Stacked crystal filter device and method of making

Details Stacked crystal filter device and method of making Stacked crystal filter device and method of making

1995-12-26

1998-10-13

Lee, Benny

Wave transmission lines and networks

Coupling networks

Electromechanical filter

310320, H03H 900

Patent

active

058218335

ABSTRACT:
A piezoelectric device includes a stacked crystal filter, a supporting substrate and an acoustic reflector between the filter and substrate for suppressing undesired resonant frequencies. The acoustic reflector includes a set of quarter wavelength layers of alternating higher and lower impedances. The reflector provides a large reflection coefficient for a bandwidth that encompasses only desired frequencies generated by the stacked crystal filter. By changing the nature of the material and the number of layers, the bandwidth and center frequency of the acoustic reflector may be varied to encompass a desired range of frequencies. To reduce the magnitude of side lobes at undesired frequencies, the impedance differences between layers of the reflector are reduced with depth into the reflector. The side lobes may also be reduced by serially connecting two stacked crystal filters having acoustic reflectors of the same material but with a different number of quarter wavelength layers.

REFERENCES:
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patent: 5057801 (1991-10-01), Kittaka et al.
patent: 5084647 (1992-01-01), Inoue et al.
patent: 5373268 (1994-12-01), Dworsky et al.
patent: 5382930 (1995-01-01), Stokes et al.
K.M. Lakin, G.R. Kline, R.S. Ketcham, and J.T. Martin, "Stacked Crystal Filters Implemented With Thin Films," in 43rd Annual Frequency Control Symposium, May 1989, pp. 536-543.
K.M. Lakin, "Equivalent Circuit Modeling of Stacked Crystal Filters," 35th Annual Symposium on Frequency Control Proc., May 1981, pp. 257-262.
A. Ballato and T. Lukaszek, "A Novel Frequency Selective Device: The Stacked Crystal Filter," 27th Annual Frequency Control Symposium Proc., Jun. 1973, pp. 262-269.
K.M. Lakin, "Modeling of Thin Film Resonators and Filters," in Proc. IEEE MTT-S Int. Microwave Symp. Dig., Jun. 1992, pp. 149-152.

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