Design and realization of transversal surface acoustic wave RF filters

Computer aided design and realization of the surface acoustic wave (SAW) RF bandpass filter with uniform interdigital transducers (IDT) with maximal bandwidth and minimal losses is presented. The configuration of the filter and transducers are determined first. Then the layout for the mask fabrication of each transducer is designed using original software IDPMPAT. After that, if needed, the design of the matching networks between the IDTs and the load and the generator is carried out. The algorithm takes as input the central frequency, bandwidth, delay, substrate and electrode type, and load and generator resistances. The output results are the IDTs positions, mask layout and the element values of the matching networks. The algorithm has been exemplified by a filter design with the central frequency of 72 MHz which was fabricated on ST-quartz. The scattering parameters of the fabricated filter are measured and the experimental results satisfy the filter specification verifying the proposed algorithm.