We explored the development of a new type of antenna structure designed to enhance the ability of a THz base station to provide multiple access. The antenna structure is based on a two-dimensional guided-wave realization of a Luneburg lens, which is a spherically (in 2D, cylindrically) symmetric optic with a gradient index from the center to the edge. This optimizes the structure for index matching, but on its own does not provide any sort of antenna gain. We modified the structure using the ideas of transformation optics, so that rays entering the edge of the lens from many different angles are all bent to emerge from a flat face on the opposite surface, with unity gain. We then couple the flat output facet to the input of a horn antenna, such that the antenna (initially very directional) can now receive from many different angles, within a spectral bandwidth of about 50 GHz.
This modified Luneburg antenna offers a unique capability to receive transmissions with nearly constant gain across a wide angular range, without sacrificing the high gain of the conventional horn antenna. We also demonstrated that this device, when used in reverse, offers a clever option for beam steering. By translating the lens across the output of a transmitting horn antenna, the output of the Luneburg lens is steered over a wide angular range, again with little variation in gain. We tested this device with a modulated data stream at 1 Gb/sec, and demonstrated error-free signals in both transmitter and receiver modes. This work lays the foundation for the use of transformation optics to modify conventional structures in unconventional ways, and could therefore point the way for many valuable opportunities in antenna design. It has been published this year in Scientific Reports.
Publications:
Amarasinghe, Yasith and Mendis, Rajind and Shrestha, Rabi and Guerboukha, Hichem and Taiber, Jochen and Koch, Martinand Mittleman, Daniel M. (2021). Broadband wide-angle terahertz antenna based on the application of transformation optics to a Luneburg lens. Scientific Reports. 11 (1) .