SPP 1655: Subproject "Integrated active antenna arrays with polarization multiplexing for broadband communications at W-band"
The main goal of this proposal is the design of a wideband, circularly polarized antenna at W-band and its subsequent integration with a CMOS power amplifier to a system-in-package which may be used as an active radiating element within an array-based transmitter. The project shall be completed in close cooperation with Prof. Georg Böck, TU Berlin, as Prof. Böck‘s group is concerned with the above mentioned CMOS power amplifier. The W-band offers a total bandwidth of 35 GHz. Unlike lower frequency bands (e.g., UWB or 60 GHz) modulation schemes with moderate complexity (3-4 bit/s/Hz) may be employed. In contrast to higher frequency bands (200 GHz and above) CMOS processes with sufficiently high cutoff frequencies are already commercially available, so that the technological barrier for the design of circuits and systems is considerably lower. Antenna arrays are advantageous because, on the one hand, they enable system scalability, which means that the link budget may be adapted to suit different application scenarios. On the other hand, they are a prerequisite for analog or digital beam steering, which may be used to communicate with users via a directed line-of-sight (LOS) connection and thus improves the link quality. One goal is the design and fabrication of a simple, small (e.g. 2x1 or 2x2) antenna array demonstrator. The designed antenna element shall be circularly polarized so that there is no need for alignment between the base station and the user‘s mobile device. Further, by utilizing two orthogonal polarizations (left- and right-handed circular polarization) the data rate is doubled. The designed antenna element thus supports two independently driven polarizations (polarization multiplexing). One goal is the design and fabrication of an active antenna element with polarization multiplexing. Since WLAN/WPAN is mainly a customer market, the employed technology is a low-cost stereolithographic process. The process has a micrometer-scale feature size and well-controlled vertical growth by deposition and curing of polymers, which enables structures (e.g. inclined walls), which cannot be fabricated with `standard` PCB or MMIC processes (due to layer thickness or limited amount of layers). Direct packaging of active components into the polymer layers leads to integrated (sub)-systems with optimally designed interconnects and, thus, lower signal losses. The basic underlying challenge of the proposal is to use these technological opportunities to achieve the best possible system performance (e.g.: wide bandwidth, low losses).