Design, prototyping and mechanical testing of a trifilar deployable helix antenna for CubeSat applications

Deployable helical antennas are often used in space in the VHF and UHF transmission bands because they provide high gain, large bandwidth, and high directivity with circular polarization while maintaining relatively low fabrication complexity. Usually, these deployable antennas are composed of a main foldable, non-conducting isolated structure which acts as the helicoid support for the main conducting wire element. Generally, these antennas need to be kept stowed during launch and deployed once in space. This paper presents an innovative type of resettable trifilar helicoid deployable antenna where three independent helix shaped metallic wires are employed to perform both functions: the deployable support structure and the main conductor as a single entity. The initial design and manufacturing process of the helix shaped metallic wires are illustrated in this work together with the respective numerical simulations to ensure the correct electrical performance and the desired deployed stiffness of the antenna expressed in terms of minimum natural frequency of vibration above 1Hz. Furthermore, various preliminary functional deployment tests of the antenna are performed and illustrated in this paper. In particular, the deployment accuracy tests need to meet the requirement of ±1mm of maximum difference between real deployed structure and its nominal dimensions. Finally, these deployment tests are used to validate the functionality of the deployment damper and the incorporated resettable mechanism. On one side the damper is necessary to control the velocity of the deployment and reduces the final mechanical shock at the end of the run and guarantees a controlled deployment dynamics, whereas the resettable mechanism ensure an easy stowage process of the antenna for repeated deployments during qualification and acceptance ground testing campaigns.