Leveraging space-time modulation for energy coupling control in electromagnetic coupled transmission lines structures

This article presents a technique for controlling energy coupling in a coupled transmission line system based on the space-time modulation concept. The per-unit-length mutual capacitance and mutual inductance of the structure are modulated in space and time. The main idea is based on the harmonic generation property of space-time modulated media. As the amplitude of harmonics is a function of modulation parameters it is demonstrated that by choosing an appropriate space-time modulation scheme energy of different harmonics can be engineered leading to crosstalk reduction. In the quest for designing an effective space-time modulation scheme, an analytical method is developed for the examination of the space-time modulated coupled transmission line. The proposed method which is based on the state space formulation and benefits from the coupled mode theory is fast and accurate making it feasible for design problems. To validate the proposed analytical method, a full-wave simulation method has been used. The time-varying nature of the problem makes the finite-difference-time-domain the most appropriate choice. The validity of the analytical method is rigorously verified against the developed finite-difference-time-domain technique. The interest in circuit design techniques in an IC-compatible fashion in microwave circuits and the introduction of tunable material such as graphene in the THz regime leads to a positive future for the proposed space-time modulation-based crosstalk reduction method.