A fully matched LTE-A carrier aggregation quadplexer based on BAW and SAW technologies

An inter-band carrier aggregation (CA) quadplexer allows doubling the download rates and is therefore an important element in upcoming mobile phone systems. In a duplexer design, both Tx and Rx filters should behave like an open-circuit for respective counter-bands at the antenna port. Additionally, they have to attain high suppression in their counter-band to get good in-band isolation. The situation gets more difficult and challenging for a CA quadplexer. Besides an open-circuit requirement for now 3 bands simultaneously, each Tx filter should achieve high suppression in the frequency range of both Rx filters in order to get high in-band and cross-isolation. The same applies for each Rx filter. Generally, it is not sufficient to simply expand the well-known topology concepts of duplexers rather a different design methodology is required. In this paper we will discuss several approaches to realize a CA quadplexer and present an implementation of a B25-B4 CA quadplexer sized 3.6×2.0×0.8mm³ utilizing the company's advanced acoustic wave filtering technologies: bulk acoustic wave (BAW) and surface acoustic wave (SAW).