Reflective array SAW narrowband filters

Experimental results are presented for a reflective-array SAW (surface acoustic wave) device that is optimized for narrowband filter applications. The filter consists of broadband input and output transducers with two weighted reflector arrays. Previous devices of this type have used reflective dot density and depth profile weighting for the reflective arrays. A unique implementation of this design technique for a 70-MHz narrowband filter is demonstrated, in which position-weighting of the reflector arrays is used. This filter has 0.2% fractional bandwidth and excellent amplitude and phase characteristics. A detailed analysis of the filter by use of a computer simulation and comparisons between the predicted and experimental responses are discussed. The proposed design approach results in a shorter die length as compared to conventional filter design and is more tolerant to fabrication defects such as shorts and opens