Research On Active And Passive Multi-functional Filtering Circuits Based On Collaborative Design

In radio frequency front ends of wireless systems,there are lots of active and passive circuits,such as filters,power amplifiers,switches,couplers and so on.Generally,they are cascaded in wireless systems,which suffer from large circuit size,high insertion loss,or efficiency degradation due to the impedance mismatching.To solve these problems,two or multiple circuits can be integrated as a multi-functional circuit for integration improvement,loss reduction or efficiency enhancement.Although there are some multi-functional circuits having been reported previously,the design theories need to be further completed and the performance in terms of miniaturization and power consumption should be further improved.Thus,novel methods for collaborative design of multiple circuits are proposed in this thesis,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 anothor circuit,which can simplify the circuit structures to reduce the size and loss.Based on the proposed collaborative-design and multifunctional-fusion methods,a lot of active,passive and dual/multi-channel filtering circuits are proposed,which include the following three sections:1.In order to improve the overall efficiency of the power amplifier,switch and filter,integration of filters and active circuits(including switches and power amplifiers)are conducted.To improve the overall efficiency by reducing the total losses of the switch and filter,coupling control method are proposed to fuse the functions of filter and switch.Then,single-and dualband filtering switches are designed using LTCC techniques.To meet the requirements of highpower and narrow-band base station applications,single-pole single-throw and single-pole double-throw filtering switches are proposed using high-Q dielectric resonators.Moreover,to avoid the efficiency degradation by the impedance mismatching between the cascaded power amplifier and filter,collaborative design of Class-F power amplifier and high-selectivity bandpass filter with cross coupling is proposed.Related research results have published several IEEE journal papers,including IEEE Transactions on Microwave Theory and Techniques and IEEE Transactions on Industrial Electronics.2.To reduce the loss and size of passive circuits,integration of filters and other passive circuits are studied.Based on the working mechanism of a conventional Marchand balun,the half-wavelength and quarter-wavelength transmission lines in the conventional Marchand balun are utilized as resonators.And then,by only adding three feeding lines to the Marchand balun,filtering responses can be fused to a balun circuit and a miniaturized LTCC filtering balun is realized.By using a common dual-mode resonator,a compact LTCC diplexer is designed with a simple structure.Two novel design methods are proposed to improve isolation of the common-resonator-based diplexer.Moreover,the channel frequencies and bandwidths of the proposed LTCC diplexer can be controlled separately.By constructing a multi-mode dielectric resonator,the circuit function of rat-race coupler can be fused into the filter structure,and then a single-cavity-configuration filtering rat-race coupler is designed with miniaturized circuit size.Related research results have published several IEEE journal papers,including IEEE Transactions on Microwave Theory and Techniques.3.For high integration,multiple filtering circuits with the same performance are integrated as one circuit.Then,dual-channel and multi-channel multi-functional filtering circuits are proposed.Based on a quad-mode dielectric resonator,two filters with the same performance are integrated as one dual-channel filter to reduce the size.And this dual-channel filter is collaborative-designed with a two-input two-output Doherty power amplifier to realize high integration and high efficiency.By analysing the electromagnetic-field properties of a cubic dielectric resonator,it is found that the three orthogonal degenerate modes of dielectric resonators can be excited for different filter channels with isolation,and then a multi-channel filters are proposed.Besides,by using a quad-mode dielectric resonator,two balanced filters or two balun filters are integrated as a high-integration dual-channel balanced filter or balun filter.Related research results have been published several IEEE Transactions on Microwave Theory and Techniques journal papers.In this thesis,the design methods or working mechanisms of the proposed multi-functional filtering circuits are detailed.The circuits are fabricated and measured to show the validity of the proposed designs.As comparison to other reported designs or products of some international componies,the proposed designs show the advantages of miniaturization or low power comsumption,which are potential in wireless applications.