Ultra low-profile self-matched SAW duplexer with a flip-chip HTCC package for W-CDMA 2100 mobile applications

Duplexers are essential components in 3G communication systems. They provide the required duplexing functionality for simultaneously transmitting and receiving RF signals over a common antenna. Duplexers in SAW/BAW filter technology have become state-of-the-art in modern 3G mobile terminals because of their small size. Current packages for self-matched SAW/BAW duplexers are composed of several LTCC layers with embedded passive elements which are essential for the duplexing functionality. In addition, they are used for impedance matching and transfer function shaping. In this paper a new integration approach for passive elements is introduced which allows ultra low-profile packaging for self-matched SAW/BAW duplexers. Therefore, miniaturized planar inductors with high Q-factors were patterned on the top of an HTCC substrate instead of the traditional realization inside an LTCC layer stack. We will present a first characterization by simulation and measurement of these inductors. Additionally, we will present a first prototypical self-matched W-CDMA 2100 SAW duplexer with a flip-chip HTCC package based on the new packaging technology. We have integrated spiral inductors with a height of 40 mum, a line spacing of 40 mum and a line width of 40 mum on the top side of an HTCC substrate inside the package. The resulting 2520 package has a typical height of 450 mum. The first measured demonstrators show a very good Tx-Rx isolation (-52 dB in both bands), out-of-band selection (Tx@Rx-Band -47 dB, Rx@Tx-Band -55 dB), and matching (at all ports <-11 dB). The presented characterization by measurement and simulation shows a very good agreement.