Properties of multisection transdirectional coupled-line couplers

Properties of multisection transdirectional coupled-line couplers

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This study is presented to explore the properties of multisection transdirectional coupled-line couplers (TRD CLCs) developed for bandwidth enhancement. Unlike conventional multisection contradirectional coupled-line couplers (CTD CLCs) comprising only CTD CLCs, the proposed multisection TRD CLCs may require the combination of transdirectional and CTD CLCs for some higher-order designs. The designs feature a central TRD CLC. A symmetrical structure with respect to the central coupler is proposed to meet the port assignments of transdirectional couplers with broadband performance on the magnitude difference as well as the phase difference of 90° between two output ports. It can offer multiple solutions for some multisection designs. Practical examples are presented for 3 dB multisection TRD CLCs with optimum coupling coefficients assigned to individual couplers to achieve maximum bandwidth. Periodic structures are used to implement coupled-line couplers. Simulation results indicate that the proposed multisection designs meet the required port assignments and offer wider bandwidth compared to a single design of the same coupling. The simulation results of the three-section design are verified experimentally and good agreement is observed.


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