Portable Agile Communication for Areas with Infrastructures Diminished (PAC-AID)
Swiss partners
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ETH Zürich: Maria Sakovsky (main applicant), Paolo Ermanni
Partners in the MENA region
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American University of Beirut, Lebanon: Joseph Costantine (main applicant), Youssef Tawk
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National Instruments, Lebanon: Michel Nassar
Presentation of the projet
This project developed a portable reconfigurable communications system for low-infrastructure areas and disaster relief. The quadrifilar helix antenna was based on a helical lattice structure whose shape change corresponded to reconfiguration of the antenna’s radiation pattern and polarization. In particular, the antenna is capable of reconfiguring between an omni-directional radiation pattern with linear polarization (for device-to-device communication on the ground) and a directional radiation pattern with circular polarization (for device-to-satellite communication). The structure was made from lightweight, inexpensive materials (custom fiber reinforced polymer (FRP) composite materials) and was designed to hold multiple shapes passively to reduce power use. As such, the developed antenna provides a portable, cost-efficient and low-power solution for the target areas. In fact, the flexibility in antenna performance allows us to do what no existing solution can – adapt to the constantly changing environment in low infrastructure and disaster stricken areas.
The following major research activities were undertaken:
- Understanding of the coupling between shape change and antenna EM reconfiguration: This activity used finite element simulations in ANSYS Electronics Desktop to model the EM performance change in a quadrifilar helix antenna corresponding to shape change in helical lattices. It was found that as the radius and spacing of the helical lattices changes, the radiation pattern of the antenna changes from directional with circular polarization to omni-directional with linear polarization. The model was used to arrive at a final antenna design and as input for structural modelling.
- Deriving the stability landscape for helical lattice structures: Analytical models were developed for the deformation of the helical lattice structures to predict their stable points (helix shapes maintained passively). The analytic models allowed for rapid parametric studies over a large design space consisting of composite material properties and helix geometry. The model was used to design a structure with stable shapes corresponding to different radiation patterns of the antenna.
- Design of a feeding network for reconfigurable antennas: In a quadrifilar helix antenna, each helix must be fed with an equal amplitude and 90° phase difference through a feeding network. Each one of the four output ports of the feeding network is fed to one of the input ports of the antenna. The developed feeding network consists of a rat race coupler and two hybrid couplers. The rat race coupler gives a 180 degrees phase shift between its two output ports. Each of the two output ports of the rat race coupler is connected to a hybrid coupler, which will ensure the 90 degrees phase shift between the four helices of the quadrifilar helix antenna.
Helix prototyping and testing: In the last activity, the helical lattice antenna was manufactured, integrated with the ground plane and feeding network, and tested to verify both mechanical (stable shapes, forces vs. helix deformation) and EM performance (operating frequency, radiation pattern, polarization characteristics). In addition, a research visit of the AUB team to ETH Zürich was conducted in Oct. 2021. The purpose of the visit was a detailed exchange of methodologies and results, finalizing the design of the antenna, and planning of joint publications.
Article in Nature Communications (2023)
Conference paper at the 2022 IEEE AP-S/URSI
Conference paper at the 2023 IEEE USNC-URSI
Conference paper at the AIAA SCITECH 2022 Forum