With the development of electronics, information, and communication industries, the radio communication systems accomplished fast growth and the quality of human life is improving rapidly under benefit of various informations.
Filter is one of the elements indispensable for microwave /millimeterwave system. Various kinds of filters have been studied and developed. The filter with better characteristics is needed for qualitative elevation of microwave system. In this work, in order to realize a band pass filter with wide-band characteristics for mobile communications, 2 GHz band pass filter was designed using ring resonator with stub. The three stage wide-band BPF was designed and fabricated. For broadband design, the ring circumference was divided by 4 sections with 1/8 wavelength and 2 sections with 1/4 wavelength which have different line impedances. The characteristics of the proposed BPF were highly improved by using three stage ring resonator. The characteristic impedance values of each sections were obtained by Powell's least square algorithm where differentiations are not needed. The measured results showed a good agreement with the theoretical results as well as ADS simulation.