A compact and low cost multilayered balun designed for SiP applications

In this paper, the design of a compact balun/matching network is described. The balun is built on multilayer organic laminates and found suitable for system-in-package (SiP) applications. A 2:1 balun was designed and fabricated using conventional printed circuit board (PCB) technology. In this design, the use of bridges and vias for centre tapping was eliminated, while maintaining the geometric symmetry of the spirals. Furthermore, the differential secondary coils are spread over two layers, such that the balun size can be made compact. Measurement results yield a wide bandwidth and good amplitude balance. This balun design is suitable for use in Bluetooth applications operating in the ISM band (2.4-2.5 GHz).