Design of Dual-Band Microstrip Filter Based on Stepped Impendence Resonator

In this letter, on the basis of the traditional λ
g
/2 SIR, the double-mode resonator was formed by using the odd-even mode analysis method to load the open stub in the center of the resonator. Using the magnetic coupling structure and the slot coupling feeding method, a center frequency of 2.45GHz/5.8GHz, 3dB relative bandwidth of 6.5%/6.6%, and insertion loss of center frequency of 0.95dB/0.98dB are finally obtained. The wave loss is -21.5dB/-26.3dB, and the maximum suppression band is 45.9dB/54.3dB dual-frequency microstrip bandpass filter. The filter has a simple structure, good effects, and strong out-of-band suppression, which has certain engineering application value.