Millimeter wave beam steering antenna platform for mobile 140 GHz wireless systems in hybrid Liquid Crystal - Nanowire Membrane technology

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In the last decade, demand has been increasing for higher data rates in wireless access systems to meet the needs for increasing capacity. This demand on high bandwidth leads inevitably to increasing operating frequencies of the systems up to the mm-wave range, where still large frequency resources are available, in particular beyond 100 GHz. However, power link budget considerations and the reduction of interference and multipath effects require high-gain narrow-beam antennas. These antennas have to be precisely oriented to avoid alignment losses, which is not an easy task. Moreover, an increasing demand is going towards mobile communication systems, where electronic beam-steering capabilities would increase the system´s performance dramatically compared to heavy and bulky mechanical systems, causing additionally high maintenance. However, this is a considerable hardware and implementation challenge, due to the lack of suitable low-cost, reliable technologies for reconfigurable mm-wave components and particular constraints in terms of systems' beam-steering rate and power consumption as well as form factor, taking compactness and flatness into account.In this context, the project aims (1) for a new technology, which meets all the system requirements at the same time, and (2) to build up an innovative development platform for further system realizations. For this approach, two recently and independently developed technologies will be merged in order to achieve higher functionality and performance with respect to the individual ones: (1) the microwave liquid crystal (LC) technology from TU Darmstadt, Germany, and (2) the metallic nanowire-filled membrane (NaM) technology from UJF in France and USP in Brazil. Small, low-profile and high-efficiency passive circuits will be possible, using the slow-wave concept. Tunable circuits such as phase shifters and switches based on the microwave liquid crystal technology will benefit from a slow-wave concept combined with the nanowire-filled membrane technology. This allows miniaturization, to fit the phase shifters into a single antenna element size of about a half-wavelength squared, and fast response times with low-profile structures, which are the major limitations of the state-of-the-art microwave liquid crystal technology and components.For a proof-of-concept and feasibility studies, a system-level demonstrator, a beam-steering antenna system in the D-band around 140 GHz will be built and tested in two use cases, in order to leverage the developments carried out. It will consist of a small-footprint antenna array and a complex feeding network, including Butler matrix and switching elements as well as phase shifters. This beam-steering antenna system is based on a new concept, using a hybrid phase-shifting approach, combining the discrete phase shift from a Butler matrix with the continuous phase shift from liquid crystal phase shifters to achieve a large scanning range with low losses at 140 GHz.