Time-Varying Electromagnetic Devices — Breaking the Limit of Reciprocity
Traditional passive electromagnetic devices often operate in a time-invariant manner as they are built with materials and structures that have time independent properties. They are subject to many well-known fundamental limits such as the reciprocity of transmission under the assumption of being non-magnetic. Utilization of transistor based active electronics may help to overcome some of these challenges but they oftentimes incur noise and power handling issues. In this talk, I will introduce the multiple initiatives supported by NSF and DARPA on the development of a new class of electromagnetic devices that are operating in a time-varying fashion. These time-varying devices including transmission lines, constructed on semiconductor or electromechanical platforms to leverage on their time-dependent property enforced through parametric modulation or switching modes. It will be demonstrated through addition of the new time dimension several aforementioned fundamental limits of reciprocity can be lifted. Potential new applications such a full-duplex radios may be developed with this novel device concept.