mR0, where m is one of −2, −1, 0, 1, or 2 and R0 is a reference reflection; wherein the base cells include electrode fingers, a width of the electrode fingers is not a multiple of λ/16, and a separation between adjacent electrode fingers is not a multiple of λ/8; wherein, in the direction of propagation, a non-zero reflection portion in each base cell has a same phase position φ±πn, where n is an integer greater than zero; wherein centers of excitations of base cells having a same sign are separated by 2πn and centers of excitations of base cells having different signs are separated by (2n−1)π, and wherein surface acoustic waves excited and reflected in at least one base cell are equal in phase in the direction of propagation and opposite in phase in a direction that is opposite to the direction of propagation.
- 2. The transducer according to claim 1 wherein in at least one base cell, one electrode finger is connected to a first bus bar and all other electrode fingers are connected to a second bus bar, the one electrode finger having a width that is not λ/8, the one electrode finger having a separation from an adjacent electrode finger that is not λ/4 or 3λ/8.
- 3. The transducer according to claim 1 wherein groups of two electrode fingers are connected to a common bus bar, one group each per exciting base cell, and wherein electrode fingers in a group of two electrode fingers each have a different finger width that is not λ/16 or 3λ/16 and a finger center separation that is not λ4.
- 4. The transducer according to claim 2 wherein, in the exciting base cells, a separation between excitation centers and reflection centers is 3λ/8.
- 5. A transducer according to claim 1 wherein electrode finger widths and separations increase in transverse direction.
- 6. A transducer according to claim 1 wherein the electrode fingers have bent edges.
- 7. A transducer according to claim 1 wherein electrode finger widths and separations are different in each base cell.
- 8. An IF filter with low insertion loss and long impulse response, which includes the transducer of claim 1.
- 9. The transducer of claim 1 wherein excitations of all exciting base cells have a substantially identical strength.
- 10. The transducer of claim 1 wherein a number of electrode fingers connected to first and second bus bars is identical for all base cells having a non-zero excitation portion.
Priority Claims (1)
Number |
Date |
Country |
Kind |
100 10 089 |
Mar 2000 |
DE |
|
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to PCT Application No. PCT/DE01/00630, filed on Feb. 19, 2001, and to German Patent Application No. 100 10 089.9, filed on Mar. 2, 2000.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/DE01/00630 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/65688 |
9/7/2001 |
WO |
A |
US Referenced Citations (9)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0255263 |
Jul 1986 |
EP |
0 255 263 |
Jul 1987 |
EP |
Non-Patent Literature Citations (2)
Entry |
Morgan D P et al: “ Low loss filters using group-type spudt transducers” Proceedings of the ultrasonics symposium, US, New York, IEEE, Bd.-Apr. 12, 1990, Seiten 31-35, XP000290030 Seite 31, rechte Spalte. |
Ventura P et al:“A new concept in spudt design: The rspudt (resonant spudt)”, Proceedings of the ultrasonics symposium, US, New York, IEEE Jan. 11, 1994, Seiten 1-6 XP00590526 ISBN: 0-7803-2013-1, Seite 1, rechts Spalte. |