A Multi-Channel, Embedded, and Geometrically Optimized Filter Bank Utilizing Advanced Packaging Topologies for Miniaturized RF Modules in IoT and Wearable Systems

This paper presents a multi-channel miniaturized RF filter bank by employing advanced packaging techniques such as geometrical optimization, strategic element positioning, and vertical 3D stacking to achieve increased functional density and reduced footprint in RF Printed-Circuit-Board (PCB) modules. Multi-layer PCBs are utilized and RF via structures are designed for showcasing vertically stacked band-pass filters and a 4-channel low-pass filter bank with cut-off frequencies ranging between 7.2 GHz and 16.5 GHz. The resulting filter bank occupying the size of nearly a single integrated circuit (IC) switch not only allows for a remarkable 3X reduction in area, but also reduces cost and manufacturing complexity, allows for easy scalability to 5G/B5G bands and additional channels, and paves the way for flexible/conformal electronics by reducing the number surface mount technology (SMT) components. Furthermore, measurement results demonstrate effectiveness in terms of minimizing signal interference and crosstalk, in addition to achieving superior performance compared to SMT filters. Finally, this paper serves to provide an overview on the design of low-pass and band-pass RF filters.