Research On Filtering Antenna Base On Coupling Matrix

As the communication channel become more and more crowed, the high suppression of stop band of the system is proposed, in order to reduce interference between channels. As the nonlinear devices of system will deteriorate suppression of the stop band, the filter is introduced in the middle of system but not meet the requirements at some system. Therefore, the filter need to add in the after of the antenna for enhancing the suppression of stop band. In the conventional communication system, antenna and filter are treated as individual device and designed independent, and then directly connected. For this design scheme, the whole performance will be easily deteriorated. Especially, the band width of antenna is close to the band width of filter. Therefore, the research of filtering antenna becomes more and more concerned. Nowadays, the most designing of filtering antenna is that antenna replaces the last resonator of the filter and the last model is obtained by simulation and optimization. As for this scheme, it will take large time to obtain a relativity good result in the process of simulation and optimization. In this thesis,We use the theory of coupling matrix and diagnosis of filter to synthesis design of filtering antenna, which can expedite the designing and optimization of filtering antenna. At the same time, we can distinguish difference between the optimization result and goal. Antenna and filter are treated as a whole to design, which can optimize the whole performance. When the antenna is ascertained, the pass-band performance of filtering antenna can be controlled by adjusted coupling strength between resonators, thereby radiation pattern and pass band selectivity of filtering antenna will be design individually. In this thesis, the major task is that coupling matrix theory is used to synthesis design of filtering antenna and provides theory guidance for designing of filtering antenna. The main contents as follows:(1)Based on the theory of coupling matrix of filter analysis and synthesis, we research the difference and same between synthesis of filtering antenna and filter. At the same time, we propose a method of cascaded filtering antenna synthesis, which similar with synthesis of coupling matrix. Detail analysis the resonance character of antenna, and research the relationship of physical dimension antenna coupling strength between resonators and radiation pattern of antenna.(2)We use coupling matrix theory and filter diagnosis technique to design a single band filtering antenna. We research the method that extraction parameter of equalization circuit of filter of cascaded resonators. Comparing the difference between the coupling matrix of actual physical model and goal coupling matrix, research the mapping relationship between the coupling strength of resonators and the physical dimension. Practicing the method of filtering antenna optimization based on coupling matrix parameters extraction.(3)We extend the method of filtering antenna synthesis and design based on the coupling matrix theory and filter diagnosis technique to design dual band filtering antenna. We can use the dual band response character of conventional dual model resonator and deduce the dual band resonator unite for dual band filtering antenna. As the current distributions of the dual model resonator are different at different frequency, the coupling coefficient of two pass-bands can be adjusted independently. Finally, we achieve a dual band cascaded filtering antenna by optimization based on parameter extraction.