A novel miniaturized bandstop filter using defected ground on system in package (SiP)

A novel wide stopband and compact bandstop filter (BSF) is proposed and realized based on defected ground structure (DGS) and meandered signal line on SiP. An equivalent circuit model is built to characterize the filter behaviors. At the same time, a condition for transmission zeros is derived. It can be observed that the equivalent circuit model reasonably agrees with the full-wave simulation and measurement results. Also, it is found that the proposed filter has high rejection over 25 dB in its stopband. The filter has a compact size of 0.21 λg × 0.19 λg, where λg is the wavelength of the center frequency of the stopband, and its -10 dB fractional bandwidth (FBW) is up to 90%.