A Passive Very Low-Frequency (VLF) Electric Field Imager

It is shown that an array of D-dot sensors can be implemented to not only detect, but for the first time, image very low-frequency electric fields. D-dot sensors sense current proportional to the time derivative of the electric field. The signal of interest is extracted from each D-dot pixel using a lock-in amplifier through an automated multiplexer. We have successfully rendered very low-frequenc...