Theory And Application Of Multiport Filtering And Power Dividing Network Based On Dielectric Resonator

The increasing requirement of wireless communication system for multi-channel operation leads to the rapid increase of the number of filters in RF front-end circuits,which brings severe challenges to the volume,power consumption and integration of the system.The miniaturization,power consumption and performance of some devices are close to the limit of the current technology,while the miniaturization of devices is usually accompanied by the deterioration of performance,so it is difficult to make further breakthroughs in the design of a single device.Therefore,the two core components(the multiport power dividing network and the filters)of the feeding network are designed together in this dissertation.The research on the theory and application of multiport filtering and power dividing network has been carried out to break through the current technical bottleneck from the perspective of system integration.The main work and innovations are as follows:1.The two key design parameters of filter,external quality factor(Q_e)and couplingcoefficient,are taken as power distribution factors for the first time.Then,a new topology of multiport filtering and power dividing network is proposed.Compared with the traditional binary tree topology,the required number of resonators in the novel topology is significantly reduced,eliminating the restriction that the number of output ports is closely related to the number of resonators.Meanwhile,the filtering response and power distribution can be designed independently,which simplifies the design process and improves the design efficiency.On this basis,the universal design approach is proposed,which can be applied to the design with arbitrary power split ratio,the single-ended/differential structure and the hybrid structure with both single-ended and differential outputs.2.Under the guidance of the proposed theory,various filtering power dividingnetworks using ring-shaped dielectric resonator are designed.Based on the analysis of the electromagnetic field of the dominant mode,the external quality factor and coupling coefficient are studied.Furthermore,three kinds of filtering power dividing networks based on dandelion,binary tree and combination typologies are respectively designed to verify the feasibility of arbitrary power split ratio,single-ended/balanced structure,high-order response and odd/even number of output ports.For the proposed filtering power dividing network based on dandelion topology,the increase of the number of output ports doesn’t increase the circuit size significantly.Compared with the reported power dividing networks,the works in this dissertation have the good features of high selectivity,low loss and compact size.3.The proposed design approach for filtering power dividing network based onsingle-mode resonator is extended to the dual-band designs based on dual-mode resonator.By analyzing the characteristic of the modes in the dual mode dielectric resonator,a regional independent control method for the Q_e under two modes is proposed,which makes the implementation of arbitrary power split ratio in the two bands simple and efficient.The generation mechanism of transmission zeros between the passbands is analyzed by coupling matrix.Then,a variety of dual-mode dual-band filtering power dividing networks with equal/unequal power split ratio,in-/anti-phase output and both of the in-phase and anti-phase outputs are designed,respectively.The phase difference and power distribution in the two bands can be controlled independently by changing the position or length of the feeding probe,which provides convenience for different applications.4.A design method of multi-mode filtering power dividing network is proposed,which has the double miniaturization advantages of multi-mode resonator and fusion design.The multiple couplings in the dividing network are simplified into the power distribution among the modes,so as to avoid falling into the analysis of complex couplings.The power distributions between modes and output ports are both represented by Q_e.Accordingly,a multi-level energy distribution/combination method is proposed to simplify the design process.Then,the dual-band equal and unequal filtering power dividing networks based on a single quad-mode dielectric resonator are designed,which proves the proposed method.5.In order to verify the application value of the proposed filtering power dividing network for antenna array with low sidelobe,a three-way prototype using ring-shaped dielectric resonator is taken as an example to feed the three-element patch antenna array.The results show that the band selectivity is good.As the element in the middle of the antenna array gets more power,the sidelobe level decreases significantly,avoiding the influence of stray signals outside the main lobe and meeting the requirement for directivity.In conclusion,the design approach for multiport filtering and power dividing network has been discussed in detail in this dissertation.Then,a variety of simulated and the physical prototypes based on single-/dual-/multi-mode dielectric resonator are designed to verify the validity of the proposed method.Finally,an example is given to illustrate its application in multi-antenna systems.