A microstrip miniaturized triple-mode filter

Multi-mode filter is advantageous to the miniaturization of device. Because of symmetry, triangular structure has dual-mode characteristics. Some people have made a dual-mode filter with a triangular support structure. Through simulating triangle resonator, We found that the first two-mode distributed on the border of resonator and the third mode is located in the center of the triangle. We can load in the center of the disc to adjust the frequency of the third mode. When the adjustment discs, the first two degenerate mode frequency substantially was unaffected. Thus, we can make a triangle having three degenerate resonator modes. By adding the appropriate coupling and perturbation, we can make a triple-mode filter. This structure is much smaller than the existing structure and easy processing, and the structure is more stable.