Antennas
The fifth generation (5G) of wireless communication systems is in the starting blocks. In opposite to preceding generations, which described the standards for communication between base stations and mobile devices, in particular smartphones, 5G summarizes lots of various communication links. Due to the Internet of things (IoT) there will be a massive machine-type communication (mMTC), which leads, together with new big data applications, to enhanced mobile broadband (eMBB). Real-time applications such as e.g. safety systems in vehicles and autonomous driving require ultra-reliable low-latency communication (URLLC). To meet these requirements there is a dense and hierarchical cellular network consisting of macro cells, micro cells and pico cells planned for 5G. Backhaul communication between base stations and later also communication links to mobile devices will be done in the millimeter wave (mmW) frequency range because of the higher available bandwidths. To compensate for high path loss at mmW frequencies, to minimize interference and to have the advantage of frequency reuse by spatial multiplexing, the base stations will need active beamforming antennas, which allow high gain adaptive beams. Beamforming can be done by large antenna arrays consisting of multiple, up to hundreds of antenna elements, whereby research on large antenna array behavior is nothing new when thinking of e.g radar applications. New research aspects under the 5G requirements are minimization of those mmW antenna arrays to be integrated into smart devices, power efficiency for long battery life and the ability of multi-user-beamforming (MU-BF) e.g. for pico-cell base stations. Research at the institute is concentrated on development of small mmW antenna arrays, of beamforming networks responsible for the adaptive phase shifts at the antenna elements and on integration aspects of such beamforming antenna systems into small devices.
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Small mmW antenna arrays
Development of small antenna arrays requires in first instance developing small antenna elements. Modal analysis established as a powerful tool at the institute, not only for the design of MIMO antenna elements, but also for creating geometrically small antennas. When combining multiple of these small antennas decoupling becomes an aspect to consider.
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Beamforming networks
To get correct phase and amplitude relations between the antenna elements requires passive or active networks behind the antennas, consisting of power dividers, combiners, couplers, attenuators and phase shifters. Connecting all these components leads to geometrically large networks. An important research aspect is miniaturization of these networks, e.g. by using multilayer technology, with having low attenuation at mmW at the same time.
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Integration aspects
As an alternative to passive beamforming networks beamformer ICs have been developed by several companies. These ICs are small compared to the antennas they control regarding phase and amplitude. Positioning of these ICs together with conventional passive beamforming networks and e.g. additional transceiver ICs and ICs for control under the antenna elements requires a multilayer structure. One focus of research is the development of an easy to fabricate modular concept for larger antenna arrays based on small element number arrays manufactured in multilayer technology. Considerations have to be made on electromagnetic behavior, but also e.g. on cooling of all active components when integrating them into small environments.
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Integration into 3D-environments
![Conformal 3D Patch Antenna Array with Beam]()
![Conformal 3D Patch Antenna Array with Beam]()
![Conformal 3D Patch Antenna Array with Beam]()
Especially the pico cell base stations will not allow integrating large 2-dimensional (planar) antenna arrays, because these base stations might be integrated into small devices, e.g. in consumer electronics devices. Latest developments in technologies like MID-LDS and 3D-printing make 3-dimensional mmW circuits and conformal antenna arrays possible. At the institute research is done on the electromagnetic behavior of those 3D structures and on how they can be used for integration of mmW beamforming antenna systems.
