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WO1990005409A1 - Dispositifs a ondes acoustiques de surface - Google Patents

Dispositifs a ondes acoustiques de surface Download PDF

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Publication number
WO1990005409A1
WO1990005409A1 PCT/AU1989/000470 AU8900470W WO9005409A1 WO 1990005409 A1 WO1990005409 A1 WO 1990005409A1 AU 8900470 W AU8900470 W AU 8900470W WO 9005409 A1 WO9005409 A1 WO 9005409A1
Authority
WO
WIPO (PCT)
Prior art keywords
fingers
acoustic wave
transponder
surface acoustic
transducer
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.)
Ceased
Application number
PCT/AU1989/000470
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English (en)
Inventor
Richard Vaughan
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.)
COSMO HOLDINGS PTY Ltd
Original Assignee
COSMO HOLDINGS PTY Ltd
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 COSMO HOLDINGS PTY Ltd filed Critical COSMO HOLDINGS PTY Ltd
Publication of WO1990005409A1 publication Critical patent/WO1990005409A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/0672—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with resonating marks
    • G06K19/0675—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with resonating marks the resonating marks being of the surface acoustic wave [SAW] kind
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/755—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using delay lines, e.g. acoustic delay lines
    • 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
    • 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
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves

Definitions

  • the present invention relates to passive surface acoustic wave (SAW) transponders or tags for use in remote identification systems.
  • SAW passive surface acoustic wave
  • Known transponders of this kind comprise a substrate of piezoelectric material having coded information inscribed thereon, serving to receive electromagnetic energy, convert it to acoustic energy, store the converted energy for a period of time, re-convert the stored energy to electromagnetic form and re-transmit the electromagnetic energy.
  • These tags thus produce a reply signal in response to the interrogation signal from the remote interrogator.
  • the reply signal is processed to recover the code unique to the interrogated tag.
  • Passive label interrogation systems employing SAW transponders are disclosed in Cole and Vaughan US patents 3,706,094, 3,755,803, 4,058,217 4,399,441. These systems incorporate a radio frequency transmitter capable of transmitting pulsed CW electromagnetic energy. Interrogation pulses are received at the remote antenna of a passive label and applied to a "launch" interdigitated transducer (IDT) on the surface of a piezoelectric substrate. This transducer converts the electrical energy received from the antenna into acoustic energy in the form of a surface acoustic wave or SAW that propagates on the substrate along a defined acoustic path.
  • IDT interdigitated transducer
  • Groups of "coding" or “tap” IDT's are arranged at intervals along this path to convert the SAW back to electrical energy and in so doing to impart either an amplitude or phase coding to the signal that is then retransmitted via the antenna to the interrogator receiver.
  • the antenna is a common antenna in the sense of acting both to receive and to re-transmit to the interrogator receiver.
  • surface acoustic waves will simultaneously be launched from the tap IDT's, but as the linear SAW delay line behaves in a reciprocal fashion, these waves will sum constructively at the launch transducer effectively to double the overall delay line response.
  • Another form of interrogator uses a FMCW (frequency modulated continuous wave) signal.
  • FMCW frequency modulated continuous wave
  • This technique is described in Australian patent specification 444,838 and in US patents 4,604,623, 4,605,929, 4,620,191, 4,623,890, 4,625,207 and 4,625,208 assigned to X-Cyte Corporation.
  • This form of receiver utilises a simple homodyne process whereby the return signal is mixed with the originally transmitted "chirp" signal in a four quadrant multiplier to generate a low audio frequency baseband signal.
  • a range of beat frequencies are generated because of the different delays of the transducers on the SAW delay line label.
  • a different audio frequency is recovered for each of the elements of the encoding pattern and the relative amplitude and/or phase of these frequency elements represents the code pattern of that particular label.
  • the encoded information is recovered by performing a spectral analysis of the baseband received signal.
  • the SAW delay line "chips" proposed in the prior art are produced on piezoelectric wafers of lithium niobate or quartz.
  • the wafers are made from thin slices sawn from a synthetic crystal grown in an autoclave under rigidly controlled conditions of pressure, temperature and purity. Angles of cutting relative to the axes of the crystal determine the combination of properties in the wafer. Because of constraints on growing the synthetic crystals, wafer slices are limited to approximately 5" in diameter or circumscribed area.
  • the wafers are mirror polished and then covered with a layer of aluminium by vapour deposition.
  • This thin metal layer is coated with a photosensitive resist which is then selectively exposed to form the desired transducer electrode pattern by means of high precision photolithography.
  • the exposed resist and the underlying metal are then removed.
  • the critical step of exposing the resist is carried out by a well-known semiconductor mask-making process using step-and-repeat cameras. This involves using a pattern generator to produce reticles, each of which is a photographic copy (much like a photographic negative) of the layout of one chip, usually at a scale 10X the final chip size. For every chip with a different code a different and very accurate reticle must be produced.
  • a lx master mask is generated using a step-and-repeat camera held on a movable stage. Each plate exposure is a ten times photoreduction of one lOx reticle. Between exposures the stage is moved by a precise amount to the next chip position, the reticle is changed to provide the pattern for the next and differently coded chip, and the plate is * exposed to transfer the chip pattern to the master mask. This process is repeated until the complete master mask area has been covered with differently coded SAW chips.
  • the master mask is used to contact print one or more working masks, which are used to contact print or expose resist on a metallised wafer. It will be clear that a different master mask is required for each wafer in order to make differently coded chips.
  • a lOx reduction direct-step-on-wafer camera is used directly to expose the resist on the metallised wafer. This eliminates the intermediate step of preparing a master mask, but still requires the lOx reticle to be changed to provide the pattern for the next and differently coded chip. It will be appreciated that a different lOx reticle is still required for each and every differently coded chip. The cost of these reticles is still a prohibitive factor in the cost of the chips themselves.
  • the unwanted metallisation is selectively etched away.
  • the number of high precision lOx reticles may be reduced by using a second process uniquely to code a number of chips produced from the same reticle.
  • This process may comprise a second photographic exposure, at a much lower resolution than that of the lOx reticle, before etching, or the use of some cutting means such as a laser trimmer after the chip has been manufactured.
  • the number of lOx reticles required is reduced by the number of unique codes that can be produced by such a secondary process for each original reticle.
  • X-Cyte Corporation Australian patent 564,844 describes one method of reducing the number of reticles and master masks. In this method delay pads insert a selectable coding delay between the transducer elements. This allows a single reticle to be used to make the master mask, which is then used to generate all wafers. A subsequent cutting operation of lower precision is then used to trim the delay pads for each chip, thus generating unique codes.
  • This technique has the disadvantage that it is applicable only to piezoelectric materials with a high piezoelectric coupling constant, such as lithium niobate, as only such materials allow sufficiently small delay pads.
  • piezoelectric materials with a low coupling coefficient, such as quartz or zinc oxide the length required for the delay pads would exceed the distance between the coding transducers.
  • many wafers can be made from a single master mask, and the master mask is made from a single reticle.
  • the tags of the present invention incorporate novel features of transducer layout.
  • the finished wafers are divided into chips which are hermetically sealed, antennas are connected, and the assembly packaged to produce the final tag. These can be costly operations, and the need exists for an improved approach to the packaging process.
  • the present invention provides methods for hermetic sealing and antenna connection which reduce the cost of these operations.
  • a principle object of the present invention is to provide an approach to the design and manufacture of such transponders which will enable reductions in manufacturing and production costs.
  • the present invention resides in a surface acoustic wave transponder comprising a plurality of tap transducers in contact with a piezoelectric material, means for the reception of an interrogating signal, means transmitting said interrogating signal as a surface acoustic wave in said material and means for retransmitting said interrogating signal modified by said tap transducers, said retransmitting means including first and second signal transmission means connected to each tap transducer, each tap transducer comprising a first set of electrically interconnected parallel fingers and a second set of electrically interconnected parallel fingers interdigitated with the fingers of the first set, characterised in that each said set of fingers is selectively connectable to one or the other of said first and second transmission means.
  • the fingers of each set are respectively connected to first and second conductive path means, and these path means are connected by interruptable connection means to each of the first and second transmission means.
  • the invention resides in a method of encoding such a transponder, comprising the steps of selectively interrupting said connection means soeh that the first set of fingers of a given tap transducer are connected to a selected one of the first and second signal transmission means and the second set of fingers is connected to the other of said signal transmission means, thereby determining the phase of the connection of that tap transducer with said transmission means.
  • a SAW transponder comprising a plurality of tap transducers in contact with a piezoelectric material, means for the reception of an interrogating signal, means transmitting said interrogating signal as a surface acoustic wave along said surface and means for retransmitting said interrogating signal modified by said tap transducers, said retransmitting means including first and second signal transmission means connected to each tap transducer, each tap transducer comprising a first set of electrically interconnected parallel fingers and a second set of electrically interconnected parallel fingers interdigitated with the fingers of the first set, characterised in that the location of the edges of the fingers of each transducer is chosen in relation to the wave length of the surface acoustic wave such that surface acoustic wave reflections f om said edges cancel.
  • a transponder is characterised in that the fingers are located at such intervals along the path of the surface acoustic wave that reflections from their edges cancel.
  • the invention resides in a SAW transponder comprising a plurality of tap transducers in contact with a piezoelectric material, means for the reception of an interrogating signal, means transmitting said interrogating signal as a surface acoustic wave along said surface and means for retransmitting said interrogating signal modified by said tap transducers, said retransmitting means including first and second signal transmission means connected to each tap transducer, each tap transducer comprising a first set of electrically interconnected parallel fingers and a second set of electrically interconnected parallel fingers interdigitated with the fingers of the first set, characterised in that a group of fingers of at least one of said tap transducers is displaced in the path of the surface acoustic wave so as to be in phase opposition to another group of fingers of the same transducer.
  • the invention provides a SAW transponder comprising a plurality of tap transducers in contact with a piezoelectric material at regular nominal spacings of surface acoustic wave path lengths, means* for the reception of an interrogating signal, means transmitting said interrogating signal as a surface acoustic wave along said surface and means for retransmitting said interrogating signal modified by said tap transducers, characterised in that a further transducer is provided, spaced by a known surface acoustic wave path length from said tap transducers.
  • the invention resides in a method of manufacturing surface acoustic wave transponders, each consisting of a layer of metallisation on a piezoelectric substrate, the method comprising the steps of applying said metallisation over an area as a repetitive pattern of individual transponder patterns, attaching a cover plate over said area, and subsequently cutting through said cover plate and said substrate in orthogonal directions to separate individual transponders.
  • the invention resides in a method of manufacturing a plurality of surface acoustic wave transponders each consisting of a layer of metallisation in contact with a piezoelectric substrate, the method comprising the steps of producing said metallisation over an area as a repetitive pattern of individual transponder patterns, attaching a transponder cover plate over each transponder pattern, and subsequently cutting through said substrate in orthogonal directions to separate individual transponders.
  • the invention resides in a surface acoustic wave transponder consisting of a layer of metallisation in contact with a piezoelectric substrate and having a contact region at at least one end, a cover plate being attached over said metallisation, characterised in that each cover plate is provided with contact regions opposed to the contact regions of the transponders and extending beyond them.
  • Figure 1 is a schematic plan view showing the layout of a transponder chip incorporating the present invention
  • Figure 2 is a detailed view of the metallisation pattern of a single transducer
  • Figure 3 illustrates a relatively phase shifted transducer
  • Figure 4 illustrates a transducer modulated in amplitude relative to that of Figure 2;
  • Figure 5 is a schematic isometric view of portion of the chip
  • Figure 6 is a schematic cross section of the chip illustrated in Figure 6;
  • FIG. 7 illustrates an alternative transducer structure
  • Figure 8 is a fragmentary plan view of a metallised substrate.
  • Figure 9 is a fragmentary bottom plan view of a cover plate.
  • FIGS. 10 (a) to (d) illustrate an economical tag construction according to a preferred form of the invention:
  • FIG. 1 The general layout of a tag incorporating the present invention is shown in Fig. 1.
  • a substrate 10 of piezoelectric material has printed thereon busbars 11 and 12, which are connected respectively to a centre fed dipole antenna (not shown) .
  • busbars 11 and 12 From the busbars 11 and 12 interdigitated fingers of conductive material project to provide a launch transducer 13 and a series of encoding tap transducers 14.
  • the returned phase information from each tap transducer on the tag is presented to the signal analysis unit as a unique frequency.
  • the signal returned by a complete tag is thus the vector sum of the signals returned by each individual tap transducer, and is equivalent to a comb line spectrum, with the number of frequency peaks corresponding to the number of tap transducers on the label and with the amplitude and relative phase of these peaks corresponding to the amplitude and phase encoded information of the delay line label.
  • the homodyne demodulated received signal is sampled at baseband by an analogue-to-digital converter. This sampled signal is then analysed by a discrete Fourier transform which separates the returned frequencies into discrete frequency bins or channels. The phase differences or amplitude ratios between these bins then becomes the tag code. If the comb line spectrum derived from the tag return does not align with the DFT analysis channels then energy from one comb line will incorrectly be assigned to an adjacent channel. This misalignment will cause inter-symbol interference between analysis channels and will degrade the readability of the tag. Misalignment can be caused by a tag being at an unexpected range, or by a Doppler shift due to a tag's velocity relative to the interrogator.
  • a separate "marker" tap transducer 15 This transducer is located as close as possible to the encoding transducers 14 but far enough away to allow discrimination of the alignment and encoding responses under conditions of severe inter-symbol interference. In the preferred embodiment this marker transducer is located three channel spacings before the encoding transducers. The launch transducer is not used for this purpose because its response is swamped by low frequency environmental clutter, and it is too far from the encoding transducers to allow accurate alignment.
  • the fingers are located along the acoustic wave path at such intervals that successive leading and trailing edges of the interdigitated fingers are respectively separated by a distance which is equal to one third of the wave length of the SAW. With equal mark space ratio, the finger width will thus be ⁇ /6.
  • each set of three successive fingers reflects a proportion of energy summing to zero, viz.,
  • ⁇ is a phase angle dependent on the finger width and being nominally equal to 60° for ⁇ /6 wide fingers having a nominally equal mark-space ratio.
  • the spacing also allows satisfactory coupling between the transducers and the SAW at the fundamental frequency of the signal.
  • the pattern of polarity of successive transducer fingers must also be chosen.
  • the fingers should be connected to the busbars 11 and 12 in the pattern illustrated in Figs. 2 to 4, if the most efficient coupling is to be achieved.
  • the polarity pattern of the fingers can be examined by plotting the stepwise approximation of the electric potential due to the fingers, and, with a knowledge of the relationship between piezoelectric displacement and electric field for the substrate material, using a Fourier transform to derive the fundamental sine wave.
  • the most efficient pattern is that which maximizes the amplitude of this fundamental sine wave.
  • the polarity pattern of the fingers for ⁇ /3 spacing repeats in sections 2 in length, and consists of phase-reversed left and right half-sections each one wavelength long. This structure maximizes the amplitude of the fundamental frequency sine wave. Other patterns, such as repeating left half-sections, will produce a fundamental frequency sine wave of less amplitude.
  • the number of fingers used in the transducer will preferably be chosen to be an integral multiple of the number of fingers in a section. In the case of ⁇ /3 spacing, the preferred number of fingers will therefore be an integral multiple of 6. While in this way SAW reflections generated at transducer discontinuities can be reduced or cancelled, it will be realised that surface acoustic waves arising from electrical regeneration at the transducers must also be controlled in a practical label by, for example and depending on the strength of the piezoelectric coefficient of the substrate, the number of fingers used for transducers and/or by the electrical impedance loading shunted across the busbars 11 and 12 of the delay line.
  • each "coding bus” 16 and 17 is connected to the opposite main busbar 11 or 12 by tracks 20 and respective bridges 21 and 22.
  • each coding bus can be connected to either busbar 11 or busbar 12 by cutting the appropriate cutting bridges.
  • cutting the bridges 21 and 22 produces an IDT at relative 0 degrees
  • cutting the bridges 18 and 19 produces an IDT at relative 180 degrees.
  • the flip connecting tracks 20 pass across the active SAW region. It is of course desirable to minimise the disturbing effect of the flip connections crossing the active SAW region.
  • the two major sources of such disturbance are reflections of the acoustic wave at the boundary discontinuities between the metallisation and the piezoelectric material, and the mass loading effect of the metallisation upon the piezoelectric material.
  • the boundary discontinuities can be minimised by correct choice of the dimension X (Fig. 2), representing the interval by which the elements are spaced along the acoustic path.
  • the dimension X is a function of the number of discontinuities across the active region.
  • Fig. 3 there are 3 leading edge discontinuities and 3 trailing edge discontinuities due to the three elements which cross the SAW active region.
  • leading edge discontinuity has been nulled.
  • trailing edges by spacing the trailing edges at multiples of (3n+l) ⁇ /3 we can null the trailing edge discontinuities.
  • the leading and trailing edges have again been treated separately as this removes the need to consider whether a trailing edge discontinuity has the same properties as a leading edge discontinuity or not.
  • the connecting track may consist of more than or less than three elements, and the above approach can be generalised correspondingly.
  • the leading edges and independently the trailing edges
  • the connecting tracks 20 consist of three elements of equal mark-space ratio.
  • elements which are of substantially greater width than the space between them For example, three elements may be provided, each of A width, spaced apart by ⁇ /3, so that successive elements are located at 4A/3 intervals.
  • the techniques which can be used selectively to remove the cuttable bridges include chemical etching or the use of a photoplotter to define the bridges to be etched.
  • Alternative approaches include laser scribing or electrical fusion, whereby contacts are provided on both the coding buses and the chip busbars to allow sufficient current to pass through the coding bridges to cause them to become open circuit.
  • the transducer shown in Fig. 2 is placed at a nominal reference position, while the Type B (90/270) transducer shown in Fig. 3 is displaced a quarter of a wavelength either towards or away from the launch transducer. Further extensions can be made to this principle to provide other types of transducers, at more phase angles and/or with different amplitude responses, to allow extension from quad phase coding to some higher level of coding.
  • the launch transducer 13 is of well known IDT design for generating a surface acoustic wave.
  • the placement of subsequent transducers is in units of a given separation. In the preferred embodiment this separation is in units of delay as realised as distance on the SAW chip. Depending on the bandwidth which is allowed for the interrogating and response signals, this may represent the distance a SAW wave travels on the surface in a period of the order of 80 to 160 nsecs.
  • the alignment transducer 15 is placed many units of separation away from the launch transducer 13 (for example approximately 960 nsecs).
  • the alignment transducer 15 is of well known IDT design.
  • the first tap or encoding transducer is reference transducer 14a, which as described above is preferably placed three separation units past the alignment transducer 15.
  • the reference transducer 14a is of the flip code design described above in relation to Fig. 2 and is preferably a type A transducer due to the manufacturing errors possible in placement over a 3 unit distance.
  • a flip coding transducers 14 spaced at consecutive one separation unit distances from each other.
  • the coding transducers 14 are a combination of type A and type B transducers, and in the illustrated embodiment fifteen of these transducers are used.
  • the number of flip coding transducers 14 is chosen to suit the particular application, within several restraints.
  • the length and therefore the cost of the SAW chips will increase with the number of tap transducers and will be inversely dependent upon the bandwidth of interrogating signal allowed by the regulatory authorities in the country concerned.
  • the code capacity will depend upon the number of bits encoded per transducer (for example, 2 bits per transducer for simple quad phase encoding) .
  • Some applications may place limits on the length of the tag, for example in the case of implantable tags for the livestock industry. While some applications may require only a small code capacity, for example twelve bits or less, others may require as many as 64 bits including error correction bits.
  • Each chip is then individually coded by appropriately selecting which cuttable bridges to cut. This is preferably done by using a pattern generator (similar to and possibly even the same pattern generator as used for the 10X reticle manufacture) directly to expose the resist over the bridges to be cut.
  • the bridges produced by the masking process are made large enough so that the photographic resolution is sufficient to cut them without needing the intermediate step of a reticle and 10X reduction.
  • the wafer is then processed to produce individually coded chips.
  • amplitude coding is added to the quad phase encoding described above. While such coding may be achieved by a simple measure such as the removal of a proportion of the fingers of a tap transducer to reduce its coupling with the substrate, this has the disadvantage of altering the capacitance of the transponder, and would therefore require individual tuning of transponders to achieve impedance matching with the antenna, depending on the amplitude coding.
  • Fig. 4 shows a transducer layout in which the transducer fingers comprise 4 groups of fingers each group having an equal number of fingers (in this example, 6).
  • the fingers of one group the left hand group as seen in Fig. 4, are displaced from the remaining groups by one half a wave length.
  • the first three groups will contribute a tapped signal with the same phase and a nominal amplitude of three units, while the fourth group will contribute an antiphase signal with an amplitude of one unit.
  • the net effect will be to supply to the busbars a tapped signal of 2 units, or one half the amplitude of a transducer in which none of the groups is displaced. Amplitude modulation is thus achieved which may be superimposed upon the quad phase modulation described above.
  • finger groups may be displaced in other ways to achieve similar results.
  • groups each comprising one eighth of the fingers of a transducer may be displaced by A/4 in opposite directions, also providing a 50% amplitude modulation.
  • changes of amplitude of more or less than 50% can be achieved by appropriate choice of the proportion of interfering fingers.
  • the present invention enables the use of inexpensive materials, rather than quartz or lithium niobate as in the prior art.
  • the present invention employs cheap borosilicate glass as the substrate material, coated with a thin film of zinc oxide.
  • the ZnO film is formed by planar RF magnetron sputtering, which allows optimal control of substrate temperature.
  • Zinc oxide is a well known piezoelectric material with a hexagonal crystalline structure, and polycrystalline ZnO films of suitable orientation, i.e. with the C axis normal to film surface, can be deposited on glass by the sputter technique.
  • the thin film substrate is a layered structure in which a piezoelectric film 10 is suitably deposited on a non piezoelectric base 23 suitably of borosilicate glass.
  • the aluminium metal for the IDT's 14 is then deposited on this film by vacuum evaporation or sputtering. The normal photolithographic processes are used to produce the chips.
  • An alternative to this method is to deposit the SAW transducers directly on the surface of the non-piezoelectric glass 23 rather than on the surface of the piezoelectric film 10.
  • the ZnO film is then formed over the top of the glass and the metal transducer fingers, the thin film serving to convert the electrical signals of the IDT into SAW waves and back again.
  • the glass base material provides the mechanical strength and serves as the SAW transmission material.
  • An important secondary function of this technique is that the ZnO film layer forms a protective barrier for the aluminium IDT's and thus increases the delay line reliability.
  • the glass base material can be chosen to have large physical dimensions limited only by the X-Y travel of the step-and-repeat camera used for the photolithographic process.
  • a large glass plate 8 inches square or more may be used as a processed wafer, capable of yielding a very large number of individual chips.
  • Selective etches are available which allow etching of either the aluminium metallisation or the zinc oxide alone.
  • the use of a larger wafer allows proportionately less wastage required for handling.
  • Figs. 8 and 9 illustrate the method of fabrication according to an aspect of the invention which enables the encapsulation of the transponders to be completed prior to the slicing of the individual transponders from the wafer or substrate.
  • rows 30 of transponder metallisation patterns are applied to a wafer, with the connection pads of longitudinally adjoining patterns being applied in a continuous area 31. (No attempt is made to show the transducers in this figure) .
  • a sealant such as an epoxy resin of low gas permeability or a glass frit is applied by silk screening to the surface of a cover plate 35 (Fig.9) of the same dimensions as the wafer.
  • the sealant is applied in the form of "moats" 36 located to surround each transponder, leaving the pads 26 outside, when the cover plate is located over the wafer.
  • the cover plate is placed over the wafer and the sealant cured or allowed to set, preferably under pneumatic pressure.
  • the moats 36 are of a height which provides a small gap between the cover plate and the wafer.
  • the cover plate is then sliced along the lines 32 in Fig. 8, to a depth which is just above the contact pads 31, and the strips of cover plate material between these pairs of cuts are removed (for example by air suction) to expose the pads 31.
  • Individual transponders are then created by slicing right through the assembly on the lines 33 and 34.
  • An antenna (not shown) is then attached to each transponder in any suitable manner.
  • a spacing sealant can be applied in the manner described to the surface of the wafer and the individual cover plates positioned over each transponder by a pick-and-place machine. After curing, the wafer is sliced in the normal way.
  • the cover plate provides mechanical support for the bonding pads and thus allows the area of active piezoelectric material to be reduced.
  • the SAW chip may be redesigned with much reduced metal contact pads.
  • the size of these pads now only need be sufficient to support the epoxy which provides the hermetic sealing for the chip.
  • Fig. 10 illustrates a SAW chip with bonding pads reduced to the minimum size necessary for hermetic sealing.
  • the glass cover plate 24 is extended in size to allow room for the metal bonding pads 25 produced by a simple process onto the cheap glass cover plate material.
  • connection of the large bonding pads 25 on the cover plate 24 with the small bonding pads 26 on the SAW chip may be achieved by using conductive epoxy 27 only in the vicinity of the pads 26.
  • the hermetic seal is then completed by placing normal epoxy 28 around the perimeter of the SAW chip, as shown in the cross-sectional view of Fig. 10(d).
  • each transponder must be equipped with an appropriately tuned antenna.
  • Such antennae may be mounted on the cover plate and connected by means of the bonding pads 25, but since the dimensions of these pads are not constrained by considerations of substrate material cost, the pads 25 " themselves may in suitable cases be dimensioned to act as antennae, providing an elegant solution to the problem of antenna attachment.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Theoretical Computer Science (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

La présente invention se rapporte à un répondeur à ondes acoustiques de surface, dans lequel des transducteurs (14) situés sur la surface d'un substrat piézo-électrique (10) modifient un signal d'interrogation. Les transducteurs sont codés en phase par connexion sélective de leurs groupes de doigts à des barres bus correspondantes (11, 12) et par déplacement relatif dans leurs positions nominales. Les doigts de transducteurs et les connexions de croisement de piste (20) sont disposés de façon à produire un effacement des ondes acoustiques de surface réfléchies. Un transducteur marqueur (15) contribue au décodage. Lors de la mise en capsules des répondeurs, on fixe une plaque de couverture (35) ou des plaques de couverture séparées (24) au substrat avant de découper séparément les répondeurs dans le substrat.
PCT/AU1989/000470 1988-11-04 1989-11-03 Dispositifs a ondes acoustiques de surface Ceased WO1990005409A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPJ1305 1988-11-04
AUPJ130588 1988-11-04

Publications (1)

Publication Number Publication Date
WO1990005409A1 true WO1990005409A1 (fr) 1990-05-17

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PCT/AU1989/000470 Ceased WO1990005409A1 (fr) 1988-11-04 1989-11-03 Dispositifs a ondes acoustiques de surface

Country Status (3)

Country Link
CA (1) CA2002179C (fr)
NZ (1) NZ231251A (fr)
WO (1) WO1990005409A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003052682A1 (fr) * 2001-12-18 2003-06-26 Rf Saw Components, Incorporated Etiquette d'identification a onde acoustique de surface comprenant un contenu d'informations et procedes de fonctionnement et de fabrication correspondants
US7264149B2 (en) 2003-09-15 2007-09-04 Hartmann Clinton S SAW identification tag discrimination methods
FR3030154A1 (fr) * 2014-12-10 2016-06-17 Sasu Frec'n'sys Dispositif de capteur a ondes elastiques de surface a reponse electrique stable
WO2021181026A1 (fr) * 2020-03-12 2021-09-16 Saint-Gobain Glass France Vitrage comprenant un element vitre comportant un dispositif de communication configure pour fonctionner par radio-frequences et par ondes acoustiques de surface

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870975A (en) * 1974-03-22 1975-03-11 Hazeltine Corp Surface wave transducer with reduced reflection coefficient
JPS5566118A (en) * 1978-11-13 1980-05-19 Matsushita Electric Ind Co Ltd Elastic surface wave device
JPS56164614A (en) * 1980-05-21 1981-12-17 Japan Radio Co Ltd Elastic surface wave device
US4342011A (en) * 1979-09-25 1982-07-27 Fujitsu Limited Surface acoustic wave device
US4410823A (en) * 1981-11-13 1983-10-18 Zenith Radio Corporation Surface acoustic wave device employing reflectors
US4535265A (en) * 1984-05-17 1985-08-13 Kabushiki Kaisha Toshiba Surface acoustic wave transducer with internal acoustic reflection
JPS60186109A (ja) * 1984-03-06 1985-09-21 Toshiba Corp 弾性表面波共振子
AU3400184A (en) * 1984-10-09 1986-04-17 X-Cyte Inc. Saw transponder
AU3400284A (en) * 1984-10-09 1986-04-17 X-Cyte Inc. Saw transponder
US4616197A (en) * 1985-12-05 1986-10-07 R. F. Monolithics, Inc. Resonator

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870975A (en) * 1974-03-22 1975-03-11 Hazeltine Corp Surface wave transducer with reduced reflection coefficient
JPS5566118A (en) * 1978-11-13 1980-05-19 Matsushita Electric Ind Co Ltd Elastic surface wave device
US4342011A (en) * 1979-09-25 1982-07-27 Fujitsu Limited Surface acoustic wave device
JPS56164614A (en) * 1980-05-21 1981-12-17 Japan Radio Co Ltd Elastic surface wave device
US4410823A (en) * 1981-11-13 1983-10-18 Zenith Radio Corporation Surface acoustic wave device employing reflectors
JPS60186109A (ja) * 1984-03-06 1985-09-21 Toshiba Corp 弾性表面波共振子
US4535265A (en) * 1984-05-17 1985-08-13 Kabushiki Kaisha Toshiba Surface acoustic wave transducer with internal acoustic reflection
AU3400184A (en) * 1984-10-09 1986-04-17 X-Cyte Inc. Saw transponder
AU3400284A (en) * 1984-10-09 1986-04-17 X-Cyte Inc. Saw transponder
US4616197A (en) * 1985-12-05 1986-10-07 R. F. Monolithics, Inc. Resonator

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, E100, page 28; & JP,A,56 164 614, (NIPPON MUSEN K.K.) 17 December 1981 (17.12.81). *
PATENT ABSTRACTS OF JAPAN, E20, page 33; & JP,A,55 066 118, (MATSUSHITA DENKI SANGYO K.K.) 19 May 1980 (19.05.80). *
PATENT ABSTRACTS OF JAPAN, E378, page 67; & JP,A,60 186 109, (TOSHIBA K.K.) 21 September 1985 (21.09.85). *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003052682A1 (fr) * 2001-12-18 2003-06-26 Rf Saw Components, Incorporated Etiquette d'identification a onde acoustique de surface comprenant un contenu d'informations et procedes de fonctionnement et de fabrication correspondants
US6966493B2 (en) 2001-12-18 2005-11-22 Rf Saw Components, Incorporated Surface acoustic wave identification tag having enhanced data content and methods of operation and manufacture thereof
US7264149B2 (en) 2003-09-15 2007-09-04 Hartmann Clinton S SAW identification tag discrimination methods
FR3030154A1 (fr) * 2014-12-10 2016-06-17 Sasu Frec'n'sys Dispositif de capteur a ondes elastiques de surface a reponse electrique stable
EP3032742A3 (fr) * 2014-12-10 2016-08-31 Sasu Frec'n'sys Dispositif de capteur à ondes élastiques de surface interrogable à distance
EP3793088A3 (fr) * 2014-12-10 2021-05-19 Sasu Frec'n'sys Dispositif de capteur a ondes elastiques de surface a reponse electrique stable
EP3965293A3 (fr) * 2014-12-10 2022-06-29 Sasu Frec'n'sys Dispositif de capteur a ondes elastiques de surface a reponse electrique stable
WO2021181026A1 (fr) * 2020-03-12 2021-09-16 Saint-Gobain Glass France Vitrage comprenant un element vitre comportant un dispositif de communication configure pour fonctionner par radio-frequences et par ondes acoustiques de surface
FR3108192A1 (fr) * 2020-03-12 2021-09-17 Saint-Gobain Glass France Vitrage comprenant un element vitre comportant un dispositif de communication configure pour fonctionner par radio-frequences et par ondes acoustiques de surface

Also Published As

Publication number Publication date
NZ231251A (en) 1993-03-26
CA2002179C (fr) 2000-05-23
CA2002179A1 (fr) 1990-05-04

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