Using spur lines to develop the microstrip bandpass filter with a wide stopband

The novel microstrip bandpass filter with a compact size is proposed in this paper. With two short-circuited stubs, one open-circuited coupled line using symmetrical feeding, and two spur lines, a wide passband can be obtained. Detailed design and synthesis procedures are provided for filter development. Moreover, the electromagnetic simulator IE3D is used; the prototype of the bandpass filter is consequently fabricated and measured. In conclusion, the agreement between measured results and the theoretical prediction validates the proposed structure.