Characterization of SAW Duplexer Inserts for LTCC RF Front-End Modules by Simulation and Measurement

The growing demand for miniaturization of mobile terminals incites design engineers to integrate the required functionality of stand-alone active and passive discrete/integrated components of the RF section, such as, e.g., antenna switches, power amplifiers, and SAW filters, into compact modules. Although being a monolithic and complex component in which all sub-systems, formerly stand-alone components, are interlocked, each of them has to be designed and optimized individually and be pieced together in a later step of the development process for the final optimization. Therefore, an efficient design strategy and a neutral test environment for the characterization by both measurement and simulation of the isolated sub-systems are needed. Being able to provide this would allow design engineers to predict reliably the properties of the sub-systems integrated in the target module. In this paper we report on practical and theoretical issues regarding the integration of duplexing functionality into LTCC modules by means of duplexer inserts. Duplexer inserts provide the necessary potential for further height reduction that is required by future developments of modules. One of the key issues that we faced was the precise characterization of the performance of duplexer inserts in the module by both measurement and simulation. We investigated models of different complexity and, therefore, different accuracy and present first experimental results of the characterization of a W-CDMA 2100 duplexer insert. Hereto, we divided the module into its subsystems and applied our new, specifically designed, neutral test/design environments for duplexer inserts in order to evaluate the usability of different approaches. We obtained the best agreement of simulation and measurement for the most complex model.