Research And Design On Electronic Magnetic Coupling Filters Based On Multilayer Configuration

As the key component for the frequency spectrum separation, microwave filters always the hot topic of mic rowave passive circuit research,and attracts extensive attentions. With the rapid development of the wireless communication s ystems, the use of the frequency spectrum becomes meticulous “piece by piece” and this leads to a strict requirement to filter selectivity capabilities. Moreover, compact size, low insertion loss also play an important role in filter performance. Base on above analysis, this thesis concentrate on generalized C hebyshev function response filter with compact size and highly selectivity.First of all, the thesis illustrates the generalized Chebyshev function synthesis theory in details. And analyzes the theory of several coupling topologies,which are widely adopted to realize generalized C hebyshev function filters. What`s more, this design focuses on the mixed electric magnetic coupling and mixed cross coupling technique, and illustrates the theory of generating limited frequency controllable transmission zeros. After this, make comparison of two main coupling techniques, cross-coupled and mixed coupling, achieve the advantages and disadvantages of dual coupling topologies.Secondly, interdigital structure is embed into the Open-Loop resonator, a compact mixed electric and magnetic(EM) coupling narrow bandpass filter with highly selectivity is designed and fabricated for the first time. Two transmission zeros generated by mixed coupling and distributes in the high- and low- rejection band respectively and improved the selectivity of proposed filter. At the same time, by properly adjusting the ratio of electric and magnetic coupling, the transmission zeros can be adjusted readily. Also analyze the effects of interd igital capacitor for filter performance. A novel defect ground structures is added in hexagon filter, and expand the frequency bandwidth successfully.And then, the electric and magnetic signal propagation in the multilayer dielectric substrate is analyzed. Base on this theory, a multilayer SIR is designed and adopted to a compact cross-coupled filter. The size of this filter is only 1/4 of that of conventional filter, as well as good selectivity and spurious suppression. The next part of this thesis is a miniaturized multilayer bandpass filter, due to large inner capacitor achieved by multilayer configuration, the size of this filter is decreased sharply. A mixed coupled filter with parallel topology is designed. The size of this miniaturized filter is only 1/16 of conventional one with good selectivity performance. At last, a novel mixed coupled Step-Impedance-Resonator is proposed to generate the mixed coupling path in a cross-coupled filter. Base on this mixed topology, a multi- transmission zeros filter with highly selectivity and miniaturized size, as well as spurious suppression is fabricated and measured. Furthermore, the mixed cross coupling technique used in this design is efficient, simple, and easy to be implemented.