Research And Design Of Grounding Structure Filter Based On Periodic Defects

With the development of communication technology,in order to meet the requirements of low passband loss,good stopband attenuation,and excellent performance,the research focus gradually changed from the dielectric surface to a grounded metal layer,and a defective ground structure(DGS)appeared.In this thesis,according to the current situation that DGS unit cannot meet higher requirements for filter performance,by changing the size and shape of the DGS structure,the performance of microwave filters is improved more effectively.The main research results of the thesis can be summarized as follows:Firstly,based on the traditional dumbbell-shaped defective ground structure(DGS)unit,the dumbbell-shaped defective ground structure is periodically cascaded to obtain a periodic DGS lowpass filter.The periodic dumbbell structure filter attenuation is-85.2d B,lower than the value of the nonperiodic.The attenuation slope of the transition band from the pass band to the stop band has been improved.The stopband bandwidth of the periodic structure is 3.88 GHz,which is 6% higher than the nonperiodic structure with a stopband width of 3.66 GHz.It is obvious that the low-pass filter of the periodic structure has stronger out-of-band suppression capability and wider stop-band bandwidth.Secondly,in order to improve the passband return loss of the dumbbell-shaped defect structure,the smoothness of the out-of-band suppression,and to reduce the size of the microwave circuit,a new type of semi-dumbbell-type defect structure is proposed.Compared with the traditional dumbbellshaped DGS structure,the half-dumbbell-shaped DGS also has a single-pole band-stop characteristic,but the attenuation characteristic curve is steeper,the slope is 8.2% higher than the dumbbell-shaped structure,and the return loss is significantly smaller.Then,the six half-dumbbell DGS were cascaded to design a periodic new DGS low-pass filter with low passband loss,good stopband attenuation,compact structure and excellent performance.Finally,a vector network analyzer was used to measure the processed filter,and the measured results were in good agreement with the simulation results.It was proved that the microwave filter based on periodic DGS meets the design index requirements,and has application value in filtering clutter and the noise reduction performance.