CA1053364A - Surface acoustic wave transmission device and method of manufacturing same - Google Patents
Surface acoustic wave transmission device and method of manufacturing sameInfo
- Publication number
- CA1053364A CA1053364A CA220,121A CA220121A CA1053364A CA 1053364 A CA1053364 A CA 1053364A CA 220121 A CA220121 A CA 220121A CA 1053364 A CA1053364 A CA 1053364A
- Authority
- CA
- Canada
- Prior art keywords
- substrate
- face
- jet
- cut
- waves
- 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
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/42—Piezoelectric device making
Abstract
Abstract of the Disclosure The present invention relates to the manufacture of sur-face acoustic wave transmission devices. The invention provides a method of cutting the edges of surface acoustic wave devices, which consists in directing on to that face designed to propa-gate said waves, a jet of abrasive particles.
Description
: : `
~o~;~3~
The present invention relates to devices designed to propagate surface acoustic waves. These devices generally comprise a substrate cut in a piezo-electric wafer and upon~
which there are deposited electrodes of inter~digitated comb shaped design. ~hese conductive comb shaped structures form, together with the substrate, electromechanical transducers designed to egchange surface acoustic waves, but mustnot,however receive vibrational energy reflected by the substrate edges.
Means which enable the sur~ace waves to be absorbed, can be arranged upon the substrate in order to surround the exchange ;-zone located between the transducers, thus inhibiting the reflection of marginal wa~es. However7 the addition of these absorber means prolongs manufacturing operations and leads to ` a structure which is more difficult to manufacture. In addition, the techniques of cutting the crystal wafer used to manufacture the substrate, may give rise to drawbacks. Cutting bg means of a laser beam is slow and tends to depolarize the crystal. ~he use of a diamond saw results in relatively rapid wear of the cutting tool and is limited to straight line cutting operations.
The use of a wire saw leaves deposits of abrasive material at the surface of the crystal and the transducer comb structures9 and these deposits have to be removed later on.
In order to overcome these drawbacks, -the invention pro-poses that cutting of the crystal should be effected by the use of a jet abrasive particles directed by a noz~le on to that face of the crystal at which the surface waves are to propagate.
The gro~md and smoothed contour which results from this method of cutting; right from the start ensures attenuation of margi-nal reflections due to thescattering which the surface acoustic :...... . . . . . . , . - . . . . . .
waves experience when reaching the scattering contour of the substrate.
~o~;~3~
The present invention relates to devices designed to propagate surface acoustic waves. These devices generally comprise a substrate cut in a piezo-electric wafer and upon~
which there are deposited electrodes of inter~digitated comb shaped design. ~hese conductive comb shaped structures form, together with the substrate, electromechanical transducers designed to egchange surface acoustic waves, but mustnot,however receive vibrational energy reflected by the substrate edges.
Means which enable the sur~ace waves to be absorbed, can be arranged upon the substrate in order to surround the exchange ;-zone located between the transducers, thus inhibiting the reflection of marginal wa~es. However7 the addition of these absorber means prolongs manufacturing operations and leads to ` a structure which is more difficult to manufacture. In addition, the techniques of cutting the crystal wafer used to manufacture the substrate, may give rise to drawbacks. Cutting bg means of a laser beam is slow and tends to depolarize the crystal. ~he use of a diamond saw results in relatively rapid wear of the cutting tool and is limited to straight line cutting operations.
The use of a wire saw leaves deposits of abrasive material at the surface of the crystal and the transducer comb structures9 and these deposits have to be removed later on.
In order to overcome these drawbacks, -the invention pro-poses that cutting of the crystal should be effected by the use of a jet abrasive particles directed by a noz~le on to that face of the crystal at which the surface waves are to propagate.
The gro~md and smoothed contour which results from this method of cutting; right from the start ensures attenuation of margi-nal reflections due to thescattering which the surface acoustic :...... . . . . . . , . - . . . . . .
waves experience when reaching the scattering contour of the substrate.
2 ` ~ i ~336~
., , , `
In accordance with the invention there is provided a surface acoustic wave transmission device comprising : a -~
substrate cut in a wafer and having at least one smooth face , , for propagating said waves, the edge of said substrate located 5 on the trajectory of said waves, being a ground scattering edge '~
obtained from the cutting of said wafer with a jet of a'bra- ' `
sive particles directed on to said smooth face; said ground ~ ' scattering edge having a mean rounded prof'ile fitting together with said smooth face.
The invention likewise relates to a method of manufacturing a surface ~coustic wave device comprising a substrate cut in a wafer having at least one smooth face designed for the propagation ,`' of said waves, the method comprises the steps of cutting, pro- ' filing and grinding the edges of said substrate in one operation 9 '`
-15 by the use of a jet abrasive particles directed on to said smooth face; the point of impact of said jet being displaced . .... . .
in relation to said smooth face in accordance with the cut it , "'', is required to produce. ` , ~or a better understanding of the present invention and `, to show how the same may be carried into effect reference will be made to the ensuring desciption and the attached figures , among which : ' - -- ~ig. 1 is an isometric view of the device in accordance ~, with the invention and of the apparatus usde to cut it; , 2 5 ~ ~ig. 2 is a p3rtial section through the device in accordance with the invention. ~' ~ he invention is concerned with the manufactureof substra~
tes which are capable of transmitting surface acoustlc waves such , ~
as'Rayleigh waves.`~hese substrat'es can be'cut in'piezo-electric ~ ,,' ;' ':
,`~ ' ,, ~ .
., , , `
In accordance with the invention there is provided a surface acoustic wave transmission device comprising : a -~
substrate cut in a wafer and having at least one smooth face , , for propagating said waves, the edge of said substrate located 5 on the trajectory of said waves, being a ground scattering edge '~
obtained from the cutting of said wafer with a jet of a'bra- ' `
sive particles directed on to said smooth face; said ground ~ ' scattering edge having a mean rounded prof'ile fitting together with said smooth face.
The invention likewise relates to a method of manufacturing a surface ~coustic wave device comprising a substrate cut in a wafer having at least one smooth face designed for the propagation ,`' of said waves, the method comprises the steps of cutting, pro- ' filing and grinding the edges of said substrate in one operation 9 '`
-15 by the use of a jet abrasive particles directed on to said smooth face; the point of impact of said jet being displaced . .... . .
in relation to said smooth face in accordance with the cut it , "'', is required to produce. ` , ~or a better understanding of the present invention and `, to show how the same may be carried into effect reference will be made to the ensuring desciption and the attached figures , among which : ' - -- ~ig. 1 is an isometric view of the device in accordance ~, with the invention and of the apparatus usde to cut it; , 2 5 ~ ~ig. 2 is a p3rtial section through the device in accordance with the invention. ~' ~ he invention is concerned with the manufactureof substra~
tes which are capable of transmitting surface acoustlc waves such , ~
as'Rayleigh waves.`~hese substrat'es can be'cut in'piezo-electric ~ ,,' ;' ':
,`~ ' ,, ~ .
3 '' '''` '- , ' .
. , , . . ~ , .
~1[)53364 wafers, in which case electrodes of inter-digitated comb shaped design are used to emit or receive the surface acoustic waves, although the invention is equally applicable to wafers formed o* different materials, in situations where the surface acoustic waves are excited by other electromechanical transducers, possibly associated with coupling prisms which effect suitable conversion of the vibra-tional modes.
In ~ig. 1, by way of non-limitati~e example there can be seen a piezo-electric wafer of lithium niobate at the surface 8 of which there have been deposited two sets of elec-trodes 10 of inter-digitated comb shaped design. These electrodes form, with the piezo-electric wafer, two electromechanical trans-ducers capable of e2changing surface acoustic waves. Since the teeth of the comb structures are orientated in the direction OX on the face 8, the propagation of the waves takes place in a directional fashion, in fact in the direction OY of the face 8, perpendicular to OX; the axis OZ is perpendicular to the face 8.
~he cutting of the wafer in accordance with the axes OX and OY
makes it possible to produce a complete surface acoustic wa~e device which can be utilised, as required, either as a delay line or a filter. ~y multiplying the numbers of electrode deposits and by carrying out other cutting operations on the wafer, several similar devices can be manufactured.
~he apparatus used to cut the wafer is essentially constitu-ted by a base 1 to which there are attached guidebars carryinga mo~ing carriage 3. One of the guide bars 4 can be screwed over its length so that by arranging for a motor 15 ~o rotate it, a straight-line displacement on the part of the carriage parallel to the axis OY is produced. ~he-carriage 3--is itself equipped with supporting bars 5 upon which there can slide a table whose rectilinear displacement parallel to the axis OX is controlled likewise by a motor 14. On the table 67 the wafer ~or cutting is ~ixed by means of spacers 7 located outside the path o~ cut. A bracket 2 fi~ed to the base 1 carries at its free end a nozzIe 12 with an agis OZ, and, around same, a ,:
, ~ os33~4 suction head 11. r~he nozzle 12 is connected to a reservoir of abrasive particles through which gas flow is made to pass in order to entrain said particles. At the exit of the nozzle 12, a jet t3 of abrasive particles is produced which particles, a~ter having struck the face 8 of the wa-fer being cut, are sucked away by the suction head 11 which communicates with an exhauster.
By way of example, the jet 13 will be a jet o~ compressed air emitted by a nozzle 12 having a bore si~e of 2/10 of a millimetre. ~his jet carries said particles having a size of 50 microns and is used to cut a lithiu~ niobate substrate ~,~t~
designed to transmit surface acoustic waves of frequencies ranging between 30 and 40 MHz. The control of the ~ and Y
displacement of the table 6 makes it possible to choose any ~-required line of cut in the plane of the face 8. The speed of cut is i~` the order of 2 to 10 mm per minute-depending upon the nature and thickness of the wafer.
Without departing from the scope of the invention9 it is equally possible to use a fixed table and device for projecting the abrasive particles which is mobile, in two directions per-pendicular to the jet axis. It is equally possible to incline the jet in relation to the face 8 of the wafer being cut but in the case of normal incidence, the profile of the cut is sgmmetrical.
The advantage of the cutting tech~ique in accordance with the invention is not solely that it makes it possible to follow an undulating contour automatically and uninterruptedly. It `
also has to be borne in mind that cutting takes place in the dry and without heating the substrate. It is therefore not necessary to clean the surface of the substrate after cutting and the risk of fracture or modification of the electromechani-cal characteristics of the substrate, is avoided.
An important advantage o~ the method of cutting proposed accordance with the invention lies in the surface finish and profile o~ the cut edges of the substrate. The cut substrate . . .
,~
-. : . , 3~ ~
has been shown in partial section in Fig. 2, along with the nozzle 12 and the sand jet 1~. It will be seen that the mean profile of the cut edge of the substrate has a radiused form~which merges with the face 8 through which the surface acoustic waves are transmitted. In addition to its radiused shape, the edge of the substrate has a ground zone 17 the grain of which is related to the grain size of the abrasive particles used. This ,', ground zone 17 ex,tends down to the base of the cut and joins the surface 8 at a point which depends upon the angle of disper~ '~
sion of the abrasive par-ticles in the jet 13. A protective screen 16 can be provided during the cutting operation in ' order to prevent stray particles from reaching the electrodes 10 on the face 8.
It surface waves are transmitted towards the edge 17, moving from the left to right along the face 8, at the ground zone they experience intense scattering in all directions, so that they are not reflected. If the size of the protuberances of high-spots in the ground zone, is of the same order of magnitude as the wavelength of the surface waves, then a ' ' a distance of only a few wavelengths is sufficient to substan-tially scatter the vibrational energy. The attenuation of the surface waves is thus very effectively ensured mainly by the '' use of the sand jet for the cutting operation.
~he attenuation of the surface acoustic waves 'by the edges cut using the sand jet, is an effective advantage if the cut edges are located in the path of the sur~ace wa~es. C,ertain edges may not be touched by the waves, due to the directional nature of the vibrational radiation emitted~by the transducers.
~owever, even if the-advantage pertaining to echo attenuation is not exploited over the whole length of a cut, it must be borne in mind that the method of cutting in accordance with the invention ne~ertheless secures the other advantages already re~erred to eerlier.
6 , 1C)533~
It goes without saying that cutting by the use of a sand jet can be carried out simultaneously by means of two jets designed to meet one another and by displacing the wafer at the point of intersection of the two jets. In this case, two nozzles must be provided, with converging axes, the nozzles being assembled at the ends of a fork; the mounting table must ~hen be opened out in order to pass one of the two jets. This solution makes it possible to increase the rate o~ cut. It also makes it possible to achieve attenuation o- surface elastic waves in situations where the latter are intended to propagate along both faces of the wafer being cut. The u-tilisation of abrasive particles of elongated section in the direction of cut, is conceivable in the case of straight-line cuts. ~y changing the alignement of the elongated $ection of the jet in relation to the direction oP cut,-it is posslble to arbitrari-ly wlden.the area subjected to abrasion. `
~ ., ' ~ .
': ~
" ' .
. .
.
- ` , : .
' `
.
. , , . . ~ , .
~1[)53364 wafers, in which case electrodes of inter-digitated comb shaped design are used to emit or receive the surface acoustic waves, although the invention is equally applicable to wafers formed o* different materials, in situations where the surface acoustic waves are excited by other electromechanical transducers, possibly associated with coupling prisms which effect suitable conversion of the vibra-tional modes.
In ~ig. 1, by way of non-limitati~e example there can be seen a piezo-electric wafer of lithium niobate at the surface 8 of which there have been deposited two sets of elec-trodes 10 of inter-digitated comb shaped design. These electrodes form, with the piezo-electric wafer, two electromechanical trans-ducers capable of e2changing surface acoustic waves. Since the teeth of the comb structures are orientated in the direction OX on the face 8, the propagation of the waves takes place in a directional fashion, in fact in the direction OY of the face 8, perpendicular to OX; the axis OZ is perpendicular to the face 8.
~he cutting of the wafer in accordance with the axes OX and OY
makes it possible to produce a complete surface acoustic wa~e device which can be utilised, as required, either as a delay line or a filter. ~y multiplying the numbers of electrode deposits and by carrying out other cutting operations on the wafer, several similar devices can be manufactured.
~he apparatus used to cut the wafer is essentially constitu-ted by a base 1 to which there are attached guidebars carryinga mo~ing carriage 3. One of the guide bars 4 can be screwed over its length so that by arranging for a motor 15 ~o rotate it, a straight-line displacement on the part of the carriage parallel to the axis OY is produced. ~he-carriage 3--is itself equipped with supporting bars 5 upon which there can slide a table whose rectilinear displacement parallel to the axis OX is controlled likewise by a motor 14. On the table 67 the wafer ~or cutting is ~ixed by means of spacers 7 located outside the path o~ cut. A bracket 2 fi~ed to the base 1 carries at its free end a nozzIe 12 with an agis OZ, and, around same, a ,:
, ~ os33~4 suction head 11. r~he nozzle 12 is connected to a reservoir of abrasive particles through which gas flow is made to pass in order to entrain said particles. At the exit of the nozzle 12, a jet t3 of abrasive particles is produced which particles, a~ter having struck the face 8 of the wa-fer being cut, are sucked away by the suction head 11 which communicates with an exhauster.
By way of example, the jet 13 will be a jet o~ compressed air emitted by a nozzle 12 having a bore si~e of 2/10 of a millimetre. ~his jet carries said particles having a size of 50 microns and is used to cut a lithiu~ niobate substrate ~,~t~
designed to transmit surface acoustic waves of frequencies ranging between 30 and 40 MHz. The control of the ~ and Y
displacement of the table 6 makes it possible to choose any ~-required line of cut in the plane of the face 8. The speed of cut is i~` the order of 2 to 10 mm per minute-depending upon the nature and thickness of the wafer.
Without departing from the scope of the invention9 it is equally possible to use a fixed table and device for projecting the abrasive particles which is mobile, in two directions per-pendicular to the jet axis. It is equally possible to incline the jet in relation to the face 8 of the wafer being cut but in the case of normal incidence, the profile of the cut is sgmmetrical.
The advantage of the cutting tech~ique in accordance with the invention is not solely that it makes it possible to follow an undulating contour automatically and uninterruptedly. It `
also has to be borne in mind that cutting takes place in the dry and without heating the substrate. It is therefore not necessary to clean the surface of the substrate after cutting and the risk of fracture or modification of the electromechani-cal characteristics of the substrate, is avoided.
An important advantage o~ the method of cutting proposed accordance with the invention lies in the surface finish and profile o~ the cut edges of the substrate. The cut substrate . . .
,~
-. : . , 3~ ~
has been shown in partial section in Fig. 2, along with the nozzle 12 and the sand jet 1~. It will be seen that the mean profile of the cut edge of the substrate has a radiused form~which merges with the face 8 through which the surface acoustic waves are transmitted. In addition to its radiused shape, the edge of the substrate has a ground zone 17 the grain of which is related to the grain size of the abrasive particles used. This ,', ground zone 17 ex,tends down to the base of the cut and joins the surface 8 at a point which depends upon the angle of disper~ '~
sion of the abrasive par-ticles in the jet 13. A protective screen 16 can be provided during the cutting operation in ' order to prevent stray particles from reaching the electrodes 10 on the face 8.
It surface waves are transmitted towards the edge 17, moving from the left to right along the face 8, at the ground zone they experience intense scattering in all directions, so that they are not reflected. If the size of the protuberances of high-spots in the ground zone, is of the same order of magnitude as the wavelength of the surface waves, then a ' ' a distance of only a few wavelengths is sufficient to substan-tially scatter the vibrational energy. The attenuation of the surface waves is thus very effectively ensured mainly by the '' use of the sand jet for the cutting operation.
~he attenuation of the surface acoustic waves 'by the edges cut using the sand jet, is an effective advantage if the cut edges are located in the path of the sur~ace wa~es. C,ertain edges may not be touched by the waves, due to the directional nature of the vibrational radiation emitted~by the transducers.
~owever, even if the-advantage pertaining to echo attenuation is not exploited over the whole length of a cut, it must be borne in mind that the method of cutting in accordance with the invention ne~ertheless secures the other advantages already re~erred to eerlier.
6 , 1C)533~
It goes without saying that cutting by the use of a sand jet can be carried out simultaneously by means of two jets designed to meet one another and by displacing the wafer at the point of intersection of the two jets. In this case, two nozzles must be provided, with converging axes, the nozzles being assembled at the ends of a fork; the mounting table must ~hen be opened out in order to pass one of the two jets. This solution makes it possible to increase the rate o~ cut. It also makes it possible to achieve attenuation o- surface elastic waves in situations where the latter are intended to propagate along both faces of the wafer being cut. The u-tilisation of abrasive particles of elongated section in the direction of cut, is conceivable in the case of straight-line cuts. ~y changing the alignement of the elongated $ection of the jet in relation to the direction oP cut,-it is posslble to arbitrari-ly wlden.the area subjected to abrasion. `
~ ., ' ~ .
': ~
" ' .
. .
.
- ` , : .
' `
.
Claims (10)
1. A surface acoustic wave transmission device compri-sing a substrate having at least one smooth face for propagating said waves, the edge of said substrate located on the trajectory of said waves, being a ground scattering edge resulting from cut-ting said edge in a wafer; a jet of abrasive particles directed on to said smooth face; the mean profile of said ground scattering edge having a radius form merging with said smooth face.
2. A transmission device as claimed in claim 1, wherein said substrate is cut in a wafer of piezo-electric material and coated with at least two sets of electrodes of inter-digitated comb shaped design, designed to emit and receive said surface acoustic waves.
3. A transmission device as claimed in claim 2, wherein said sets of electrodes are located on one and the same face of said substrate.
4. A transmission device as claimed in claim 2, wherein one of said sets is located on one main face of said substrate; the other of said sets is located on the other main face of said subs-trate, opposite said first main face; said main faces being connec-ted to one another at one end of the substrate, by an edge whose surface is not ground whereby ensuring continuity of transmission of said surface elastic waves from one to the other of said main faces.
5. A method of manufacturing a surface acoustic wave device comprising a substrate cut in a wafer having at least one smooth face designed to propagate said waves, said method comprising the steps of cutting, profiling and grinding the edges of said subs-trate in a single operation using jet of abrasive particles reach ing said smooth face at a zone of impact; said jet being displaced in relation to said smooth face for causing said zone of impact to follow within said smooth surface the line of cut which is to be produced.
6. Method as claimed in claim 5, wherein cutting is effected by means of two jets having converging axes and respecti-vely reaching said smooth face and a face of said substrate oppo-site said smooth face at two zones of impact; said wafer being displaced in relation to the point of intersection of said axes for causing said zones of impact to follow said line of end.
7. Method as claimed in claim 5, wherein said jet is directed perpendicularly on to said smooth face.
8. Method as claimed in claim 5, wherein the section of said jet is substantially circular.
9. Method as claimed in claim 5, wherein the section of said jet is elongated and can be orientated in relation to the di-rection of cut.
10. Method as claimed in claim 5, wherein said abrasive particles are sand particles.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7405202A FR2261653B1 (en) | 1974-02-15 | 1974-02-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1053364A true CA1053364A (en) | 1979-04-24 |
Family
ID=9134970
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA220,121A Expired CA1053364A (en) | 1974-02-15 | 1975-02-14 | Surface acoustic wave transmission device and method of manufacturing same |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4051448A (en) |
| JP (1) | JPS5815971B2 (en) |
| CA (1) | CA1053364A (en) |
| DE (1) | DE2505818A1 (en) |
| FR (1) | FR2261653B1 (en) |
| GB (1) | GB1498646A (en) |
| IT (1) | IT1029696B (en) |
| YU (1) | YU32075A (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2458901A1 (en) * | 1979-06-06 | 1981-01-02 | Thomson Csf | MAGNETOSTATIC WAVE DEVICE HAVING ATTENUATING MEANS AND METHOD FOR MANUFACTURING THE SAME |
| CA1252711A (en) * | 1984-09-27 | 1989-04-18 | Richard A. Herrington | Ultra-high pressure abrasive jet cutting of glass |
| BR8604330A (en) * | 1985-09-16 | 1987-05-12 | Libbey Owens Ford Co | PROCESS AND APPLIANCE FOR GLASS CUTTING WITH RADIAL EDGE THROUGH ABRASIVE FLUID JET |
| JPH02269058A (en) * | 1989-03-14 | 1990-11-02 | Seiko Epson Corp | Liquid drop jet device by use of rayleigh mode surface acoustic wave |
| US5022047A (en) * | 1989-08-07 | 1991-06-04 | Omnipoint Data Corporation | Spread spectrum correlator |
| US5016255A (en) * | 1989-08-07 | 1991-05-14 | Omnipoint Data Company, Incorporated | Asymmetric spread spectrum correlator |
| US5499265A (en) * | 1989-08-07 | 1996-03-12 | Omnipoint Data Company, Incorporated | Spread spectrum correlator |
| EP0540664A4 (en) * | 1990-07-23 | 1993-06-09 | Omnipoint Corporation | Sawc phase-detection method and apparatus |
| US5081642A (en) * | 1990-08-06 | 1992-01-14 | Omnipoint Data Company, Incorporated | Reciprocal saw correlator method and apparatus |
| WO1992007434A1 (en) | 1990-10-23 | 1992-04-30 | Omnipoint Corporation | Method and apparatus for establishing spread spectrum communications |
| US5402413A (en) * | 1991-04-08 | 1995-03-28 | Omnipoint Corporation | Three-cell wireless communication system |
| AU2140092A (en) * | 1991-05-13 | 1992-12-30 | Omnipoint Corporation | Dual mode transmitter and receiver |
| US5285469A (en) | 1991-06-03 | 1994-02-08 | Omnipoint Data Corporation | Spread spectrum wireless telephone system |
| WO1993012597A1 (en) * | 1991-12-16 | 1993-06-24 | Omnipoint Corporation | Spread-spectrum data publishing system |
| GB2264659B (en) * | 1992-02-29 | 1995-05-24 | Rolls Royce Plc | Abrasive fluid jet machining |
| US5355389A (en) * | 1993-01-13 | 1994-10-11 | Omnipoint Corporation | Reciprocal mode saw correlator method and apparatus |
| EP0622897B1 (en) * | 1993-04-28 | 2001-03-07 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave device and method of manufacturing the same |
| DE102014110405A1 (en) | 2014-07-23 | 2016-01-28 | Epcos Ag | Piezoelectric transformer |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3781721A (en) * | 1972-11-30 | 1973-12-25 | Hughes Aircraft Co | Acoustic surface wave device eliminating spurious end reflections |
| FR2212080A5 (en) * | 1972-12-22 | 1974-07-19 | Thomson Csf | |
| JPS5418544B2 (en) * | 1973-01-20 | 1979-07-09 | ||
| US3887887A (en) * | 1973-12-28 | 1975-06-03 | Texas Instruments Inc | Acoustic bulk mode suppressor |
-
1974
- 1974-02-15 FR FR7405202A patent/FR2261653B1/fr not_active Expired
-
1975
- 1975-02-12 GB GB6059/75A patent/GB1498646A/en not_active Expired
- 1975-02-12 DE DE19752505818 patent/DE2505818A1/en not_active Ceased
- 1975-02-12 IT IT48127/75A patent/IT1029696B/en active
- 1975-02-12 YU YU00320/75A patent/YU32075A/en unknown
- 1975-02-14 US US05/550,036 patent/US4051448A/en not_active Expired - Lifetime
- 1975-02-14 JP JP50018684A patent/JPS5815971B2/en not_active Expired
- 1975-02-14 CA CA220,121A patent/CA1053364A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1498646A (en) | 1978-01-25 |
| YU32075A (en) | 1982-05-31 |
| IT1029696B (en) | 1979-03-20 |
| JPS50120291A (en) | 1975-09-20 |
| DE2505818A1 (en) | 1975-08-21 |
| JPS5815971B2 (en) | 1983-03-29 |
| US4051448A (en) | 1977-09-27 |
| FR2261653A1 (en) | 1975-09-12 |
| FR2261653B1 (en) | 1978-01-06 |
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