Design of wide-stopband microstrip bandpass filter with assistance of spur lines

A novel microstrip bandpass filter with compact size is proposed. 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. Agreement between measured results and the theoretical prediction validates the proposed structure.