Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1984-10-30
1986-07-15
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310313C, H01L 4108
Patent
active
046008527
ABSTRACT:
A surface acoustic wave (SAW) filter consists of two acoustically coupled transducers built on the same piezoelectric film or substrate. The transducers are constructed by depositing a conducting comb structure having interdigitated fingers on the substrate. Spacer elements are placed between gaps of the same polarity within the comb structure. The addition of the spacer elements permit non-zero gap weights of the same sign to follow one another, in contrast to the standard structure which forces these sources to alternate in sign. This added flexibility results in new withdrawal weighted structures that significantly increase the bandwidth over which the rejection band performance is good and also reduces passband ripple. The increase in the accuracy of the withdrawal weighting permissible with these new structures improves filter performance.
REFERENCES:
patent: 3748603 (1973-07-01), Wojcik
patent: 4200849 (1980-04-01), Malocha
patent: 4516093 (1985-05-01), Nyffeler
"Synthesis of High Performance SAW Filters with Nonuniformly Spaced Fingers" by E. M. Garber et al., Proceedings of the Ultrasonics Symposium, pp. 27-32 (1983).
"Impulse Model Design of Acoustic Surface-Wave Filters" by C. S. Hartmann et al., IEEE Transactions on Sonics and Ultrasonics, V.SU-20, No. 2, pp. 80-93 (1973).
"Universal Method for Compensation of SAW Diffraction and Other Second Order Effects" by W. R. Mader et al., IEEE Ultrasonics Symposium, pp. 23-28 (1982).
"Transverse Electrostatic End Effects in Interdigital Transducers" R. S. Wagers, IEEE Cat. #76 Ultrasonics Symposium, pp. 536-539 (1976).
"Weighting Interdigital Surface Wave Transducers by Selective Withdrawal of Electrodes" by C. S. Hartmann, IEEE Cat. #73 Ultrasonics Symposium, pp. 423-426, (1973).
Budd Mark O.
Massachusetts Institute of Technology
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