DCS Tx filters using AlN resonators with iridium electrodes

In this paper we present the design methodology, fabrication technology and characterization of bulk acoustic wave (BAW) filters for the DCS Tx-band at 1.75GHz. The filters are fabricated with solidly mounted A1N-based resonators (SMR) using iridium metallic electrodes, in an attempt to increase the effective electromechanical coupling factor of the BAW devices and achieve the bandwidth requirements of DCS filters. The design and optimization of the filters is performed with a simulation tool that uses a circuital model to compute the filter frequency response. Tx filters with balanced inputs and outputs and different topologies are designed and fabricated. The experimental filter response is compared with the simulations to determine the suitability of each design. Bandwidth DCS requirements are fulfilled by using Ir/A1N/Ir stacks.