Accurate modeling and simulation of SAW RF filters

The popularity of wireless services and the increasing demand for higher quality, new services, and the need for higher data rates will boost the cellular terminal market. Today, third generation (3G) systems exist in many metropolitan areas. In addition, wireless LAN systems, such as Bluetooth or IEEE 802.11-based systems, are emerging. The key components in the microwave section of the mobile terminals of these systems incorporate - apart from active radio frequency integrated circuits (RFICs) and RF modules - a multitude of passive components. The most unique passive components used in the microwave section are surface acoustic wave (SAW) filters. Due to the progress of integration in the active part of the systems the component count in modern terminals is decreasing. On the other hand, the average number of SAW RF filters per cellular phone is increasing due to multi-band terminals. As a consequence, the passive components outnumber the RFICs by far in today´s systems. The market is demanding smaller and smaller terminals and, thus, the size of all components has to be reduced. Further reduction of component count and required PCB area is obtained by integration of passive components and SAW devices using low-temperature co-fired ceramic (LTCC). The trend or reducing the size dramatically while keeping or even improving the performance of the RF filters requires accurate software tools for the simulation of all relevant effects and interactions. In the past it was sufficient to predict the acoustic behavior on the SAW chip, but higher operating frequencies, up to 2.5 GHz, and stringent specifications up to 6 GHz demand to account for electromagnetic (EM) effects, too. The combination of accurate acoustic simulation tools together with 2.5/3D EM simulation software packages allows to predict and optimize the performance of SAW filters and SAW-based front-end modules.