In this article, a new structure for balanced directional couplers (BDCs) in single-layer technology is presented for the first time. An innovative combination of single-section coupled lines, microstrip to coplanar waveguide (CPW) crossovers, and 180° transmission lines (TLs) as an alternative for baluns are used to create the single-layer balanced structure. Furthermore, the theoretical design procedure of the proposed BDC including mixed-mode scattering matrix, even- and odd-mode analysis, and phase analysis is discussed in detail. To demonstrate the performance of the proposed structure, a BDC is designed and fabricated at 2.4 GHz on Rogers RO4003C substrate. The measurement results show that a 15-dB differential coupling level with 3-dB ripple in the frequency range of 1.7–3.3 GHz has been achieved. Also, great common-mode suppression is obtained in full operational bandwidth. The proposed BDC can be used as a signal sampler in fully balanced radio frequency (RF) systems.

中文翻译：

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基于交叉结构的单层平衡定向耦合器设计

在本文中，首次介绍了单层技术中平衡定向耦合器 (BDC) 的新结构。单节耦合线、微带到共面波导 (CPW) 交叉和 180° 传输线 (TL) 的创新组合作为巴伦的替代品，用于创建单层平衡结构。此外，详细讨论了所提出的 BDC 的理论设计过程，包括混合模式散射矩阵、偶模和奇模分析以及相位分析。为了证明所提出结构的性能，在 Rogers RO4003C 衬底上设计和制造了一个 BDC，频率为 2.4 GHz。测量结果表明，在 1.7–3.3 GHz 的频率范围内实现了 15 dB 的差分耦合电平和 3 dB 的纹波。还，在全工作带宽内获得了很好的共模抑制。建议的 BDC 可用作全平衡射频 (RF) 系统中的信号采样器。