A compact BT/WiFi dual-band dual-mode RF front-end module

A compact BT/WiFi dual-band dual-mode RF front-end module (FEM) with LTCC-based embedded passives is presented in this paper. The proposed RF FEM is composed of a diplexer, three baluns, and a matching network, which are realized in the LTCC substrate. Furthermore, an SPDT, an SP3T, a dual-band power amplifier, and low noise amplifiers are placed on top of the substrate. The compact and low-profile embedded diplexer and baluns are designed and implemented with LC lumped-element approach, resulting in a quite low insertion loss and a good amplitude/phase balance. These passive components and DC bias lines are stacked up with four inner ground planes for minimizing unexpected coupling effect as well as space saving. The size of the proposed RF FEM is only 4.5 mm × 4.5 mm with a total thickness of 1.2 mm. The implemented RF FEM provides a P1dB of more than 20 dBm and sufficient adjacent channel power characteristics at both frequency bands. In BT path, we obtain an average insertion loss of about 3.4 dB with good amplitude and phase balance. Also, the FEM has an overall gain of about 6.7 dB at 2.45 GHz and about 8 dB at 5.5 GHz for WiFi Rx operations.