3-D-Printed Shaped and Material-Optimized Lenses for Next-Generation Spaceborne Wind Scatterometer Weather Radars

Current spaceborne wind scatterometers have shown failure due to mechanical wear from moving parts used to conically scan a directive beam. In order to eliminate the risk of mechanical rotation failure, an antenna design with no moving parts that achieve the conical beam sweep is desirable. In this article, a lightweight, 3-D-printed, inhomogeneous lens antenna is presented as an all-electronic alternative. Compared to the previous on-axis fed lenses, the real-life application requiring conical scanning necessitates significant developments regarding the synthesis, optimization, and prototyping of the off-axis fed lens. The lens antenna is designed using curved-ray geometrical optics coupled to particle swarm optimization to determine the optimum lens surface shapes and material inhomogeneity while obtaining a design with minimum volume and therefore mass. An 18 cm lens is designed using this approach. Instructions on how to 3-D-print the inhomogeneous lens are given using a unit cell design, which permits additive manufacturing using fused deposition modeling (FDM) techniques. The lens is measured for far-field pattern performance at various locations along with the ring-shaped focus of the azimuthally symmetric lens. The measurements agree well with predictions obtained by full-wave simulations. These all-electronic alternatives are expected to prolong the lifetime of future spaceborne wind scatterometers.

I. Introduction

Scatterometer weather radars produce data of immense scientific value for ocean winds measurements and related applications, including weather forecast, ocean usable wind power assessment [1]–[7], and various additional applications, including vegetation phenology monitoring, soil moisture estimation, sea-ice mass freeze, and thaw detection in polar regions, among others [8]–[12]. Spaceborne scatterometer observations aid the prediction of hurricanes and cyclones allowing prompt warning to people near the area at risk [13]–[16]. In particular, an article published by Popular Science is entitled “Today’s hurricanes kill way fewer Americans, and NOAA’s satellites are the reason why” [17].