Method for Improving the Performance of BAW Resonators and Filters

This paper presents a BAW resonator structure, including the irregular shape and the frame region at the edge of top electrode to smooth electric response and suppress spurious modes. The NRN method based on Generalized Chebyshev Filter synthesis is introduced to design a BAW ladder filter. By controlling the location of the transmission zero, a higher isolation is obtained in the proper frequency domain. Using such methodology, Band 25 Rx BAW ladder filter is obtained with an insertion loss of 1.2 dB in the passband and an isolation of 52 dB in the Tx band.