This paper explains why the electromagnetic coupling between interconnect main Ω-shape and straight I-lines of printed circuit board (PCB) can be source of bandpass (BP) negative group delay (NGD) behavior. The investigation on the NGD effect is established from an innovative microstrip circuit having medusa shape. The medusa topology analytical description is based on the equivalent circuit and S-matrix model. Then, the group delay (GD) response enabling to explain the existence of the BP NGD function is defined. As proof-of-concept (POC), the influences of the medusa circuit constituting interconnect line (IL) lengths and interspaces on the BP NGD behavior are illustrated by parametric study. The NGD behavior is explained by the variations of the NGD value and NGD center frequency. More importantly, two NGD medusa prototypes were designed, fabricated, simulated and tested. The BP NGD responses of the two-medusa circuit POCs are validated by a very good agreement between the calculations, simulations and experimentations. The test results confirm that the medusa circuit POCs generate BP NGD responses with NGD level and center frequency of about −1.6 ns and 2.76 GHz respectively.

中文翻译：

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美杜莎形互连结构的NGD研究

本文解释了为什么互连主要 Ω 形和印刷电路板 (PCB) 的直线 I 线之间的电磁耦合可以成为带通 (BP) 负群延迟 (NGD) 行为的来源。NGD 效应的研究是从具有美杜莎形状的创新微带电路中建立起来的。美杜莎拓扑解析描述基于等效电路和S矩阵模型。然后，定义了能够解释 BP NGD 函数存在的群延迟 (GD) 响应。作为概念验证 (POC)，通过参数研究说明了构成互连线 (IL) 长度和间隙的美杜莎电路对 BP NGD 行为的影响。NGD 行为由 NGD 值和 NGD 中心频率的变化来解释。更重要的是，设计了两个NGD美杜莎原型，制造、模拟和测试。两个美杜莎电路 POC 的 BP NGD 响应通过计算、模拟和实验之间非常好的一致性得到验证。测试结果证实，美杜莎电路 POC 产生 BP NGD 响应，NGD 电平和中心频率分别约为 -1.6 ns 和 2.76 GHz。