A Research On Filtering Antenna Applied In Wireless Communication System

The wireless communication systems are in the direction towards miniaturization and integration.This trend puts forward higher requirements on the RF front-ends,especially for the two key components:filters and antennas.In order to suppress unwanted interference signals,high rejection bandpass filters are typically required after the receiving/transmitting antennas.The conventinal scheme is to design the antenna and the filter separately,and then use an impedance matching network to cascade the two compenents.However,this scheme will inevitably increase the system volume and complexity,as well as introducing additional losses by the matching network.In response to this important issue,researchers have proposed and developed theories and methods for the collaborative design of filters and antennas,a new type of multifunctional microwave device,which is named filtering antenna,is proposed and widely researched.The filtering antennas have both the filtering function of the filters and the radiation function of the antennas,which can effectively reduce the system volume and loss,as well as improving the overall performance.It indicates that the filtering antenna is very valuable for research,and has good application prospects.Based on the research status of filtering antennas,this thesis has proposeed the following theories and design methods for the filtering antenna:(1)A filtering antenna design method based on the principle of multipath coupling cancellation is proposed,and a dual-patch filtering antenna model fed by an F-shaped structure is established.Due to the phase difference between the radiation fields from the two patches,radiation nulls would be generated,bandpass filtering response could be realized without any extra filtering circuits.The design shows the characteristics of simple structure,broadband,high gain,high selectivity,etc.(2)A filtering antenna design method based on the principle of SIW cavity dual-mode resonance is proposed,and a compact circularly polarized filtering antenna model is established.The dual-mode(TE₁₀₂/TE₂₀₁ mode)SIW cavity mode characteristics and filtering characteristics provide necessary conditions for the realization of the circularly polarized radiation and filtering function.By introducing sparse vias,the magnetic coupling between the SIW cavity and the radiation patches is realized,and the original filtering performance of the cavity is retained.By introducing the folding structure,the beam splitting problem due to the excessively large radiation aperture is solved.(3)A filtering antenna design method based on the bandpass filter(BPF)prototype is proposed,and a microstrip filtering antenna model is established.By introducing the hybrid electromagnetic coupling scheme,the filtering performance is further improved.The technology exhibits the characteristics of simple design process,simple model,and good filtering performance.The technology solves the problem of excessive dependence on filtering circuits and complex bandstop/bandpass parasitic structures of existing technologies.