Compact Harmonic Suppression Low-Pass Filters With Stacked Dual RDL Structures Using 3-D Glass-Based Advanced Packaging Technology

Abstract

Two compact low-pass filters (LPFs) with high harmonic suppression are designed using the 3-D glass-based advanced packaging technology. In these two LPF designs, a new multilayer inductor is introduced by virtue of stacked dual redistribution layer (RDL) structures, which can achieve higher Q factor and much larger inductance in the operating bands. To achieve high harmonic suppression, these two LPFs are designed with multiple transmission zeros generated outside each operating band and fabricated on the through-glass-via (TGV) technology. The compact size of these two LPF designs can be achieved by virtue of the high Q performance and large inductance of the multilayer inductors. These two LPFs (called LPF 1 and LPF 2), which are operating in the bands of dc—0.5 and 0.1–0.5 GHz, can achieve insertion losses lower than 1.2 and 1.5 dB and return losses better than 17 and 16 dB, respectively. More than 25-dB harmonic suppression is achieved up to 6 GHz ( $24~f_{{0}}$ ) by LPF 1, whereas 18-dB rejection is achieved up to 6 GHz ( $30~f_{{0}}$ ) by LPF 2. The sizes of these two LPFs are only $2.0\times 1.0\times 0.35$ mm and $2.0\times 1.5\times 0.35$ mm, respectively. The simulation and measured results show good consistency.