Engineers designing transmitting antennas at long wavelengths have for decades struggled to make antennas compact, efficient, and broadband. These challenges are especially pronounced in the Very Low Frequency (VLF, 3-30 kHz) band, where wavelengths are 10-100 km. Existing VLF transmitters have either extremely short range, or extremely large size with little bandwidth. Solving this problem would impact several defense and civilian applications, including hemisphere-scale subsea communications, underground sensing and detection, navigation and timing, and even space radiation belt remediation. We propose a radical new antenna concept in which we use high-speed time-variation to break the fundamental limits inherent to conventional antennas. Conventional impedance-matching techniques work only in a narrow frequency band, but our technique is a time-domain matching scheme which inherently works at all frequencies. The limitation is the need for components that can simultaneously handle high-speed (ns-scale) and high power. In Phase I, we will investigate available and customizable components, and explore the achievable trade space of bandwidth-free antenna specifications. An existing proof-of-concept will be scaled it up to a higher-power prototype, enabling groundbreaking demonstrations. Concepts for an even higher power prototype that could be built in a Phase II will be designed, enabling demonstrations to build commercial interest.
