Research And Design Of SIW Filter Power Divider With Isolation Characteristics

With the rapid development of modern communication system,the requirement for miniaturization of microwave and radio-frequency(RF)circuits is increasingly high.Filters and power dividers are important components of RF front-end which are connected in cascade in traditional RF circuits.The filtering power divider is a combination of filter and power divider in function.Because of its characteristics of filtering and power dividing,the filtering power divider has become an important means of realizing miniaturized RF frontend,and has a broad application prospect.As the substrate integrated waveguide(SIW)structure has the advantages of low cost,low loss and high integration,it provides a solution for high frequency power dividers.In this thesis,filtering power dividers with good isolation are studied and designed based on SIW structure.Firstly,a novel isolation structure—resistor across half-mode substrate integrated waveguide(HMSIW)structure(resistor-across-HMSIW structure),is proposed in order to improve the isolation between outputs.Moreover,the relationship of the value of the isolation resistor in the ideal circuit model and the physical circuit model is analyzed.An SIW filtering power divider is designed and fabricated based on the isolation structure in this thesis.Better than 22 dB of isolation in the SIW filtering power can be realized while two transmission zeroes are introduced by cross-coupled in order to improve the selection characteristic of SIW filtering power divider.Secondly,isolation structure with double resistances across coupled lines is proposed in order to improve the isolation of two passbands in the dual-band filtering power divider.By using this isolation structure,a dual-band filtering power divider based on SIW triangular cavity is designed.The design parameters and the design method of the isolation structure of the dual-band filtering power divider are analyzed in this thesis.Better than 20 dB of isolation can be obtained in both passbands.Finally,the design method of resistor-across-HMSIW structure in filtering unequal power divider is analyzed.Two SIW filtering unequal power dividers with different bandwidth and power ratio are designed to demonstrate the design method.