Improved Bandwidth Carbon Fiber Reinforced Plastic Structural Antenna Design for near-HF Remote Sensing Applications

Abstract

This work presents an improved bandwidth antenna design for the HF Sounder radar installed on a Twin Otter. This is achieved by replacing the original steel tube dipole antenna with a larger and more aerodynamic carbon fiber reinforced plastic (CFRP) antenna. CFRP is a sufficiently conductive material and its density is about 20% the density of 4130-steel, so by replacing the original steel design with a CFRP design, a larger antenna can be supported, resulting in an expected wider operational bandwidth. Initially several aerodynamic cross-sections are considered for the larger antenna, and a trade study is performed to compare the various designs to the original tube design. This trade study considers electrical performance (specifically bandwidth), implications to aircraft range, and assessment of the structural design. From the initial trade study, two aerodynamic shapes are considered for further assessment—an ellipse with a t/c ratio of 0.33 and a NACA 0024 airfoil. Based on this study, a 2 in. x 8 in. NACA 0024 antenna is manufactured and physically tested. Experimental electrical testing has verified that the newly developed CFRP antenna works as simulated and has 1.7 times improved bandwidth compared to the tube antenna. The airfoil antenna design is expected to improve the bandwidth, is expected to improve the vehicle range, and initial sizing suggests that the structural concept is feasible.