Design Of The UWB Microstrip Bandpass Filter Based On DGS

Nowadays, more and more experts and scholars pay attention to the ultra-wideband(UWB) technology in the wireless communication system because of its unique advantages.As one of the most critical passive devices in the UWB systems, the UWB band-pass filterensures the scope of the spectrum of the signal to meet the requirements of the UWB system,so its design methods become a hotspot. At the same time, There are some base band signalinterference within the range of the ultra wideband3.1GHz~10.6GHz, such as5.15~5.35GHz and5.725~5.85GHz at the wireless local area network (WLAN) signal and6.8GHzat a radio frequency identification (RFID) signal. Therefore, the ultra-wideband notch filterhas important practical significance.This thesis is mainly for the design and the implementation of the band-notchedtechnique of the UWB band pass filter, work done as follows:Firstly, we extract the equivalent circuit of the dumbbell-shaped defected groundstructure (DGS) and analyze its transmission characteristics. On the basis of this, throughcascading the dumbbell-shape and loading open side in the microstrip line, we realize alow-pass characteristic. Furthermore, the wide stop band characteristics of the UWB filter isrealized through the combination with the stop band narrower UWB band pass filter.Secondly, based on the traditional dumbbell DGS deformation, we obtain the compositeU-shaped DGS with a narrow circuit lateral size, when the structure is coupled with thestepped impedance transmission line, the design of the ultra-wideband filter is realized. Onthe basis of it, by using the method of metal joint floor grooving achieve the effect of a notchat5.725GHz~5.85GHz, realize the function of filtering narrow-band interference signal ofWLAN in UWB frequency range. in order to further achieve the effect of a notch at8GHz, weslit on the step impedance transmission line to distinguish the C-band（4~8GHz） and theX-band（8~12GHz）.Again, we put forward a kind of ring type DGS with microstrip line coupling structureand deduce its equivalent circuit model, which realize the ultra-wideband effect, but poor inthe high-frequency side. This makes the general stop band distinguished with difficulty.Therefore, loading a parallel coupling side in the microstrip line and changing the location ofthe microstrip line could obtain the excellent effect of sideband ultra wideband filter. In addition, by adding open ring DGS on it, reached the function of filtered5.15~5.35GHz and5.725~5.85GHz at WLAN signal and6.8GHz at RFID signals.Finally, we use electromagnetic simulation software HFSS10.0simulate the above filters,the simulation results show that the design of microstrip filters in line with the desiredfunctionality.