US2373431A - Electric wave filter - Google Patents

Electric wave filter Download PDF

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Publication number
US2373431A
US2373431A US481089A US48108943A US2373431A US 2373431 A US2373431 A US 2373431A US 481089 A US481089 A US 481089A US 48108943 A US48108943 A US 48108943A US 2373431 A US2373431 A US 2373431A
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US
United States
Prior art keywords
crystal
shear
mode
plate
vibration
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US481089A
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English (en)
Inventor
Roger A Sykes
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US481089A priority Critical patent/US2373431A/en
Application granted granted Critical
Publication of US2373431A publication Critical patent/US2373431A/en
Priority to CH272696D priority patent/CH272696A/fr
Priority to FR948664D priority patent/FR948664A/fr
Priority to GB21775/47A priority patent/GB631772A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/60—Electric coupling means therefor
    • 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
    • H03H9/10—Mounting in enclosures
    • H03H9/1007—Mounting in enclosures for bulk acoustic wave [BAW] devices
    • H03H9/1014—Mounting in enclosures for bulk acoustic wave [BAW] devices the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the BAW device
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/542—Filters comprising resonators of piezoelectric or electrostrictive material including passive elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • H03H9/566—Electric coupling means therefor

Definitions

  • This invention relates to electric wave filters and more particularly to narrow band-pass piezoelectric filters.
  • An object of the invention is to simplify and cheapen filters of the type required to select a single frequency electric current or a narrow band of currents at frequencies of the order of 2000 kilocycles.
  • Another object is to improve the attenuation characteristics lof a piezoelectric narrow bandpass filter operated at a midband frequency of the Order of 2000 kilocycles.
  • ⁇ An additional object of the invention is to reduce the effects of undesired modes of vibration which tend to be induced in AT type crystals driven in shear modes of vibration.
  • An additional object is to obtain narrow bandpass filter characteristics with two divided coating AT cut quartz crystals similar to those obtained with singly resonant crystals.
  • Another object is to operate an AT type crystal in a fundamental shear mode of vibration while inhibiting deleterious flexural mode oscillations.
  • a still further object of the invention isr to obtain narrow band filter characteristics with AT cut crystals similar to those obtained with singly resonant crystals.
  • one pair of terminals of an AT cut quartz crystal filter is connected between a ground electrode on one side of the crystal plate and two outer electrodes posi- ⁇ tioned at different points along the X axis on the opposite side of the crystal plate while one terminal of the other pair of terminals is connected to an electrode intermediate the two outer electrodes and the other terminal is connected to the ground electrode.
  • each crystal face is provided with three electrodes arranged at different positions along the X axis, the outer electrodes on one face and the intermediate electrode on the other being connected to the common ground terminals of each pair of terminals while the remaining terminals are connected respectively one to the remaining outer pair of electrodes and the other to the remaining intermediate electrode.
  • the two filter sections may be advantageously connected'in tandem to constitute a band-pass filter having satisfactory attenuation at each side of the band.
  • Thetwo sections may, moreover, be mounted in the Same container on-a single supporting structure.
  • the most prominent resonances in AT cut crystals are of two types, shear and fiexure.
  • the fundamental high frequency shear resonance results in a deformation which possesses some char- ⁇ acteristics in common with that of certain ilexure vibrations. It is possible, however, to excite still higher frequency shear vibrations by a dispositibn of electrodes that induces distortions which are not so conducive to initiation of flexural vibrations.
  • even multiple harmonics of flexure will be driven by and strongly coupled to shear modes of vibration having a frequency which is an odd order overtone oi' the fundamental shear frequency.
  • odd harmonics of iiexure will be driven by and strongly coupled to shear modes having a frequency which is an even order overtone of the fundamental shear frequency.
  • Fig. 1 illustrates the displacements which occur in an AT cut quartz crystal operating in XY' shear vibration
  • Fig. 6 indicates the measured resonances of a completely plated AT crystal plotted with respect to the ratio of X to Y;
  • Fig. 'I indicates the measured resonances of an Fig. 8 illustrates schematically a piezoelectric ance with this invention
  • Fig. 9 shows the plating of the two principal faces oi the crystal element of Fis. e;
  • Fis. 10 illustrates schematically a narrow bandpass piezoelectric iilter section having characteristics complimentary to those of Fig. 8
  • Fis. ll shows the electrode plating or the crystal oi his. lo;
  • Fis. l2 illustrates schematically a narrow bandpass lter comprising tandem sections similar to those of lilas. d and lo;
  • Fis. i3 portrays the frequency selective or attenuation characteristic oi the filter of Fis. 12,
  • am@ v Fiss. le and. i5 are respectively face and side views of one structural embodiment of the piezoelectric iata of the nlter of Fis. 12 with parts oi the container broken away.
  • Fis. l there is shown, in solid lines an edae View of an AT cut quartz crystal element, the length of which extends parallel to the X anis and the thiclmess to the Y axis with an upper electrode coating l and a lower electrode coating E2.
  • the disarmament under conditions of XY' shear resonance is shown exaggerated by the broken lines.
  • the upper corners A and B are displaced to the richt as indicated at A' and B'; the lower corners C and D to the left as indicated at C' and. 1D.
  • the displacement will reverse.
  • points A and B moving to the left ofV their normal zero positions and points C and D to the right.
  • Fig. 2 shows in mmllar fashion the ilrst even order mode nexure vibration in the XY' plane.
  • the upper corners A and B are displaced to the right at A".
  • Fig. 3 illustrates an AT cut quartz crystal element with two upper electrodes 3 and l displaced from eachother in the lensth or X direction and one lower electrode d.
  • This piezoelectric crystal is designed to be excited in the ilrst even order multiple frequency shear mode of vibration in the XY' plane.
  • the upper corners A and B are displaced respectively to the left at A' ⁇ and to the right et B', the corresponding lower corners C and D being displaced respectively to the right at C' and the left at D'.
  • the shear vibration and the exural vibration frequencies of the structures which have been shown are functions oi' both their X and 'if' dimensions. If, however, the X dimension be made very large relative to the Y' dimension the XY' shear resonant frequency is dependent primarily upon the Y dimension. It will be evident, therefore. that if the X dimension is great enough half that dimension or XY/ will still be 'large enough nemesi filter section of narrow pees-band type in accordrelatlve to the Y' dimension so that Y will primarily determine the oscillation frequency. It
  • shear mode vibration oi the XY' type discussed iu connection with Fis. 1 may be denoted as the mimi; XY' shear mode.
  • the mode of Fig. 3 in which the number ci sectional shears along the X axis is 2, may be designated as the mmall XY' shear mode.
  • rig. 5 shows the displacement which occurs in the case of an AT- cut quartz crystal having three plates on its upper surface with the two outer plates polarized in a manner opposite to the central plate.
  • Ii such a crystal be excited by an alternating electromotive force of the proper frequency it will execute shear vibrations in the XY' plane at a resonance frequency of the third order which, although determined primarily by the Y' dimension. is a somewhat higher frequency for the same dimension of crystal than the modes of oscillation produced by the systems .of Figs. l and 3.,v
  • any order of frequency of resonance for the shear mode of vibration may be had depending upon thenumber of reversals of motion along the X axis.
  • Even order harmonics of the ilexure will be driven by and tend toA be strongly coupled to the shear modes having an odd velue for n such as nimm.
  • Fig. 6 shows the measured frequencies of resonance for a completely plated .AT cutcrystal i' mm. thick, the, graphs being plotted with frequencies as ordinates and with ratio of X to Y' as abscissae. These results are for an approximately square crystal. 'I'he dotted lines represent even order ilexure modes along the X dimension. Broken lines indicate the predicted positions of flexural resonance for various ratios of X -to Y. Graphs in solid lines show mimll; mman, and mimh modes of XY' shear vibration. It will be apparent that as the ratio X/Y, increases the absolute frequencies 'of these different shear modes of vibration approach each other, the higher mode remaining, however, at high frequency. For example, at
  • Fig. 7 shows the measured resonances of the crystal plating arrangement of Fig. 3 with the crystal driven between one top plate and ground las, for example, between plate 3 and 5 and the resulting electromotive force measured between the other top plateand ground as between plates 4 and 5.
  • a filter we may expect to measure resonances correspond-- ing to both even and odd flexures along the X axis for the reason that the two top plates 3 and-4 may assume the same as well as opposite polarities.
  • the coupling is high between even mode shears and odd mode flexures and between the odd mode shears and even mode exures but that it is quite low between like order shears and ilexures.
  • Fig. 8 there is shown an AT quartz crystal adapted for operation in an odd shear mode, the coating being split so that there is no tendency for generating shears corresponding to even values for n. With no even value for n there will be no odd flexure harmonics along .X.
  • the top coatings 6 andl electrically connected together to a terminal 8 of the filter section are spaced in the direction of the X axis from a central coating 9 which is electrically connected to a terminal I of the filter section.
  • a coating II electrically connected to the filter terminals I2 and I3.
  • Fig. 9 shows the structural arrangement of the electrodes in more detail.
  • the coatingss, 1 and 9v may be formed by first plating the entire crystal and then removing the plating along the solid lines. This permits coatings 6 and 1 to be connected by the narrow integral strip I4. It/also permits the lower coating I I to be integrally connected with a marginal surrounding strip I51on the upper face ⁇ of the potential thus removing piezoelectric stress from the marginal portion of the crystal to reduce the coupling between the odd shear mode vibration and even mode flexural vibration. Moreover, the ground potential plate I I is also integrally connectedfto a separating shielding conducting* strip I6 positioned between the top coatings B and 'I on the one hand and the top coating 9 on the other to reduce any capacitance coupling between these electrodes. As indicated in Fig. 9 the end tenth Aof the surface measured along the X axis may be left uncoated at each end of the crystal.
  • Figs. 9 and 11 of the drawings both the upper and lower surfaces 28 and 29 of the same crystal are shown, one above the other with the plating which covers both surfaces and the intervenlng edge. Although the entire surface of the crystal may be plated and then divided along the solid lines as has previously been stated, in the Figs. 9 and 11, the plating is shown extending only part way toward the ends of the top and bottom surfaces of the crystal.
  • Fig. 10 shows diagrammatically an AT cut quartz plate lter section differing from that of Fig. 8 in that it is provided with three upper electrodes I8, I9, and three corresponding lower electrodes 2
  • Consequentlm' such a lter may operate with an attenuation characteristic which is relatively high beyond each cut-oif frequency.
  • the small shielding coating strips I5, I6 xnay ⁇ 1 produce a small force tending tc excite even order shears. For that reason it is expedient to keep them as narrow as is feasible.
  • Fig. 13 The transmission characteristic measured on an actual lter designed as indicated in Fig. 12 is disclosed in Fig. 13.
  • This graph discloses a pass band at approximately 2064 kilocycles with an ⁇ at tenuation of at least 25 decibels in the frequency region adjacent the cut-olf frequencies of the band.
  • Figs. 14 and 15 show the mounting of the electromechanical structure of the filter of Fig. 12.
  • a base 35 of dielectric material is provided with the usual lead in plug connectors 36, 31 etc'. and an evacuated metal shell 38 is sealed to the base.
  • a metal plate 39 is mounted upon a spring 40 which cushions the plate 39 from shocks.
  • the plate 39 is given lateral support by the bowed spring 4I, the down turned ends 42 of which iit ⁇ closely within the' shell 38.
  • the spring 40 is anchored at its ends to the base 35 and the two springs are connected to plate 39 by screws 43 and 44.
  • a piezoelectric element 45 which may correspond in all respects to the disclosure of Figs. and 11. Element 45 may be held in position the rst face and the other to the coating on the opposite face.
  • An unbalanced piezoelectric lter comprising an AT cut quartz plate having two substantially parallel faces. one face having two outer coatings separated from each other in the X axis direction by an intermediate coating and the cpposite face having a ground or low potential coating passing around a margin of the plate to the first face to extend around the entire edge portion of the rst face outside the three coatings thereof. and to extend between the inner coatings and in contact with plate 39 by means of phosphor bronze spring clamping members 46 and 41 each provided with anvil contacts 48.
  • the anvil 48 of member 41 provides both mechanical and electrica1 contact at a point on the coating I8 and that of member 41 on the strip 50 integrally connected withplate 22.
  • piezoelectric element 52 positioned against the back' oi grounded metal plate 39 may be held in fixed position and electrically connected in circuit.
  • the grounded coating Il of element 52 is the only coating on that side of the element 5 2 it is unnecessary to provide the countersunk area of the back of metallic plate 39.
  • a piezoelectric ilter comprising an AT cut quartz plate having two substantially parallel faces, three conducting coatings on one face physically separated from each other in the direction of the X axis. a coating on the opposite face, a-pair of iter terminals connected respectively one to the -outer coatings of the first face and the other'to the coating on the opposite face,-
  • An AT cut quartz plate having two principal substantially parallel opposite faces, three electrodes separated from eachother in the X direction on each of the two principal faces, a rst pair of terminals of which one is connected to the outermost electrodes of one surface and the other is connected to the central electrode on that same surface and the outermost electrodes on the other surface, and a second pair of terminals of which one is connected to the central electrode on the second face and the other is connected tothe second terminal of the iirst pair.
  • a band-pass filter comprising two tandem sections, the ilrst consisting of a single quartz resonator vibrating in a shear mode and having three electrodes on one face spaced from each other in the direction of the X axis and a single electrode on the opposite face, one pair of terminals having a conductor connected to the two outer electrodes on the rst face and a second conductor connected to the single electrode, a second pair of terminals having a conductor connected to the inner electrode on the first face and a second conductor connected to the single electrode, the second section consisting of a single vquartz resonator vibrating in a shear mode and having on each of its two principal faces three electrodes spaced from each other inthe direction of the X axis,' an electrical connection fromthe single electrode of the first section resonator to e the outer electrodes on one face and the inner ⁇ electrode on the other face of the second section, a second electrical connection from the outer electrodes on the first resonator to the
  • An electric wave filter comprising two piezoelectric plates each having divided electrical coatings whereby the plates may be excited in harmonic modes of vibration, a ilat metallic member to form a common ground connection for said plates, means for holding said piezoelectric plates each in contact with one side of said metallic member.- one side of s aid metallic' member having a recessed portion whereby ungrounded electrode surfaces of the contiguous piezoelectric plate may be maintained out of contact with the grounded member.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
US481089A 1943-03-30 1943-03-30 Electric wave filter Expired - Lifetime US2373431A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US481089A US2373431A (en) 1943-03-30 1943-03-30 Electric wave filter
CH272696D CH272696A (fr) 1943-03-30 1947-06-09 Filtre d'ondes piézoélectrique à bande passante étroite.
FR948664D FR948664A (fr) 1943-03-30 1947-06-30 Filtre d'ondes électriques
GB21775/47A GB631772A (en) 1943-03-30 1947-08-07 Improvements in electric wave filters incorporating piezoelectric crystal elements

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US481089A US2373431A (en) 1943-03-30 1943-03-30 Electric wave filter

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US2373431A true US2373431A (en) 1945-04-10

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CH (1) CH272696A (fr)
FR (1) FR948664A (fr)
GB (1) GB631772A (fr)

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2524781A (en) * 1945-06-18 1950-10-10 Standard Telephones Cables Ltd Filter
US2943278A (en) * 1958-11-17 1960-06-28 Oskar E Mattiat Piezoelectric filter transformer
US2965861A (en) * 1957-09-18 1960-12-20 Collins Radio Co Thickness-shear-mode mechanical filter
US2988714A (en) * 1957-09-12 1961-06-13 Gen Electric Piezoelectric filter network
US3018451A (en) * 1958-12-04 1962-01-23 Mattiat Oskar Piezoelectric resonator with oppositely poled ring and spot
US3078427A (en) * 1958-05-30 1963-02-19 Siemens Ag Electromechanical filter with piezoelectric drive
DE1209336B (de) * 1960-12-01 1966-01-20 Bosch Arma Corp Als randfreie Kreisscheibe ausgebildeter Biegeschwingungswandler zur Erzeugung von Schallschwingungen
US3396327A (en) * 1961-12-27 1968-08-06 Toyotsushinki Kabushiki Kaisha Thickness shear vibration type, crystal electromechanical filter
US3437848A (en) * 1964-09-24 1969-04-08 Telefunken Patent Piezoelectric plate filter
DE2005918A1 (de) * 1969-02-10 1970-08-06 Western Electric Co Siebschaltung
US3633134A (en) * 1969-10-10 1972-01-04 Motorola Inc Crystal band pass filter circuit
US3656180A (en) * 1970-08-12 1972-04-11 Bell Telephone Labor Inc Crystal filter
US3739304A (en) * 1971-09-27 1973-06-12 Bell Telephone Labor Inc Resonator interconnections in monolithic crystal filters
US3750279A (en) * 1970-09-11 1973-08-07 Braun Ag Dry shaver construction
US3792294A (en) * 1972-10-19 1974-02-12 Bell Telephone Labor Inc Rectangular at-cut crystal plate
DE2343505A1 (de) * 1972-08-31 1974-03-07 Nippon Musical Instruments Mfg Keramischer filterschaltkreis
JPS4977811U (fr) * 1972-10-21 1974-07-05
US3944862A (en) * 1973-05-02 1976-03-16 Kabushiki Kaisha Suwa Seikosha X-cut quartz resonator using non overlaping electrodes
US3944951A (en) * 1974-11-21 1976-03-16 Bell Telephone Laboratories, Incorporated Monolithic crystal filter
US20160072041A1 (en) * 2013-04-18 2016-03-10 Cornell University Monolithic pzt actuator, stage, and method for making

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2524781A (en) * 1945-06-18 1950-10-10 Standard Telephones Cables Ltd Filter
US2988714A (en) * 1957-09-12 1961-06-13 Gen Electric Piezoelectric filter network
US2965861A (en) * 1957-09-18 1960-12-20 Collins Radio Co Thickness-shear-mode mechanical filter
US3078427A (en) * 1958-05-30 1963-02-19 Siemens Ag Electromechanical filter with piezoelectric drive
US2943278A (en) * 1958-11-17 1960-06-28 Oskar E Mattiat Piezoelectric filter transformer
US3018451A (en) * 1958-12-04 1962-01-23 Mattiat Oskar Piezoelectric resonator with oppositely poled ring and spot
DE1209336B (de) * 1960-12-01 1966-01-20 Bosch Arma Corp Als randfreie Kreisscheibe ausgebildeter Biegeschwingungswandler zur Erzeugung von Schallschwingungen
US3396327A (en) * 1961-12-27 1968-08-06 Toyotsushinki Kabushiki Kaisha Thickness shear vibration type, crystal electromechanical filter
US3437848A (en) * 1964-09-24 1969-04-08 Telefunken Patent Piezoelectric plate filter
DE2005918A1 (de) * 1969-02-10 1970-08-06 Western Electric Co Siebschaltung
US3633134A (en) * 1969-10-10 1972-01-04 Motorola Inc Crystal band pass filter circuit
US3656180A (en) * 1970-08-12 1972-04-11 Bell Telephone Labor Inc Crystal filter
US3750279A (en) * 1970-09-11 1973-08-07 Braun Ag Dry shaver construction
US3739304A (en) * 1971-09-27 1973-06-12 Bell Telephone Labor Inc Resonator interconnections in monolithic crystal filters
DE2343505A1 (de) * 1972-08-31 1974-03-07 Nippon Musical Instruments Mfg Keramischer filterschaltkreis
US3792294A (en) * 1972-10-19 1974-02-12 Bell Telephone Labor Inc Rectangular at-cut crystal plate
JPS4977811U (fr) * 1972-10-21 1974-07-05
US3944862A (en) * 1973-05-02 1976-03-16 Kabushiki Kaisha Suwa Seikosha X-cut quartz resonator using non overlaping electrodes
US3944951A (en) * 1974-11-21 1976-03-16 Bell Telephone Laboratories, Incorporated Monolithic crystal filter
US20160072041A1 (en) * 2013-04-18 2016-03-10 Cornell University Monolithic pzt actuator, stage, and method for making
US10158063B2 (en) * 2013-04-18 2018-12-18 Cornell University Monolithic PZT actuator, stage, and method for making

Also Published As

Publication number Publication date
FR948664A (fr) 1949-08-08
GB631772A (en) 1949-11-09
CH272696A (fr) 1950-12-31

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