Research On Unbalanced-balanced Power Division Filter Circuit Based On Double-sided Parallel Stripline

With the rapid development of modern wireless communication technology,radio frequency(RF)front-end system is moving towards the trends of high performance,miniaturization,low cost and high integration.And some significant components of RF front-end system will affect the performance of the whole system,such as filters,power dividers and baluns.However,the existing method of device integration is to cascade them directly,which not only does not reduce the number of passive devices,but also introduces unnecessary losses.So how to improve the integration of these passive devices is of great significance to the high performance design of RF front-end system.On the other hand,balanced circuits have the advantages of noise suppression and electromagnetic crosstalk reduction.Therefore many active and passive components have been designed into balanced circuits,such as balanced amplifiers,balanced antennas and so on.However,all the input and output ports of these devices are balanced ports and cannot be directly connected to unbalanced circuits,so it's essential to design the transformation of unbalanced-to-balanced.Based on the above background,this paper will focus on the unbalanced-to-balanced filtering power divider(UBTB FPD)which integrates the functions of power division,signal selection and balun.In this paper,an UBTB FPD with wideband common mode(CM)suppression and a dual-band UBTB FPD with equal or unequal power ratio are proposed.The specific research contents of this paper are as follows:1.Firstly,this paper summarized the research background and current situation of UBTB FPD to clarify the significance of the work in this paper.Then the theoretical foundation related to this paper has been introduced in detail,including the S parameter matrix of multi-port device,the technical index and design principle of UBTB FPD,as well as the working characteristics of DSPSL.It will provide theoretical foundations for the research of this paper.2.An UBTB FPD with wideband CM suppression has been proposed in this paper.To effectively realize high suppression of CM noise and improve the rejection of second harmonics for the differential-mode(DM)transmission,a hybrid structure constructed with DSPSL and HMDGS are adopted.Meanwhile,by employing two pairs of dual-mode resonators symmetrically coupled with a stepped-impedance input feed line,wideband filtering performance is achieved.In the end,to realize high selectivity,an adjustable transmission zero was introduced by adding a DSPSL stub at the end of the input feed line.3.A dual-band UBTB FPD and an unequal FPD are proposed based on DSPSL.As a further study,this structure also achieves wideband CM suppression.Besides,by employing step impedance stubs loaded quarter-wavelength(?/4)three-line coupled structure,a dual-wideband filtering performance with high selectivity is achieved.Meanwhile,two resistors are adopted to obtain good isolation between two balanced output ports.Finally,a dual-band UBTB FPD is obtained,which integrates power distribution,frequency selection,conversion from single-ended signals to balanced signals and dual-band response.Finally,as an extension of this study,a dual-band UBTB FPD with a power ratio of 2:1 is obtained by changing the coupling coefficients between the central line and the two side lines.