Ferrites for Tunable RF and Microwave Devices

1999 ◽  
Vol 603 ◽  
Author(s):  
Gerald F. Dionne
Keyword(s):  
Low Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Phase Shifters ◽  
Full Potential ◽  
Cryogenic Temperatures ◽  
Variable Permeability ◽  
Ferrite Devices ◽  
Q Factors ◽  
Insertion Losses ◽  
Rf Signal

AbstractMicrowave systems for communications and radar require control of propagation of the rf signal. Devices that accomplish this function include phase shifters, isolators and circulators, and tunable filters. In many instances, these devices are magnetic and are based on the variable permeability of electrically insulating ferrimagnetic oxides (ferrites). Recent advances in microwave ferrite devices have featured superconductor circuitry that promises to virtually eliminate insertion losses due to rf surface resistance. Lower conduction losses allow the use of small lightweight microstrip configurations in place of traditional bulky waveguide structures. For operation at cryogenic temperatures ferrimagnetic spinels and garnets will require chemical alteration to realize the full potential of these devices. Challenges include the reduction of magnetocrystalline anisotropy to optimize switching energies and speeds, and the elimination of fast-relaxing impurities in the magnetic garnets that can increase magnetic losses and degrade resonator Q factors at low temperatures.

Effects of the Co-Presence of Conflicting Magnetic Anisotropy in Ba Ferrite Particles

2010 ◽  
Vol 67 ◽  
pp. 108-112
Author(s):  
Giancarlo Bottoni
Keyword(s):  
Thermal Stability ◽  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Low Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Shape Anisotropy ◽  
Recording Media ◽  
Magnetization Switching ◽  
Crystalline Anisotropy ◽  
Thermal Stability Of

In Ba ferrite particles magnetocrystalline and shape anisotropies are contemporarily present and conflicting. The strength and evolution of the two anisotropies are studied, through the dependence of the anisotropy constants on temperature. While in pure Ba ferrite particles the anisotropy is uniaxial at all temperatures, since the magnetocrystalline anisotropy clearly prevails on shape anisotropy, in particles modified for employment in recording media the two anisotropies are comparable and at low temperatures the shape anisotropy result stronger than the crystalline anisotropy. Besides the irregular shape of the particles introduces further preferred directions for the magnetization. The Co/Ti-doped particles show a multiple axes anisotropy. The macroscopic magnetic properties are found in relationship with the evolution of the anisotropy. Also the influence that the presence of such multiple anisotropy has on the magnetization switching and on the thermal stability of the magnetization of the Ba ferrite particles is analyzed.

scholarly journals Internal Friction and Young's Modulus Measurements on SiO2 and Ta2O5 Films Done with an Ultra-High Q Silicon-Wafer Suspension

2015 ◽  
Vol 60 (1) ◽  
pp. 365-370 ◽  
Author(s):  
M. Granata ◽  
L. Balzarini ◽  
J. Degallaix ◽  
V. Dolique ◽  
R. Flaminio ◽  
...  
Keyword(s):  
Thin Films ◽  
Internal Friction ◽  
Silicon Wafer ◽  
Room Temperature ◽  
Suspension System ◽  
Cryogenic Temperatures ◽  
Resonant Frequencies ◽  
High Q ◽  
Key Features ◽  
Q Factors

Abstract In order to study the internal friction of thin films a nodal suspension system called GeNS (Gentle Nodal Suspension) has been developed. The key features of this system are: i) the possibility to use substrates easily available like silicon wafers; ii) extremely low excess losses coming from the suspension system which allows to measure Q factors in excess of 2×108 on 3” diameter wafers; iii) reproducibility of measurements within few percent on mechanical losses and 0.01% on resonant frequencies; iv) absence of clamping; v) the capability to operate at cryogenic temperatures. Measurements at cryogenic temperatures on SiO2 and at room temperature only on Ta2O5 films deposited on silicon are presented.

RF Microwave Switches Based on Reversible Metal-Semiconductor Transition Properties of VO2 Thin Films: An Attractive Way To Realise Simple RF Microelectronic Devices

2008 ◽  
Vol 1129 ◽  
Author(s):  
Frédéric Dumas-Bouchiat ◽  
Corinne Champeaux ◽  
Alain Catherinot ◽  
Julien Givernaud ◽  
Aurelian Crunteanu ◽  
...  
Keyword(s):  
Thin Films ◽  
Geometrical Parameters ◽  
Si Substrates ◽  
Thermally Activated ◽  
Microelectronic Devices ◽  
Microwave Switches ◽  
Vo2 Thin Films ◽  
Insertion Losses ◽  
Rf Signal

AbstractMicrowave switches in both shunt and series configurations are developped using semiconductor to metal (SC-M) transition of vanadium dioxide (VO2) thin films deposited by in situ pulsed laser deposition on C-plane sapphire and SiO2/Si substrates. The influence of geometrical parameters such as the length of the switch is shown. The VO2-based switches exhibit up to 30-40 dB average isolation of the radio-frequency (RF) signal on a very wide frequency band (500 MHz-35 GHz) with weak insertion losses, when thermally activated. Furthermore, they can be electrically activated. Finally these VO2-based switches are integrated in the fabrication of innovative tunable band-stop filters which consist in a transmission line coupled with four U-shaped resonators and operate in 9-11 GHz frequency range. Its tunability is demonstrated using electrical activation of each VO2-based switch.

Power Efficient Scheduling and Hybrid Precoding for Time Modulated Arrays

2019 ◽  
Author(s):  
José P. González-Coma ◽  
Luis Castedo
Keyword(s):  
Power Efficiency ◽  
Scheduling Algorithm ◽  
Multiple Input Multiple Output ◽  
Computer Experiments ◽  
Phase Shifters ◽  
Power Efficient ◽  
Input Multiple Output ◽  
Analog Transmission ◽  
Insertion Losses ◽  
Reduced Power Consumption

We consider power efficient scheduling and precoding solutions for multiantenna hybrid digital-analog transmission systems that use Time-Modulated Arrays (TMAs) in the analog domain. TMAs perform beamforming with switches instead of conventional Phase Shifters (PSs). The extremely low insertion losses of switches, together with their reduced power consumption and cost make TMAs attractive in emerging technologies like massive Multiple-Input Multiple-Output (MIMO) and millimeter wave (mmWave) systems. We propose a novel analog processing network based on TMAs and provide an angular scheduling algorithm that overcomes the limitations of conventional approaches. Next, we pose a convex optimization problem to determine the analog precoder. This formulation allows us to account for the Sideband Radiation (SR) effect inherent to TMAs, and achieve remarkable power efficiencies with a very low impact on performance. Computer experiments results show that the proposed design, while presenting a significantly better power efficiency, achieves a throughput similar to that obtained with other strategies based on angular selection for conventional architectures.<br>

scholarly journals Anisotropic longitudinal electronic relaxation affects DNP at cryogenic temperatures

2017 ◽  
Vol 19 (24) ◽  
pp. 16087-16094 ◽  
Author(s):  
E. M. M. Weber ◽  
H. Vezin ◽  
J. G. Kempf ◽  
G. Bodenhausen ◽  
D. Abergél ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Spectral Diffusion ◽  
Electronic Relaxation ◽  
Cryogenic Temperatures ◽  
Nitroxide Radicals

Anisotropic longitudinal electronic relaxation in nitroxide radicals can impact DNP at low temperatures in cases of slow spectral diffusion.

scholarly journals Phase Shifters with Tunable Reflective Method Using Inductive Coupled Lines

2017 ◽  
Vol 6 (01) ◽  
pp. 08-13
Author(s):  
Prof. Nitin Sherje
Keyword(s):  
Phase Shifter ◽  
Phase Shifters ◽  
Design System ◽  
Low Area ◽  
Type Phase ◽  
Proposed Model ◽  
Coupled Lines ◽  
Large Phase ◽  
Phase Range ◽  
Insertion Losses

A coupler forms essential aspect of a phase shifters with tunable reflector, which is a 3 decibel quadrature coupler (λ/4). In this paper, a model which shows that by reducing the length of the coupler a wide phase range is achieved for a reflective type phase shifter. The approach used in this method is by having a variable instead of constant Even and Odd impedances. The ultimate aim is to design a Reflective Type Phase Shifter which has a very low area, low return and insertion losses and a large phase range. The proposed model is done using Advanced Design System (ADS) and the results are verified for the frequency of 2.4GHz.

Magnetization reversal and magnetic anisotropy of Fe, Ni and Co nanowires in nanoporous alumina membranes

2001 ◽  
Vol 674 ◽  
Author(s):  
M. Kröll ◽  
L. J. de Jongh ◽  
F. Luis ◽  
P. Paulus ◽  
G. Schmid
Keyword(s):  
Magnetic Anisotropy ◽  
Magnetization Reversal ◽  
Low Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Small Diameter ◽  
Anisotropy Constant ◽  
Magnetic Domains ◽  
Alumina Membranes ◽  
Subsequent Propagation ◽  
Co Nanowires

ABSTRACTThe magnetization reversal and magnetic anisotropy of Fe, Ni and Co nanowires is studied at low temperatures. All nanowires show a strong shape anisotropy with the easy axis being parallel to the long axis of the wires. Co nanowires additionally show a temperature dependent magnetocrystalline anisotropy along the hexagonal c-axis, which is directed nearly perpendicular to the long axis of the wires, as is confirmed by X-Ray diffraction measurements [1] and reported by Strijkers et al. who performed NMR measurements on samples prepared in a similar way [2]. Therefore, at low temperatures and for large wire diameters a competition between magnetocrystalline and shape anisotropies can be observed. Co wires with a small diameter, however, do not show a significant magnetocrystalline anisotropy. Fcc-Co, which is only known as a high-temperature Co modification and which does not have a large magnetocrystalline anisotropy constant, becomes the predominant Co modification here [1,3]. Investigations on the size dependence of the switching field for Fe and Ni nanowires provide information about the magnetization reversal process, which takes place via a nucleation of small magnetic domains probably at the end of the wires, and subsequent propagation of the domain wall along the wire.

scholarly journals Characterization of the piezoresistance in highly doped p-type 3C-SiC at cryogenic temperatures

RSC Advances ◽  
2018 ◽  
Vol 8 (52) ◽  
pp. 29976-29979 ◽  
Author(s):  
Hoang-Phuong Phan ◽  
Karen M. Dowling ◽  
Tuan-Khoa Nguyen ◽  
Caitlin A. Chapin ◽  
Toan Dinh ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Gauge Factor ◽  
Cryogenic Temperatures ◽  
Sensing Applications ◽  
P Type

The piezoresistance in crystalline 3C-SiC epitaxially grown on Si was investigated at low temperatures down to 150 K. The large gauge factor in 3C-SiC indicates its feasibility for sensing applications in cryogenic environments.

scholarly journals Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 625 ◽  
Author(s):  
Le Thanh Hung Nguyen ◽  
Jae-Sik Hwang ◽  
Myung-Sung Kim ◽  
Jeong-Hyeon Kim ◽  
Seul-Kee Kim ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Low Temperatures ◽  
316L Stainless Steel ◽  
Charpy Impact ◽  
Cryogenic Temperatures ◽  
Absorbed Energy ◽  
Impact Properties ◽  
Charging Time ◽  
The Impact

316L stainless steel is a promising material candidate for a hydrogen containment system. However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement (HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study, 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology, respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel.

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