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StatusOngoing
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Status date2025-02-20
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Activity Code7C.040
Low profile, completely electronically steerable Ka-band user terminal antennas have a great market potential in the field of the satellite communications.
Developing such a reconfigurable antenna completely electronic with limited thickness, large field of view and limited overall power consumption is difficult and expensive to develop with current conventional technologies.
In the last years several technologies have been showing promising results to improve on this. Using liquid crystal technology as reconfigurable phase shifters is one possible, promising example.
The objective of this activity is to design, manufacture and test an antenna breadboard representative of a low profile, actively scanning transmit-receive satellite user terminal full size antenna based on liquid crystals.
The project has several challenges to face mainly due to the complexity of the integration activity and the joint use of conventional and novel technologies such as the liquid crystal-based devices.
Being innovative, the proposed solution comes with a dose of risk, where potential manufacturing issues are expected especially for large liquid crystal-filled cavities.
The use of liquid crystal for Ka-band application is not without cost and the main limitations associated need to be investigated.
Particularly, a) RF insertion losses, b) switching times; c) dielectric anisotropy and viscosity; d) sensitivity and stability versus temperature and humidity; e) cost of materials, are all aspects that require further characterization in addition to the information provided by the supplier of the liquid-crystal mixture.
The most important activity benefits stand in the use of low profile, electronically steerable Ka-band user terminal antennas with limited thickness, low weight, increased cost-effectiveness, large field of view and limited overall power consumption to be used in several types of satellite networks and onboard different mobile platforms.
From the point of view of applicable mobile platforms, possible field of use ranges from land mobile and maritime to airborne, with different constraints and requirements. In particular, the low-profile characteristic may represent a benefit in those situations where aesthetics (e.g. marine yacht), aerodynamic shape (e.g. aircrafts) and vertical encumbrance ( e.g. trains, land mobile) are key factors and therefore play a crucial role.
Hence, apart from the satellite communication providers and users, the potential stakeholders are the ones who are strongly interested in integrating relevant technological improvements to the new generation of platforms, such as aerospace, shipbuilding and automotive company.
The demonstrator developed within the project supports and possess the following features and capabilities:
- Low profile characteristics thanks to the use of planar phased array antenna and printed circuit board-based technologies;
- 2D main beam steering, through the combination of mechanical (azimuth axis) and electronic beam scanning (elevation axis) technology;
- Possibility of selecting fully digital or hybrid electronic main beam scanning mode with the joint use of digital and liquid crystal phase shifters.
- Active multi-channel beamforming network providing the required power gain for GEO satellite communication even in presence of low input power level;
- Polarization switching by means of a Low-profile Linear-to Circular polarization converter;
- Phase shift Control Unit with thermoregulation functionalities directly integrated onto the azimuth axis of the antenna assembly.
The architecture of the antenna system being developed is composed of two separated radiating apertures working in the sub-bands 19.7-20.2 GHz (reception) and 29.5-30.0 GHz (transmission) respectively.
In order to achieve the needed 2D main beam scanning capability, a hybrid mechanical-electronic pointing system is required where the elevation scan is performed electronically while the azimuth scan is done mechanically.
Therefore these apertures are suitable for being arranged on a rotating structure integrating a rotary joint.
As each antenna is linearly polarized, a linear-to-circular polarization converter is adopted to achieve the intended circular polarization.
For the design of the radiating apertures, two liquid crystal-based solutions are investigated, respectively a phased antenna array solution with liquid-crystal phase shifters and a metasurface antenna solution composed of liquid crystal-filled unit cells.
Regardless of the selected technology, the RF signal is fed through a reconfigurable feeding and combining network, where the reconfigurability is achieved by the presence of the liquid crystal and its driving and biasing control unit.
The tasks covered by the project activities, each one corresponding to a working phase, are organised sequentially as follows:
- Task 1: Identification of promising liquid-crystal materials;
- Task 2: Identification of promising reconfigurable antenna concepts based on liquid crystals;
- Task 3: Preliminary design and analysis;
- Task 4: Critical Breadboarding;
- Task 5: Detailed Design;
- Task 6: Demonstrator antenna manufacturing and test;
- Task 7: Antenna final design update. Lessons learnt and roadmap.
with the following milestone review being scheduled as:
- Negotiation/kick-off meeting;
- Concept Selection Review (CSR);
- Preliminary Design Review (PDR);
- Test Review Board (TRB);
- Final Review;
- Final Presentation.
The LPASAAD project has been completed after being developed from feasibility study to demo.
Within the frame of the project, the following main results have been achieved:
- A manufacturing process that integrates conventional PCB techniques and RF technologies on glass substrates was investigated, tested and implemented.
- An active phased array antenna optionally equipped with liquid crystal phase shifters have been prototyped, tested and fully integrated into the transmitting antenna subassembly of a technological demonstrator.
- The possibility to steer the radiation main beam in an arbitrary direction has been experimentally demonstrated by means of a measurement campaign over manufactured prototypes.
The ability of the satellite terminal technological demonstrator developed within the program to establish a round-trip communication link by leveraging the cooperation with a receiving conventional dish antenna have been successfully proven outdoor.
