In this paper, the size of the dual-mode microstrip ring resonator is reduced by adding four open stubs, and bandpass filters having 100 MHz bandwidth are designed at the center frequency of 2 GHz. The size of the ring resonator can be controlled by varying the capacitance of the stubs, and the bandpass filter can be designed in two cases, which are two combinations of the stubs. Two bandpass filters are designed and fabricated by using the two-stage bandpass filter circuit model of the proposed structure, and the measured results show good agreement with the simulated results.