SIMULATIONS OF THE GENERATION OF TERAHERTZ RADIATION BY PHOTOMIXING IN LASER-ASSISTED FIELD EMISSION TO OPTIMIZE THE SIGNAL-TO-NOISE RATIO

Quantum simulations and experiments show that photomixing in laser-assisted field emission has promise as a new method for wide-band tunable sources of radiation at terahertz frequencies. The tunable bandwidth is only limited by the means for coupling power from the oscillations in the field emission current from photomixing, and not by the processes that generate this current. Photomixing is simulated as a stationary stochastic process in which the frequencies and phases of the incident optical radiation are random variables. The waveform of the current is determined by solving the Schrödinger equation at discrete time steps for which the effective potential barrier is a superposition of the incident radiation field and the static barrier. These samples satisfy the criteria of a Poisson process to allow for the discrete emission of electrons at a specified total current. The one-sided power spectral density for this current is calculated with the FFT to produce periodogram estimates. The simulations show that the signal-to-noise ratio may be increased by (1) raising the power flux density of each laser, (2) raising the DC static current, (3) reducing the linewidth of each laser, and (4) using a static current density of no more than 1010 A/m.

Download Full-text

Signal-to-noise ratio improvement of common-gate CMOS LNA for Ultra-Wide-Band

APCCAS 2008 - 2008 IEEE Asia Pacific Conference on Circuits and Systems ◽

10.1109/apccas.2008.4745984 ◽

2008 ◽

Author(s):

Teppei Hayashi ◽

Hiroki Sato ◽

Akira Hyogo ◽

Keitaro Sekine

Keyword(s):

Signal To Noise Ratio ◽

Wide Band ◽

Ultra Wide Band ◽

Signal To Noise ◽

Common Gate ◽

Cmos Lna ◽

Noise Ratio

Download Full-text

Optimization of the signal-to-noise ratio for terahertz radiation generated by photomixing in laser-assisted field emission

10.1117/12.546860 ◽

2004 ◽

Author(s):

Mark J. Hagmann

Keyword(s):

Field Emission ◽

Terahertz Radiation ◽

Signal To Noise Ratio ◽

Signal To Noise ◽

Noise Ratio

Download Full-text

Parameter Simulation and Design of an Airborne Hyperspectral Imaging LiDAR System

Remote Sensing ◽

10.3390/rs13245123 ◽

2021 ◽

Vol 13 (24) ◽

pp. 5123

Author(s):

Liyong Qian ◽

Decheng Wu ◽

Dong Liu ◽

Shalei Song ◽

Shuo Shi ◽

...

Keyword(s):

Remote Sensing ◽

Spectral Density ◽

Hyperspectral Imaging ◽

Optical Fibers ◽

Signal To Noise Ratio ◽

Design Parameters ◽

Signal To Noise ◽

Lidar System ◽

Power Spectral ◽

Noise Ratio

With continuous technological development, the future development trend of LiDAR in the field of remote sensing and mapping is to obtain the elevation and spectral information of ground targets simultaneously. Airborne hyperspectral imaging LiDAR inherits the advantages of active and passive remote sensing detection. This paper presents a simulation method to determine the design parameters of an airborne hyperspectral imaging LiDAR system. In accordance with the hyperspectral imaging LiDAR equation and optical design principles, the atmospheric transmission model and the reflectance spectrum of specific ground targets are utilized. The design parameters and laser emission spectrum of the hyperspectral LiDAR system are considered, and the signal-to-noise ratio of the system is obtained through simulation. Without considering the effect of detector gain and electronic amplification on the signal-to-noise ratio, three optical fibers are coupled into a detection channel, and the power spectral density emitted by the supercontinuum laser is simulated by assuming that the signal-to-noise ratio is equal to 1. The power spectral density emitted by the laser must not be less than 15 mW/nm in the shortwave direction. During the simulation process, the design parameters of the hyperspectral LiDAR system are preliminarily demonstrated, and the feasibility of the hyperspectral imaging LiDAR system design is theoretically guaranteed in combination with the design requirements of the supercontinuum laser. The spectral resolution of a single optical fiber of the hyperspectral LiDAR system is set to 2.5 nm. In the actual prototype system, multiple optical fibers can be coupled into a detection channel in accordance with application needs to further improve the signal-to-noise ratio of hyperspectral LiDAR system detection.

Download Full-text

Design and Implementation of Key Technologies of Carrier Synchronization in Wireless Communication System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.602-605.3329 ◽

2014 ◽

Vol 602-605 ◽

pp. 3329-3332

Author(s):

Guo Qing Dang ◽

Xiao Yan Cheng

Keyword(s):

Wireless Communication ◽

Communication System ◽

Signal To Noise Ratio ◽

Low Complexity ◽

Carrier Synchronization ◽

Signal To Noise ◽

Wireless Communication System ◽

Low Snr ◽

Noise Ratio ◽

The One

Noise multiple and user interference are the two important influencing factors that carrier synchronization technology in the wireless communication system faces. On the one hand, the phase locked loop and data aided carrier synchronization device is faced with poor estimation precision and slow convergence speed. On the other hand frequency offset and channel estimation problem need to be solved in multi-input multi-output (MIMO) communication system collaboration under the condition of dry low signal to noise ratio. So research of carrier synchronization algorithm of low complexity, high precision in view of the low SNR and multi-user communication system is becoming an important issue. 1. Carrier synchronization technology in wireless communication system of low signal-to-noise ratio and multiuser

Download Full-text

Determination of the Best Emulsion for the Microscopy of Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096886 ◽

1981 ◽

Vol 39 ◽

pp. 32-33

Author(s):

David A. Grano ◽

Kenneth H. Downing

Keyword(s):

Spatial Frequency ◽

Information Transfer ◽

Signal To Noise Ratio ◽

Experimental Situation ◽

Photographic Emulsion ◽

Modulation Transfer ◽

Signal To Noise ◽

Frequency Space ◽

Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Download Full-text

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097703 ◽

1981 ◽

Vol 39 ◽

pp. 226-227

Author(s):

W. Kunath ◽

K. Weiss ◽

E. Zeitler

Keyword(s):

Signal To Noise Ratio ◽

Carbon Support ◽

Electronic System ◽

Optic Axis ◽

Hollow Cone ◽

Signal To Noise ◽

Bright Field ◽

Noise Ratio ◽

Single Field ◽

Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

Download Full-text

Information capacity and bandwidth limitations in the SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152392 ◽

1989 ◽

Vol 47 ◽

pp. 84-85

Author(s):

D. C. Joy ◽

R. D. Bunn

Keyword(s):

Signal To Noise Ratio ◽

Critical Dimension ◽

Information Capacity ◽

Acquisition Time ◽

Signal To Noise ◽

Sem Image ◽

Probe Size ◽

Minimum Number ◽

Noise Ratio ◽

Signal Channel

The information available from an SEM image is limited both by the inherent signal to noise ratio that characterizes the image and as a result of the transformations that it may undergo as it is passed through the amplifying circuits of the instrument. In applications such as Critical Dimension Metrology it is necessary to be able to quantify these limitations in order to be able to assess the likely precision of any measurement made with the microscope.The information capacity of an SEM signal, defined as the minimum number of bits needed to encode the output signal, depends on the signal to noise ratio of the image - which in turn depends on the probe size and source brightness and acquisition time per pixel - and on the efficiency of the specimen in producing the signal that is being observed. A detailed analysis of the secondary electron case shows that the information capacity C (bits/pixel) of the SEM signal channel could be written as :

Download Full-text

Speech Reception in the Presence of Classroom Noise

Language Speech and Hearing Services in Schools ◽

10.1044/0161-1461.1004.221 ◽

1979 ◽

Vol 10 (4) ◽

pp. 221-230 ◽

Cited By ~ 2

Author(s):

Veronica Smyth

Keyword(s):

Signal To Noise Ratio ◽

Learning Processes ◽

Speech Discrimination ◽

Signal To Noise ◽

Speech Reception ◽

Monosyllabic Words ◽

Noise Ratio

Three hundred children from five to 12 years of age were required to discriminate simple, familiar, monosyllabic words under two conditions: 1) quiet, and 2) in the presence of background classroom noise. Of the sample, 45.3% made errors in speech discrimination in the presence of background classroom noise. The effect was most marked in children younger than seven years six months. The results are discussed considering the signal-to-noise ratio and the possible effects of unwanted classroom noise on learning processes.

Download Full-text

Quantifying the Effects of Background Speech Babble on Preschool Children's Novel Word Learning in a Multisession Paradigm: A Preliminary Study

Journal of Speech Language and Hearing Research ◽

10.1044/2019_jslhr-h-19-0083 ◽

2020 ◽

Vol 63 (1) ◽

pp. 345-356

Author(s):

Meital Avivi-Reich ◽

Megan Y. Roberts ◽

Tina M. Grieco-Calub

Keyword(s):

Word Learning ◽

Signal To Noise Ratio ◽

Preschool Age ◽

Exposure Condition ◽

Signal To Noise ◽

Verbal Recall ◽

Referent Selection ◽

Main Effect ◽

Noise Ratio ◽

Novel Word Learning

Purpose This study tested the effects of background speech babble on novel word learning in preschool children with a multisession paradigm. Method Eight 3-year-old children were exposed to a total of 8 novel word–object pairs across 2 story books presented digitally. Each story contained 4 novel consonant–vowel–consonant nonwords. Children were exposed to both stories, one in quiet and one in the presence of 4-talker babble presented at 0-dB signal-to-noise ratio. After each story, children's learning was tested with a referent selection task and a verbal recall (naming) task. Children were exposed to and tested on the novel word–object pairs on 5 separate days within a 2-week span. Results A significant main effect of session was found for both referent selection and verbal recall. There was also a significant main effect of exposure condition on referent selection performance, with more referents correctly selected for word–object pairs that were presented in quiet compared to pairs presented in speech babble. Finally, children's verbal recall of novel words was statistically better than baseline performance (i.e., 0%) on Sessions 3–5 for words exposed in quiet, but only on Session 5 for words exposed in speech babble. Conclusions These findings suggest that background speech babble at 0-dB signal-to-noise ratio disrupts novel word learning in preschool-age children. As a result, children may need more time and more exposures of a novel word before they can recognize or verbally recall it.

Download Full-text