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Innovative Design Principles for SAW Components

Based on an efficient physical model, new designs have been proposed for SAW filters in the recent years and their transmission behaviour has been studied. The following innovations have been introduced into the SAW-based filter technology in the last five years:

 

Transversely coupled (waveguide coupled) resonator filters:

  • Use of higher waveguide modes (higher than 2nd order) for shaping the passband.
    Effect: Wider bandwidth without changing the waveguide parameters.
  • Combination of waveguide modes (transverse modes) and cavity modes (longitudinal modes) for shaping the passband (see sketch below).
    • cav_mode
    Layout example for a transverse coupled system combining waveguide and cavity modes

    Effect: Implementation of four-pole filters without cascading or parallel connection of two-pole filters, a wider bandwidth, steeper skirts (smaller shape factor).

    d_guide
    Layout example for waveguide coupling of two one-port SAW resonators with different properties
  • Waveguide coupling of one-port SAW resonators with different properties (for instance with different resonance frequencies)

    • For all of the items mentioned above we have developed computer programs for the analysis of their SAW properties..

Filters using reflections on or within the IDTs (Interdigital Transducer):

  • Variation of the reflector finger positions in SPUDTs (Single Phase Unidirectional Transducer) and RSPUDTs (Resonant SPUDT).
    Effect: Adjusting or compensating a sloped passband.
    We have developed a program to determine not only the transduction and reflection coefficients but optionally also the reflector finger positions by optimisation.
  • Multiple reflections on the SPUDTs of a SPUDT filter.
    Effect: Prolongation of the impulse response.

 

Filters composed of SFITs (Slanted Finger Interdigital Transducer):

  • In contrast to the approach taken by other groups, our analysis takes diffraction into account. Therefore, we are able to treat SFIT filters with small apertures by means of our analysis program.
    slant
    Layout principle of a filter consisting of two SFITs
  • Our activities concerning innovative SAW design principles are characterised by an intense co-operation with industrial enterprises (VI TELEFILTER Teltow, Germany; Vectron Technologies Inc. Hudson, NH, USA; SAW Components Dresden, Germany).

Contact:

Dr. Günter Martin
IFW Dresden e.V.
'Magnetic and acoustic resonances' (Dept. 15)
Surface Dynamics Group
P.O.Box 270116
D-01171 Dresden, Germany
phone: ++49/351/4659 688
fax: ++49/351/4659 313

e-mail: g.martin + @ifw-dresden.de (Sorry, but we try to prevent automatic SPAM)
Contact


 

Dr. Günter Martin
IFW Dresden e.V.
'Magnetic and acoustic resonances' (Dept. 15)
Surface Dynamics Group
P.O.Box 270116
D-01171 Dresden, Germany
phone: ++49/351/4659 688
fax: ++49/351/4659 313
e-mail: g.martin + @ifw-dresden.de

(Sorry, but we try to prevent automatic SPAM)