论文标题
在两个均匀的耦合线路中实现异常退化点的一般条件
General Conditions to Realize Exceptional Points of Degeneracy in Two Uniform Coupled Transmission Lines
论文作者
论文摘要
我们介绍了一般条件，以实现两个均匀（即沿Z）的第四阶特殊点（EPD），即无损和无增益耦合传输线（CTL），即退化带边缘（DBE）。到目前为止，DBE仅在周期性结构中显示。相比之下，这里考虑的CTL均匀，并细分为四种情况，在这些情况下，两个TL支持正向传播，向后传播和evanevansent模式的组合（当忽略相互耦合时）。我们首次证明，当有适当的耦合之间存在适当的耦合：（i）传播模式和逃生模式，（ii）向后和向后传播模式，或（iii）四种逃生模式（每个方向两个）。我们还表明，由于退化模式不在相位不发展，因此在k = 0时表现出第四阶EPD的均匀CTL的负载质量因子对串联损失是可靠的。我们还提供了使用具有非常小波长单位细胞长度的周期性串联电容器表现出DBE的均匀CTL的微带实现。最后，我们显示了对支持耦合传播和逃生模式的CTL实现的生存DBE的实验验证。
We present the general conditions to realize a fourth order exceptional point of degeneracy (EPD) in two uniform (i.e., invariant along z) lossless and gainless coupled transmission lines (CTLs), namely, a degenerate band edge (DBE). Until now the DBE has been shown only in periodic structures. In contrast, the CTLs considered here are uniform and subdivided into four cases where the two TLs support combinations of forward propagation, backward propagation and evanescent modes (when neglecting the mutual coupling). We demonstrate for the first time that a DBE is supported in uniform CTLs when there is proper coupling between: (i) propagating modes and evanescent modes, (ii) forward and backward propagating modes, or (iii) four evanescent modes (two in each direction). We also show that the loaded quality factor of uniform CTLs exhibiting a fourth order EPD at k=0 is robust to series losses due to the fact that the degenerate modes do not advance in phase. We also provide a microstrip possible implementation of a uniform CTL exhibiting a DBE using periodic series capacitors with very sub-wavelength unit-cell length. Finally, we show an experimental verification of the existence DBE for a microstrip implementation of a CTL supporting coupled propagating and evanescent modes.
