A behavioral model of a BAW resonator realized in VerilogA is presented. VerilogA models can be integrated in all leading RF design tools allowing simulations of BAW filters at a system and circuit level. In that way a coupled design of the conventional electronics and the electro-mechanical BAW is now possible. By using the presented model the system designer has the possibility to optimize both the conventional electronic and BAW components according to the system requirements simultaneously. The VerilogA model has been verified by performing optimization in Cadence and ADS.