SURFACE-ACOUSTIC-WAVE (SAW) FILTERS FOR MOBILE COMMUNICATION-SYSTEMS

The new mobile communication systems as GSM, PCN and DECT allow economical use of frequency allocation, digital radio quality and roaming in the entire European area. The demands posed by these innovative cellular systems are fuelling progress in SAW technology. The main filter requirements are high selectivity for suppression of spurious signals, low insertion loss for reduced power consumption and miniaturized SMD packages for small handheld units. SAW filters with these features are key components in most of the existing mobile telephone systems. To reduce the inherently high insertion loss of conventional SAW devices a variety of special low-loss techniques has been developed each optimized for a specific application. In this paper we will present the characteristics of some typical low-loss SAW filters for IF and RF filtering in the systems EAMPS, NMT900, GSM, CT-2, PCN and DECT. Customer requirements and the filter performance will be discussed. Finally the trends of future SAW applications for mobile communication systems will be pointed out.