Additive manufacturing for radio frequency applications

• Main Author: Chia, Jie Xiang
• Other Authors: Li King Ho Holden
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Mechanical engineering; Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/163606
• Institution: Nanyang Technological University

This thesis investigates various materials with their corresponding dielectric properties and how Radio Frequency (RF) wave propagation is affected by them. Several common plastics and additive manufacturing filaments were tested using waveguide structures, which will eventually be used for horn antenna applications. After which, the effects of varying infill percentages and different types of infill patterns on the RF performance are explored, which is the fundamental building block of fused deposition modelling technology where the 3D model is 3D printed layer by layer. By exploring several parameters and carrying out simulations and experiments, it is found out that the infill densities perform better at lower infill percentages in general regardless of the pattern type. This helps to reduce the weight of dielectric components for RF applications and the infill feature is something that only additive manufacturing can offer over conventional manufacturing. It is also found that when the infill percentage goes too high (too close to being solid), the RF performance of the dielectric degrades as the infill density increases. This is due to the higher infill percentages resulting in many infill lines inside the cross section of the geometry. Due to the increased number of infill lines, the RF wave that propagates orthogonally to the dielectric geometry faces many air-dielectric medium interfaces which causes many reflections and transmittances due to the different dielectric constants. Therefore, very high infill density percentages lead to much more interferences inside the block and can be constructive or destructive in nature, which is why the RF performance tends to be worse than lower infill percentages. This phenomenon is known as Fabry-Perot Interference. This infill patterned geometry was shown in this project where a hollow block with infill structures instead of a solid block was fabricated to reduce the weight of the horn antenna. The 3D printed horn antenna’s performance was able to be tweaked to meet the desired goals by incorporating conformal surface profiles and by varying the infill density at low infill percentages. The two applications: (1) A 3D printed dielectric window for WR90 horn antennas where the effects of using hollow or shelled dielectric windows with infill and (2) a 3D printed dielectric loaded TEM horn antenna demonstrated the use of additive manufacturing, which has brought about customizability of dielectrics into the field of RF applications. This shows potential in a multidisciplinary field combining mechanical engineering (Additive Manufacturing) and electrical and electronics engineering (Radio Frequency Engineering).