A Simple Blass Matrix Design Strategy for Multibeam Arbitrary Linear Antenna Arrays

Multibeam antenna arrays are currently recognized as one of the enabling technologies for the next-generation communication standards. One of the key components of these systems is the beamforming network (BFN) that implements the array element excitations. This article addresses this issue by presenting a novel strategy to realize an analog feeding network, which allows an arbitrary linear array (LA) to radiate multiple arbitrary beams. In particular, an iterative procedure is conceived to design a Blass matrix using an identical directional coupler for all nodes, resulting in a very simple structure suitable for large-scale production. Two applications with arbitrary directions are illustrated as proofs-of-concept for the developed architecture: a dual-beam configuration with a null involving an aperiodic LA, and a four-beam configuration involving a periodic LA. For this second application, the effectiveness of the proposed solution is further verified by full-wave simulations and experimental measurements carried out on a fabricated prototype

Fine-tuning the electrostatic properties of an alkali-linked organic adlayer on a metal substrate

The performance of modern organic electronic devices is often determined by the electronic level alignment at a metal–organic interface. This property can be controlled by introducing an interfacial electrostatic dipole via the insertion of a stable interlayer between the metallic and the organic phases. Here, we use density functional theory to investigate the electrostatic properties of an assembled structure formed by alkali metals coadsorbed with 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules on a Ag(100) substrate. We find that the interfacial dipole buildup is regulated by the interplay of adsorption energetics, steric constraints and charge transfer effects, so that choosing chemical substitutions within TCNQ and different alkali metals provides a rich playground to control the systems’ electrostatics and in particular fine-tune its work-function shift

Changes in hydrogen storage properties of binary mixtures of intermetallic compounds submitted to mechanical milling

Electrochemical loading of hydrogen in single and binary mixtures of the intermetallic compounds, TiNi, TiFe, Zr30Ni70 and Zr70Ni30 have been investigated after energetic mechanical milling. Enhanced hydrogen storage of the 50/50 (by weight) TiNi/ZrNi binary mixtures are only found after high energy milling (450 rpm for 12 h). The high energy milled 50/50 and 30/70 TiFe/Zr30Ni70 binary mixtures exhibited good electrochemical loading (98 mA h g−1) at 25 °C but this capacity was decreased by 12% on increasing the temperature to 55 °C. On the other hand, the 70/30 TiFe/Zr30Ni70 binary mixtures showed a 65% increase in the hydrogen capacity with temperature over the same range. High energy milling of the TiFe with carbon materials again led to a substantial increase in the storage capacity but here, this was attributed to a partial reduction of the surface oxides by the graphite/activated carbon. Thermal analysis of the samples using high pressure differential scanning calorimetry on the milled Zr70Ni30 sample showed a rapid deterioration of the hydrogen absorption/desorption features with thermal cycling over the range 100–310 °C due to sintering of the samples