Research On Novel Filtering Power Dividers Based On Planar Transmission Line Resonators

With the continuous development of modern wireless communication technology,highly integration and cost reduction of circuit modules are largely demanded for the RF(radio frequency)front-end communication systems.To accommodate to this trend,a design concept of functional integration for components is accordingly raised.Due to the advantages of high performance,size miniaturization and low lost,functional integrated circuits are promising to be extensively applied to the wireless communication systems.On the other hand,in the RF front-end systems,both functions of frequency selection and power division are usually required,making filters and power dividers indispensable on this occasion.Therefore,how to carry out the functional integration design for filters and power dividers and realize high performance and size miniaturized filtering power dividers becomes one of the current research hotpots.In view of some issues and defects in the design methods and performances for the present reports of filtering power dividers,a series of novel and efficient solutions are proposed based on transmission line resonators in this dissertation.Meanwhile,several novel filtering power dividers for different applications were designed based on the printed circuit board(PCB)technology.The main content of this dissertation is as follows:1.Researching new coupling schemes of stepped-impedance resonators and proposing new design methods of filtering response and isolation network for dual-band filtering power dividers: Firstly,by studying a new coupling scheme of two three-quarter wavelength open-circuited stepped-impedance resonators(SIRs),a dual-band filtering power divider with multiple transmission zeros and high selectivity is designed.Herein,to achieve good port-to-port isolation and impedance matching,a new way to obtain the location and the resistance of involved isolation resistor is presented according to the principle of impedance transformation.By simulation and experiment,the feasibility of proposed method is verified.Then,a novel self-coupled approach of SIR is proposed by further investigating the threequarter wavelength open-circuited SIR.Compared with the traditional counterpart,this selfcoupled SIR can achieve a larger ratio of the first two resonant frequencies.By using this property,a novel dual-band filtering circuit with a wide range of controllable frequency ratio is designed.2.Proposing new implementation methods for wideband isolation performance of power dividers based on the coupled three-line and researching the novel designs of high performance wideband filtering power dividers with microstrip and coplanar waveguide(CPW)resonators: Firstly,by using a short-circuited input feeding line and a pair of multimode resonators connected by an isolation resistor,a high selective wideband filtering power divider is designed,where the isolation performance is determined by both of short-circuited feeding line and resistor.Then,based on the broadside coupling of microstrip line and CPW resonators,a miniaturized filtering power divider with ultra-wide bandwidth is proposed and high isolation over the wide passband is achieved by designing an impedance transformer with good matching performance at all frequencies.Finally,by coupling the short-circuited input feeding line with several single-mode stub resonators,a dual-wideband filtering power divider is proposed.Both of theoretical and experimental results indicate that these designed wideband filtering power dividers exhibit high frequency selectivity and good port-to-port isolation.3.Proposing a new differential feeding structure based on the coupled three-line form and researching the novel design of balanced-to-balanced filtering power divider with impedance transformation: At the beginning,the relationship between mixed-mode Sparameters of a six-port symmetrical network and its even-/odd-mode equivalent circuit bisections is derived for guidance.Accordingly,the design principles of a balanced filtering power divider,including the filtering response,isolation performance,common-mode suppression as well as cross-mode conversion,can be respectively obtained.Then,by combining a three-line differential feeding structure with a microstrip multi-mode resonator,a compact balun bandpass filter(BPF)exhibiting balance to unbalance transformation is proposed.Meanwhile,according to the property of coupled-lines,the impedance transformation between balanced and unbalanced ports is analyzed.Finally,an impedance transforming balanced-to-balanced filtering power divider is presented with the designed balun BPF and additional lumped elements.Both simulation and measurement results verify the efficiency of the proposed design method.4.Proposing a new design method of isolation network for out-of-phase power divider and researching the novel designs of out-of-phase filtering power dividers with different bandwidths based on the slotline and microstrip resonators: Firstly,according to the design principles,an out-of-phase power divider prototype with perfect isolation and impedance matching at the center frequency is proposed by using a microstrip-to-slotline transition.Then,by wisely integrating the multi-mode resonators and stepped-impedance resonator with the proposed structure,two types of out-of-phase power dividers with narrowband and wideband filtering responses have been achieved,respectively.Both simulated and measured results indicate that the designed circuits exhibit good balanced phase performance,high selective filtering response and high level of port-to-port isolation.