A Microstrip Bandpass Filter With Ultra-Wide Stopband

This paper develops a novel microstrip bandpass filter with ultra-wide stopband. With the assistance of open stubs and interdigital capacitors, a very wide stopband with a sufficient rejection level can be achieved easily. Detailed design and synthesis procedures are provided. Moreover, the electromagnetic simulator IE3D is used, and the prototype of the bandpass filter is fabricated and measured. Good agreement between measured and theoretically predicted results demonstrates feasibility of the proposed filter.