Monopole Antenna Radiation Pattern Control via 3-D-Printed Dielectrics

3-D printing technology has attracted growing interest of many researchers in the area of antenna design as a new prototyping and manufacturing technology. It is capable of forming arbitrary 3-D structures with lower cost and shorter prototyping time. This paper aims to present a novel methodology to control antenna radiation pattern based on 3-D printing of specially designed dielectric material, which realizes spatially dependent dielectric constants around the antenna. As a proof-ofconcept, we propose a design of a quarter-wavelength monopole antenna surrounded by a 3-D-printed polymer structure with an optimized dielectric property distribution. Unlike the conventional donut-shaped pattern of a quarter-wavelength monopole antenna, one-beam and multiple-beam patterns are obtained using a genetic-algorithm-based optimization. Different dielectric constant spatial distributions are realized by changing the ratio of the dielectric to air at the unit cell level in the entire antenna volume. A two-beam monopole prototype is designed, fabricated, and tested. The measurement results demonstrate agreement with the simulation results. The proposed design method enables another degree of freedom for antenna design, which can be extended to other types of antennas.