Research And Integrated Design Of Microstrip Filters And Antennas

With the development of the electronic communication equipment,the microwave and RF circuits with miniaturization and integration are attracting more and more attention.In the communication equipment,the filters and antennas are the key device with can not be replaced.Filters and antennas with better function can greatly optimize the performance of the communication equipment.Therefore,how to design a small and easily machined filter or antenna have become a hot research field.In this paper,several filters and antennas have been designed and simulated,and also a filtering antenna has been designed.The main contents are as follows:(1)Based on the spiral resonator with open and short stubs,three filters have been designed,including three-mode bandpass filter,dual-band bandpass filter and dual-band bandstop filter.Firstly,a spiral resonator with three modes has been analyzed by odd-and even-mode analysis.The influence parameter on three resonant mode is also studied.Next,by changing the length of the stubs,three resonant modes can be moved to different frequencies and thus different filters can be designed.When the three resonant modes are close to each other,a bandpass filter with three resonant modes can be obtain.However,if the first mode is far away from the other resonant modes,which caused by the change of stubs length,a dual-band passband can be achieved.Similarly,if the third mode is apart from the other mode,a bandstop can be designed utilized different feedline.(2)Three different planar microstrip antennas have been designed,whose bandwidth is widened by using diverse methods.A planar quasi yagi antenna is designed and several parasitic patches and short stubs are added to the antenna to create a new resonant mode,thus the bandwidth of antenna can be greatly increased.Then a coplanar waveguide fed UWB antenna using embedded E-shaped structure with WLAN band-rejection.In order to shield the signal interference from the WLAN,a pair of L-shaped stubs is added to the ground of the UWB antenna.Finally,two patch antennas with parasitic patches and shorting pins are presented.The parasitic patches can introduced extra mode to increase the operation bandwidth of antenna,while the shorting pins are working as the can optimize the impedance of the antenna,leading to the bandwidth optimization.(3)A planar filtering antenna has been designed.Without changing the size of the antenna,a bandstop filter is added to the structure of a quasi yagi antenna,resulting in the selectivity of the antenna at the higher frequencies is optimized.The principle of band stop filter is analyzed and the null points and resonant modes are calculated by using the ABCD matrix and odd-and even-analysis.Owing to the bandstop filter,the superfluous gain of antenna can be suppressed and the interference from other signal frequency can be prevented.