Utilizing Advanced Manufacturing Techniques to Increase Bandwidth Capabilities of D-Dot Antennas

Antennas that are uniquely designed to measure the time derivative electric displacement field are commonly referred to as D-dots. Such measurements can be integrated to yield information about an applied electric field (E-field). This is particularly useful in pulsed power and radio frequency (RF) applications where voltage dividers cannot be used. This class of antennas was first introduced in the 1960s as a reliable method of measuring E-fields from a distance. Commercial D-dots are sold in free-field and grounded configurations with both having an operating bandwidth limit of around 10 GHz. The operating bandwidth is inversely proportional to the size of the D-dot's sensing element. As the sensing element size decreases, the operating bandwidth increases. Legacy manufacturing techniques limit how small the D-dot's sensing element can be made, but the advent of additive manufacturing methods offers the potential to reliably create D-dot antennas with extended frequency ranges. This article discusses the design process and measured results for three metal 3-D printed ground reference D-dots designed to have an operating bandwidth from 0 to 5.5, 10, and 12 GHz. The bandwidth capabilities are quantified by comparing experimental data to the analytical gain of a D-dot. The analytical gain is derived using circuit equations from the D-dot's low-frequency equivalent circuit. Low frequency in this case refers to frequencies less than the stated bandwidth. The results indicate that utilizing 3-D printing methods can reliably produce D-dots capable of measuring frequencies larger than 12 GHz.