A new synthesis method for broadband dispersive 180° reflecting arrays in SAW devices

An increasing number of SAW filter configurations contains 180° reflecting arrays. For broadband applications chirped reflectors are needed. The design of unweighted dispersive arrays yields unbearable deviations from a flat stopband. To tackle this problem we have worked out a sophisticated synthesis method using finger width- and phase-weighting which are the best suitable techniques for broadband reflectors. Using the stationary phase principle and the infinite array approximation we can compute the reflection factor of each finger in a dispersive array with slowly varying pitch. We present an iterative design procedure based on the relation between the frequency response of a dispersive array and the local reflectivity. The feasibility of our synthesis procedure is confirmed by experimental results