PAGE CONTENTS
Objectives
The demand for high data rate mobile communications has continuously increased in the last years and a massive expansion of mobile satellite terminal market into new domains is expected in the future. The beam steering antenna is the main cost item of a mobile satellite terminal. However, the established antenna beam steering architectures cannot meet all the demands of many new civil markets, such as low cost, low power consumption, and low profile. The objective of the proposed activity is to develop an innovative low-profile beam scanning antenna solution based on a totally mechanic mechanism and suitable for VSAT applications. The objective was to cover a percent band of 10%. Starting from a TRL 2, objective of this project was to reach a technological readiness level of 5, to proceed then to the industrialization and qualification phases. The proposed solution may find application in various market segments which require advanced and interactive services, like internet connection on-board high-speed trains, long range buses, ships and airplanes, and, in general, transmission and reception of real time audio-video information with high bidirectional data rate for public utility/rescue/recreational vehicles travelling in remote areas (e.g. telemedicine or security and emergency management).
Challenges
The target of the project is to develop a beam-steering solution, which is based on mechanical scan where the volume of the antenna does not change; therefore, trivial 3D rotation of static antennas is not an option. The solution, based on flat Risley prisms, allows to have low-profile beam-scanning antennas, has the difficulty of controlling the grating lobes generated by the period pattern of the flat Metascreens, and this is the key challenge that had to be tackled.
System Architecture
The selected architecture is based on two separate apertures (one for TX, one for RX, at Ka-band). Each aperture is composed of a primary radiator topped by two rotating metasurface-based screens (sometimes referred to as either Metalenses or Metascreens) which are free to rotate independently. The primary radiators are low-profile reflectors which have been custom designed using in-house proprietary codes. One peculiarity of the two reflectors (for TX and RX) is that they have the same reflector shape, while only the feed (which is field-mountable) is different. The two metascreens of each aperture are identical, and they exploit the Pancharatnam-Berry phase effect in order to provide the desired beam tilting. This allows to obtain the beam scanning effect which according to the Risley prisms, which in this case are implemented in a low-profile configuration with controlled levels of the grating lobes. Each antenna has also dual switching circular polarization capabilities, in order to adapt to work at different geographical locations.
Plan
The project plan included the investigation of two alternative solutions to be implemented. After the preliminary design phase and the critical design phase, the solution based on rotating Metascreens has been selected as baseline solution. Next, the full terminal has been designed, manufactured and tested. The tests have shown the capability of the terminal to receive a signal from a GEO satellite (Eutelsat KA-SAT) for different attitudes of the terminal (rotation along its three axes).
Current Status
The project has reached its termination, after the outdoor tests that showed the possibility for the terminal to receive the signal from a GEO satellite, after repointing the beam due to the attitude change in the terminal orientation.
