"Design of Low Profile Transmitarray Antennas with Wide Mechanical Beam Steering at Millimeter-Waves" paper, co-authored by Ávaro Vaquero (Universidad de Oviedo), Jorge Teixeira (IST-IT), Sérgio Matos (IST-IT), Manuel Arrebola (Universidad de Oviedo), Jorge Costa (IST-IT), João Felício (IST-IT), Carlos Fernandes (IST-IT) and Nelson Fonseca (ESA), 

The paper appeared in the top accessed documents of the IEEE Transactions on Antennas and Propagation (Vol. 71, Nº 4, pp. 3713 - 3718) for the month of April 2023. 

With the growing trend of using millimeter waves for the next generation of broadband wireless access mobile communication satellites, the need is rising for extremely low-cost, compact beam scanning antenna solutions for the mass consumer market.

Phased-array antennas, the traditional choice for demanding electronic beam scanning applications, may be unattractive for individual users, due to the excessive weight, cost, and power consumption, inherent to its complexity.

Mechanical focal antenna systems, based on thin, planar metamaterial lenses, known as transmit-arrays, present an interesting compromise between performance and the other referred drawbacks of phased-arrays. The focal system is basically composed of a primary feed, e.g. a waveguide aperture, and the planar lens that collimates the beam. The beam is scanned by mechanically displacing the feed out from the focal point. When designing compact terminals with high gain and short focal length to reduce the antenna profile, the aberrations caused by the mechanical movement become the main limiting factor of the maximum scanning range.

Researchers around the world have been working around ways to reduce the focal length while maintaining a wide beam scanning angular range. Benefitting from the flexibility provided by artificial metamaterial lenses, our innovative approach was to design the lens with multiple focal points, collocated along a straight line parallel to the lens, much closer than in the conventional single focus approach. In this way, smaller aberrations are distributed among the multiple focal beams in the shared aperture.

We demonstrated the concept at 30 GHz, over 2 GHz bandwidth, with maximum 25 dBi gain beam, scanned between -50º to +50º over 360º azimuth. The focal lens is reduced by 65% compared to the conventional design. The metamaterial lens is 3D-printed and weighs about 400 g. However, the lens can be fabricated with PCB technique, halving the antenna weight.

This work was a collaboration between the Antennas and Propagation group of IT in Lisbon, and the Teoria de La Señal Y Comunicaciones group from the University of Oviedo, Spain

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