Common-mode filter using cavity-backed defected ground structure for multilayer PCB

A simple but effective common-mode noise suppression filter using cavity-backed defected ground structure (DGS) is proposed for the application of multilayer printed circuit board (PCB). This filter adds a substrate-filled metallic cavity beneath a conventional DGS. Due to the shielding effect of the cavity, the back-radiation of the DGS can be significantly reduced, while the filtering behavior of the DGS is retained in the resonant frequency band. The frequency responses and design parameters of the proposed filter are analyzed via full-wave simulation. An equivalent circuit model is also built based on the simulation result to understand the filtering behavior. It shows that an improved signal integrity (SI) is obtained with good EMI performance for a multilayer PCB.