| Modern wireless communication systems are developing rapidly to miniaturization,low cost,high integration and high performance.Antenna and filter are the key devices in the transceiver front end of the radio frequency communication systems.The antenna and filter are usually designed independently.Therefore,the separated antenna and filter need to be connected through additional transmission lines to make the signal power forward.The extra transmission lines inevitably increase the system size,bring extra loss,and may deteriorate the system performance.To address this problem,the integration of the antenna and filter(called filtering antenna)has been widely studied in recent years.Filtering antenna has both filtering and radiation functions.Over the passband,it can not only achieve good radiation characteristics,but also obtain high gain selectivity and high gain flatten.Compared with conventional independent antennas,filtering antenna has great advantages.Commonly,the key indicators of antenna,including radiation gain,main beam width and sidelobe level,largely determine the performance of the entire wireless system.But these indicators are always interacting with each other and hence a trade-off consideration is required in practical engineering.Low sidelobe has become a hot and challenging topic in the design of high performance antenna array.The lower sidelobe can improve the signal-to-noise ratio,reduce the clutter signal interference outside the main beam,and effectively improve the anti-interference ability of the wireless system.In this work,the waveguide structure is utilized to study and explore the filtering antenna array.First,a single unit coupled resonator filtering antenna based on the coupling matrix theory is analyzed and studied.Then the multipath coupled resonators are introduced symmetrically to realize an eight-unit array with uniform excitation,which effectively improves the radiation gain.Further,in order to achieve low sidelobe,an approach of design of non-uniform excitation filtering antenna array based on coupling matrix is proposed.Experiments are carried out on a non-uniform eight-unit waveguide array to verify the effectiveness of the approach.The simulated and measured results show that the non-uniform eight-unit waveguide filtering antenna array has excellent filtering and radiation performance,including: high gain selectivity,high gain flatness,high efficiency and low sidelobe.The designed array is suitable for practical wireless communication systems and has been published on IEEE Transactions on Microwave Theory and Techniques.As an extension of this work,to deal with more complex coupling topology in the future,this thesis finally explores an approach of coupling matrix optimization based on reinforcement learning,and experiments are carried out to verify the feasibility of the proposed optimization approach. |
