Research On Novel Electric Tunable Microwave Components And Antennas

In recent years,with the continuous development and progress of wireless communication technology,the requirement for tunable or integrated components and antennas has increased.The portability and miniaturization trend of the development of radio frequency equipment urgently needs filters and antennas with simple structures and excellent performance.In addition,various novel materials are favored by more and more scholars.As a new type of carbon-based material,graphene has the characteristics of electric and magnetic field controllability,good optical and thermal conductivity,mechanical flexibility and so on,which brings new innovative ideas for the stage of microwave and millimeter wave.In this context,this thesis mainly studies a filter with electrically adjustable working center frequency and bandwidth at the same time,a filtering antenna with adjustable zero point and multiple function,and a tunable antenna based on graphene ink.The main research aspects of the thesis include:(1)A new type of tunable bandpass filter with simple circuit structure based on coupled line structure and varactor tuning technology is devised.The formula for the design of filter is strictly inferred,and the operating basic of the tunable filter is explained.By discussing the different positions of the ports,the superiority of the diagonal port design is obtained by force of contrast.For the sake of explaining the scalability of the filter structure in more detail,a third-order tunable filter is simulated by introducing an additional capacitor.With the purpose of proving the validity of the design,the second order tunable filter is designed,manufactured and measured.The adjustable center frequency of the finally processed prototype is 0.494?1.257 GHz(87.15%),and the 3-dB adjustable bandwidth is 0.282?0.943 GHz(334%).The relevant research has been published in IEEE Access which can be retrieved by SCI.(2)On the basis of the principle of open circuit resonator,a filtering antenna adopting CPW and differential fed mode and possessing with multi-functions is designed.Through the discussion of the parameters of two pairs of slots,the regulatability of the filter zeros is analyzed and explained in detail.Considering the bandwidth range and selectivity,a CPW differential filtering antenna was designed and processed.Its working frequency(|Sdd11|<-10 dB)of 3.27?4.54 GHz(1.27 GHz,32.52%),and the maximum gain of 9.11 dBi,are obtained.The antenna combines multiple functions with characteristics of wide-band,CPW and differential fed,filtering response and high gain.The relevant research has been applied for invention patent and authorized.(3)A tunable slot antenna based on graphene material is designed.The tunable antenna is composed of a traditional "open" slot antenna and graphene ink material loaded at the end.When the surface conductivity of the graphene ink changes,the antenna can achieve adjustable working bandwidth.The printed graphene inks deposited onto the antenna are made of graphene powder and graphene oxide aqueous dispersion.Graphene oxide sheets function as effective surfactants rendering assistance to form uniform inks;meanwhile,the tailored blending proportions endow the graphene inks with optimized original resistances.Dried graphene inks display alterable electrical resistance under DC voltages and the variation in the resistance affects radiation of the antenna.The slot antenna realizes an operating bandwidth(reflection coefficient |S11|<-10 dB)from 2.83 GHz to 6 GHz and a maximum frequency shift of 0.54 GHz after applying DC voltage less than 15 V.The related research has been published in Nanoscale which can be retrieved by SCI.