Simulation modeling and correction method for balance performance of RF SAW filters

In mobile phone RF stages, the balanced SAW filter has assumed an important role. In order to suppress signal distortion, amplitude and phase imbalance are required to be reduced. This paper describes a new simulation modeling of balance performance. The developed 8-port F-matrices model includes the effect of coupling capacitances and the end effect of excitation intensity of SAW using a modified Smith´s equivalent circuit model. The simulation results show good agreement with measured results for 3IDT type DMS filters. Moreover, a correction design using an optimization program with the developed simulator engine has been carried out, and less than half level imbalance characteristics have been successfully obtained for 5IDT type DCS-RX filters.