Design And Research Of Microstrip Filter Based On DGS

Defected Ground Structure(DGS)is a periodic or aperiodic defect pattern etched on the ground plane of a circuit,which changes the effective dielectric constant of the dielectric substrate and improves the effective inductance and capacitance of the transmission line,can be used to form high-performance filters or to improve the performance of microwave integrated circuits.Traditional dumbbell DGS structure is simple,but its size is large and the frequency characteristics are not ideal.Based on the study of traditional dumbbell-shaped DGS structure,this paper proposes a new type of fence-type DGS structure.Compared with the dumbbell structure,the new structure shows 58% reduction in area,46.9% increase in steep factor,and-25.4dB in S21.The results show that the fence type DGS structure is more conducive to the design of high performance and miniaturized microwave millimeter wave integrated circuits.Based on the study of the fence-type DGS structure,a novel fifth-order ultra-wideband stopband microstrip low-pass filter is designed by cascading the new DGS structure.Simulation and test results show that the filter stopband broadens by 20% compared with the traditional DGS filter,and has high frequency selectivity.At the same time,the circuit size is 28 mm * 13 mm,which achieves the filter miniaturization.A a new type of ultra-wide stopband CPW low-pass filter is designed by using non-periodic cascaded five-cell fence-type DGS and H-type shunt parallel sections.At last,based on the research of the ring-slot resonator DGS structure,an ultra-wideband bandpass filter is designed and the structure is optimized.The out-of-band selectivity is improved by increasing the coupling length of the microstrip line.Using the low-pass filter with fence-type DGS to improve the out-of band suppression of the structure.Based on the embedded U-shaped open-circuit branch,a single-notch and double-notch ultra-wideband filters are designed respectively.