US3795878A - Flexural vibrator as resonator for mechanical filters - Google Patents

Flexural vibrator as resonator for mechanical filters Download PDF

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Publication number
US3795878A
US3795878A US00318935A US3795878DA US3795878A US 3795878 A US3795878 A US 3795878A US 00318935 A US00318935 A US 00318935A US 3795878D A US3795878D A US 3795878DA US 3795878 A US3795878 A US 3795878A
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United States
Prior art keywords
vibrator
flexural
vibrations
resonator
holding element
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Expired - Lifetime
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US00318935A
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English (en)
Inventor
H Schussler
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Licentia Patent Verwaltungs GmbH
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Licentia Patent Verwaltungs GmbH
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Priority claimed from DE19712165552 external-priority patent/DE2165552C3/de
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/05—Holders or supports
    • H03H9/0504—Holders or supports for bulk acoustic wave devices
    • H03H9/0514—Holders or supports for bulk acoustic wave devices consisting of mounting pads or bumps

Definitions

  • flexural vibrators In such prior known flexural vibrators, one common characteristic feature is the holding elements which are connected at the vibration nodes. These holding elements are usually provided in the form of rods mounted on a base plate. When the flexural vibrator is vibrated, 'the rods experience torsional vibrations substantially SUMMARY OF THE INVENTION Anobject of the present invention is to provide a resonator which can be easily constructed while avoiding the drawbacks discussed above.
  • a further object of the present invention is to construct a resonator which can have a circular cross section and is mounted in such a manner that undesirable vibrations are attenuated.
  • the flexural vibrator constructed in accordance with the present invention which is used as a resonator for mechanical filters, is connected with a base plate by one or more holding elements.
  • Each holding element is connected to the resonator at a substantial distance from the vibration nodes and is formed so as to constitue a quasi (2nl/4))t flexural coupling line for the flexural vibrations established within the vibrator in the desired vibration direction of the vibrator perpendicular to the longitudinal axis of the holding element at the center transmission frequency of the filter.
  • the holding element substantially acts as a longitudinal coupler for the undesirable flexural vibrations of the flexural vibrator in a direction parallel to the longitudinal axis of the holding element and perpendicular to the base plate.
  • the high coupling factor with respect to the base plate which is exhibited by the holding element provides for detuning and strong attenuation of the undesirable vibration.
  • the high coupling factor is obtained if the length of the holding elements is less than one-quarter of the wavelength of the longitudinal vibrations of the holding elements at approximately the center transmission frequency of the filter.
  • the flexural vibrator according to the present invention exhibits a preferential vibration direction, which is the desired direction of vibration, and detunes and attenuates any vibrations in the undesired direction substantially independently of the cross-sectional shape of the flexural vibrator.
  • the vibrator therefore, can have a circular cross section, which is desirable for manufacturing purposes/A square cross section, which is also considered undesirable in conventional flexural vibrators can also be used in accordance with the present invention.
  • the holding elements also are preferably constructed with a circular cross section in order to facilitate their fabrication.
  • FIG. la is a front elevational view of a resonator mounted in accordance with prior known techniques and showing the desired torsional vibrations produced within the holding elements.
  • FIG. lb is a top plan view of the embodiment shown in FIG. la.
  • FIG. 10 is a view similar to FIG. 1a but illustrating the occurrence of an undesirable vibration in the vibrator.
  • FIG. 2a is a front elevational view of a resonator mounted in accordance with the present invention.
  • FIG. 2b is a top plan view of the embodiment shown in FIG. la.
  • FIG. 2c is a view similar to FIG. 2a but illustrating the occurrence of an undesirable vibration in the vibrator.
  • FIG. 2d is a side view of the embodiment shown in FIG. 2a, taken in the direction of the arrow II of FIG. 20.
  • a flexural vibrator l is mounted in a known manner on a base plate 3 by holding elements 2.
  • the desired vibration direction 6 (FIG. 1b) is perpendicular to the longitudinal axis of the flexural vibrator 1 and parallel to the base plate 3.
  • This de sired vibration establishes the vibration nodes identified by the dot-dash lines 4.
  • the occurrence of other undesirable flexural vibrations is possible in a direction perpendicular to the longitudinal axis of the flexural vibration l inclined with respect to the base plate 3.
  • An example of such vibration is shown in FIG. 1c in which the flexural vibrator I vibrates in the undesirable direction 7 perpendicular to the base plate 3 and with vibration nodes 5.
  • the holding elements 2 are disposed coaxially with the node lines 4 associated with the desired vibrations 6. As long as the vibrator l of FIG. 1 vibrates exclusively in the desired direction 6, the holding elements 2 experience torsional vibrations 8 (FIG. Ia). Flexural vibrations of resonator 1 in the undesirable direction 7 lead to flexural vibrations 9 (FIG. 10) ofthe holding elements in the direction along the longitudinal axis of the resonator 1.
  • the holding elements 2 are dimensioned so that their torsional vibrations 8 only slightly attenuate the vibrations of resonator I in the desired direction 6, the holding elements 2 also produce only a slight attenuation of the vibrations in the undesirable direction 7 even with the occurrence of the flexural vibrations 9.
  • the holding elements 2 in accordance with the present invention as shown in FIG. 2 are connected to the flexural vibrator at positions offset from the node lines 4, but are oriented parallel thereto. Their precise spacing from, and the direction in which they are spaced from, the node lines has no significant influence on the achievement of the desired results.
  • the holding elements 2 of FIG. 2 Since placing of the holding elements 2 of FIG. 2 outside of the node lines 4 will influence the natural frequency ofthe vibratory system consisting of these holding elements 2 and the actual resonator 1, it becomes desirable to design the holding elements so that they constitute quasi 2n-l/4A flexural coupling lines for the flexural vibrations established in the vibrzir l elements to experience longitudinal vibrations 11, the holding element 2, designed in accordance with the above equation, exhibits a substantially rigid coupling to the base plate 3 (FIG. 2) thus producing a strong attenuation of the undesirable vibrations.
  • This high coupling factor can be obtained if the holding elements are designed with a length less than one-quarter of the wavelength of the longitudinal vibrations of the holding elements at approximately the center transmission frequency of the filter.
  • the vibrators l In a practical filter with a center frequency of about 50 kc/s and a total bandwidth of 3.6 kc/s the vibrators l have a length of about 16 mm and a diameter of about 3.5 mm. In such a vibrator, in case of flexural vibrations the vibration nodes have a distance of about 3.6 mm from the ends of the vibrator. In the same filter the holding elements 2 have a diameter of 0.5 mm and a length of about 3.3 mm. The distance between the points of attachment of the elements 2 to the vibrator I and a vibration node may be 2.5 mm and the holding elements 2 may be situated between or outside the nodes.
  • the vibrators consist of a hardened steel alloy with a high Young modulus and a low temperature coefficient, preferably of the well known NiSpanC.
  • the material of the holding elements is not critical in respect to the temperature coefficient and may be normal steel.
  • a flexural vibrator for use as a resonator in a me chanical filter and exhibiting vibration nodes upon being flexurally vibrated and having at least one holding element connecting the vibrator to a base plate, the improvement wherein said holding element is connected to said vibrator at a substantial distance from the vibration nodes and is formed to constitute a quasi (2n l/4) flexural coupling line for the flexural vibrations established within said vibrator in a direction perpendicular to the longitudinal axis of said holding element at the center transmission frequency of the filter.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
US00318935A 1971-12-30 1972-12-27 Flexural vibrator as resonator for mechanical filters Expired - Lifetime US3795878A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19712165552 DE2165552C3 (de) 1971-12-30 Biegeschwinger als Resonator für mechanische Filter

Publications (1)

Publication Number Publication Date
US3795878A true US3795878A (en) 1974-03-05

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US00318935A Expired - Lifetime US3795878A (en) 1971-12-30 1972-12-27 Flexural vibrator as resonator for mechanical filters

Country Status (6)

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US (1) US3795878A (enExample)
JP (1) JPS52658B2 (enExample)
FR (1) FR2170616A5 (enExample)
IL (1) IL41197A (enExample)
IT (1) IT972958B (enExample)
SE (1) SE382725B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6420202B1 (en) * 2000-05-16 2002-07-16 Agere Systems Guardian Corp. Method for shaping thin film resonators to shape acoustic modes therein

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1541982A1 (de) * 1967-08-28 1970-04-16 Siemens Ag Aus mechanischen Biegeresonatoren bestehendes elektromechanisches Bandfilter

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1541982A1 (de) * 1967-08-28 1970-04-16 Siemens Ag Aus mechanischen Biegeresonatoren bestehendes elektromechanisches Bandfilter

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6420202B1 (en) * 2000-05-16 2002-07-16 Agere Systems Guardian Corp. Method for shaping thin film resonators to shape acoustic modes therein

Also Published As

Publication number Publication date
DE2165552A1 (de) 1973-07-05
JPS52658B2 (enExample) 1977-01-10
SE382725B (sv) 1976-02-09
IT972958B (it) 1974-05-31
DE2165552B2 (de) 1976-04-01
IL41197A (en) 1975-06-25
FR2170616A5 (enExample) 1973-09-14
JPS4873875A (enExample) 1973-10-05
IL41197A0 (en) 1973-02-28

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