This article proposes a novel substrate integrated suspended line (SISL) platform with multiple inner boards, and it uses all FR4 material with very low cost. A new coupling scheme which significantly eliminates the dielectric loss is proposed. When compared with the conventional multilayer coupled-line circuits where the coupling is from one metal layer to another metal layer on the same board, the proposed coupling scheme is between different inner boards, and there is almost no lossy substrate in the coupling region. As demonstration cases, a broadside coupled-line coupler and a coupled-line Marchand balun are designed, fabricated, and measured. The obtained performances are excellent when compared with the state of art, though very low-cost FR4 materials are used. The proposed coupled-line circuits based on multiple inner board SISL using FR4 material have advantages of low loss, low cost, and self-packaging.

中文翻译：

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具有多个内板的低成本基板集成吊线平台及其在耦合线路电路中的应用

本文提出了一种具有多个内板的新型基板集成悬浮线（SISL）平台，该平台以非常低的成本使用了所有FR4材料。提出了一种新的耦合方案，可以显着消除介电损耗。当与传统的多层耦合线路电路进行比较时，传统的多层耦合线路电路是在同一板上从一个金属层到另一金属层进行耦合的，因此所提出的耦合方案是在不同的内板之间进行的，并且在耦合区域中几乎没有损耗的基板。作为演示案例，设计，制造和测量了宽边耦合线耦合器和马尔肯巴伦耦合线。尽管使用了非常便宜的FR4材料，但是与现有技术相比，所获得的性能非常出色。