Classifications

• • 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
  • H03H9/02535—Details of surface acoustic wave devices
  • H03H9/02818—Means for compensation or elimination of undesirable effects
  • H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
  • H03H9/0285—Means for compensation or elimination of undesirable effects of reflections of triple transit echo
• • 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
  • H03H9/02535—Details of surface acoustic wave devices
  • H03H9/02543—Characteristics of substrate, e.g. cutting angles

Definitions

• This invention relates to surface wave acoustic de ⁇ vices and more particularly to an improved configuration 5 for a- filter substrate.
• the filter described therein includes a substantially rectang ⁇ ular substrate that may be constructed from, for example, 20 lithium niobate. At a lower corner of one end of the sub ⁇ strate is deposited an input transducer in the form of a series of interdigitated conductive elements. At the upper corner of the opposite end of the substrate is de ⁇ posited a similarly arranged output tranducer, also in- 25 eluding a series of interdigitated conductive elements.
• a multi-strip coupler and a reflector are also included in the filter.
• the coupler causes signals launched by the transducer to be directed in quadrature to both the output transducer and the reflector.
• the reflector results in substantial cancellation of "triple-transit" signals as thoroughly described in the cited patent. This is a highly desirable effect because the triple-transit signals result in a ripple and other undesirable anomalies in the phase and frequency responses of filter.
• the subject invention is directed- to an improved sub-, strate configuration that not only attenuates the level of reflected signals but also significantly reduces the amount of substrate material required.
• the reduction in substrate surface area results in a substantial reduction in the total cost of the device, largely because of the expense of the niobium component of, for example, a lithium niobate substrate.
• the invention is a surface wave acoustic filter com ⁇ prising aluminum transducers deposited on a triangularly configured lithium niobate substrate.
• the length of the sides of the substrate assum values equal to approximately 6.05, 9.25 and 11.05 milli ⁇ meters respectively.
• the triangular configuration not only reduces by a factor of about one-half the amount of substrate material required but also attenuates the degree of signal reflection encountered.
• the sole drawing is a pictorial representation of the subject SAW filter.
• the subject surface wave acoustic filter includes, inter alia, a triangular substrate 1, which, in a preferred embodiment, is constructed from a piezoelectric material such as lithium niobate. Deposited on the substrate are an input transducer 5, an output transducer -2, a reflector 3 and a 3db coupler 4.
• the above elements are typically constructed from an electrically conductive material such as aluminum. The specific operation and configuration are not part of this invention but, nevertheless, are, for , edification, detailed in the patent cited above.
• the filter substrate is triangularly configured and comprises first, second and third sides 11, 12 and 13, respectively.
• the second side has a nominal dimension F, of 9.25 millimeters (mm).
• the third side of the substrate forms an angle, alpha, with an imaginary line that is perpendicular to the second side and has a length, J, nominally equal to 5.75 mm.
• alpha has a •nominal value of 18 degrees. From the above it can be demonstrated that the nominal lengths of sides 11, 12 and 13 (given the nominal value of alpha) are 11.05, 9.25 and 6.05 mm respectively.
• the length F, of the second side 12 may vary from 7 to 12 millimeters, the dimension J may vary from 3.0 to 10.0 mm, and the angle alpha may vary from 0 degrees to 36 degrees.
• the first side of the substrate may vary from approximately 7.6 to 17.2 mm, the second side from 7.0 to 12.0 mm, and the third side from 3.0 to 12.3 mm respectively.
• the thickness of the substrate may vary from approximately 0.1 to 1.0 mm, and again, may
• the input trans ⁇ ducer 5 has an eight-sided perimeter, four sides (51, 53,
• the output transducer 2 is substantially 0 rectangular and comprises sides 21 and 23, parallel to the first side of the substrate, and sides 22 and 24, arranged substantially perpendicular to it.
• the reflector 3 has two sides 31 and 33 substantially parallel to the second side, a side 32 substantially perpendicular to it and a
• the input and output transducers, coup ⁇ ler and reflector are not considered an essential aspect of the subject invention, but have been described to fa ⁇ cilitate a complete understanding of the subject inven ⁇ tion. 5
• the relevant dimensions of the substrat input and output transducers, .3db coupler and filter may be derived from the drawing and the table included therein. In practice those dimensions may vary, in millimeters, as follows:
• the triangularly configured substrate exhibits at least two salient advantages.
• the surface area of the substrate may be estimated at approximately one-half of the substrate required in other known structures.
• the surface wave reflections from the output transducer, and therefore the triple-transit reflections are substantially reduced as a result of the triangular configuration.
• the subject invention is useful as a signal process ing device in various types of electronic equipment and, in particular, as a surface acoustic wave filter for tel vision receivers.

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• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=22161174

Family Applications (1)

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Family Cites Families (4)

• 1981
  • 1981-04-06 WO PCT/US1981/000452 patent/WO1982003511A1/en unknown
  • 1981-04-06 EP EP19810901756 patent/EP0076253A1/de not_active Withdrawn

Non-Patent Citations (1)

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