Research On Synthesis Design Method Of High-Selectivity Filtering Antenna

High integration and miniaturization are the developing directions of RF devices in wireless communication systems.Antenna and bandpass filters are indispensable passive devices.In traditional design,filters and antennas are designed separately and connected by a cascading network.This approach is not only bulky but also introduces additional losses,such as the loss of the matching network and the loss of port connections.In recent years,the integration of filtering function into antenna has become a research hotspot.This kind of antenna with integrated filtering function is called filtering antenna.The filtering antenna can not only reduce the loss of the communication system,but also reduce the complexity of the circuit.Based on the filter synthesis theory,this dissertation studies the synthesis design of the filtering antenna and puts forward the synthesis design technology of filtering antenna with different radiation structures.The main contributions of this dissertation are as follows:1.Synthesis design method of filter antenna based on microstrip resonator feeding has been studied.Firstly,a new dipole structure based on microstrip resonator conversion is proposed.The structure has not only a dipole structure but also a resonator structure,which means that it has not only the function of a dipole but also the function of a resonator.Based on this structure,a dual-polarization filtering dipole antenna is designed using the filter synthesis theory,which not only obtains the third-order filtering characteristics but also the gain in the passband is very flat.Secondly,a feeding probe structure based on microstrip resonator conversion is proposed.The feeding structure is equivalent to a resonator for the synthesis design of the filtering antenna.The CT topology filtering antenna and the CQ topology filtering antenna are designed by using the dual-probe feeding structure and cross-coupling,and both of them obtain high selectivity filtering performance.This part has been published in IEEE Trans.on AP and IEEE Trans.on MTT,and has been granted 1 invention patent.2.Synthesis design method of filtering antenna based on multi-mode cavity resonator has been studied.Firstly,a high selectivity cavity slot antenna is designed using a triple-mode rectangular resonator.Three resonant modes in the multi-mode rectangular cavity can be excited simultaneously by rotating and offsetting the slots,and transmission zeros are introduced on both sides of the passband to improve antenna selectivity.In order to improve the gain of the antenna,a grid-slotted patch is loaded above the antenna.The gain is increased by 4d Bi without affecting the filtering characteristics.Secondly,a mixed-mode cavity resonator structure is proposed.This structure can be rapidly designed according to the coupling matrix of different transmission zero distributions.Three filtering antennas with different zero distributions and a high selectivity filtering antenna array are designed based on the mixed-mode cavity resonator.This part has been published in IEEE Trans.on AP and IEEE Trans.on MTT,and has been granted 1 invention patent.3.Synthesis design method of filtering antenna based on a coaxial cavity resonator has been studied.A coaxial waveguide antenna with all metal posts structure is proposed.The filtering antenna can be designed only by configuring metal posts of different heights in the standard waveguide.Because some metal posts are coaxial resonators and some are coupling structures,the height of different metal posts can be determined according to the filter synthesis theory.A third-order coaxial waveguide filtering antenna with tunable center frequencies and bandwidths is realized by replacing the metal post with tuning screws.In addition,a coaxial waveguide filtering antenna with high selectivity is designed by combining the coaxial resonator with the resonant coupling structure to introduce the transmission zero,which can not only improve the selectivity of the antenna,but also suppress the out-of-band radiation characteristics.This part has been published in IEEE Trans.on AP and IEEE Trans.on MTT,and has been granted 1 invention patent.4.To reduce the size of the cavity radiation structure,the radiant metal block is proposed and used to design a filtering antenna.The current radiation modes of rectangular metal blocks are studied by the characteristic mode analysis theory and one of the characteristic current modes is used as the working mode.Compared with the cavity slot antenna,the proposed radiant metal block not only has higher gain but also has better out-of-band suppression characteristics.A second-order filtering antenna and a third-order filtering antenna array are designed by combining the radiating metal block with the cavity resonator,both of which obtain good filtering characteristics and high gain.This part has been published in IEEE Trans.on AP,and a patent has been applied for the invention.5.To solve the problem of complex topology networks in traditional filtering antenna arrays,the synthesis design method of filtering antenna arrays based on the high-order mode cavity resonator is studied.A method of near-field wavefront phase compensation is proposed to design a high-order cavity antenna array,which solves the problem of large sidelobe in traditional high-order cavity antenna arrays due to the long distance of radiation elements.A synthesis design method for a high-order mode antenna array is presented.A Chebyshev response filtering antenna array and a high selectivity filtering antenna array are designed based on the TE₅₀₁ mode cavity resonator.This part has been published in IEEE Trans.on AP.