Time-Varying Electromagnetic Devices: Breaking the Fundamental Limits of Passives
Passive electromagnetic devices such as transmission lines, filters and antennas are essential parts of a wireless system. They often dominate the system’s efficiency, bandwidth and noise performance. Traditional passives 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 line, limit of quality factors of passive filters and limit of efficiency bandwidth product in electrically small antennas. 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, filters and antennas may be 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 the addition of the new time dimension the aforementioned fundamental limits of passives can be lifted. Potential new applications such a full-duplex radios, tunable RF front-ends and broadband VLF transmitters may be developed with this novel device concept.