296 research outputs found
Conformal Antenna Array for Millimeter-Wave Communications: Performance Evaluation
In this paper, we study the influence of the radius of a cylindrical
supporting structure on radiation properties of a conformal millimeter-wave
antenna array. Bent antenna array structures on cylindrical surfaces may have
important applications in future mobile devices. Small radii may be needed if
the antenna is printed on the edges of mobile devices and in items which human
beings are wearing, such as wrist watches, bracelets and rings. The antenna
under study consists of four linear series-fed arrays of four patch elements
and is operating at 58.8 GHz with linear polarization. The antenna array is
fabricated on polytetrafluoroethylene substrate with thickness of 0.127 mm due
to its good plasticity properties and low losses. Results for both planar and
conformal antenna arrays show rather good agreement between simulation and
measurements. The results show that conformal antenna structures allow
achieving large angular coverage and may allow beam-steering implementations if
switches are used to select between different arrays around a cylindrical
supporting structure.Comment: Keywords: conformal antenna, millimeter-wave communications, patch
antenna array. 11 pages, 10 figures, 1 tabl
Luminescence Spectroscopy of Semiconductor Surfaces and Interfaces
Low energy cathodoluminescence spectroscopy (CLS) employing incident electron energies in the range of a few kV or less enable measurement of electronic structure near semiconductor surfaces and interfaces. Coupled with photoluminescence spectroscopy (PL), the CLS technique has been extended to characterize electronic structure tens of nanometers below the free surface at metal-semiconductor and semiconductor-semiconductor junctions. CLS has revealed discrete, deep electronic states for clean and metallized semiconductor surfaces as a function of atomic ordering as well as vicinal surfaces as a function of misorientation. A combination of CLS and PL reveals deep level features associated with strain relaxation and dislocations at heterojunction interfaces as well as variations in epilayer growth conditions. Such observations demonstrate the existence of discrete, deep levels in the semiconductor band gap and their sensitivity to chemical and atomic structure near surfaces and interfaces. Furthermore, the energies and densities of such deep levels provide a consistent picture of Fermi level stabilization and band bending at semiconductor contacts. Finally, our results indicate that deep level CLS/PL measurements are an effective, in-situ probe of surface and interface quality
Elastic-plastic transition in MBE-grown GaSb semiconducting crystal examined by noindentation
The present paper concerns the elastic-plastic nanodeformation of Te-doped GaSb crystals grown by molecular
beam epitaxy on the n-type of GaSb substrate. The conventional analysis of nanoindentation data obtained with
sharp triangular (Berkovich) and spherical tip revealed the elastic modulus (E = 83:07 1:78 GPa), hardness
(H = 5:19 0:25 GPa) and âtrue hardnessâ (HT = 5:73 0:04 GPa). The registered pop-in event which indicates
the elasticâplastic transition in GaSb crystal points towards the corresponding yield strength ( Y = 3:8 0:1 GPa).
The origin of incipient plasticity in GaSb crystal is discussed in terms of elastic-plastic deformation energy concept
Digital Technologies for Transport and Mobility: Challenges, Trends and Perspectives
This white paper aims at presenting the ideas emerging from the different fields pertaining to transport and mobility, to describe the capacities of current state-of-the-art digital technologies and the perspectives that are expected to shape the future of transport and mobility
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