Maximilian Pitschi

SAW filter solutions to the needs of 3G cellular phones

Services based on third-generation (3G) cellular phone standards like W-CDMA or cdma-2000 will be launched in the very near future. They will bring together mobile telephony and applications such as internet communication, digital picture transmission or video conferencing that require high data rates. This objective and other provisions in the new standards lead to significantly changed requirements on the surface acoustic wave (SAW) filters employed in the IF and RF stages of 3G cell phones when compared to second-generation (2G) systems. The present contribution discusses the main issues involved in the design of SAW filters for 3G cell phones, with an emphasis on W-CDMA. The key point is that the need for miniaturization, higher operating frequencies and improved performance can only be met by a proper choice of material system, filter technique and package technology. In particular for the RF filters, it is essential to include in the simulation model a correct electrical description of the miniaturized package. State-of-the-art examples serve to illustrate these points.

Full-wave Characterisation of RF Ceramic Packages

The characterization of small complex ceramic packages with (monolithically) integrated microwave circuits is investigated using full-wave methods. In order to correctly design packaged radio frequency (RF) chips, the consideration of the package has become an indispendible part of the chip design process, as the electrical properties of the package have a great impact on the performance of the RF chips. For an effective simulation, a segmentation between the chip and its immediate environment, such as, the package, is investigated, and a suitable interface between chip and package is proposed to prove the validity of the interface, the simulation of the packaged RF device, which is pieced together from the full-wave simulation of the package and the simulation of the RF chip, is compared to the corresponding measurement. Simulation and measurement of the packaged RF device agree very well.

Comparison of different electromagnetic models of bulk acoustic wave resonators and filters

High-performance and miniatuarized bulk acoustic wave (BAW) devices require accurate and sophisticated computer aided design methods. Different modeling and simulation methods have to be applied depending on the simulated device, its complexity, available computational resources, and required accuracy. In order to model all relevant effects that are important to accurately characterize a device, it is important to know what details to model, how to model them, and to what extent. This paper presents and compares different electromagnetic models of mirror-type BAW resonators that are simulated with a 3D finite element method electromagnetic solver. The impact of meshing effects of the 3D electromagnetic solver on the simulated resonator and filter performances is discussed. Additionally, a simulation method is presented in which the acoustic and electromagnetic effects are simulated together. The combined simulation of the acoustic and electromagnetic effects is accomplished by incorporating the acoustic effects into the electromagnetic simulation by applying a frequency-dependent, complex-valued, equivalent permittivity for the piezo material. For the examined electromagnetic BAW resonator models the electromagnetic effects, computational effort, accuracy, and applicability are discussed. By considering the different enhancements introduced in the proposed electromagnetic BAW models, it is possible to improve the agreement of measurement and simulation.

Enhanced electromagnetic modeling of bulk acoustic wave resonators and filters

With the rapid miniaturization and increasing performance demands of bulk acoustic wave (BAW) devices, more accurate and sophisticated design and modeling methods are required. Accurate simulation results and appropriate software tools as well as their correct application are essential for a precise characterization of BAW devices. Depending on the simulated device, its complexity, required accuracy and available computational resources, different modeling and simulation methods have to be applied. For this modeling task it is important to know what details to model, how to model them and at what extent. In order to capture all relevant effects that are important to characterize the device with high accuracy, deep knowledge of the simulation softwares working principles as well as its computational limits and capabilities are necessary. This paper presents different enhanced electromagnetic models of mirror-type BAW resonators that are simulated with a 3D electromagnetic solver, whereas the acoustic effects are computed with a 1D solver. The electromagnetic effects of different resonator models are analyzed by fitting the simulated resonator admittance to an equivalent lumped circuit and comparing the fitted values. Further, the effects of the electromagnetic mesh-cell-density in simulations for the different resonator models are analyzed. The computational costs for these resonator models are shortly discussed by comparing mesh size, required memory and computational time. With the understanding of the model and electromagnetic mesh properties from the resonator simulations, an enhanced electromagnetic BAW duplexer model is simulated and compared to a measurement. The simulations of BAW resonators and duplexers can be improved by appropriate electromagnetic modeling and specific knowledge about the simulated device.

Messaufnahmen für die Vermessung von Hochfrequenz-Filtern

Zusammenfassung Die exakte Charakterisierung von Hochfrequenzfiltern mit Isolationen bis zu −60 dB stellt eine große messtechnische Herausforderung dar. Hierfür müssen die elektromagnetischen Wechselwirkungen der Messaufnahmen mit den Hochfrequenzbauelementen exakt analysiert und anschließend durch Anpassung der Messaufnahmengeometrien auf ein Minimum reduziert werden. Abstract Accurate characterization of high-frequency filters with high isolations down to −60dB is a challenging measurement task, as not only electromagnetic coupling between test-fixtures and devices have to be analyzed, but also the test-fixtures have to be properly designed to minimize coupling effects.