Research And Design Of Filters Based On Defected Ground Structure

Microwave Integrated Circuits(MIC) and Radio Frequency Integrated Circuits(RFIC) require filters with sharp cut-off, wide stop band, compact size and good insertion loss characteristics, which led to the investigation of filters based on Defected Ground Structure(DGS). Moreover, filters based on DGS has been studied by many researchers.The basic theories and design methods of DGS are mainly analyzed and studied in this thesis, and applied to the design of microwave filters. Work done as follows:First, adding DGS to parallel coupled line filter can change the transmission characteristics. Then with pattern transformation, the new filter is compact, coupling, and it has the ultra-wide band(UWB) feature. The passband is from 3.1 to 10.6 GHz. In addition, an improved DGS based on the traditional DGS can provide good transmission characteristics. Then load open stub on microstrip line to cascade the improved DGS to achieve good low-pass feature. The stopband of the new filter is more than 15 GHz. Moreover, the combination of this new structure and a stepped impedance UWB filter with narrow band-stop can provide the wide band-stop characteristics. The stopband of the new filter is from 12.7GHz to 20 GHz, and the stopband rejection is below-20 dB. Above actual tests are based on the vector network analyzer. The experimental results show good agreement with the simulation results, which verifies the actual reliability of the design.Several filters based on DGS have been design in this thesis, and their transmission characteristics have been analyzed and studied. The conclusion of this thesis has some reference value to the design of microwave filters.