Journal articles on the topic 'Signals attenuation'
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Lysenko, Iu Iu, Yu V. Kuts, V. M. Uchanin, and V. F. Petryk. "Research of oscillation mode in automated pulsed eddy current testing systems." Information extraction and processing 2021, no. 49 (December 17, 2021): 9–18. http://dx.doi.org/10.15407/vidbir2021.49.009.
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The formation and analysis of eddy current probe signals obtained in pulsed excitation mode is considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of inspected object parameters evaluation. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allowed proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signals phase and amplitude characteristics. Developed algorithm and the proposed methodology was implemented for evaluation of eddy current signals parameters and related characteristics of testing objects. This method was experimentally verified on a series of different test specimens. The obtained results confirm the possibility to apply the proposed informative signals to solve some problems concerned with automated eddy current testing. The formation and analysis of eddy current probe signals obtained in pulsed excitation mode are considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of automated eddy current testing. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allows proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signal phase and amplitude characteristics. Methods of increasing the accuracy of determining the eddy current probe signals attenuation and frequency using trends of signals phase and amplitude characteristics are considered. The proposed signal processing method was verified by modeling the process of determining the eddy current probe signals attenuation and the frequency from the signal with Gaussian noise. Algorithmic and software were developed based on the simulation results and the proposed improved methodology was implemented for determining signals parameters and related parameters and characteristics of testing objects.
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Matsushima, Jun, Makoto Suzuki, Ippei Matsugi, Yoshibumi Kato, and Shuichi Rokugawa. "Attenuation estimation using sweep signals in ultrasonic laboratory measurements." GEOPHYSICS 79, no. 3 (May 1, 2014): V115—V130. http://dx.doi.org/10.1190/geo2013-0281.1.
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It is important to obtain reliable attenuation results from experimental data to elucidate the physical mechanism responsible for ultrasonic wave attenuation. For attenuation estimation, a time window is often used to compute the frequencies of the direct-arrival waveforms. However, the effect of windowing distorts the spectral distribution due to a spectral leakage effect, degrading the attenuation estimates. We propose a method that enables accurate measurement of ultrasonic attenuation using sweep signals under the assumptions that velocity dispersion can be ignored and the quality factor [Formula: see text] is not dependent on frequency. We obtained the spectral amplitude of the sweep signal in the frequency-time domain using the continuous wavelet transform and estimated attenuation in the time-scale spectrum domain using the spectral-ratio method. This method is independent of the effect of windowing, whereas the windowing effect underestimates the attenuation results. In the absence of noise, the estimated attenuation results using sweep signals are in perfect agreement with the given input values, and the accuracy of the estimated attenuation results from windowed pulse waveforms depends on the extraction window length. However, our numerical experiments demonstrated that the proposed method is largely influenced by the existence of overlapping sweep events such as multiple reflections between the source and receiver transducer. Thus, applicability of the proposed method is limited to highly attenuative media, in which overlapping events are much smaller than direct sweep signals because these multiple reflected events are largely attenuated. Application of the proposed method to laboratory experimental data yielded similar underestimation of the attenuation results due to the windowing effect in the case of highly attenuative media. We also evaluated the usefulness of observing compressed pulse waveforms with shorter duration from the crosscorrelation of sweep waveforms than the case of pulse generation.
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Huang, Yaping, Hanyong Bao, and Xuemei Qi. "Seismic Random Noise Attenuation Method Based on Variational Mode Decomposition and Correlation Coefficients." Electronics 7, no. 11 (October 28, 2018): 280. http://dx.doi.org/10.3390/electronics7110280.
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Seismic data is easily affected by random noise during field data acquisition. Therefore, random noise attenuation plays an important role in seismic data processing and interpretation. According to decomposition characteristics of seismic signals by using variational mode decomposition (VMD) and the constraint conditions of correlation coefficients, this paper puts forward a method for random noise attenuation in seismic data, which is called variational mode decomposition correlation coefficients VMDC. Firstly, the original signals were decomposed into intrinsic mode functions (IMFs) with different characteristics by VMD. Then, the correlation coefficients between each IMF and the original signal were calculated. Next, based on the differences among correlation coefficients of effective signals and random noise as well as the original signals, the corresponding treatment was carried out, and the effective signals were reconstructed. Finally, the random noise attenuation was realized. After adding random noise to simple sine signals and the synthetic seismic record, the improved complementary ensemble empirical mode decomposition (ICEEMD) and VMDC were used for testing. The testing results indicate that the proposed VMDC has better random noise attenuation effects. It was also used in real-world seismic data noise attenuation. The results also show that it could effectively improve the signal-to-noise ratio (SNR) of seismic data and could provide high-quality basic data for further interpretation of seismic data.
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Wang, Xiang Hong, Hong Wei Hu, and Zhi Yong Zhang. "Attenuation of Acoustic Emission Signals in Structural Interfaces." Advanced Materials Research 569 (September 2012): 343–46. http://dx.doi.org/10.4028/www.scientific.net/amr.569.343.
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Received acoustic emission (AE) signals are transmitted across structural interfaces in many real-world applications. This paper studies attenuation of the signals across two common structural interfaces. The experimental results indicate that interface has effects on attenuation, which depends on the relative scales of structures. Signal energy is strengthened due to multiple flections of signals on the small-size structure when an interface is constructed by different scales. Thus the received signals are distorted worse than the original signals. So it is a better way to mount sensors on a simple structure with a size as much as a structure incurred AE sources.
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Salomonsson, Göran, and Benny Löfström. "Analysis of a System for Ultrasonic Imaging of Attenuation and Texture in Soft Tissue." Ultrasonic Imaging 7, no. 3 (July 1985): 225–43. http://dx.doi.org/10.1177/016173468500700303.
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Attenuation in tissue decreases both the amplitude and the bandwidth of a reflected ultrasonic signal. Only the amplitude is restored in conventional ultrasonic equipment by amplifying the signal in a time-gain-compensator. This paper describes a method for restoring both the amplitude and bandwidth of the signal and an implemention of this method is proposed. This consists of two main parts: a device for estimating the attenuation and a time-variable circuit. The time-variable circuit is controlled by the estimated attenuation such that its transfer function approximates the inverse of the transfer function of the attenuation within the transducer passband. Its output is then almost independent of the attenuation and contains information on the texture of the tissue. Both the texture and attenuation estimates are displayed graphically. The quality of the image of the texture can be improved by choosing a wideband transducer, since it is almost exclusively dependent of transducer bandwidth. The performance of the method is studied using both simulated signals and signals measured in vitro.
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Kupchenko, L. F., A. S. Rybiak, and А. V. Ponomar. "Compensation method for atmospheric attenuation of laser radiation in active electro-optical systems with dynamic spectral processing of optical signals." Semiconductor Physics, Quantum Electronics and Optoelectronics 25, no. 02 (June 30, 2022): 211–18. http://dx.doi.org/10.15407/spqeo25.02.211.
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This paper describes the compensation method for atmospheric attenuation of laser radiation, which can be implemented in active electro-optical systems with pre-detector dynamic spectral processing of optical signals. In these electro-optical systems, the spectral flux of sensing radiation is formed using multispectral laser signals based on a priori information about the spectral reflectance of the target and background. The sensing signal formed in this way ensures maximum suppression of the background signal at the output of system with minimal attenuation of the target signal. The influence of atmospheric radiation attenuation on operation of an active electro-optical system with dynamic spectral processing has been analyzed. It has been shown that the laser radiation attenuation in the atmosphere significantly affects the efficiency of dynamic spectral processing of optical signals (leads to a decrease in the target image contrast). The developed compensation method for atmospheric attenuation of radiation in active electro-optical systems with dynamic spectral processing is based on the fact that the spectral intensity of the sensing radiation is formed not only on the basis of a priori data on spectral characteristics of the target and background, but also takes into account the spectral transmittance of the optical radiation propagation medium.
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Zribi, Mehrez, Erwan Motte, Pascal Fanise, and Walid Zouaoui. "Low-Cost GPS Receivers for the Monitoring of Sunflower Cover Dynamics." Journal of Sensors 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6941739.
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The aim of this research is to analyze the potential use of Global Navigation Satellite System (GNSS) signals for the monitoring of in situ vegetation characteristics. An instrument, based on the use of a pair of low-cost receivers and antennas, providing continuous measurements of all the available Global Positioning System (GPS) satellite signals is proposed for the determination of signal attenuation caused by a sunflower cover. Experimental campaigns with this instrument, combined with ground truth measurements of the vegetation, were performed over a nonirrigated sunflower test field for a period of more than two months, corresponding to a significant portion of the vegetation cycle. A method is proposed for the analysis of the signal attenuation data as a function of elevation and azimuth angles. A high correlation is observed between the vegetation’s water content and the GPS signals attenuation, and an empirical modeling is tested for the retrieval of signal behavior as a function of vegetation water content (VWC). The VWC was estimated from GNSS signals on a daily basis, over the full length of the study period.
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Abdorahimi, Danial, and Ali M. Sadeghioon. "Comparison of Radio Frequency Path Loss Models in Soil for Wireless Underground Sensor Networks." Journal of Sensor and Actuator Networks 8, no. 2 (June 22, 2019): 35. http://dx.doi.org/10.3390/jsan8020035.
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A wireless Underground Sensor Network (WUSN) is a group of sensors that collectively communicate through the underground medium. Radio Frequency (RF) signal transmission of the sensors through the ground is the most challenging aspects of a WUSN due to the high attenuation of the electromagnetic (EM) signal in the soil. Signals are often required to travel through soils with a high density or water content and generally through a non-isotropic and non-homogenous soil mixture with different boundaries, both of which can attenuate the signal sharply. The variability of the these conditions and complexity of the behaviour of signal attenuation with respect to these parameters makes accurate estimation of EM signal attenuation in soil challenging. Two main EM signal attenuation models exist to estimate attenuation (modified-Friis and Complex Refractive Index Model-Fresnel (CRIM-Fresnel). These were reviewed and a methodology was developed in order to measure the attenuation of the EM signals in the laboratory. Results from the laboratory measurements were compared with the estimation values calculated from the attenuation models. These comparisons showed a large difference between the estimated values by the models. In addition, analysis of the comparison tests showed that the CRIM-Fresnel model provides a better estimation of attenuation in samples with lower permittivity values while the modified-Friis model had a higher accuracy in samples with higher clay/water content which have higher permittivity values.
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Koda, Yusuke, Koji Yamamoto, Takayuki Nishio, and Masahiro Morikura. "Measurement Method of Temporal Attenuation by Human Body in Off-the-Shelf 60 GHz WLAN with HMM-Based Transmission State Estimation." Wireless Communications and Mobile Computing 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/7846936.
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This paper discusses a measurement method of time-variant attenuation of IEEE 802.11ad wireless LAN signals in the 60 GHz band induced by human blockage. The IEEE 802.11ad access point (AP) transmits frames intermittently, not continuously. Thus, to obtain the time-varying signal attenuation, it is required to estimate the duration in which the AP transmitted signals. To estimate whether the AP transmitted signals or not at each sampling point, this paper applies a simple two-state hidden Markov model. In addition, the validity of the model is tested based on Bayesian information criterion in order to prevent model overfitting and consequent invalid results. The measurement method is validated in that the distribution of the time duration in which the signal attenuates by 5 dB is consistent with the existing statistical model and the range of the measured time duration in which the signal attenuation decreases from 5 dB to 0 dB is similar to that in the previous report.
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RODRÍGUEZ, O. C., S. JESUS, Y. STEPHAN, X. DEMOULIN, M. PORTER, and E. COELHO. "NONLINEAR SOLITON INTERACTION WITH ACOUSTIC SIGNALS: FOCUSING EFFECTS." Journal of Computational Acoustics 08, no. 02 (June 2000): 347–63. http://dx.doi.org/10.1142/s0218396x0000025x.
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The problem of nonlinear interaction of solitary wave packets with acoustic signals has been intensively studied in recent years. A key goal is to explain the observed transmission loss of shallow-water propagating signals, which has been found to be strongly time-dependent, anisotropic, and sometimes exhibited unexpected attenuation versus frequency. Much of the existing literature considers the problem of signal attenuation in a static environment, without considering additional effects arising from groups of solitons evolving both in range and time. Hydrographic and acoustic data from the INTIMATE'96 experiment clearly exhibit the effects of soliton packets. However, in contrast with reported observations of signal attenuation, the observed transmission loss shows a pronounced signal enhancement that behaves like a focusing effect. This focusing is correlated with peaks in current, temperature, and surface tide. That correlation suggests that the nonlinear interaction of solitary wave packets with acoustic signals can lead to a focusing of the signal. To clarify this issue, hydrographic data was used to generate physically consistent distributions of "soliton-like" fields of temperature and sound velocity. These distributions were then used as input for a range-dependent normal-mode model. The results strongly support the hypothesis that the soliton field causes the observed signal enhancement.
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Qin, Yu Ping. "Effect of Electrode Size on Signal Attenuation in Intra-Body Communication." Applied Mechanics and Materials 427-429 (September 2013): 2029–32. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2029.
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In the galvanic coupling intra-body communication, transmitting and receiving of signals require coupling between electrodes and human tissue. Electrode size has a direct effect upon signal attenuation so as to influence signal transmission. To analyze the exact effect of electrode size on signal attenuation, the volume conductor model of human forearm is built with COMSOL Multiphysics 4.2a.It can be found from the simulation experiment that, signal attenuation declines with the increase of electrode size, which lays the foundation for subsequent experiments.
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Han, Meng, Zenglin Zhang, Jie Yang, Jiayun Zheng, and Wenting Han. "An Attenuation Model of Node Signals in Wireless Underground Sensor Networks." Remote Sensing 13, no. 22 (November 18, 2021): 4642. http://dx.doi.org/10.3390/rs13224642.
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Wireless underground sensor networks (WUSN) consist of sensor nodes that are operated in the soil medium. To evaluate the signal attenuation law of WUSN nodes, in this study, a WUSN node signal transmission test platform was built in the laboratory. The signal intensity data of WUSN nodes under different experimental conditions were obtained by orthogonal test. The WUSN node signal attenuation model was established. The test results show that the transmission of WUSN node signals in the soil medium is seriously affected by soil moisture content, node burial depth, soil compactness, and horizontal distance between nodes. The R2 of the models was between 0.790 and 0.893, and the RMSE of the models was between 2.489 and 4.192 dbm. Then, the WUSN node signal attenuation model involving the four factors was established. The R2 and RMSE of the model were, respectively, 0.822 and 4.87 dbm. The WUSN node signal attenuation model established in this paper can facilitate WUSN node deployment.
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Zahradník, Pavel, Ermukhamed Bektaevich Aynakulov, Radek Klof, and Boris Šimák. "A SIMPLE ECHO ATTENUATION IN SIGNALS." Neural Network World 26, no. 3 (2016): 305–15. http://dx.doi.org/10.14311/nnw.2016.26.017.
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Barr, R., and K. B. Young. "Omega Navigation in the Shadow of Antarctica." Journal of Navigation 42, no. 2 (May 1989): 236–47. http://dx.doi.org/10.1017/s0373463300014442.
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1. INTRODUCTION. Very-low-frequency radio waves were used to implement the Omega navigation system because of their low attenuation (2–4 dB/1000 km) when propagating globally in the waveguide formed between the Earth and the ionosphere. However, it became apparent in the early seventies, throughout the period when the majority of the stations of the Omega network were commissioned, that VLF signals propagating over permafrost or glacial ice could suffer anomalously large attenuations, of greater than 20 dB/1000 km, especially during the daytime. In the Northern Hemisphere problems have arisen with the heavy attenuation of Omega signals propagating over the Greenland ice sheet. In particular a very bad region for Omega coverage occurs around Winnipeg in Canada (the ‘Winnipeg Hole’). In this area Omega North Dakota suffers from ‘near field’ effects, Omega Liberia is contaminated by trans-equatorial modal effects and Omega Norway is removed by the attenuation of its signals when crossing the Greenland ice-cap. There have even been discussions on the feasibility of constructing extra VLF transmitters in Canada to alleviate this problem.
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Mao, Feilong, Saiyin Fang, Ming Li, Changlin Huang, Tingting Deng, Yue Zhao, and Gezhou Qin. "Study on Attenuation Characteristics of Acoustic Emission Signals with Different Frequencies in Wood." Sensors 22, no. 16 (August 11, 2022): 5991. http://dx.doi.org/10.3390/s22165991.
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To study the effect of frequency on the attenuation characteristics of acoustic emission signals in wood, in this paper, two types of hard wood and soft wood were studied separately, and the energy attenuation model of the propagation process of AE sources with different frequencies was established. First, using the piezoelectric inverse effect of the AE sensor, an arbitrary waveform generator was used to generate frequency-tunable pulses in the range of 1 kHz to 150 kHz as the AE source, where the AE source energy could be regulated by the output voltage level. Then, five AE sensors were placed at equal intervals of 100 mm on the surface of the specimen to collect AE signals, and the sampling frequency was set to 500 kHz. Finally, the energy value of AE signal of each sensor was calculated based on the AC principle, and the energy attenuation model was established by exponential fitting. The results showed that both the amplitude and energy of the AE signals of different frequencies showed negative exponential decay with the increase of propagation distance, and, at the same frequency, the change of AE source energy level had no significant effect on its attenuation rate. Compared with hard wood, the energy attenuation of the AE signal of soft wood was more sensitive to the change of frequency, and, at the same frequency, the attenuation rate of soft wood was smaller than that of hard wood.
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Knipp, B. S., J. A. Zagzebski, T. A. Wilson, F. Dong, and E. L. Madsen. "Attenuation and Backscatter Estimation Using Video Signal Analysis Applied to B-Mode Images." Ultrasonic Imaging 19, no. 3 (July 1997): 221–33. http://dx.doi.org/10.1177/016173469701900305.
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Most methods for in vivo quantitation of ultrasound attenuation and backscatter are not available clinically because they rely upon acquiring and analyzing radio frequency (rf) echo signals. This paper describes a technique to estimate ultrasound attenuation and backscatter from B-mode image data. The video signal analysis (VSA) technique utilizes images of a reference phantom, taken using the same instrument settings used to record images from the patient or sample, to account for effects of the transducer beam, system gain and signal processing on image data. A ‘gray-scale look-up table’ is derived to convert image pixel value data within a region of interest to echo signal amplitudes relative to echo signals from the same depth in the reference phantom. These relative echo levels enable estimates of attenuation and backscatter in the region of interest. VSA was used to quantify acoustic properties of test phantoms using 3 different clinical scanners and various transducers. The level of agreement between results obtained with different ultrasound imaging systems was very good. VSA attenuation and backscatter levels also compare favorably with attenuation coefficients and backscatter coefficients obtained using rf analysis.
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Isabona, Joseph, Agbotiname Lucky Imoize, Stephen Ojo, Cheng-Chi Lee, and Chun-Ta Li. "Atmospheric Propagation Modelling for Terrestrial Radio Frequency Communication Links in a Tropical Wet and Dry Savanna Climate." Information 13, no. 3 (March 7, 2022): 141. http://dx.doi.org/10.3390/info13030141.
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Atmospheric impairment-induced attenuation is the prominent source of signal degradation in radio wave communication channels. The computation-based modeling of radio wave attenuation over the atmosphere is the stepwise application of relevant radio propagation models, data, and procedures to effectively and prognostically estimate the losses of the propagated radio signals that have been induced by atmospheric constituents. This contribution aims to perform a detailed prognostic evaluation of radio wave propagation attenuation due to rain, free space, gases, and cloud over the atmosphere at the ultra-high frequency band. This aim has been achieved by employing relevant empirical atmospheric data and suitable propagation models for robust prognostic modeling using experimental measurements. Additionally, the extrapolative attenuation estimation results and the performance analysis were accomplished by engaging different stepwise propagation models and computation parameters often utilized in Earth–satellite and terrestrial communications. Results indicate that steady attenuation loss levels rise with increasing signal carrier frequency where free space is more dominant. The attenuation levels attained due to rain, cloud, atmospheric gases, and free space are also dependent on droplet depths, sizes, composition, and statistical distribution. While moderate and heavy rain depths achieved 3 dB and 4 dB attenuations, the attenuation due to light rainfall attained a 2.5 dB level. The results also revealed that attenuation intensity levels induced by atmospheric gases and cloud effects are less than that of rain. The prognostic-based empirical attenuation modeling results can provide first-hand information to radio transmission engineers on link budgets concerning various atmospheric impairment effects during radio frequency network design, deployment, and management, essentially at the ultra-high frequency band.
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Kolyadenko, Yu Yu, and N. А. Chursanov. "5 G communication network signal propagation models." Radiotekhnika, no. 205 (July 2, 2021): 161–68. http://dx.doi.org/10.30837/rt.2021.2.205.17.
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The next generation 5G / IMT-2020 technology, like any new technology, brings its own specific features to all aspects related to the practice of its application. One of these particularly important aspects is electromagnetic compatibility. At the stage of preparation for the introduction of 5G radio networks, called NewRadio, it is necessary to take early measures to assess effectively the electromagnetic compatibility conditions for these networks based on a thorough analysis of the features of 5G technology. Correct and accurate assessments of these conditions means successful provision of the electromagnetic compatibility of radio equipment of new networks.
The World Radio Communication Conference WRC-15 identified new radio frequency bands for 5G, including centimeter and millimeter wave bands. In general, this RF spectrum is located in three regions: below 1 GHz, 1 GHz to 6 GHz, and above 6 GHz (up to 100 GHz). From the EMC standpoint, the following can be distinguished as the main features of this spectrum: different nature of losses during signal propagation, in particular, a significant influence of additional factors (gases – oxygen, water vapor, etc.) on the level of losses previously unknown in cellular communication.
The mathematical model of signal propagation of 5 G communication networks has been developed which takes into account: the attenuation of signals in free space; attenuation of signals caused by the influence of walls and floor slabs, loss of signal energy, when space is filled with various objects; attenuation of signals caused by loss of energy of radio waves, when propagating through rains; signal attenuation due to loss of radio wave energy due to fog; signal attenuation, when propagating through tree leaves, slow and fast random fading.
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Hu, Tao, Gérard Lachapelle, and Richard Klukas. "Controlled GPS Signal Simulation for Indoors." Journal of Navigation 60, no. 2 (April 20, 2007): 265–80. http://dx.doi.org/10.1017/s037346330700416x.
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For certain applications such as E911/E999/E112, GPS chipset receiver manufacturers will possibly have to test their products to ensure these fulfill mandated performance specifications for a variety of outdoor and indoor conditions. As opposed to testing in the field, laboratory testing is totally repeatable and controllable, and may be less costly. Hardware GPS signal simulators are now able to simulate signals under a variety of attenuation and multipath conditions. In indoor environments, GPS signals suffer not only from severe attenuation and multipath but from complex variations thereof. A method to simulate indoor GPS signals such that the stochastic characteristics of the simulated signals match those of actual GPS signals received in situ by a high sensitivity GPS receiver in various indoor environments is presented. Probability density functions and correlation coefficients are used to demonstrate the similarity between field and simulated data in terms of signal power fading and estimated pseudorange error. The results clearly demonstrate the feasibility of the approach.
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Shen, Xi, and Defeng David Huang. "Retrieval of Raindrop Size Distribution Using Dual-Polarized Microwave Signals from LEO Satellites: A Feasibility Study through Simulations." Sensors 21, no. 19 (September 24, 2021): 6389. http://dx.doi.org/10.3390/s21196389.
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In this paper, a novel approach for raindrop size distribution retrieval using dual-polarized microwave signals from low Earth orbit satellites is proposed. The feasibility of this approach is studied through modelling and simulating the retrieval system which includes multiple ground receivers equipped with signal-to-noise ratio estimators and a low Earth orbit satellite communicating with the receivers using both vertically and horizontally polarized signals. Our analysis suggests that the dual-polarized links offer the opportunity to estimate two independent raindrop size distribution parameters. To achieve that, the vertical and horizontal polarization attenuations need to be measured at low elevation angles where the difference between them is more distinct. Two synthetic rain fields are generated to test the performance of the retrieval. Simulation results suggest that the specific attenuations for both link types can be retrieved through a least-squares algorithm. They also confirm that the specific attenuation ratio of vertically to horizontally polarized signals can be used to retrieve the slope and intercept parameters of raindrop size distribution.
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Tang, Jie, Yi-Ran Liu, Li-Jiang Zhang, Xing-Chang Fu, Xiao-Mei Xue, Guang Qian, Ning Zhao, and Tong Zhang. "Flexible Thermo-Optic Variable Attenuator based on Long-Range Surface Plasmon-Polariton Waveguides." Micromachines 9, no. 8 (July 26, 2018): 369. http://dx.doi.org/10.3390/mi9080369.
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A flexible thermo-optic variable attenuator based on long-range surface plasmon-polariton (LRSPP) waveguide for microwave photonic application was investigated. Low-loss polymer materials and high-quality silver strip were served as cladding layers and core layer of the LRSPP waveguide, respectively. By using finite element method (FEM), the thermal distribution and the optical field distribution have been carefully optimized. The fabricated device was characterized by end-fire excitation with a 1550 nm laser. The transmission performance of high-speed data and microwave modulated optical signal was measured while using a broadband microwave photonics link. The results indicated that the propagation loss of the LRSPP waveguide was about 1.92 dB/cm. The maximum attenuation of optical signal was about 28 dB at a driving voltage of 4.17 V, and the variable attenuation of microwave signals was obviously observed by applying different driving voltage to the heater. This flexible plasmonic variable attenuator is promising for chip-scale interconnection in high-density photonic integrated circuits and data transmission and amplitude control in microwave photonic systems.
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Eschlwech, Philipp, and Erwin Biebl. "Target simulation for UHF RFID DoA estimation systems." Advances in Radio Science 17 (September 19, 2019): 109–18. http://dx.doi.org/10.5194/ars-17-109-2019.
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Abstract. In this work a new method for the evaluation of UHF RFID Direction of Arrival (DoA) estimation systems is developed and demonstrated. Instead of simulating the system performance or manually measuring it in realistic or ideal environments, a method for the evaluation of DoA systems using received signals produced by a target simulator is proposed. The simulator generates the signals for each channel of the DoA estimator by attenuating and phase shifting the signals of an UHF RFID chip to replicate the signal propagation conditions for a chosen tag distance and arrival angle. This combines the advantages of the simulative approach and real world evaluation: it is fast, reproducible and doesn't require special measurement environments. To facilitate this method, plane and spherical wave signal models for the simulation of RFID targets are derived, multichannel phase-shifting and attenuation hardware for the simulation of such signals is presented and a demonstrative evaluation of a RFID DoA estimation system is performed, replicating evaluation scenarios in non reflective and multipath environments.
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Leung, T., and C. A. Balanis. "Attenuation distortion of transient signals in microstrip." IEEE Transactions on Microwave Theory and Techniques 36, no. 4 (April 1988): 765–69. http://dx.doi.org/10.1109/22.3585.
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Lacan, Igor, and Joe McBride. "City Trees and Municipal Wi-Fi Networks: Compatibility or Conflict?" Arboriculture & Urban Forestry 35, no. 4 (July 1, 2009): 203–10. http://dx.doi.org/10.48044/jauf.2009.034.
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Conflict between city trees and infrastructure remains a problem in urban forestry. Municipal Wi-Fi, a citywide wireless computer network, may become a part of urban infrastructure, and because trees can diminish Wi-Fi signals, potential exists for conflict between urban trees and municipal Wi-Fi. This study examines attenuation of Wi-Fi signals in the City of Mountain View, California, U.S. by positioning a wireless-equipped computer so that trees obstructed the line-of-sight (LOS) between the computer and a Wi-Fi access point. Signal attenuation ranged from < 2 dB to 19 dB (mean: 5.6 dB), depending on the number and types of trees present. Although trees significantly attenuated signals, they did not diminish the average signal strength below -75 dBm (the minimum for a Wi-Fi connection) in any of the tests. A general linear model (r2 = 0.55) indicated that some tree characteristics (tree size, canopy depth, leaf type), but not others (number of trees in LOS, presence of leaves, leaf size, and shape) helped explain variation in signal attenuation. As long as the effect of urban trees is taken into account during planning of Wi-Fi networks, trees should not interfere with municipal Wi-Fi operation.
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Makarov, Daniil, Aleksandr Borisov, Anatoly Ostylovsky, Viktor Ivanov, and Dmitry Kharlamov. "Use of navigation satellite signals to determine stocks of stem wood." E3S Web of Conferences 223 (2020): 03018. http://dx.doi.org/10.1051/e3sconf/202022303018.
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The method for determining the stocks of stem wood using the measurement data of the linear attenuation coefficients of signals navigation satellites L1 range and general taxometric characteristics of the forest is presented. A variant of determining the stocks of stem wood by differences in contributions to the attenuation by layers of crowns and trunks is considered, taking into account the coordinate referencing of the trajectory of the probe signal in the tree stand.
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TERZIĆ, MIRA. "ATTENUATION OF LASER-GENERATED ACOUSTIC SIGNALS IN LIQUIDS." International Journal of Modern Physics B 05, no. 15 (September 1991): 2563–71. http://dx.doi.org/10.1142/s0217979291001012.
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The dependence of the optoacoustic wave amplitude in liquids on propagation distance was investigated for various values of the diffraction parameter. The results of the theoretical model are discussed and the computed results are compared to the experimental data obtained from optoacoustic waves generated in water and in n-heptane by means of a hybride CO 2 laser, for rigid and free boundary conditions of the liquid. The coefficients for amplitude attenuation based solely on diffraction, i.e. diffraction attenuation coefficient, are evaluated, as are the total attenuation coefficients. A simple method to correct experimental diffraction data obtained with non-ideal liquids is proposed.
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Chen, Siyu, Hang Sun, Min Weng, Shijie Wen, Le Li, and Bingqing Liu. "Design and Research of Channel Circuit Based on Broadband Power Line Carrier." Journal of Physics: Conference Series 2433, no. 1 (February 1, 2023): 012017. http://dx.doi.org/10.1088/1742-6596/2433/1/012017.
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Abstract In order to effectively improve the anti-attenuation, anti-noise and anti-impedance change capabilities of the low-voltage narrowband power line carrier communication unit, reduce the carrier signal coupling attenuation, and highly fidelity signal power encoded and modulated by the carrier chip, an improved high-speed power line carrier communication transceiver circuit is designed. Using 303.13kHz~357.81kHz as sub-carrier signal frequency can effectively avoid the random noise generated by high-power power electronic equipment and household appliances below 35kHz. At the same time, to prevent the frequency crosstalk of power line carrier products with 270kHz and 421kHz as the center frequency, the Y-coupling capacitor and sixth order Butterworth band-pass filter circuit are used to design the signal receiving and transmitting circuit of the communication unit to isolate unwanted signals. The experimental simulation of the designed circuit is carried out on the circuit simulation software Multisim 12. The results show that the designed power line carrier communication transceiver circuit can effectively control the signal coupling attenuation within 4dB, and the filtering of unwanted signals can also reach 41.7dB, which has good application value.
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Barwick, S., D. Besson, P. Gorham, and D. Saltzberg. "South Polar in situ radio-frequency ice attenuation." Journal of Glaciology 51, no. 173 (2005): 231–38. http://dx.doi.org/10.3189/172756505781829467.
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AbstractWe have determined the in situ electric field attenuation length Lα (defined as the length over which the signal amplitude diminishes by a factor 1/e) for radio-frequency signals broadcast vertically through South Polar ice and reflected off the underlying bed. Conservatively assuming a bedrock field reflectivity for f = 380 MHz, and T = –50°C; the errors incorporate uncertainties in R. This value is consistent with previous estimates that the radiofrequency attenuation length exceeds the attenuation length at optical frequencies by an order of magnitude.
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Islam, Md Rafiqul, Zain Elabdin Omer Elshaikh, Othman O. Khalifa, Ahm Zahirul Alam, Sheroz Khan, and A. W. Naji. "PREDICTION OF SIGNAL ATTENUATION DUE TO DUSTSTORMS USING MIE SCATTERING." IIUM Engineering Journal 11, no. 1 (May 26, 2010): 71–87. http://dx.doi.org/10.31436/iiumej.v11i1.42.
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The present trend in radio design calls for the use of frequencies above 40 GHz for short links carrying wide-band digital communication signals. In order to utilize the new frequency band efficiently, signal attenuation studies due to duststorms is needed urgently for desert areas. This paper presents a mathematical model which has been developed to predict the signal attenuation due to duststorm. The proposed model enables the convenient calculation of the signal path attenuation based on Mie solution of Maxwell's equations for the scattering of electromagnetic wave by dust particles. The predicted values from the proposed mathematical model are compared with the measured values observed in Saudi Arabia and Sudan and show relatively close agreement.
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Li, Baolin, Nan Li, Enyuan Wang, Xuelong Li, Zhibo Zhang, Xin Zhang, and Yue Niu. "Discriminant Model of Coal Mining Microseismic and Blasting Signals Based on Waveform Characteristics." Shock and Vibration 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/6059239.
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Generally, there are two important types of microseismic (MS) signals caused by mining and blasting activities at coal mines. The waveform characteristics of MS signals using FFT, STA/LTA method, and envelope analysis were studied to distinguish these two types of MS signals. The main results are as follows: the dominant frequency and duration of two types of signals are significantly different. The following peak envelope curves of two types of MS signals fit a power function. The power exponent was obtained to describe the attenuated speed of the MS signals. The attenuation of the coal mining MS signals is slower and more fluctuant than that of the blasting signal. Waveform characteristics consisting of the dominant frequency, duration, and attenuation coefficient were extracted as the discriminating parameters. The discriminating performance of these parameters was compared and discussed. Based on the waveform characteristics, a discriminant model for coal mining MS and blasting signals was established by using Fisher linear discriminant method and its performance was checked. The results show that the accuracy of the discriminant model is more than 85%, which can meet the requirements of MS monitoring at coal mines.
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Djibo, Moumouni, Wendyam Boris Serge Ouedraogo, Ali Doumounia, Serge Sanou, Moumouni Sawadogo, Idrissa Guira, and François Zougmoré. "ESTIMATION DE LA VISIBILITÉ MÉTÉOROLOGIQUE À L’AIDE DES LIENS MICRO-ONDES COMMERCIAUX DE TÉLÉCOMMUNICATIONS." Journal de Physique de la SOAPHYS 3, no. 1 (November 15, 2021): C21A03–1—C21A03–4. http://dx.doi.org/10.46411/jpsoaphys.2021.01.03.
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Several factors can attenuate radio signal between transmitting and receiving antenna. One can cite: vegetation, atmospheric gases, fog, water vapor, transmission instruments, rain, temperature, etc... The sources of attenuation differ according to the climate and the relief of each continent or even each country. In this work we aim to show that there is link between microwave signal attenuation and weather visibility in the presence of dust. Weather visibility is a very important factor for the safety of road, sea, rail and air transportation. In the presence of dust, the visibility is strongly reduced and there is also a strong attenuation of the microwave signal propagating between two antennas. By performing a linear regression on the attenuation-visibility scatter plot, we propose a method for real-time estimation of the visibility knowing the microwave signals attenuation. A correlation measurement between the visibility estimated by our method from the real attenuation data of the mobile phone operator Telecel Faso SA (Burkina Faso) and the visibility measured by the National Meteorological Agency of Burkina Faso (ANAM) gave a correlation coefficient of 0.86.
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Hong, Sang Gi, Hakjune Lee, Hoesung Yang, Junho Jin, Hyesun Lee, and Kangbok Lee. "Experimental Study of Microwave Attenuation in a Compartment Fire." Journal of Electromagnetic Engineering and Science 21, no. 3 (July 31, 2021): 249–51. http://dx.doi.org/10.26866/jees.2021.3.l.2.
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In this letter, we show the experimental results of microwave attenuation characteristics for representative communication frequencies (UHF, public safety long-term evolution [PSLTE], LoRa, Wi-Fi, and LTE) in a compartment fire. We used kerosene, lumber, and urethane foam as fuels, which can be easily found in homes, and measured the signal intensity with three antenna heights to investigate the effect of the flame and smoke. In the compartment environment, the ionized particles were the dominant attenuation factor of the signals. Furthermore, measurements revealed that the attenuation depends on frequencies and fuel types. In particular, large attenuation was observed at particular frequencies when burning lumber and urethane foam.
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Xing, Can Hua, De Xiang Zhang, and Tao Zhao. "Two-Dimensional Laser Detection Front End Circuit and Algorithm." Advanced Materials Research 748 (August 2013): 549–54. http://dx.doi.org/10.4028/www.scientific.net/amr.748.549.
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This paper describes the design of a two-dimensional photoelectric detector, in which silicon photovoltaic cells are used as photoelectric receiver, and laser signal is converted into electrical signals. The weak electrical signals can be amplified by the high power low noise with variable magnification amplifier controlled by single-chip microcontroller PIC. Then using the variable attenuator MAX521 complete selectable attenuation for the analog signal. The detector is able to adapt for high-precision detection of the laser light source in the case of changes in the strength of the near and far distances and light. The practicality and detection performance of the receiver can be ensured. This two-dimensional photoelectric detector is particularly applicable to the construction site where are special requirements for some installation accuracy, which can be a good solution to the problem of excessive error of the traditional installation process.
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Yuan, Yijun, Xu Si, and Yue Zheng. "Ground-roll attenuation using generative adversarial networks." GEOPHYSICS 85, no. 4 (June 13, 2020): WA255—WA267. http://dx.doi.org/10.1190/geo2019-0414.1.
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Ground roll is a persistent problem in land seismic data. This type of coherent noise often contaminates seismic signals and severely reduces the signal-to-noise ratio of seismic data. A variety of methods for addressing ground-roll attenuation have been developed. However, existing methods are limited, especially when using real land seismic data. For example, when ground roll and reflections overlap in the time or frequency domains, traditional methods cannot completely separate them and they often distort the signals during the suppression process. We have developed a generative adversarial network (GAN) to attenuate ground roll in seismic data. Unlike traditional methods for ground-roll attenuation dependent on various filters, the GAN method is based on a large training data set that includes pairs of data with and without ground roll. After training the neural network with the training data, the network can identify and filter out any noise in the data. To fulfill this purpose, the proposed method uses a generator and a discriminator. Through network training, the generator learns to create the data that can fool the discriminator, and the discriminator can then distinguish between the data produced by the generator and the training data. As a result of the competition between generators and discriminators, generators produce better images whereas discriminators accurately recognize targets. Tests on synthetic and real land seismic data show that the proposed method effectively reveals reflections masked by the ground roll and obtains better results in the attenuation of ground roll and in the preservation of signals compared to the three other methods.
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Zhao, Xing, Ping Lu, Yanyan Zhang, Jianxiong Chen, and Xiaoyang Li. "Swell-noise attenuation: A deep learning approach." Leading Edge 38, no. 12 (December 2019): 934–42. http://dx.doi.org/10.1190/tle38120934.1.
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Noise attenuation for ordinary images using machine learning technology has achieved great success in the computer vision field. However, directly applying these models to seismic data would not be effective since the evaluation criteria from the geophysical domain require a high-quality visualized image and the ability to maintain original seismic signals from the contaminated wavelets. This paper introduces an approach equipped with a specially designed deep learning model that can effectively attenuate swell noise with different intensities and characteristics from shot gathers with a relatively simple workflow applicable to marine seismic data sets. Three significant benefits are introduced from the proposed deep learning model. First, our deep learning model doesn't need to consume a pure swell-noise model. Instead, a contaminated swell-noise model derived from field data sets (which may contain other noises or primary signals) can be used for training. Second, inspired by the conventional algorithm for coherent noise attenuation, our neural network model is designed to learn and detect the swell noise rather than inferring the attenuated seismic data. Third, several comparisons (signal-to-noise ratio, mean squared error, and intensities of residual swell noises) indicate that the deep learning approach has the capability to remove swell noise without harming the primary signals. The proposed deep learning-based approach can be considered as an alternative approach that combines and takes advantage of both the conventional and data-driven method to better serve swell-noise attenuation. The comparable results also indicate that the deep learning method has strong potential to solve other coherent noise-attenuation tasks for seismic data.
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Kim, Tae-Dong, and In-Su Yeom. "Attenuation of Microwaves Received From a Drone Owing to Smoke Obscuration." Fire Science and Engineering 35, no. 1 (February 28, 2021): 128–31. http://dx.doi.org/10.7731/kifse.c40cb6c6.
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The objective of this study is to analyze the effect of smoke obscuration on the signal sensitivity of microwaves received from a drone. A spectrum analyzer and a directional antenna were employed for analyzing the received signal sensitivity and measuring the mean received power, both before and after the drone entered the smoke layer for one min in the fire training area. The drone operated in the range of 2.4 GHz to 2.48 GHz. It is found that the received power before entering the smoke layer is –39.3 dBm, at which signals and image data can be received. However, upon entering the smoke layer, the received power is reduced to –47 dBm, at which signals and image data cannot be received. Hence, the received power undergoes an attenuation of approximately 7.7 dBm (5.9 mW) owing to smoke obscuration, which causes communication outage. Based on this study, it can be concluded that the received power undergoes attenuation owing to smoke obscuration during fires. Furthermore, if a communication problem occurs due to microwave attenuation, it affects the drone’s operation.
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Bourqui, Jeremie, John Garrett, and Elise Fear. "Measurement and Analysis of Microwave Frequency Signals Transmitted through the Breast." International Journal of Biomedical Imaging 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/562563.
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Microwave approaches to breast imaging include the measurement of signals transmitted through and reflected from the breast. Prototype systems typically feature sensors separated from the breast, resulting in measurements that include the effects of the environment and system. To gain insight into transmission of microwave signals through the breast, a system that places sensors in direct contact with the breast is proposed. The system also includes a lossy immersion medium that enables measurement of the signal passing through the breast while significantly attenuating signals traveling along other paths. Collecting measurements at different separations between sensors also provides the opportunity to estimate the average electrical properties of the breast tissues. After validation through simulations and measurements, a study of 10 volunteers was performed. Results indicate symmetry between the right and left breast and demonstrate differences in attenuation, maximum frequency for reliable measurement, and average properties that likely relate to variations in breast composition.
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Dai, Jing, Rui Zhou, and Shi Tang. "Design Method of DLMS Adaptive Filter Based on FPGA." Applied Mechanics and Materials 182-183 (June 2012): 685–89. http://dx.doi.org/10.4028/www.scientific.net/amm.182-183.685.
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This paper proposed DLMS algorithm which is suitable for real-time signal processing. The algorithm adopts hardware multiplier and pipeline technology to accelerate the operation of the system. By analyzing the time sequence and spectrum of the output signals, the attenuation of the interference signals is about 51dB. It can further demonstrate the high quality and high speed of the DLMS algorithm to filter out the interference signals, and well handle the relationship between the resources and speed of FPGA to meet the requirements of high-speed signal processing.
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Falodun, S. E., J. S. Ojo, and O. L. Ojo. "Analysis of visibility effects on free space earth-to-satellite optical link based on measurement data in Nigeria." Nigeria Journal of Pure and Applied Physics 9, no. 1 (April 21, 2020): 41–45. http://dx.doi.org/10.4314/njpap.v9i1.8.
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The effect of atmospheric variables on signals propagating from earth to space are of concern in the design and performance of wireless communications systems. Since atmospheric effects which led to atmospheric losses (attenuations, fading and scintillation) are location-dependent, climatological phenomena such as fog, snow, rain, and haze has much effect on Free Space Optical (FSO) and can cause reduction in the link availability. This paper analysed the effect of fog on FSO communication links from earth to satellite links over five selected locations (Ikeja, Akure, Enugu, Jos and Port-Harcourt) in Nigeria. One year (2012) visibility data obtained at Nigeria Meteorological Agency (NIMET) have been used to estimate the specific attenuation caused by fog on FSO communication links in the selected locations. Link margin was deduced in all the five locations. The estimated specific attenuation caused by fog was based on operating frequencies associated with a typical commercial FSO. The result shows that at 352 THz frequency, Ikeja recorded the highest value of about 38.60 dB/km for the specific attenuation due to fog on FSO link followed by Akure with value of about 30.33 dB/km. Enugu recorded the least estimated attenuation of about 14.19 dB/km . The implication of the result is that Ikeja and Akure will suffer more signal loss, while Enugu will suffer less signal loss. Result on link margin performed on FSO link also showed that Ikeja has the highest link margin of -109.79 dB, Port-Harcourt with link margin value of -91.99 dB while Jos experienced lowest link margin of about -37.48 dB.
Keywords: Free space optical systems; Fog induced specific attenuation; Earth-space links; Link margin
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Sun, Zheng, and Shuang Duan. "Reconstruction of Endoscopic Photoacoustic Tomographic Images for Attenuating Acoustic Tissues: A Preliminary Study." Journal of Medical Imaging and Health Informatics 10, no. 11 (November 1, 2020): 2722–27. http://dx.doi.org/10.1166/jmihi.2020.3206.
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Biological endoscopic photoacoustic tomography (EPAT) Has been rapidly developed in the past decades as a hybrid functional imaging modality with multi-physics coupling. The acoustic inhomogeneity of biological tissues results in acoustic reflection, scattering, diffusion and absorption, thus the attenuated photoacoustic signals measured by the detector. The idealized assumptions on the acoustic homogeneity usually lead to reconstructed images with reduced quality and imaging depth. This paper focuses on a preliminary study of EPAT image reconstruction accounting for acoustic attenuation. The correlation equation related to ideal and measured photoacoustic signals is deduced. The equation is then solved by using singular value decomposition (SVD) to recover the approximation of the ideal signals from the measured signals. Finally, the cross-sectional images of optical distribution are reconstructed from the ideal signals. Numerical results indicate that this method can effectively reduce image artifacts caused by acoustic attenuation and improve image focusing. Comparison results suggest that it outperforms the method of correcting the frequency-dependent attenuation which requires the prior knowledge about attenuation coefficients of tissues.
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Ponnle, Akinlolu A., Oluwabukola A. Ojediran, and Samuel A. Oyetunji. "An Alternative Experimental Method for Determination of Light Beam Attenuation Coefficient in Underwater Wireless Optical Communication." European Journal of Electrical Engineering and Computer Science 6, no. 3 (June 13, 2022): 19–26. http://dx.doi.org/10.24018/ejece.2022.6.3.439.
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In wireless optical communication systems, the transmission of optical signals via the channel (air or water) is affected by absorption and scattering. These reduce the signal strength (attenuation) and transmission distance of the signals. In pure water, the blue-green region of the visible light gives low attenuation. Some models have been developed to characterize the underwater optical channel such as Beer Lambert’s law, Radiative Transfer equation and Monte Carlo model. In underwater optical communication, optical power meters are an invaluable tool in the determination of attenuation coefficients. However, optical power meters for underwater optical communication are very expensive. There is a need to be able to determine the attenuation in the underwater optical communication channel at a low cost, especially in the absence of underwater optical power meters. In this paper, we present an alternative low-cost experimental method of obtaining the approximate attenuation coefficient of the visible light beam in underwater optical wireless communication without the use of optical power meters. A wireless visible light communication system was set up experimentally for underwater measurements involving an oscilloscope as the only measuring device. The system uses sub-carrier frequency modulation; a white light-emitting diode array for the transmitter, and a solar panel at the receiver front end. A theoretical transmission model was developed from the experimental setup based on the line of sight method in an unbounded medium, Beer Lambert’s law, and the received sub-carrier signals; in order to provide an alternative method of determining approximately the attenuation coefficient of the underwater medium. Experiments were performed in air, clear water and in saline water. The attenuation in the air was used as a reference upon which attenuation in the clear water and the saline water was based. The saline water has a salt concentration of 6.7 g/100 mL by weight and a total dissolved solid of 86.2 ppt. The trend of the measured received sub-carrier signals showed deviation from the developed theoretical model, and the model was therefore adjusted to conform to the experimental results. From the adjusted model, the attenuation coefficient of 0.0007379 cm-1 and 0.02447 cm-1 were obtained for clear water and the saline water respectively. The method is simple, straightforward, easy to set up in a laboratory, low cost and can be applied to visible light of any wavelength.
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Podoprigora, Vladimir, Anatoly Sorokin, and Dmitriy Kharlamov. "Peculiarities the navigation satellites signals scattering in the layered structure of the tree stand." E3S Web of Conferences 223 (2020): 03017. http://dx.doi.org/10.1051/e3sconf/202022303017.
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A scattering and attenuation processes of navigation satellite signals in the forest interaction with tree trank and crown layers a tree stand are presented. The influence of the boundaries soil - tree stand – crown - air on the characteristics of radio signals scattering after interaction with forest is considered. Structural and electro physical features of tree stand elements in the processes of interaction with signals of the L 1 range and experimental data on signal transformations the forest are analyzed.
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Al-Nuaimi, M. O., and A. M. Hammoudeh. "Attenuation functions of microwave signals propagated through trees." Electronics Letters 29, no. 14 (1993): 1307. http://dx.doi.org/10.1049/el:19930872.
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Deán-Ben, X. Luís, Daniel Razansky, and Vasilis Ntziachristos. "The effects of acoustic attenuation in optoacoustic signals." Physics in Medicine and Biology 56, no. 18 (August 26, 2011): 6129–48. http://dx.doi.org/10.1088/0031-9155/56/18/021.
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Sorokin, A. V., A. P. Shepeta, V. A. Nenashev, and G. M. Wattimena. "Comparative characteristics of anti-collision processing of radio signal from identification tags on surface acoustic waves." Information and Control Systems, no. 1 (February 19, 2019): 48–56. http://dx.doi.org/10.31799/1684-8853-2019-1-48-56.
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Introduction:Collision of information signals is a common problem in the measurement of physical magnitudes, such as temperature, pressure, stress, etc., with acoustic-electronic sensors. This problem is caused by overlapping response signals in the time domain, which makes it difficult to interpret correctly the device identification codes or the sensor data received.Purpose:Analysis of anticollision algorithms for radio-frequency tag code detection and identification by response information signals from acoustic-electronic devices which use the methods of time, frequency and frequency-time division of the response radio signals.Methods:Probabilistic methods for calculating the parameters of digital detectors of radio pulse bursts with given false alarm values and gaussian white noise background; individual code group identification methods when studying the attenuation of acoustic-electric signal during their propagation in the tag substrate, taking into account the dependence of the attenuation on the tag topology.Results:We have derived analytical expressions to calculate the probability of the correct identification of each tag, taking into account the dependence on tag topology, attenuation characteristics, the anti-collision signal processing methods and the signal-to-noise ratios. Curves which allow you to compare the advantages and disadvantages of the considered anti-collision signal processing methods are calculated and shown in the article. The analysis of the graphic charts demonstrating the correct identification probability has shown that identification tags with frequency-time coding have better ratios as compared to frequency or time methods of collision prevention.Practical relevance:The obtained result allows you to effectively evaluate the condition of technical objects, improving the predictability and prevention of possible environmental and man-made disasters.
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Mayowa, Gbalaja. "Assessment of Radio Waves Propagation Pattern from Radio Stations in Lokoja and Okene, Kogi State, Nigeria." Advanced Journal of Science, Technology and Engineering 2, no. 1 (November 30, 2022): 78–92. http://dx.doi.org/10.52589/ajste-au9cs6sp.
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Okene, Lokoja and their environs have been experiencing radio signal distortions and have been of great concern to the citizens due to bad quality signals and signal attenuation increase. This study assesses the patterns of radio wave propagation from five radio stations in Lokoja and Okene, Kogi State, Nigeria. Equipment, a field strength metre was used to measure signal strengths and quality of radio signals. Six locations in both Lokoja, Okene and the environs were selected for each radio station. The approximate distances between the transmitting and receiving antennas were determined. Thirty-five locations were measured inclusive of the five radio stations and the six selected positions. Three locations in Okene and another three locations in Lokoja were used. Thereafter, calculations of the signal wavelengths of each radio station and the free space path-loss of signals were calculated at the positions. Factors such as reflections by buildings, mountains and vegetation cover, refractions by the rivers, streams, rainfall and absorption of the human abdomen were looked into at such areas as likely causes of signal attenuation. Good locations to site FM radio stations were determined from the results. The approximate distances from the stations to establish booster stations in order to receive news adequately were also determined.
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Liu, Yang, and Bingxiu Li. "Streaming orthogonal prediction filter in the t-x domain for random noise attenuation." GEOPHYSICS 83, no. 4 (July 1, 2018): F41—F48. http://dx.doi.org/10.1190/geo2017-0322.1.
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In seismic exploration, there are many sources of random noise, for example, scattering from a complex surface. Prediction filters (PFs) have been widely used for random noise attenuation, but these typically assume that the seismic signal is stationary. Seismic signals are fundamentally nonstationary. Stationary PFs fail in the presence of nonstationary events, even if the data are cut into overlapping windows (“patching”). We have developed an adaptive PF method based on streaming and orthogonalization for random noise attenuation in the [Formula: see text]-[Formula: see text] domain. Instead of using patching or regularization, the streaming orthogonal PF (SOPF) takes full advantage of the streaming method, which generates the signal value as each new noisy data value arrives. The streaming signal-and-noise orthogonalization further improves the signal recovery ability of the SOPF. The streaming characteristic makes the proposed method faster than iterative approaches. In comparison with [Formula: see text]-[Formula: see text] deconvolution and [Formula: see text]-[Formula: see text] regularized nonstationary autoregression, we tested the feasibility of the proposed method in attenuating random noise on two synthetic data sets. Field-data examples confirm that the [Formula: see text]-[Formula: see text] SOPF has a reasonable denoising ability in practice.
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Chen, Qing Hua, Yan Mei Li, Ying Jun Chen, and Wen Gang Wu. "Development of MEMS VOA with only One Shutter for Dual Signals Simultaneous Operation." Advanced Materials Research 709 (June 2013): 481–84. http://dx.doi.org/10.4028/www.scientific.net/amr.709.481.
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A MEMS variable optical attenuator (VOA) with only one shutter for dual signals simultaneous operation is designed for advanced tuning functions. Theoretical electro-mechanism model has also been developed to provide optimization for the VOA design. In experiment, the fabricated VOA device has demonstrated a over 40-dB attenuation range with respect to the driving voltage of one shutter, and it has also realized low polarization-dependent performance. The superior specifications make this device very promising for optical network systems and laboratory equipment.
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Shi, Lei, Shurong Yuan, and Bo Yao. "Unconventionally Designed Tracking Loop Adaptable to Plasma Sheath Channel for Hypersonic Vehicles." Sensors 21, no. 1 (December 22, 2020): 21. http://dx.doi.org/10.3390/s21010021.
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An aircraft that moves through the atmosphere at hypersonic speed is covered by plasma sheath, which causes random and fast time-varying amplitude attenuation and phase fluctuation in received signals. This paper comprehensively analyzes the mechanism of the amplitude attenuation effects on a traditional phase-locked loop (PLL), which is always ignored in traditional scenarios (such as satellite telemetry and vehicle communication). Simulation results and theoretical analysis showed that traditional PLL does not work reliably for signal carrier tracking with the severe time-varying amplitude attenuation of the plasma sheath channel. In this paper, an unconventionally designed Kalman filter (KF) tracking loop that is aware of phase dynamics and amplitude attenuation fluctuation for hypersonic vehicles is proposed. To introduce time-varying amplitude attenuation into the proposed KF-based tracking loop, the amplitude attenuation is first modeled with an autoregressive model. The statistical characteristics of the amplitude and phase fluctuation are then incorporated into the state equation and observation equation. Simulation results indicate that the proposed tracking loop is stable when the signal-to-noise ratio is −10 dB with the Ka band, even in the most severe flight environment for hypersonic vehicles.
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Koliadenko, Yulia, Mykyta Chursanov, and Oleksii Koliadenko. "Methods of monitoring and control of parameters of signals and elements of the mobile communication network when solving the problem of electromagnetic compatibility." Problemi telekomunìkacìj, no. 2(27) (December 11, 2020): 3–15. http://dx.doi.org/10.30837/pt.2020.2.01.
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To ensure the electromagnetic compatibility of mobile networks, it is necessary to monitor and control: radio frequency resource, frequency and power of signals in the allocated frequency resource, group delay time, resistance parameters to linear attenuation and attenuation associated with multi-beam signal transmission, polarization signal parameters, location (coordinates) of moving sources. The evaluation of parameters based on the results of measurements is currently carried out based on observations, and decision-making is carried out based on sample statistics. The use of methods for measuring the parameters of network elements and communication signals against the background of thermal noise is proposed. The measurement methods are based on the recursive Robbins-Monroe algorithm for estimating such parameters as random variables and the recursive Kalman-Bussey algorithm for estimating random processes. The efficiency analysis of recursive algorithms of optimal estimation of random variables and random processes is carried out. The advantage of recursive estimation methods is that, in practice, they are more effective than statistical processing methods, as they provide real-time estimation and do not require a waste of time for accumulation and processing. In addition to noise, extraneous signals are concentrated in the spectrum with the measured signal in radio communication channels. This fact determines the problem relevance of extracting from the additive mixture of signals and interference of useful signals that come from measurements. Methods for measuring the parameters of network elements and communication signals in the conditions of external signals have been developed. The possibility of using in the meters of parameters of mobile communication networks adaptive noise compensators with adaptive reference reception channel is considered, reducing the power of extraneous signals by 20 … 30 decibels and more.