Investigations on design technologies for SAW quadplexer with narrow duplex gap

Carrier aggregation (CA) is an inevitable technology to improve the data transfer rate with widening operation bandwidths, while the current frequency assignment of cellular bands is dispersed over. In the frequency division duplex (FDD) CA, acoustic multiplexers are one of the most important key devices. This paper describes the design technologies for the surface acoustic wave (SAW) multiplexers, such as filter topologies, matching network configurations, SAW characteristics and so on. In the case of narrow duplex gap bandwidth such as Band4 and Band25, the characteristics of SAW resonators such as unloaded quality factor (Q) and out-of band impedances act as extremely important role to realize the low insertion loss and the steep skirt characteristics. In order to solve these challenges, a new type high Q SAW resonator that is named IHP-SAW is introduced. The results of a novel quadplexer of Band4-Band25 using those technologies show enhanced performances