Abstract
An ultra-compact deployable helical antenna is presented, designed to enhance space-based reception of Automatic Identification System signals for maritime surveillance. The radio frequency performance (i.e. peak gain and directionality) is simulated at 162 MHz using ANSYS High Frequency Structure Simulator and evaluated over a range [0.5–8] of helical turns. Established and commercially available omnidirectional antennas suffer interference caused by the large number of incoming signals. A 7-turn helix with planar ground plane is proposed as a compact directional-antenna solution, which produces a peak gain of 11.21±0.14 dBi and half-power beam width of 46.5±0.5 degrees. Manufacturing the helical structure using bistable composite enables uniquely high packaging efficiencies. The helix has a deployed axial length of 3.22 m, a diameter of 58 cm, and a stowed (i.e. coiled) height and diameter of 5 cm — the stowed-to-deployed volume ratio is approximately 1:9,800 (0.01%). The use of ultra-thin and lightweight composite results in an estimated mass of 163 grams. The structural stability (i.e. natural vibration frequency) is also investigated to evaluate the risk an unstable deployed antenna may have on the radio frequency performance. The first vibration mode of the 7-turn helix is at 0.032 Hz indicating the need for additional stiffening.