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Low-Cost Metasurface Leaky-Wave Antenna for Mobile Satellite Communications

Periodic Reporting for period 2 - MELASAT (Low-Cost Metasurface Leaky-Wave Antenna for Mobile Satellite Communications)

Reporting period: 2017-05-03 to 2018-05-02

Nowadays, having an inexpensive broadband internet connection no matter where you are is an increasing social demand. In order to have internet access independently on the user’s location, satellite communication is the best solution, since it does not rely on available infrastructure. In this way, by means of a terminal that can communicate continuously with a satellite, users could benefit from a fast data connection anywhere in the world, even when traveling in an airplane, a ship or train. Additionally, a low-cost technology for broadband satellite connectivity could be a viable solution to provide poor countries and isolated areas with broadband internet without strong investments.

Commercial solutions for ground terminals are based on parabolic reflector antennas with mechanical steering. Although they are cost-effective solutions, they require frequent maintenance and are significantly bulky. For low-profile antennas, phased arrays that perform electronic steering can be an appealing alternative, since they can be printed in planar technology and are fast changing the pointing angle. However, they have a corporative feeding network and, additionally, in order to get high gain, the array must contain a significant number of elements and phase shifters, thus leading to expensive and complex structures.

The project investigates a novel low-cost antenna solution for broadband satellite connectivity, so that inexpensive broadband internet connection can be provided without need of deployed infrastructure. With such a technology, the satellite industry could provide enhanced connectivity that would open vast new markets at an unprecedented scale.

More specifically, the project goal is the development of an antenna technology that has the advantages of printed technology (light weight and low profile) but reduces costs and complexity of phased arrays. This technology entails a real challenge and an important market niche that this project is trying to cover. As solution, we propose the combined use of Huygens' metasurfaces with leaky-wave antennas (LWAs) to meet the challenging requirements for broadband mobile satellite communications (broadband beam steering with high gain) at lower costs and complexity than the state-of-the-art solutions. The proposal consists specifically of a parallel-plate waveguide with the top plate being a bianisotropic Huygens' metasurface that allows the desired radiated field to be obtained so that the needed gain and scan angle range are accomplished.
The main objective of the project is to develop a low-cost antenna technology for mobile satellite communications based on the use of Huygens' metasurfaces in leaky-wave antennas (LWAs). The principal challenge to accomplish the main goal was the investigation of novel concepts related to the innovative combination of LWAs and metasurfaces. Particularly, the developed concept is a parallel-plate waveguide in which the top plate is replaced by a bianisotropic Huygens' metasurface. This concept has demonstrated significant potential, since it allows arbitrary field transformation from the field inside the waveguide and important flexibility in the radiation parameters. The theoretical derivation of this novel concept has been developed, leading to closed-form expressions for the design. Different design examples have been carried out based on a well-established design methodology and several prototypes have been built and measured. So, it can be said that a new antenna technology has been developed based on the innovative concept of Huygens' metasurfaces. Therefore, the main goal of the project has been successfully accomplished.

Several preliminary designs proving the mentioned flexibility of the radiation parameters (control of the pointing direction, the leakage factor, the waveguide height, etc.) were presented at the European Conference on Antennas and Propagation (Paris, March 2017). Further on, several conference papers have been published (for instance, 2nd AT-RASC URSI in Gran Canaria, 2018). Finally, a journal paper containing the whole theoretical derivation of the concept and the results of several prototypes is going to be published in the IEEE Transactions on Antennas and Propagation (accepted for publication).
Bianisotropic Huygens' metasurfaces are a recently-proposed concept that provides arbitrary electromagnetic field transformation with a surface made of passive and lossless particles. This novel concept has not been previously applied to the design of a leaky-wave antenna (LWA). Therefore, the concept developed in this project is a contribution to the state of the art of planar antennas and application of the metasurfaces. The advantage of the use of such a metasurface to build a LWA is the resulting powerful flexibility of the radiation parameters, and then, of the radiation pattern, with a low-profile and cost-effective technology. This progress paves the way to the development of a very competitive technology that significantly decreases the costs and complexity of current ground antenna solutions for mobile satellite communications.

The developed antenna technology is not restricted to be used in satellite communication systems, but it is of application for other relevant systems such as 5G or automotive radars. Therefore, it is expected that the results of this project have a strong impact in other widely used applications and, thence, in European society.

The contribution presented at the European Conference on Antennas and Propagation was selected as finalist for the Best Paper Award in Electromagnetics and Antenna Theory.
General antenna solution concept.