| With the increasing complexity of wireless communication systems,the research on miniaturized and high-performance broadband bandpass filters becomes more important.Traditional band-pass filter designs suffer from large size and narrow stop-band range,making them difficult to use widely in modern systems.By using the defected ground structure(DGS),the filter can obtain a wide stop-band characteristic on the premise of satisfying the light weight.In this thesis,the study focused on the broadband filter based on the DGS and the characteristics of the broadband stopband,and the following work has been completed:Firstly,the dumbbell-shaped DGS and its transmission characteristics were analyzed.On the basis of this structure,through deformation,four-unit cascade dumbbell-shaped DGS and rectangular DGS were obtained.According to two kinds of DGS units,two kinds of wide stopband filters were designed and simulated.To the four-unit cascaded dumbbell-type DGS wide stopband filter,the filter achieved that the passband range was 5.92 GHz to 11 GHz and the bandwidth of-30 dB insertion loss stopband was 17.62 GHz to 41.98 GHz.The wide stopband filter based on rectangular DGS had a passband range of 6.92 GHz to 10.68 GHz,and a stopband range of 11.46 GHz to 34.8GHz under-20 dB insertion loss.The stopband range of two filter designs were greater than three times the center frequency of the passband,thus achieving a wide stopband.Secondly,using the compensation effect of DGS on the coupled microstrip line as the entry point,two broadband filters based on letter-shaped resonators resonator were designed.Among them,the simulation results of the broadband filter using the H-type resonator showed that the passband range is 8.0 to 13.2GHz,and the stopband range is 14.1GHz to 35.0GHz under the-15 dB insertion loss,which is greater than three times the passband center frequency.Finally,the rectangular ring DGS structure was obtained based on the traditional circular ring DGS structure deformed.After analyzing the structure,a filter based on the rectangular ring DGS was proposed.The simulation results showed that the filter achieves that passband range is 6.06 GHz to 10.86 GHz,and the stopband range under-20 dB insertion loss is greater than four times the center frequency of the passband.After actual processing and testing,the test results showed that the passband range is from 6.1GHz to 10.08 GHz,and the stopband range was greater than twice the passband center frequency under-20 dB insertion loss. |
