Balanced‐to‐unbalanced and balanced‐to‐balanced filtering rat‐race couplers using multilayer substate integrated waveguide cavities

Abstract

This study reports a class of balanced-to-unbalanced (BTU) and balanced-to-balanced (BTB) filtering rat-race couplers (FRCs) based on multilayer substrate integrated waveguide (SIW) cavities. Input and output ports can perform the functions of balanced and unbalanced terminals to implement various operating states. The theoretical designs consisting of the mixed-mode scattering matrix and mode analysis are discussed in detail. Good differential-mode (DM) bandpass filtering (BPF) responses are obtained by two pairs of orthogonal degenerate modes in multilayer SIW cavities. Meanwhile, high common-mode (CM) suppression and port-to-port isolation are realized inherently due to mode distributions of the square SIW resonator. Accordingly, to verify the design concept, two types of BTU FRCs and one type of BTB FRC are designed and fabricated, respectively. Moreover, the measured results agree well with the simulated ones, exhibiting high performances in terms of CM suppression, magnitude/phase imbalance as well as port matching/isolation characteristics. K E Y W O R D Sbalanced-to-balanced, balanced-to-unbalanced, filtering rat-race couplers, substate integrated waveguideThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Analysis and design of weak coupling coupler based on the half mode substrate integrated waveguide

“…The performance will decline when these couplers achieve the same coupling. Currently, some proposed SIW coupler architectures [10–15, 18–20] can accomplish a weak coupling by changing parameters, but the performance will deteriorate seriously, and the directivity can hardly be used as an indicator to measure, which can also prove the superiority of the weak coupler proposed in this study.…”

“…The SIW couplers with different coupling structures are proposed in [10][11][12][13][14][15][18][19][20]. However, the biggest problem with these coupling structures is that the design variables are single, and the coupling coefficient cannot be effectively controlled.…”

“…The propagation constant γ 1 and equivalent length l 1 can be obtained by bringing w 1 into equations ( 19) and ( 20). 4) Taking the coupling degree C required by design and other calculated variables into equations (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), and calculating the equivalent width w 2 of coupling branch. 5) Optimizing L smm and W s in the electromagnetic simulation software, and adjusting the coupling and isolation in the entire frequency band.…”