One compact microstrip low-pass filter using conventional elliptical headed dumbbell shaped defected ground structure (DGS) is proposed in this work. An equivalent circuit model is provided to depict the DGS unit. The proposed structure with main dimension parameters has been analyzed as a design guide, which can be used to fabricate the filter. The H-shape open stub has been introduced which increases the equivalent parallel capacitance to improve the out-band suppression. The proposed LPF shows low cut-off frequency response, low insertion loss, sharp transition and fairly good rejection in stop-band. Finally, one 5th order equivalent Butterworth filter has been designed using 5 arrays of DGS units. The five array DGS filter, including stubs provides the rejection in stop-band from 2. 8GHz to higher frequencies. Defected ground structures (DGS) have shown increasing potential for implementation in different applications: MIC, MMIC, and RFIC. They provide sharp, distinct electromagnetic band-gap and high slow wave factor, which lead to smaller size circuits and lots of engineering challenges to fulfill the requirements of modern communication systems.

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