Towards high-impedance surfaces realization using single-layer arrays of electrically small particles

2013 ◽  
Author(s):  
Y. Ra'di ◽  
V. S. Asadchy ◽  
S. A. Tretyakov
Keyword(s):  
Single Layer ◽  
Small Particles ◽  
High Impedance

scholarly journals Performance Enhancement of mm-Wave Phased Arrays for Mobile Terminals Through Grounded Coplanar Waveguide Feeding Networks With via Fences

2021 ◽  
Vol 2 ◽  
Author(s):  
Jae-Yeong Lee ◽  
Jaehyun Choi ◽  
Bumhyun Kim ◽  
Yerim Oh ◽  
Wonbin Hong
Keyword(s):  
Phased Arrays ◽  
Performance Enhancement ◽  
Coplanar Waveguide ◽  
Experimental Studies ◽  
Single Layer ◽  
Power Divider ◽  
Electromagnetic Bandgap ◽  
Mobile Terminals ◽  
One Dimensional ◽  
High Impedance

This paper presents a design methodology focused on feeding networks that can improve the insertion loss and coverage efficiencies of millimeter-wave (mm-Wave) phased arrays in mobile terminals. This enhancement is accomplished by using a grounded coplanar waveguide (GCPW) transmission line (TL) with via fences fabricated on single-layer FR-4 PCB. The exemplified 8-element phased arrays incorporating a compact one-dimensional electromagnetic bandgap (1-D EBG) antenna are fed through a 1 × 8 T-junction power divider, which includes the predetermined phased delay lines. To achieve high radiation performance with minimum leakage power or spurious waves in the T-junction power divider, an island-shape GCPW TL topology with via fences featuring high-impedance surfaces (HIS) is devised and fabricated. For further investigation on the radiation performance and spherical coverage of the mm-Wave mobile antenna, a mobile device prototype equipped with two sets of the 8-element phased arrays is prepared and studied. Through extensive simulation and experimental studies, it can be ascertained that the proposed GCPW TL topology with via fences can improve the realized gain at a coverage efficiency of 50% by more than 3 dB, between 26 and 36 GHz.

Stabilization, Characterization and Optical Applications of Niobium and Tantalum Oxide Sols Prepared Via Alkoxide Routes

1990 ◽  
Vol 180 ◽  
Author(s):  
Stephen Parraud ◽  
Liliane G. Hubert-Pfalzgraf ◽  
Herve Floch
Keyword(s):  
Spin Coating ◽  
Tantalum Oxide ◽  
Pulse Length ◽  
Single Layer ◽  
Colloidal Suspensions ◽  
Laser Damage ◽  
Threshold Values ◽  
Small Particles ◽  
Optical Applications ◽  
Hydrolysis Of

ABSTRACTHydrolysis of niobium and tantalum pentaethoxides in ethanol and in the presence of basic (ammonia, tetramethylammonium hydroxide, di and triethylamine) or acidic (nitric or hydrochloric acids) additives was investigated. Triethylamine gives monodispersed, small particles of amorphous M2O5,nH2O (M = Nb, Ta). These colloidal suspensions were used to obtain thin films by spin-coating techniques. The coatings display a thickness of 100–300 nm and a refractive index around 1.7. Laser damage tests at 1064 nm wavelength with a pulse length of 3 ns were carried out on the single layer systems. The threshold values (one-onone) are in favor of the Ta2O5 coatings with an average of 14.5 ± 2.1 J/cm2 , by comparison with 8.3 ± 1.6 J/cm2 for the Nb2O5 films.

Highly Reproducible Electric Bistability in an Organic Single Layer Device with Ag Top Electrode

2006 ◽  
Vol 965 ◽  
Author(s):  
Masaya Terai ◽  
Katsuhiko Fujita ◽  
Tetsuo Tsutsui
Keyword(s):  
Single Layer ◽  
Organic Layer ◽  
Charge Accumulation ◽  
Organic Film ◽  
Static Charge ◽  
Working Mechanism ◽  
High Impedance ◽  
Bistable State ◽  
The Difference ◽  
Sandwiched Structure

ABSTRACTHigh reproducible electrical bistability was observed and we deliberated its working mechanism through measurements of dynamic dielectric response in single organic layer sandwiched structure using top Ag electrode. The electrical transition between high-impedance state (OFF state) and low-impedance state (ON state) happened by the change of applied voltage patterns. Distinction between the OFF state and the ON state was not induced by change of static charge accumulation but reflected the difference of the response of mobile electric careers in the organic film. We proposed plausible working mechanism of transition from the pristine state to the bistable state. Namely, the electrical bistable state of our device is generated by penetration of Ag nanoparticles and creation of charge pathways across the organic film.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Crystalline order to a resolution of 4.7 A in the sheath of Methanospirilium hungatii: A cross-beta structure

1984 ◽  
Vol 42 ◽  
pp. 214-215
Author(s):  
Murray Stewart ◽  
T.J. Beveridge ◽  
D. Sprott
Keyword(s):  
Cell Wall ◽  
Single Layer ◽  
Uranyl Acetate ◽  
Optical Diffraction ◽  
Tube Axis ◽  
Basic Subunit ◽  
Beta Structure ◽  
Diffraction Patterns ◽  
Protein Treatment ◽  
General Appearance

The archaebacterium Methanospirillum hungatii has a sheath as part of its cell wall which is composed mainly of protein. Treatment with dithiothreitol or NaOH released the intact sheaths and electron micrographs of this material negatively stained with uranyl acetate showed flattened hollow tubes, about 0.5 μm diameter and several microns long, in which the patterns from the top and bottom were superimposed. Single layers, derived from broken tubes, were also seen and were more simply analysed. Figure 1 shows the general appearance of a single layer. There was a faint axial periodicity at 28.5 A, which was stronger at irregular multiples of 28.5 A (3 and 4 times were most common), and fine striations were also seen at about 3° to the tube axis. Low angle electron diffraction patterns (not shown) and optical diffraction patterns (Fig. 2) from these layers showed a complex meridian (as a result of the irregular nature of the repeat along the tube axis) which showed a clear maximum at 28.5 A, consistent with the basic subunit spacing.

Dynamic Scanning Electron Microscopy of Small Particles

1975 ◽  
Vol 33 ◽  
pp. 280-281
Author(s):  
W. Krakow ◽  
W. C. Nixon
Keyword(s):  
Electron Microscopy ◽  
Low Noise ◽  
Time Sequence ◽  
Field Of View ◽  
Video Tape ◽  
Small Particles ◽  
Polystyrene Spheres ◽  
Field Distributions ◽  
Dynamic Scanning ◽  
Scanning Electron

The scanning electron microscope (SEM) can be run at television scanning rates and used with a video tape recorder to observe dynamic specimen changes. With a conventional tungsten source, a low noise TV image is obtained with a field of view sufficient to cover the area of the specimen to be recorded. Contrast and resolution considerations have been elucidated and many changing specimens have been studied at TV rates.To extend the work on measuring the magnitude of charge and field distributions of small particles in the SEM, we have investigated their motion and electrostatic interaction at TV rates. Fig. 1 shows a time sequence of polystyrene spheres on a conducting grating surface inclined to the microscope axis. In (la) there are four particles present in the field of view, while in (lb) a fifth particle has moved into view.

The Shadow Widths of Very Small Particles are Formed Independently of the Metal Cap Build Up on the Particle

1981 ◽  
Vol 39 ◽  
pp. 568-569
Author(s):  
George C. Ruben
Keyword(s):  
Gold Particle ◽  
Film Surface ◽  
Small Particles ◽  
Geometric Process ◽  
Metal Free ◽  
Shadow Area

The formation of shadows behind small particles has been thought to be a geometric process (GP) where the metal cap build up on the particle creates a shadow width the same size as or larger than the particle. This GP cannot explain why gold particle shadow widths are generally larger than the gold particle and may have no appreciable metal cap build up (fig. 1). Ruben and Telford have suggested that particle shadow widths are formed by the width dependent deflection of shadow metal (SM) lateral to and infront of the particle. The trajectory of the deflected SM is determined by the incoming shadow angle (45°). Since there can be up to 1.4 times (at 45°) more SM directly striking the particle than the film surface, a ridge of metal nuclei lateral to and infront of the particle can be formed. This ridge in turn can prevent some SM from directly landing in the metal free shadow area. However, the SM that does land in the shadow area (not blocked by the particle or its ridge) does not stick and apparently surface migrates into the SM film behind the particle.

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

SREM observation of the interaction between the in-situ deposited Pd small particles and MgO cleavage surface

1986 ◽  
Vol 44 ◽  
pp. 382-383
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Small Particle ◽  
Small Particles ◽  
Cleavage Surface ◽  
Metallic Particles ◽  
Microscopy Technique ◽  
Ceramic Surfaces ◽  
Reflection Electron Microscopy ◽  
New Perspective

The understanding of the interactions between the small metallic particles and ceramic surfaces has been studied by many catalyst scientists. We had developed Scanning Reflection Electron Microscopy technique to study surface structure of MgO hulk cleaved surface and the interaction with the small particle of metals. Resolutions of 10Å has shown the periodic array of surface atomic steps on MgO. The SREM observation of the interaction between the metallic particles and the surface may provide a new perspective on such processes.

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