Design of weighted reflectors and their application to surface acoustic wave bandpass filter

This paper proposes a method of designing surface acoustic wave (SAW) weighted reflectors using an adaptive nonlinear least-squares algorithm. In the method, the total reflector length, the weighting function, the film thickness and pitch of the grating electrodes are all simultaneously optimised. The optimally designed reflector possesses the stopband width of 4 MHz at the centre frequency of 200 MHz with very steep response in the transition region and off-stopband reflectivities of nearly -80 dB. The electrode width-weighted reflectors were fabricated and applied to tilter devices employing a multistrip coupler. The experimental result was in good agreement with theoretical prediction.