The design of SAW RAC's using arrays of thin metal dots

Many successful dot array SAW devices including RAC's, resonators and band-pass filters have been reported, but the wide range of dot parameters, including dot dimensions, spacing and pattern, which allows flexibility in design, has not previously been utilized. This paper reports on the design of an RAC (reflecting array compressor) with a TB product of 1000, the emphasis being to exploit some of this flexibility. The design has been implemented using YZ LiNbO/sub 3/ with thin metal dots as the reflectors. It makes use of the wide range of reflectivities available from electrical effects in a novel weighting scheme based on dot size. The dots have been designed so that the sensitivity to over-etch is minimal. The array, which is sparse and near-periodic, has been designed to reduce unwanted reflections. This is least successful in the case of SAW to bulk wave reflection and the consequent loss due to this cause is accounted for in the design. The design approach is quite general and should be of use for other devices.<
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