A novel UWB bandpass filter based on double interdigital structure

In this paper, a novel ultra-wideband (UWB) filter with double interdigital structures and periodic slow wave structures is proposed. By using these structures, the performance of the microstrip bandpass filter has been improved significantly. The slow wave structures are constructed by the periodic fishbone structures and the ground etching periodic square holes. This novel filter is very compact and has a wide passband of 5.4GHz from 2.4GHz to 7.8GHz and the fractional bandwidth is about 106%. The simulation results and measurement data have verified the proposed UWB filter.