Bandpass Filter Design Using Quad-Mode Stub-Loaded Loop Resonator

A novel microstrip bandpass filter using a quad-mode stub-loaded loop resonator(QMSLLR) is proposed. The QMSLLR is a square loop with the four sections loaded with short stubs, the lengths of which determine the distribution of the frequencies. Odd-even mode method is applied for analyzing the frequencies. For both the input and output couplings, two feeding lines perpendicular to each other are used. The simulation and physical processing prove that the structure is suitable for the design of a medium band or even narrow band bandpass quad-mode Filter.