Active and Passive Multi-Functional Filtering Circuits Based on Collaborative Techniques

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In radio frequency front ends, there are lots of active and passive circuits, such as filters, power amplifiers (PAs), switches, couplers and so on. Generally, they are cascaded in wireless systems, which suffer from the large size, high loss, or efficiency degradation due to impedance mismatching. To solve these problems, novel methods for collaborative designs of multiple circuits are proposed, and overall performance is improved by the complementation of different circuits. Design methods for fusion of multiple circuits are also proposed by constructing one circuit function into another circuit, which can simplify the structures to reduce the size and loss. Lots of active and passive multi-functional filtering circuits are proposed, including the following three sections: 𝟭. To improve overall efficiency of the PA, switch, and filter, integration of filters and active circuits are conducted. To reduce the total loss and improve isolation of the switch and filter, coupling control method is proposed to fuse the functions of filter and switch. To avoid efficiency degradation by impedance mismatching, the collaborative design of a class-F PA and a high-selectivity filter is presented. 𝟮. To reduce the loss and size, filters are integrated with other passive circuits. The functions of a balun circuit and a rat-race coupler are fused to a filter to realize the miniaturized filtering balun and filtering rat-race coupler, respectively. By using a common dual-mode resonator, a compact LTCC diplexer with controllable frequencies and bandwidths is designed. 𝟯. For high integration, dual-/multi-channel filtering circuits are proposed. Based on a quad-mode dielectric resonator, two filters are integrated as one dual-channel filter, and then collaborative-designed with a two-input two-output Doherty PA for high integration and high efficiency. For further integration, multi-channel filters and dual-channel balanced/balun filters are also proposed. In this thesis, design methods and working mechanisms of proposed multi-functional filtering circuits are detailed. Measured results are given to show the validity of the proposed designs. As compared to reported designs or products from some international companies, the proposed designs show advantages of miniaturization or low power consumption, which are useful in wireless applications.
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