scholarly journals Comparative Assessment of GaN as a Microwave Source with Si and SiC for Mixed Mode Operation at Submillimetre Wave Band of Frequency

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Pranati Panda ◽  
Satya Narayan Padhi ◽  
Gana Nath Dash
Keyword(s):  
Low Noise ◽  
Comparative Assessment ◽  
Wave Band ◽  
Simulation Methods ◽  
Microwave Source ◽  
Mode Operation ◽  
The Mean ◽  
Carrier Velocity ◽  
Microwave Sources ◽  
Submillimetre Wave

The potentials of GaN, SiC, and Si for application as microwave sources in mixed tunnelling avalanche transit time mode operation at submillimetre wave (sub-mm wave) frequency around 0.35 terahertz (THz) are investigated using some computer simulation methods. Design criteria to choose width, doping concentration, and area are highlighted. From the results of our simulation we observed that the Si diode produces the least power output of 41 mW followed by the GaN diode with 760 mW and the SiC diode with 2.89 W. In addition, the GaN diode has more noise than the SiC diode (by 5 dB) as well as the Si diode (by 10 dB). The drastically different performance between the GaN and the SiC diode is attributed to the incorporation of disparate carrier velocity in GaN which were not being used by other authors. In spite of the low power and high noise of the GaN compared to the SiC diode, the presence of several peaks in the mean square noise voltage curves and the existence of several minima in the noise measure curves would open a new direction in the design of GaN low-noise ATT diodes capable of multifrequency tuning like a DAR diode.

scholarly journals Review of the high-power vacuum tube microwave sources based on Cherenkov radiation

2020 ◽  
Author(s):  
Weiye Xu
Keyword(s):  
Output Power ◽  
High Power ◽  
Traveling Wave ◽  
Cherenkov Radiation ◽  
Continuous Wave ◽  
Vacuum Tube ◽  
Microwave Source ◽  
Vacuum Tubes ◽  
Traveling Wave Tubes ◽  
Microwave Sources

Since the first vacuum tube (X-ray tube) was invented by Wilhelm Röntgen in Germany, after more than one hundred years of development, the average power density of the vacuum tube microwave source has reached the order of 108 [MW][GHz]2. In the high-power microwave field, the vacuum devices are still the mainstream microwave sources for applications such as scientific instruments, communications, radars, magnetic confinement fusion heating, microwave weapons, etc. The principles of microwave generation by vacuum tube microwave sources include Cherenkov or Smith-Purcell radiation, transition radiation, and Bremsstrahlung. In this paper, the vacuum tube microwave sources based on Cherenkov radiation were reviewed. Among them, the multi-wave Cherenkov generators can produce 15 GW output power in X-band. Cherenkov radiation vacuum tubes that can achieve continuous-wave operation include Traveling Wave Tubes and Magnetrons, with output power up to 1MW. Cherenkov radiation vacuum tubes that can generate frequencies of the order of 100 GHz and above include Traveling Wave Tubes, Backward Wave Oscillators, Magnetrons, Surface Wave Oscillators, Orotrons, etc.

Design of low-noise solid-state microwave sources

1966 ◽  
Vol 31 (4) ◽  
pp. 209 ◽  
Author(s):  
J. Frilley ◽  
G. Grandchamp
Keyword(s):  
Solid State ◽  
Low Noise ◽  
Microwave Sources

scholarly journals A validation study of reconstructed rapid prototyping models produced by two technologies

2017 ◽  
Vol 87 (5) ◽  
pp. 782-787 ◽  
Author(s):  
Christian Andreas Dietrich ◽  
Andreas Ender ◽  
Stefan Baumgartner ◽  
Albert Mehl
Keyword(s):  
Rapid Prototyping ◽  
Validation Study ◽  
Statistical Significance ◽  
Three Dimensional ◽  
Comparative Assessment ◽  
Precision Measurements ◽  
Mean Deviation ◽  
The Mean ◽  
Dimensional Errors ◽  
Stereolithographic Models

ABSTRACT Objective: To determine the accuracy (trueness and precision) of two different rapid prototyping (RP) techniques for the physical reproduction of three-dimensional (3D) digital orthodontic study casts, a comparative assessment using two 3D STL files of two different maxillary dentitions (two cases) as a reference was accomplished. Materials and Methods: Five RP replicas per case were fabricated using both stereolithography (SLA) and the PolyJet system. The 20 reproduced casts were digitized with a highly accurate reference scanner, and surface superimpositions were performed. Precision was measured by superimposing the digitized replicas within each case with themselves. Superimposing the digitized replicas with the corresponding STL reference files assessed trueness. Statistical significance between the two tested RP procedures was evaluated with independent-sample t-tests (P < .05). Results: The SLA and PolyJet replicas showed statistically significant differences for trueness and precision. The precision of both tested RP systems was high, with mean deviations in stereolithographic models of 23 (±6) μm and in PolyJet replicas of 46 (±13) μm. The mean deviation for trueness in stereolithographic replicas was 109 (±4) μm, while in PolyJet replicas, it was 66 (±14) μm. Conclusions: Comparing the STL reference files, the PolyJet replicas showed higher trueness than the SLA models. But the precision measurements favored the SLA technique. The dimensional errors observed in this study were a maximum of 127 μm. In the present study, both types of reproduced digital orthodontic models are suitable for diagnostics and treatment planning.

scholarly journals User influence on the mean effective gain for data mode operation of mobile handsets

2012 ◽  
Author(s):  
J. O. Nielsen ◽  
B. Yanakiev ◽  
I. B. Bonev ◽  
M. Christensen ◽  
G. F. Pedersen ◽  
...  
Keyword(s):  
Mode Operation ◽  
User Influence ◽  
The Mean

scholarly journals Abundant proteins contribute strongly to noise in the growth rate of optimally growing bacteria

2020 ◽  
Author(s):  
L.H.J. Krah ◽  
R. Hermsen
Keyword(s):  
Growth Rate ◽  
Low Noise ◽  
Cellular Growth ◽  
Bacterial Cells ◽  
Noise Levels ◽  
Physiological Variables ◽  
Stochastic Fluctuations ◽  
Two Factors ◽  
The Mean ◽  
Related Proteins

AbstractIn bacterial cells, protein expression is a highly stochastic process. At the same time, physiological variables such as the cellular growth rate also fluctuate significantly. A common intuition is that, due to their relatively high noise amplitudes, proteins with a low mean expression level are the most important causes of these fluctuations on a larger, physiological scale. Noise in highly expressed proteins, whose stochastic fluctuations are relatively small, is often ignored. In this work, we challenge this intuition by developing a theory that predicts the contribution of a protein’s expression noise to the noise in the instantaneous, cellular growth rate. Using mathematical analysis, we decomposed the contribution of each protein into two factors: the noise amplitude of the protein, and the sensitivity of the growth rate to fluctuations in that protein’s concentration. Next, we incorporated evolution, which has shaped the mean abundances of growth-related proteins to optimise the growth rate, causing protein abundances, but also cellular sensitivities to be non-random. We show that in cells that grow optimally fast, the growth rate is most sensitive to fluctuations in highly abundant proteins. This causes such proteins to overall contribute strongly to the noise in the growth-rate, despite their low noise levels. The results are confirmed in a stochastic toy model of cellular growth.

scholarly journals The Microwave Sources for EPR Spectroscopy

2017 ◽  
pp. 18-25
Author(s):  
Mariusz Hruszowiec ◽  
Kacper Nowak ◽  
Bogusław Szlachetko ◽  
Michał Grzelak ◽  
Wojciech Czarczyński ◽  
...  
Keyword(s):  
Epr Spectroscopy ◽  
Traveling Wave ◽  
Material Science ◽  
Rapid Development ◽  
Traveling Wave Tube ◽  
Wave Tube ◽  
Backward Wave Oscillator ◽  
Microwave Source ◽  
Wave Oscillator ◽  
Microwave Sources

Rapid development of many scientific and technical disciplines, especially in material science and material engineering increases a demand for quick, accurate and cheap techniques of materials investigations. The EPR spectroscopy meets these requirements and it is used in many fields of science including biology, chemistry and physics. For proper work, the EPR spectrometer needs a microwave source, which are reviewed in this paper. Vacuum tubes as well as semiconductor generators are presented such as magnetron, klystron, traveling wave tube, backward wave oscillator, orotron, gyrotron, Gunn and IMPATT diodes. In this paper main advantages of gyrotron usage, such as stability and an increased spectral resolution in application to EPR spectroscopy is discussed. The most promising and reliable microwave source is suggested.

scholarly journals A low-noise on-chip coherent microwave source

2021 ◽  
Author(s):  
Chengyu Yan ◽  
Juha Hassel ◽  
Visa Vesterinen ◽  
Jinli Zhang ◽  
Joni Ikonen ◽  
...  
Keyword(s):  
Low Noise ◽  
Microwave Source ◽  
On Chip
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