Research On Integrated Filtering Antenna Based On Multi-mode Resonance

With the development and revolution of wireless communication technology,the requirements for miniaturization and integration of wireless devices are becoming more and more urgent.Recently,we need to solve the problem of integration of passive devices.Antennas and filters are both indispensable parts of the RF front-end(RFFE).As we know,it is traditional to design the filtering antenna by designing the filter and the antenna independently.Then both of them are cascaded with the matching structure which will increase the system size and the loss.It will be an effective way to solve this problem by integrating the filter and antenna which can help to realize miniaturization and improve efficiency at the same time.Based on the study and investigation of domestic and overseas research status,this thesis will use the multi-mode resonance technology to design several filtering antenna.The specific work is as follows:1.Single-band and dual-band filtering antennas are designed in the form of slot antennas.Firstly,a multi-radiation null SIW slot filtering antenna is designed.It is equipment with four radiation zeros outside the passband,which effectively improves the frequency selectivity.Besides,we give the electric field distribution and principle analysis of the radiation nulls.Based on this filtering antenna,another slot filtering antenna with high selectivity and controllable radiation nulls is designed.It realizes several properties including reducing the size,keeping the high selectivity and low profile and making the radiation nulls be separately controllable.The filtering antenna is processed and tested which presents a center frequency of 5.37 GHz and a-10 dB impedance relative bandwidth of 7.64%.The measured gain and radiation patterns are in good agreement with the simulation results.Finally,we design a dual-band SIW slot filtering antenna.The ratio of center frequency of the two passbands is 1.2.The gains of both of the passbands show little difference and they are smooth and steady.There are two radiation nulls between the passbands that contribute to high selectivity.2.Single-band and dual-band filtering antennas are designed in the form of patch antennas.Firstly,we design a filtering antenna with high-gain and high selectivity operating at 3.5GHz.It has two radiation nulls out of band and good band-pass characteristics.The filtering antenna is processed and tested which presents the-10 dB impedance relativebandwidth of 12.6%,and the gain higher than 7.8 dB.After that,this antenna is applied for creating a four-element MIMO array.By placing the antennas orthogonally and adjusting the gap and offset,isolation higher than 27 dB is achieved.Then a dual-band patch filtering antenna with passband center frequency ratio of 1.34 is designed..A single-layer substrate is used to contribute to reduce the processing costs and the structure profile.Additionally,it can be observed that the antenna has a compact structure.We have introduced two radiation nulls that can improve the frequency selectivity between the two passbands.This antenna does not use additional filtering structures and the gain of it is hardly reduced when compared with conventional patch antennas.