US3663899A - Surface-wave electro-acoustic filter - Google Patents

Surface-wave electro-acoustic filter Download PDF

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Publication number
US3663899A
US3663899A US25158A US3663899DA US3663899A US 3663899 A US3663899 A US 3663899A US 25158 A US25158 A US 25158A US 3663899D A US3663899D A US 3663899DA US 3663899 A US3663899 A US 3663899A
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United States
Prior art keywords
teeth
plate
filter
comb
electrodes
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Expired - Lifetime
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US25158A
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English (en)
Inventor
Eugene Dieulesaint
Pierre Hartemann
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Thales SA
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Thomson CSF SA
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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 devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14517—Means for weighting
    • H03H9/1452—Means for weighting by finger overlap length, apodisation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14517—Means for weighting
    • H03H9/14526—Finger withdrawal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic

Definitions

  • An electro-acoustic surface-wave (Rayleigh waves) device comprises a piezoelectric plate equipped with two transducers Apt. 16, France one at least f is constituted two cmb shaped elec trodes having interleaved teeth. At least one of the electrodes U.S. T, 3 have teeth of a length the envelope of which is the [51] Int.
  • One form of electro-acoustical delay lines is constituted by a plateor wafer of piezoelectric material, for example quartz, to which two transducers are applied, at least one of which is formed of two comb-shaped metal electrodes the teeth of the combed structures being interleaved with one another.
  • a plateor wafer of piezoelectric material for example quartz
  • two transducers are applied, at least one of which is formed of two comb-shaped metal electrodes the teeth of the combed structures being interleaved with one another.
  • acoustic surface waves, or Rayleigh waves are produced; an electrical signal is then picked up by the other transducer after a delay equivalent to the time taken. by the acoustic waves to propagate from one transducer'to the other.
  • Each pair of teeth in a comb-shaped transducer exhibits resonance for an acoustic surface-wave whose halfwavelength is equal to the distance between two adjacent teeth.
  • the length of the teeth being substantially higher than the half wavelength the vibratory energy is confined within a narrow radiated beam substantially perpendicular to the length of the teeth.
  • the waves emanating from different pairs of teeth have trajectories of different lengths; consequently, these waves interfere with one another.
  • the transducers are the more selective the larger the number of teeth being used, but the output electrical signals which excite a combshaped transducer are much attenuated if their frequencies deviate from the normal design frequency of the transducer.
  • the present invention is directed to eIectro-acoustic elements with comb-shaped, interlaced electrodes which process signals withina determinate frequency band so that the device can be used not only as a delay line but also as a filter.
  • the signal input transducer at least, is constituted by electrodes with a large number of teeth; the teeth of at least one of the electrodes have dissimilar lengths, with a tooth tip envelope having the shape of the Fourier transform of the transfer function presented by the device when operating as a filter.
  • a plate. 3 of piezoelectric material (such as quartz, cadmium sulphide, lithium methaniobate, piezoelectric ceramic, etc. etc. has two transducers l and 2 applied to one face.
  • the transducers are spaced from one another and respectively made up of two metal electrodes 1A, 1B and 2A, 28, formed of thin layers of metal and comb-shaped in general form, the teeth of the two electrodes of one transducer being interleaved with those of the other.
  • One of the transducers 2 has the conventional form used in surface-wave (acoustic) delay lines; in this transducer 2, the teeth are equidistant from one another and of equal length and can be small in number, there being provided for example.
  • the other transducer 1 has teeth which, while equidistant are more numerous, numbering for example 100 or more; the teeth of one of the electrodes 1A of this transducer are equal in length but those of the other, 15, have difierent lengths and
  • the invention will described byway of example with as lying between two limits F1 and F2 situated to either side of a center frequency Fo, the latter being the resonance frequency of the transducer 1 having the larger number of teeth and having electrode 18 whose teeth are dissimilar in length.
  • the filter effect which can be obtained in the structure in accordance with the invention derives chiefly from the design of this electrode 18 with the dissimilar teeth.
  • the envelope describing the tips of the teeth having the form corresponding to the function sin x/x, results in a structure having a pulse response defined by a wave modulated by sin .x/x, which wave corresponds to the transmission characteristic (or transfer function), of a band-pass filter.
  • the filter effect results from the fact that the pulse response is a function of the geometrical dimensions of the comb electrode structures.
  • both electrodes of one transducer have teeth of variable length; or alternatively, the two transducers may have similar structures, with numerous teeth, at least one electrode group of each of them having teeth which vary in length in accordance with the Fourier transform of the transfer function.
  • the envelope defining the teeth of dissimilar length can have a form other than that described by the function sin x/x.
  • the envelope of the teeth of dissimilar length has a form similar to the Fourier transfonn of the transfer function which it is desired to obtain in operation of the filter device.
  • it is the combination of the envelopes which has the fonn of a Fourier transform.
  • the transfer function which results is the square of the transfer function of one transducer.
  • the device with the described structure constitutes a delay line of the kind which will delay an electrical pulse proportionally to the distance separating the transducers and, additionally will act as a filter. If a continuous signal'is applied to one of the transducers then thisdevice acts as a bandpass filter capable of passing signals whose frequency F is defined the rectangular, for example triangular, trapezoidal, semisinusoidal, Gauss function, and so on are equally feasible.
  • F the rectangular, for example triangular, trapezoidal, semisinusoidal, Gauss function, and so on are equally feasible.
  • one or the other of these transforms can be adopted to define the envelope of the teeth.
  • the pass band increases with decrease in the number of I teeth.
  • the number of teeth is substantially proportional to the quotient of the center frequency F0 and the band width.
  • the spacing betweenthe teeth determines the center frequency P0 of the device. I
  • phase reversal can be produced by connecting to the same electrode two adjacent teeth separated by a distance equal to the halfwavelength of the acoustic wave as seen at point 4.
  • the device can operate at frequencies in the order of several'hundreds megahertz.
  • the speed of propagation of the acoustic surface-waves is around 3,200 m/sec.; the wavelength is thus 32 microns at I00 mHz.
  • the comb-shaped transducers two adjacent teeth are spaced apart by half a wavelength; generally speaking, the distance is split equally between the width of a tooth, that is to say the metallized part, and the space between two teeth; up to around I50 ml-Iz, these transducers can be produced by conventional photolithography techniques.
  • the pulse response of the filter As concerns the lengths of the teeth, it is necessary to compute the pulse response of the filter.
  • This response being the Fourier transform of the desired transfer function, it can be fully detennined as a time function. Assuming that the pulse response is plotted on a time scale, it is very simple to associate to this scale a distance scale, taking into account the known value C of the propagation velocity. The distance scale can then be divided at intervals M2 equal to the spacing of the teeth, and each ordinate value of the pulse response curve will then give the length of the teeth. 7
  • certain teeth of the transducers can be omitted, either in order to empirically modify the transmission characteristics of the device or to obtain special effects.
  • the piezoelectric plate is a crystal, having X and Y crystallographic axes particular cleavage planes are desirable.
  • the temperature coefficient can be reduced if an X-cut is used with a direction of propagation making an angle of some 30 with the Y-axis.
  • a surface-wave electro-acoustic filter comprising a plate (3) of piezoelectric material
  • two transducers l, 2) applied to said plate at least one of which comprises two metal electrodes (1A, 1B) in combshaped form having interleaved teeth, at least one of the comb-shaped electrodes (18) having teeth of dissimilar length, the envelope described by the tips of the teeth of said electrode being essentially the curve defining the Fourier transform of the transfer function of the device when operating as a filter; and the number of teeth in the electrode with dissimilar length teeth being sufficiently large for the envelope or envelopes to define the major undulations and lobes in said transform.
  • a filter as claimed in claim 1 acting as a bandpass filter, wherein the envelope of the teeth of the combination of the envelopes of the teeth, is approximately the curve following the law described by the function y sin .x/x x and y being coordinates respectively associated with the spacing and the lengths of said teeths.
  • a device as claimed in claim 1 wherein the piezoelectric plate (3) is made of quartz.
  • a device as claimed in claim 1 wherein two adjacent teeth are connected to one and the same electrode at points (4) which correspond to a change in sign in the Fourier transform.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
US25158A 1969-04-16 1970-04-02 Surface-wave electro-acoustic filter Expired - Lifetime US3663899A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR6911765A FR2040881A5 (xx) 1969-04-16 1969-04-16

Publications (1)

Publication Number Publication Date
US3663899A true US3663899A (en) 1972-05-16

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US25158A Expired - Lifetime US3663899A (en) 1969-04-16 1970-04-02 Surface-wave electro-acoustic filter

Country Status (6)

Country Link
US (1) US3663899A (xx)
DE (1) DE2016109C3 (xx)
FR (1) FR2040881A5 (xx)
GB (1) GB1295909A (xx)
NL (1) NL172810C (xx)
SE (1) SE364611B (xx)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3755761A (en) * 1971-12-30 1973-08-28 Texas Instruments Inc Surface wave transversal frequency filter
US3845420A (en) * 1973-03-02 1974-10-29 Raytheon Co Surface acoustic wave phase control device
US3855556A (en) * 1973-04-02 1974-12-17 Texas Instruments Inc Selectable frequency bandpass filter
DE2531551A1 (de) * 1974-07-15 1976-01-29 Nippon Telegraph & Telephone Elastisches oberflaechenwellenfilter
US3979702A (en) * 1974-04-08 1976-09-07 The Magnavox Company Apparatus and method for oversampled transducers in acoustic surface wave devices
JPS51158736U (xx) * 1975-06-11 1976-12-17
US4005378A (en) * 1975-11-25 1977-01-25 The United States Of America As Represented By The Secretary Of The Air Force Surface acoustic wave filter
US4030050A (en) * 1974-09-26 1977-06-14 Plessey Handel Und Investments A.G. Acoustic surface wave filters
US4037181A (en) * 1975-03-12 1977-07-19 Murata Manufacturing Co., Ltd. Acoustic surface wave filter devices
US4160219A (en) * 1976-04-26 1979-07-03 Siemens Aktiengesellschaft Transducer electrodes for filters or delay lines utilizing surface wave principles
US4229506A (en) * 1977-09-17 1980-10-21 Murata Manufacturing Co., Ltd. Piezoelectric crystalline film of zinc oxide and method for making same
US4385377A (en) * 1978-01-16 1983-05-24 Texas Instruments Incorporated Pulse position time division surface wave device transmitter
US4458221A (en) * 1981-09-11 1984-07-03 Tokyo Shibaura Denki Kabushiki Kaisha Surface acoustic wave filter
US4463327A (en) * 1981-09-09 1984-07-31 Tokyo Shibaura Denki Kabushiki Kaisha Surface acoustic wave device
US4485364A (en) * 1983-05-17 1984-11-27 Zenith Electronics Corporation Reflection-compensated surface acoustic wave transducer
US4630112A (en) * 1982-11-24 1986-12-16 Hitachi, Ltd. Descrambling apparatus for a television signal
FR2612711A1 (fr) * 1987-03-19 1988-09-23 Thomson Csf Procede de correction d'un dispositif a ondes de surface, notamment pour un filtre dispersif
US5019742A (en) * 1986-03-12 1991-05-28 Northern Telecom Limited Saw device with apodized IDT
DE4227340A1 (de) * 1991-08-22 1993-02-25 Hitachi Ltd Oberflaechenwellen-bauelement und kommunikationseinrichtung, die ein solches bauelement verwendet
US6570471B2 (en) * 2000-09-28 2003-05-27 Fujitsu Limited Surface acoustic wave ladder filter having at least one resonator with electrode finger pairs in inverted orientation
US20140001917A1 (en) * 2012-06-28 2014-01-02 Taiyo Yuden Co., Ltd. Acoustic wave device and method of fabricating the same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2167405B1 (xx) * 1972-01-14 1976-06-11 Thomson Csf

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2759044A (en) * 1950-11-24 1956-08-14 Bell Telephone Labor Inc Beam aperature correction in horizontal and vertical direction
US2922965A (en) * 1956-08-09 1960-01-26 Bell Telephone Labor Inc Aperture equalizer and phase correction for television
US3150275A (en) * 1959-07-17 1964-09-22 Corning Glass Works Sectional transducer
US3310761A (en) * 1963-06-18 1967-03-21 Joseph B Brauer Tapped microwave acoustic delay line
US3376572A (en) * 1966-09-15 1968-04-02 Rca Corp Electroacoustic wave shaping device
US3446975A (en) * 1966-11-07 1969-05-27 Zenith Radio Corp Acousto-electric filter utilizing surface wave propagation in which the center frequency is determined by a conductivity pattern resulting from an optical image

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2759044A (en) * 1950-11-24 1956-08-14 Bell Telephone Labor Inc Beam aperature correction in horizontal and vertical direction
US2922965A (en) * 1956-08-09 1960-01-26 Bell Telephone Labor Inc Aperture equalizer and phase correction for television
US3150275A (en) * 1959-07-17 1964-09-22 Corning Glass Works Sectional transducer
US3310761A (en) * 1963-06-18 1967-03-21 Joseph B Brauer Tapped microwave acoustic delay line
US3376572A (en) * 1966-09-15 1968-04-02 Rca Corp Electroacoustic wave shaping device
US3446975A (en) * 1966-11-07 1969-05-27 Zenith Radio Corp Acousto-electric filter utilizing surface wave propagation in which the center frequency is determined by a conductivity pattern resulting from an optical image

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3755761A (en) * 1971-12-30 1973-08-28 Texas Instruments Inc Surface wave transversal frequency filter
US3845420A (en) * 1973-03-02 1974-10-29 Raytheon Co Surface acoustic wave phase control device
US3855556A (en) * 1973-04-02 1974-12-17 Texas Instruments Inc Selectable frequency bandpass filter
US3979702A (en) * 1974-04-08 1976-09-07 The Magnavox Company Apparatus and method for oversampled transducers in acoustic surface wave devices
DE2531551A1 (de) * 1974-07-15 1976-01-29 Nippon Telegraph & Telephone Elastisches oberflaechenwellenfilter
US4007433A (en) * 1974-07-15 1977-02-08 Nippon Telegraph And Telephone Public Corporation Elastic surface wave filter
US4030050A (en) * 1974-09-26 1977-06-14 Plessey Handel Und Investments A.G. Acoustic surface wave filters
US4037181A (en) * 1975-03-12 1977-07-19 Murata Manufacturing Co., Ltd. Acoustic surface wave filter devices
JPS51158736U (xx) * 1975-06-11 1976-12-17
US4005378A (en) * 1975-11-25 1977-01-25 The United States Of America As Represented By The Secretary Of The Air Force Surface acoustic wave filter
US4160219A (en) * 1976-04-26 1979-07-03 Siemens Aktiengesellschaft Transducer electrodes for filters or delay lines utilizing surface wave principles
US4229506A (en) * 1977-09-17 1980-10-21 Murata Manufacturing Co., Ltd. Piezoelectric crystalline film of zinc oxide and method for making same
US4385377A (en) * 1978-01-16 1983-05-24 Texas Instruments Incorporated Pulse position time division surface wave device transmitter
US4463327A (en) * 1981-09-09 1984-07-31 Tokyo Shibaura Denki Kabushiki Kaisha Surface acoustic wave device
US4458221A (en) * 1981-09-11 1984-07-03 Tokyo Shibaura Denki Kabushiki Kaisha Surface acoustic wave filter
US4630112A (en) * 1982-11-24 1986-12-16 Hitachi, Ltd. Descrambling apparatus for a television signal
US4485364A (en) * 1983-05-17 1984-11-27 Zenith Electronics Corporation Reflection-compensated surface acoustic wave transducer
US5019742A (en) * 1986-03-12 1991-05-28 Northern Telecom Limited Saw device with apodized IDT
FR2612711A1 (fr) * 1987-03-19 1988-09-23 Thomson Csf Procede de correction d'un dispositif a ondes de surface, notamment pour un filtre dispersif
EP0285481A1 (fr) * 1987-03-19 1988-10-05 Thomson-Csf Procédé de correction d'un dispositif à ondes de surface, notamment pour un filtre dispersif
US4916416A (en) * 1987-03-19 1990-04-10 Thomson-Csf Method for the correction of a surface wave device, especially for a reflective array compressor
DE4227340A1 (de) * 1991-08-22 1993-02-25 Hitachi Ltd Oberflaechenwellen-bauelement und kommunikationseinrichtung, die ein solches bauelement verwendet
US6570471B2 (en) * 2000-09-28 2003-05-27 Fujitsu Limited Surface acoustic wave ladder filter having at least one resonator with electrode finger pairs in inverted orientation
US20140001917A1 (en) * 2012-06-28 2014-01-02 Taiyo Yuden Co., Ltd. Acoustic wave device and method of fabricating the same
US9608193B2 (en) * 2012-06-28 2017-03-28 Taiyo Yuden Co., Ltd. Acoustic wave device and method of fabricating the same

Also Published As

Publication number Publication date
FR2040881A5 (xx) 1971-01-22
GB1295909A (xx) 1972-11-08
NL7005390A (xx) 1970-10-20
DE2016109B2 (de) 1978-03-02
NL172810B (nl) 1983-05-16
SE364611B (xx) 1974-02-25
DE2016109C3 (de) 1978-11-30
DE2016109A1 (de) 1970-10-22
NL172810C (nl) 1983-10-17

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