Hybrid Beamforming for dual-polarized antenna

International audienceRecently, dual-polarized antenna has attracted strong attention in Millimeter wave (mmWave) systems. It provides an additional degree-of-freedom in wireless communication, yielding higher throughput. Nowadays, with the development of antenna technology, dual-polarized large scale antenna arrays can be realized inexpensively. However, several challenges must be addressed when using dual-polarized antennas in practical transmission such as mobile phone rotation and non-ideal polarization isolation. We address these challenges in the frame of dual-polarized hybrid beamformers. In this paper, we analyze the performance of dual-polarized beamforming based on two popular techniques: Beam steering and Orthogonal Matching Pursuit. Three categories of dual-polarized beam steering are analyzed : (1) same ray : the two polarizations are sent on the same ray, (2) different ray-same polarization : the two polarizations are sent on different pathes, and the receiver uses the same polarization as the emitter, (3) different ray-different polarization : the receiver uses the orthogonal polarization w.r.t. the emitter. An algorithm to choose the rays and polarizations to use, taking the mobile rotation into account, is also developed. Moreover, we develop a hybrid beamforming algorithm inspired by Orthogonal Matching Pursuit that approaches the fully digital beamforming data-rate and outperforms beam steering. Its developed version-Orthogonal based Matching Pursuit-is also introduced to reduce the computational complexity and overcome the unavailability of the Angle of Arrival

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements