Highly Sensitive Exceptional Degeneracy in Coupled Transmission Lines With Balanced Gain and loss

We proposed a highly sensitive circuit scheme based on an exceptional point of degeneracy (EPD) using two finite-length coupled transmission lines terminated on balanced gain and loss. EPD is a point in a system's parameter space in which two or more eigenmodes coalesce in both their resonance frequency and eigenvectors into a single degenerate eigenmode by varying the system's parameter. We demonstrate that two PT-symmetric finite-length coupled transmission lines (CTLs), can generate an EPD at a desired frequency. We find the EPDs in this circuit and the bifurcation diagram that exhibits the ultra-sensitivity behavior to the system's perturbations. The very high sensitivity induced by an EPD can be used to conceive a new generation of high-sensitive sensors.