Selection of micro-acoustic technologies for the realization of single-ended / balanced WCDMA duplexers

With the increasing number of frequency bands for WCDMA applications, also the need for miniaturized duplexer solutions increases in order to realize multi-band, multi-mode mobile phones. With SAW and BAW, two well established micro-acoustic technologies are available. For the realization of competitive CDMA duplexers like for the US-PCS band, so far the focus has been mainly on the provision of resonators with high quality factors and reduced temperature coefficient of frequency to realize filters with highest guaranteed steepness of filter skirts. With the large variety of duplexer requirements in the new WCDMA bands and the trend towards single-ended / balanced operation in the RX path, the constraints for technology selection have somewhat changed. Only when considering all critical parameters like center frequency, TX-RX bandgap, filter bandwidth, and insertion attenuation requirements, individual technology solutions for the different WCDMA frequency bands can be identified in order to provide superior duplexer solutions with respect to cost, size, quality, and performance.