SAW devices and their wireless communications applications - IEEE Microwave Magazine

65 ISSN 1527-3342/02/$17.00©2002 IEEE IEEE magazine Today’s second-generation (2G) wireless communications market is very dynamic with high growth rates. Soon, third-generation (3G) systems will start operation. Moreover, wireless local-area network (LAN) systems, such as Bluetooth or IEEE 802.11-based systems, are emerging. The key components in the microwave portion [both in the radio(RF) and intermediate-frequency (IF) sections] of the mobile terminals of these systems incorporate—apart from active RF 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. The component count for modern terminals is decreasing due to the progress of integration in the active part of the systems. On the other hand, the number of SAW RF filters is increasing for multiband terminals. As a consequence, passive components outnumber RFICs by far in today’s systems. The market is demanding smaller and smaller terminals, thus, the size of all components has to be reduced. The size of typical SAW RF filters shrank significantly over the last couple of years, and, for example, a footprint of 1 mm for an RF filter is feasible in the near future using new packaging techniques. For SAW IF filters (e.g., for IS-95 terminals), the footprint has been reduced by more than 80% over the last four years. Further reduction in component count and, therefore, size has been obtained by adding additional functionality to SAW devices. The integration of passive components and SAW devices using low-temperature cofired ceramic (LTCC) technologies reduces the required printed circuit board (PCB) area further. Today, SAW modules, such as for multiband terminals, are available. Such modules include SAW RF filters for the different frequency bands, p-i-n diodes for switching, and C.C.W. Ruppel is with EPCOS AG in Munich, Germany. L. Reindl is with Clausthal University of Technology, Germany. R. Weigel is with Johannes Kepler University, Linz, Austria.  D IG IT A L V IS IO N /E P C O S A G

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