EP0118272A2
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EP
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Mechanically coupled electrical filter
Assignee: Fujitsu Ltd
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Filing: 1984-02-27
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Granted: —
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Expires: 2004-02-27
Abstract
Abstract A mechanically coupled electrical filter comprises two longitudinal mode vibrators 20a, 20b mechanically coupled together by a coupler 52. Each of the vibrators 20a, 20b is set up with a piezoelectric ceramic member 11a, 11b and constant modulus alloy members 21a, 21a', 21b, 21b' mounted separately on its top and bottom surfaces. The two constant modulus alloy members 21a, 21a'; 21b, 2Tb' on each ceramic member 11 a, 11 b have the same configuration, a frequency-temperature characteristic opposite to that of the piezoelectric ceramic member 11 a, 11 b, and have their centres aligned with the centre of the piezoelectric ceramic member 11 a; 11b. Such configurations of the two longitud- nal mode vibrators 20a, 20b suppress higher order harmonic and spurious vibrations and so filter out these components. In use an electrical signal is applied across the alloy members 21a, 21a' of the input side vibrator 20a and results in its resonating at its fundamental frequency. This vibration is then mechanically coupled to the output side vibrator 20b with the result that it then resonates at substantially only its fundamental frequency. The mechanical vibration of the output side vibrator 20b generates an output electrical signal across its alloy members 21b, 21b' which is substantially only at the fundamental frequency.
Inventors
- 👤 Takashi Gounji
- 👤 Teruo Kawatsu
- 👤 Yoshihiko Kasai
- 👤 Chikao Takeuchi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 17:30
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/54; H03H9/56; H03H9/562
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
195 words
A mechanically coupled electrical filter comprising: an input side piezoelectric ceramic member (20a) and an output side piezoelectric ceramic member (20b); constant modulus alloy members (21a, 21a', 21b, 21b') separately mounted on top and bottom surfaces of each of the piezoelectric ceramic members (lla, IIb); and, at least one coupler (52) mechanically coupling the input and output side piezoelectric ceramic members (20a, 20b) and connected to the constant modulus alloy members (21a and 21b or 21a' and 21b') on the top or bottom surfaces of the ceramic members (20a, 20b); each of the piezoelectric ceramic members (lla and llb) being polarized in a direction along its thickness and being arranged to vibrate in a longitudinal mode, each having top and bottom constant modulus alloy members (21a, 21a' or 21b, 21b') with a similar configuration, each having the frequency-temperature characteristic of its constant modulus alloy members (21a, 21a' or 21b, 21b') opposite to that of its piezoelectric ceramic member (lla or llb), and each being centrally symmetric so that the top and bottom constant modulus alloy members (21a, 21a'; 21b, 21b') and their corresponding piezoelectric ceramic member (lla, lIb) have their centres aligned with one another.
Claim 2
Dependent Claim
195 words
A mechanically coupled electrical filter comprising: an input side piezoelectric ceramic member (20a) and an output side piezoelectric ceramic member (20b); constant modulus alloy members (21a, 21a', 21b, 21b') separately mounted on top and bottom surfaces of each of the piezoelectric ceramic members (lla, IIb); and, at least one coupler (52) mechanically coupling the input and output side piezoelectric ceramic members (20a, 20b) and connected to the constant modulus alloy members (21a and 21b or 21a' and 21b') on the top or bottom surfaces of the ceramic members (20a, 20b); each of the piezoelectric ceramic members (lla and llb) being polarized in a direction along its thickness and being arranged to vibrate in a longitudinal mode, each having top and bottom constant modulus alloy members (21a, 21a' or 21b, 21b') with a similar configuration, each having the frequency-temperature characteristic of its constant modulus alloy members (21a, 21a' or 21b, 21b') opposite to that of its piezoelectric ceramic member (lla or llb), and each being centrally symmetric so that the top and bottom constant modulus alloy members (21a, 21a'; 21b, 21b') and their corresponding piezoelectric ceramic member (lla, lIb) have their centres aligned with one another.
Claim 3
Dependent Claim
45 words
A mechanically coupled filter according to claim 1, wherein the top and bottom surfaces of each of the piezoelectric ceramic members (lla, lIb) are covered by metal films (12a, 12a', 12b, 12b') to which the constant modulus alloy members (21a, 21a', 21b, 21b') are attached.
Claim 4
Dependent Claim
28 words
A mechanically coupled filter according to claim 2, wherein each constant modulus alloy member (21a, 21a', 21b, 21b') is shorter than its corresponding piezoelectric ceramic member (lla, llb).
Claim 5
Dependent Claim
83 words
A mechanically coupled filter according to claim 2 or 3, wherein the length Lp (Figure 7) of at least one of the piezoelectric ceramic members (20a, 20b) and the length L of both of its top and bottom constant modulus alloy members (21a, 21a', 21b, 21b') satisfy the relationship L M ≒ 2Lp and the metal films (12a, 12a', 12b, 12b') are removed from adjacent the ends of the members (21a, 21a', 21b, 21b'), to suppress the generation of a third order harmonic.
Claim 6
Dependent Claim
26 words
A mechanically coupled filter according to claim 4, wherein said at least one piezoelectric ceramic member (20a, 20b) is the output side piezoelectric ceramic member (20b).
Claim 7
Dependent Claim
33 words
A mechanically coupled filter according to claim 4 or 5, wherein all of the metal films (12a, 12a', 12b, 12b') located outside the constant modulus alloy members (21a, 21a', 21b, 21b') are removed.
Claim 8
Dependent Claim
74 words
A mechanically coupled filter according to any one of the preceding claims, which also includes a support wire (51) which is connected to either the top or bottom constant modulus alloy members at their respective centres, so that it is connected to the respective nodal points of the input and output piezoelectric ceramic members (20a, 20b), the coupler (52) being coupled between the ceramic members (20a, 20b) at points other than the nodal points.
Claim 9
Dependent Claim
59 words
A mechanically coupled filter according to any one of the preceding claims, wherein the constant modulus alloy members (21a, 21a', 21b, 21b') have the form of strips and the ratio between the thickness tp of the piezoelectric ceramic member (lla, llb) and the thickness t M of each of the strips (21a, 21a', 21b, 21b') is about 0.05, i.e.,
Claim 10
Dependent Claim
59 words
A mechanically coupled filter according to any one of claims 1 to 7, wherein the constant modulus alloy members (21a, 21a', 21b, 21b') have the form of plates (121a, 121a', 121b, 121b') and the thickness t P of the piezoelectric ceramic member (lla, llb) is about twice the thickness t M of the metal plates (121a, 121a', 121b, 121b').
Claim 11
Dependent Claim
67 words
A mechanically coupled filter according to claim 9, wherein the lengths Lp of the two piezoelectric ceramic members (lla, llb) are substantially the same as each other, and the length L Ma of the metal plates (121a, 121a') on the input side is different from the length L Mb of the metal plates (121b, 121b') on the output side, so that higher order harmonic vibrations are suppressed.
Claim 12
Dependent Claim
57 words
A mechanically coupled filter according to claim 9 or 10, wherein couplers (184, 184') are connected, at both ends, to either the top or bottom metal plates (182a, 182b; 182a', 182b') at respective points other than individual nodal points, the couplers being shaped as plates and being formed integrally with the metal plates (182a, 182b; 182a', 182b').
Claim 13
Dependent Claim
97 words
A mechanically coupled filter according to claim 9 or 10, wherein a support member (204') is connected to either the top or bottom metal plates (202a, 202b; 202a'; 202b'), at their respective centres, so that it is connected to the respective nodal points of the input and output side piezoelectric ceramic members (203a, 203b), the coupler (204) being coupled between the ceramic members (203a, 203b) at points other than the nodal points, both the support member (204') and the coupler (204) being shaped as plates and being formed integrally with the metal plates (202a, 202b; 202a', 202b').
Claim 14
Dependent Claim
46 words
A mechanically coupled filter according to any one of claims 9 to 12, wherein the thickness of the input side piezoelectric ceramic member (183a) is different from the thickness of the output side piezoelectric ceramic member (183b), so that the thickness-extensional spurious vibration modes are suppressed.
Claim 15
Dependent Claim
65 words
A mechanically coupled filter according to any one of claims 9 to 13, wherein the width of the input side piezoelectric ceramic member (203a) and also its top and bottom metal plates (202a, 202a') is different from the width of the output side piezoelectric ceramic member (203b) and also its top and bottom metal plates (202b, 202b'), so that width-extensional spurious vibration modes are suppressed.
References Cited (Backward Citations)
No citation records indexed.
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