Stripline SIR bandpass filter with high selectivity

This paper presents a stripline SIR bandpass filter with high skirt selectivity. The bandpass filter has a good performance on the out-of-band rejection by adding some through metallized holes on both sides of the substrate. It is easy to integrate by using a structure of transition between microstrip to stripline. To validate the proposed concept, a filter working at 12.5GHz with 5% fractional bandwidth was designed and fabricated by standard PCB process. Measured results are in accord well with the simulated results, showing good performance of the filter.