Design And Research Of Miniaturized Broadband Antenna Based On Parasitic Cell Structure

In recent years,with the rapid development of wireless communication technology,the performance requirements for wireless communication equipment are also increasing.As an indispensable part of the RF circuit front-end transceiver signal,the antenna faces many challenges both in performance requirements and in structural design.First,the broadband transmission,multi-band transmission of the antenna and the need to suppress external electromagnetic interference.Second,the antenna structure should meet the requirements of miniaturization and compactness.Therefore,by loading the parasitic element structure on the basis of the ordinary microstrip antenna,on the one hand,multiple resonant frequency points can be generated to achieve the multi-frequency characteristics of the antenna;on the other hand,the adjacent working bands can be coupled to broaden the frequency bandwidth of the antenna.Also,parasitic modules are effectively arranged to meet the requirements of miniaturization,compactness and low power consumption.In this paper,the parasitic element technology is mainly used to study how to broaden the antenna bandwidth,realize the characteristics of multi-band operation and reduce the antenna size.At the same time,the differences of antenna performance caused by different parasitic element structures are discussed,and several antennas are designed for verification.The specific contents are as follows:Firstly,a dual-band microstrip antenna based on asymmetric distributed parasitic elements is designed.The high-frequency bandwidth is expanded by loading a rectangular parasitic patch above the rectangular radiation patch with a T-shaped slot.The rectangular parasitic patch is loaded on the right side to suppress the cross polarization caused by eccentric feeding of the antenna.The rectangular coupling slot is opened near the strip of the metal grounding plate to realize the effective transmission of electromagnetic wave energy between the active patch and the parasitic element.The analysis is carried out from the aspects of antenna structure design and evolution,feed design and equivalent circuit.Finally,the dual-frequency broadband characteristics of the antenna are realized,with 3.40~3.70 GHz(8.57 %)and 5.49~6.18 GHz(11.9 %)bands covered,and the overall structure of the antenna is simple.Secondly,based on the dual-frequency broadband antenna,the approximate rectangular defected ground structure(DGS)is introduced.By loading a closed parasitic ring in the center of the DGS,the flow direction of the surface current of the ring in the ring is changed to realize the three-frequency broadband characteristics of the antenna.The principle of DGS,parasitic ring structure and feed structure impedance matching network are analyzed.Through the optimization and simulation of antenna parameters,the coverage bands of antenna are 2.10~2.67 GHz(23.9 %),3.35~4.15 GHz(21.3 %)and 7 ~ 8.07 GHz(14.2 %),respectively.It can be used in WLAN/WIMAX/duplex mode n77 and other commonly used microwave band systems.Thirdly,an ultra-wideband fractal slot microstrip antenna loaded with parasitic patches is designed.Through the combination of coplanar waveguide feeding form and fractal structure,coupled with the joint action of fractal circular patches in the parasitic layer,the ultra-wideband characteristics of the microstrip antenna are finally realized.The covered band is 2.38~7.03 GHz,and the relative bandwidth can reach 98.83 %.The maximum measured peak gain in the working band is 5.3 d Bi.In this paper,the effects of the rectangular rotating fractal structure and the fractal iteration order on the antenna performance are analyzed and compared.The final size of the antenna is determined by optimizing the fractal structure parameters and loading the parasitic layer parameters.Finally,the actual test and performance comparison are carried out.Fourthly,under the concept of ultra-wideband antenna,in order to avoid the interference of ultra-wideband system on common communication bands,an ultra-wideband multiple notch microstrip antenna is designed.The antenna loaded four C-shaped parasitic bands with different sizes on both sides of the feeder,and opened a rectangular ring resonator with an opening in the rectangular active radiation patch with a defect angle.From the analysis of the notch characteristics,input impedance and equivalent circuit model,the five-fold notch characteristics of the antenna were finally realized.The notch bands were covered by 2.31~2.6 GHz,3.16~3.78 GHz,5.69~6.02 GHz,7.21~7.51 GHz and 8.93~10.97 GHz,respectively.The electromagnetic interference between UWB communication system and common bands such as ISM/WIMAX/WLAN/C band is effectively suppressed to meet the design requirements,and the flexibility of antenna design is also enhanced.There are 78 figures,8 tables and72 references.