Investigation And Design Of SIW Balanced Passive Devices With High CM Suppression

Balanced passive components become more and more popular in modern high-speed wireless communication systems due to their advantages of noise immunity,low electromagnetic interference.The substrate integrated waveguide(SIW)technology has been widely used in the designs of microwave and millimeter-wave devices,which has the advantages of low profile,low insertion loss,high power capacity,and ease of integration with planar circuits.In this dissersation,a novel balanced SIW filter,power divider,directional coupler,filtering crossover and balun filter with compact structure and high common-mode suppression are developed based on SIW technology.The main works and innovations in this thesis are summarized as follows:1.A compact balanced bandpass filter(BPF)with high selectivity and good common-mode(CM) suppression is proposed by adopting the TM dual-mode SIW cavity.The SIW cavity is connected to the input and output by the way of microstrip-slotline transition.Under differential-mode(DM) operation,two TM modes(TM₁₂₀,TM₂₁₀)of the SIW cavity can be effectively excited,and simultaneously two transmission zeros(TZs)can be generated near the passband edges. Meanwhile,by designing the rotation angle and size of coupling slots reasonably,the deep stopband performance can be realized over a wide frequency range.Furthermore,the CM signal is effectively rejected because the magnetic current cannot be transferred to the coupling slot from the virtual open-ended microstrip feedline.The balanced BPF prototype is implemented and fabricated.The measured results agree well with simulated ones.2.Based on the boundary conditions of perfect electric/magnetic conductor(PEC/PMC),some compact multilayer balanced SIW or HMSIW passive devices are presented by two vertically stacked identical SIW or HMSIW single-ended ones and an aperture etched on the common ground between them.Under common-mode(CM)operation,the aperture is PMC.When the height of SIW is less than?_g/4,the space between PEC and PMC cannot transmit electromagnetic wave and the edge of aperture is open circuit.So,the aperture structure in SIW can effectively cut off CM noise over a wide frequency range.For the HMSIW,the spoof surface plasmon polariton(SSPP)structure is further loaded in the aperture near the open circuit plane to suppress the slot line mode.The CM suppression can be basically made independent of the DM response,which is very important to simplify the design and tuning processes.For the verification,balanced SIW filter,SIW power divider and HMSIW directional coupler are designed with high CM suppression.Finally,the balanced SIW filter and HMSIW directional coupler are fabricated and measured,and the measured results agree well with simulated ones.3.The differential transmission and inherent CM suppression characteristic of SIW is studied and analyzed.Then,the compact balanced BPF and filtering crossover are proposed with intrinsic CM suppression by using a single-layered SIW cavity and a microstrip differential transition structure.For the design of balanced SIW BPF,the differential-mode(DM)equivalent half circuit is single-ended SIW filter with height halved.Then,a compact SIW balanced filtering crossover with good performance is proposed using the degenerate modes TE₁₀₂,TE₂₀₁.Finally, because the electric field distribution and resonance characteristics of SIW cavity under differential and single-end excitation remain unchanged,a third-order balun filter with excellent amplitude imbalance and 180°phase difference characteristics is designed.The balanced filter and filtering crossover are fabricated and measured,and the measured results agree well with simulated ones.