Realization of a microstrip triple-mode bandpass filter using a square-loop resonator

This paper introduces a microstrip triple-mode resonator that is realized by adding an additional path to an already reported microstrip square-loop dual-mode resonator. The additional path is realized by a meander half wavelength strip that is connected to two opposite corners of the square-loop resonator. A third order pseudo-elliptic bandpass filter utilizing this resonator is presented. Good agreement is achieved between the theoretical, simulated and measured results.