Study And Design Of Innovative Balanced Devices In Radio Frequency Front-end

With the diversified development of wireless communication technology,it is an urgent affair and imperative trend for the radio frequency front-end(RFFE)to become multifunctional and highly integrated.Under such situation,on the one hand,the RFFE devices themselves are required to have various functions and compact sizes.On the other hand,in the increasingly complex electromagnetic environment,the more closely arranged electronic equipment and the more densely distributed signal transmission lines will all increase the difficulty of signal transmission.Fortunately,the balanced circuits can not only effectively suppress the common-mode(CM)signal,but also improve the system anti-noise and electromagnetic interference ability,so they are widely used in the RFFE.The power divider and the diplexer are both the core passive components of RFFE,so the research on the balanced power divider and the diplexer has important scientific significance and engineering value.Compared with the traditional single-ended power divider,the multi-function balanced power divider is perfect fusion of power division,port isolation,balanced-to-unbalanced signal conversion and CM suppression,which is of great significance to the integration of microwave circuits.And the diplexer can allow an antenna receive and transmit two or even multiple frequency signals at the same time,which will no doubt reduce the number of antennas in the communication system and further help the miniaturization of the system.Therefore,the balanced diplexer with the ability of noise immunity has also become a research hotspot.Aiming at relieving the strain of spectrum resources and improving the integration of the system and anti-noise ability,this dissertation focuses on designing the wideband filtering balanced power divider,multi-band filtering balanced power divider and multi-band balanced diplexer.Specially,the main contribution of this work is summarized as below:Firstly,a novel power division topology is proposed based on Gysel power divider,which is embedded multi-mode resonator to realize the wideband filtering function.At the same time,the effective transmission of differential-mode(DM)signals and good in-band CM suppression are realized by taking advantage of the different electrical characteristics of the circuit under DM excitation and CM excitation.Secondly,a compact balanced-to-unbalanced power divider with wide stopband and wide CM suppression is proposed.The power divider uses a U-shaped feed structure coupled with the stepped impedance resonator through the slot.Under different signal excitations,a bandpass coupling line or a stopband coupling line is formed respectively,thus realizing the full stopband suppression of common-mode signals.Subsequently,the resonant characteristics of the short-ended stepped-impedance resonator are analyzed.Moreover,the hybrid electromagnetic coupling technology is used to design a new cascade way of the resonators,closely followed by designing a two-order dual-band balanced-to-unbalanced filtering power divider with flexible frequency ratio and good frequency band selectivity and CM rejection capability.Finally,the resonant characteristics of the multi-branch stepped impedance resonator are analyzed,and two designs of unbalanced-to-balanced four passbands diplexers are presented by the direct feed to resonators via the single-terminal transmission line for the energy conversion between unbalanced port and balanced port.And the two schemes have both good frequency band selectivity and high isolation.In order to verify the correctness of the theoretical derivation and the feasibility of the design schemes,the above designed devices have been simulated and manufactured.Tested results of those fabricated circuits are well agree with the simulated ones.