We propose to design a compact, multiple purpose electromagnetic sensor for monitoring the extremely low frequency (ELF), very low frequency (VLF), and low frequency (LF) spectrum. Our goal is to design a modular, low cost sensor capable of being configured for multiple applications and capable of being employed in remote, unattended sensor networks. We describe three applications or scenarios that form the basis for a requirements-driven sensor design. These scenarios involve the need for sensors to detect, monitor, and characterize underground facilities capable of producing or testing weapons of mass destruction. Technical objectives are to identify sets of application-specific sensor performance characteristics and to incorporate these characteristics into a flexible design. The three function areas of antenna design, noise reduction techniques, and signal processing hold the key to sensor operation at different frequencies and with different signal extraction requirements. Our modular design will maximize the functions in common modules and thereby minimize the changes necessary for different applications.
