Today, aeronautical broadband services enabled by satellites are becoming a reality. The services, which are or will be offered using these broadband data links, range from increasing passenger comfort (live TV, Internet onboard) to providing real-time ATM functions (in-flight monitoring) and improving safety/security aspects (live video-connection to ground). Current aeronautical antenna solutions have drawbacks in terms of cost (active phased arrays) or drag (dish antennas).
The project aims to develop a reliable and low cost solution for electrical beam steering in Ku- or Ka-band onboard mobile platforms. It is based on the global concept called ReflectArray and the industrial implementation is clearly a lower cost alternative compared to active phased array antennae. In addition, the quasi-planar integration of these antenna types will produce almost no additional drag. For the key building block of the antenna, the phase shifter, two solutions will be considered in parallel until a decisive milestone is reached to choose the most suitable technology for the final ReflectArray approach:
- high-power handling RF-MEMS technologies
- high-power handling ferroelectric materials.
These two solutions are considered by the consortium to be the best technical alternatives for phase shifting up to Ka-band today and are predicted to increase their performance levels while keeping costs at the lowest level, because of their full compatibility with collective fabrication processes.
It is expected that a clear view about the future of the broadband SatCom market and the requirements for next-generation mobile antennas will be gained. Following these indications, phase shifting circuits, based on the two technologies, will be assessed. Finally, a partial ReflectArray antenna will be built, which will demonstrate the cost-effectiveness and performance of the chosen approach. In addition, a software tool for modelling the main reliability aspects of the RF-MEMS technology will be developed.
Initially, the complexity of the application will be addressed at the system level by looking at the global (operational, functional) requirements for the ReflectArray antenna and at a market analysis about next-generation broadband SatCom services. Based on that, the requirements for the unitary cells of the antenna array and thus for the phase shifters will be derived.
This definition of specifications will be followed by two cycles of modelling and electrical-mechanical design, processing and subsequent characterisation of the two key technologies under investigation (RF-MEMS and ferroelectric material). Possible implementations of the phase shifters range from free-space to guided-wave circuit topologies. After a decisive milestone, the most promising technology will enter into another cycle of development of the optimised phase shifter for the antenna demonstrator.
This demonstrator itself will be a partial ReflectArray antenna. It will consist of 20 to 30 unitary cells, compared to around 1 000 cells envisioned for the future target product. The main commitment is for this demonstrator to be representative of the low cost collective fabrication and assembly method developed throughout the project.
As the demonstrator is for aeronautical applications, high attention is paid during the whole project to the issue of reliability under these demanding conditions in terms of temperature, vibrations and signal strength. Therefore, extensive tests on the reliability of both technologies will accompany the different stages of the project and extra efforts will be made regarding the proper modelling of the main reliability aspects by developing a suitable software tool.
The project has built the foundation for the development of a full-scale Ku-Band SatCom antenna, with the potential of advanced electrical beam-steering using low-cost fabrication processes.
Besides the organization of two workshops on ferroelectric microwave components and on RF-MEMS power handling and reliability, the project results led to the publication of 41 articles and conference contributions.
Within the RETINA project, a successful development of advanced phase shifting technologies (RFMEMS and ferroelectric capacitors) was performed, which led to the realisation of a partial reflect array antenna, demonstrating electrical beam steering in the operational SatCom bandwidth.