height profile. They have better power-handling capability than SAW filters and achieve steeper roll-off characteristics. This results in better 'edge of band' performance. The benefit apart from the roll-off characteristic and height profile is that BAR devices are inherently more temperature resilient than SAW devices and are therefore more tolerant of modules with densely populated heat sources (transceivers and power amplifiers). However, this does not mean they are temperature insensitive. BAR filters and SAW filters all drift with temperature and depending on operational requirements may require the application of temperature-compensation techniques. However, present compensation techniques compro- mise Q. Twelve months ago a typical BAW duplexer took up a footprint of about 5 by 5 mm² with an insertion height of 1.35 mm. In the US PCS band or 1900/2100 band these devices had an insertion loss of about 3.6 dB on the receive path and 2.7 dB on the transmit path and delivered RX/TX isolation of 57 dB in the TX band and 44 dB in the RX band. A typical latest generation FBAR duplexer takes up a footprint of about 2 by 2.5mm² and has an insertion height of 0.95 mm max. In the US PCS band or UMTS1900 band these devices have a typical insertion loss of about 1.4 dB on the receive path and 1.4 dB on the transmit path and deliver RX/TX isolation of 61 dB in the TX band and 66 dB in the RX band. More miniaturised versions (smaller than 2 by 1.6 mm) are under development. SAW filters also continue to improve and new packaging techniques (two filters in one package) offer space and cost savings. FBAR filters and SAW filters could now be regarded as mature technologies but as such are both still capable of substantial further development. Developments include new packaging techniques. For example, FBAR devices are encapsulated using wafer-to-wafer bonding, a technique presently being extending to miniaturised RF point filters and RF amplifiers within a hermetically sealed 0402 package. SAW filters are, however, also con