Rain Attenuation at Millimeter Wave and Low-THz Frequencies Norouzian, Fatemeh; Marchetti, Emidio; Gashinova, Marina ...
IEEE transactions on antennas and propagation,
2020-Jan., 2020-1-00, 20200101, Volume:
68, Issue:
1
Journal Article
Peer reviewed
Wave attenuation through rain with different rainfall rates at millimeter wave ( f = 77 GHz) and low-terahertz (Low-THz) ( f = 300 GHz) frequencies is studied in this article. Rain has pronounced ...impacts on electromagnetic wave propagation and one of the well-known effects is attenuation of the transmitted wave. Attenuation at both frequencies and hydrometeor properties rainfall rate and drop size distribution (DSD) are measured simultaneously. The measured DSD is fit with gamma and Weibull distributions and is also compared to the frequently used distribution Marshall and Palmer (MP) model; Weibull is shown to be a better fit to the measured DSDs. Theoretical prediction of attenuation as a function of rainfall rate (up to about 20 mm/h) is determined using Mie scattering theory, and the fit gamma and Weibull, and MP distribution models; as well as using the International Telecommunications Union Radiocommunication Sector (ITU-R) recommendation. The calculations are evaluated by comparing them to the experiment. The measured results at 77 GHz best agree with the ITU-R recommendation whereas at 300 GHz, the calculation based on Mie scattering and the Weibull distribution exhibits the best fit to the measured data. The measured data that exceed the theoretical prediction are analyzed and interpreted based on their corresponding observed drop size properties, for the first time.
The World Federation for Ultrasound in Medicine and Biology (WFUMB) has promoted the development of this document on multiparametric ultrasound. Part 2 is a guidance on the use of the available tools ...for the quantification of liver fat content with ultrasound. These are attenuation coefficient, backscatter coefficient, and speed of sound. All of them use the raw data of the ultrasound beam to estimate liver fat content. This guidance has the aim of helping the reader in understanding how they work and interpret the results. Confounding factors are discussed and a standardized protocol for measurement acquisition is suggested to mitigate them.
The recommendations were based on published studies and experts’ opinion but were not formally graded because the body of evidence remained low at the time of drafting this document.
Abstract
For over 50 years, pure or doped silica glass optical fibres have been an unrivalled platform for the transmission of laser light and optical data at wavelengths from the visible to the near ...infra-red. Rayleigh scattering, arising from frozen-in density fluctuations in the glass, fundamentally limits the minimum attenuation of these fibres and hence restricts their application, especially at shorter wavelengths. Guiding light in hollow (air) core fibres offers a potential way to overcome this insurmountable attenuation limit set by the glass’s scattering, but requires reduction of all the other loss-inducing mechanisms. Here we report hollow core fibres, of nested antiresonant design, with losses comparable or lower than achievable in solid glass fibres around technologically relevant wavelengths of 660, 850, and 1060 nm. Their lower than Rayleigh scattering loss in an air-guiding structure offers the potential for advances in quantum communications, data transmission, and laser power delivery.
This paper presents an investigation of wave propagation through granite after different high-temperature treatments by using a pendulum impact setup. Propagation coefficients (attenuation ...coefficient and wavenumber) were successfully introduced to describe the attenuation of longitudinal waves through granite after high-temperature treatment. The attenuation rate of the longitudinal wave through the granite after different high-temperature treatments was obtained. In addition, the effects of temperature, amplitude and wavelength of longitudinal waves on the propagation coefficient and attenuation rate were discussed. The experimental results show that the propagation coefficient and the attenuation rate increase with increasing temperature. The attenuation rate decreases with increasing wavelength, while the propagation coefficient is not influenced by the wavelength. Meanwhile, the propagation coefficient and the attenuation rate are not influenced by the amplitude of the longitudinal wave.
Millimeter wave (mmWave) communication is a key technology for fifth generation (5G) and beyond communication networks. However, the communication quality of the radio link can be largely affected by ...rain attenuation, which should be carefully taken into consideration when calculating the link budget. In this paper, we present results of weather data collected with a PWS100 disdrometer and mmWave channel measurements at 25.84 GHz (K band) and 77.52 GHz (E band) using a custom-designed channel sounder. The rain statistics, including rain intensity, rain events, and rain drop size distribution (DSD) are investigated for one year. The rain attenuation is predicted using the DSD model with Mie scattering and from the model in ITU-R P.838-3. The distance factor in ITU-R P.530-17 is found to be inappropriate for a short-range link. The wet antenna effect is investigated and additional protection of the antenna radomes is demonstrated to reduce the wet antenna effect on the measured attenuation.
Atmospheric elements affect signal propagation and cause significant signal loss called atmospheric attenuation, especially in high-frequency range including sub-THz frequencies. Atmospheric ...attenuation mainly consists of gaseous, fog, and rain attenuation and the traditional approach considers them separately to develop good prediction models. However, the traditional models are not accurate and even unavailable for the high-frequency range such as sub-THz frequencies. In this letter, we propose a new attenuation model to predict atmospheric attenuation for terrestrial line-of-sight (LoS) propagation at high frequencies like sub-THz. The proposed model is based on Gaussian Process Regression (GPR). To train our model with a big measurement dataset, we use a scalable variant of GPR called Blockbox Matrix-Matrix Gaussian Process (BBMM-GP). We validate our model with a dataset obtained from a long-term measurement campaign at sub-THz frequencies. Our experiments show that our model significantly outperforms the existing model. We also show that our model provides reliable prediction intervals of atmospheric attenuation.
Phase fraction of oil-water two-phase flow is important to the process control and optimization. In this paper, a prediction model based on the mechanism of ultrasound attenuations in oil-water ...mixture is presented to estimate the phase fraction. This model consists of physical parameters of the two-phase flow and ultrasound frequency, by incorporating the scattering and attenuation of ultrasound in different flow patterns of the oil-water two-phase flow. The nonlinear relationship between ultrasound attenuation coefficient and phase fraction is corrected. An array of 16 ultrasonic transducers with 1-MHz center frequency and 20-Vpp sine acoustic signal is presented to implement this method, and a measuring system was designed and tested on a multiphase flow loop with actual flow experiments. The proposed prediction model showed a good agreement with the online phase fraction calibration in the flow experiments. The average error is 2.3% in water continuous flow, while in 2.8% in oil continuous flow. These findings and the mechanism prediction model provide basic foundations for the phase fraction estimation of oil-water two-phase flow by using the ultrasound attenuation technique.
This paper theoretically and experimentally investigate the spectrum attenuation of free space optical (FSO) communication systems operating at visible and near infrared (NIR) wavelengths (0.6 μm <; ...λ <; 1.6 μm) under fog and smoke in a controlled laboratory condition. Fog and smoke are generated and controlled homogeneously along a dedicated atmospheric chamber of length 5.5 m. A new wavelength dependent empirical model is proposed to predict the fog and smoke attenuation operating at visible and NIR wavelengths. Comparison of the new proposed model with the measured continuous attenuation spectrum from visible-NIR in the fog and smoke channels shows a close relationship than the semi-empirical Kim and Kruse fog models. The experimental results also show the selection for the possible appropriate wavelengths from visible-NIR for FSO links to achieve the maximum link span in dense fog conditions.
Underwater imaging is an important topic in maritime research. Due to the existence of dust-like particles in water medium, underwater images are vulnerable to the effect of low contrast and color ...cast. In this paper, we propose a novel underwater image restoration method based on a non-local prior, namely, adaptive attenuation-curve prior. This prior relies on the statistical distribution of pixel values. That is, all pixel values of a clear image can be partitioned into several hundred distinct clusters in RGB space, and the pixel values in each cluster will be distributed on a curve with a power function form after attenuated by water in varying degrees. Specifically, we can estimate the transmission for each pixel according to its distribution on the curves. Then, we estimate the attenuation factor to compensate for the transmission. To prevent over saturation and reduce the noise of the recovered images, we propose the saturation constraints to adjust the transmission of the three color channels. Qualitative and quantitative results demonstrate that our proposed method can achieve better performance, compared with the state-of-the-art approaches. Moreover, our proposed method can be further extended to restore other kinds of degraded images, such as hazy images.
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