scholarly journals Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

2020 ◽  
Author(s):  
Bin Sun ◽  
Kai Xie ◽  
Yan Liu ◽  
Yujin Zhang ◽  
Shaoshuai Guo ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Phase Shift ◽  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Low Frequency ◽  
Experimental Results ◽  
Time Varying ◽  
Dynamic Effects ◽  
Shared Time ◽  
Theoretical Results

In this paper, we reveal the dynamic effects of time-varying plasma on low-frequency (LF) electromagnetic (EM) wave propagation. The time-varying attenuation, time-varying phase shift, and power spectrum of the LF EM waves are presented. By using the frequency division multiplexing method, LF EM waves at the four discrete frequencies simultaneously penetrate through a shared time-varying plasma in one shock tube experiment. The experimental results indicate that the time-varying attenuation and phase shift of the LF EM wave are determined by the time-varying behavior of the plasma, and they are positively related to the electron density and frequency of the LF EM waves. The theoretical results are well consistent with the experimental results. Moreover, in the frequency domain, the time-varying plasma causes spectrum expansion of the LF EM waves. These results help us deeply understand the propagation process of LF EM waves in time-varying plasma and design LF communication systems.

scholarly journals Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

2020 ◽  
Author(s):  
Bin Sun ◽  
Kai Xie ◽  
Yan Liu ◽  
Yujin Zhang ◽  
Shaoshuai Guo ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Phase Shift ◽  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Low Frequency ◽  
Experimental Results ◽  
Time Varying ◽  
Dynamic Effects ◽  
Shared Time ◽  
Theoretical Results

In this paper, we reveal the dynamic effects of time-varying plasma on low-frequency (LF) electromagnetic (EM) wave propagation. The time-varying attenuation, time-varying phase shift, and power spectrum of the LF EM waves are presented. By using the frequency division multiplexing method, LF EM waves at the four discrete frequencies simultaneously penetrate through a shared time-varying plasma in one shock tube experiment. The experimental results indicate that the time-varying attenuation and phase shift of the LF EM wave are determined by the time-varying behavior of the plasma, and they are positively related to the electron density and frequency of the LF EM waves. The theoretical results are well consistent with the experimental results. Moreover, in the frequency domain, the time-varying plasma causes spectrum expansion of the LF EM waves. These results help us deeply understand the propagation process of LF EM waves in time-varying plasma and design LF communication systems.

scholarly journals A Recursive Algorithm for Indoor Positioning Using Pulse-Echo Ultrasonic Signals

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5042
Author(s):  
Salvatore A. Pullano ◽  
Maria Giovanna Bianco ◽  
Davide C. Critello ◽  
Michele Menniti ◽  
Antonio La Gatta ◽  
...  
Keyword(s):  
Communication Systems ◽  
Polyvinylidene Fluoride ◽  
Cross Correlation ◽  
Recursive Algorithm ◽  
Low Frequency ◽  
Correlation Method ◽  
Experimental Results ◽  
Ultrasonic Signals ◽  
Average Improvement ◽  
Pulse Echo

Low frequency ultrasounds in air are widely used for real-time applications in short-range communication systems and environmental monitoring, in both structured and unstructured environments. One of the parameters widely evaluated in pulse-echo ultrasonic measurements is the time of flight (TOF), which can be evaluated with an increased accuracy and complexity by using different techniques. Hereafter, a nonstandard cross-correlation method is investigated for TOF estimations. The procedure, based on the use of template signals, was implemented to improve the accuracy of recursive TOF evaluations. Tests have been carried out through a couple of 60 kHz custom-designed polyvinylidene fluoride (PVDF) hemicylindrical ultrasonic transducers. The experimental results were then compared with the standard threshold and cross-correlation techniques for method validation and characterization. An average improvement of 30% and 19%, in terms of standard error (SE), was observed. Moreover, the experimental results evidenced an enhancement in repeatability of about 10% in the use of a recursive positioning system.

Electromagnetic wave propagation and inequalities for moments of chord lengths

2004 ◽  
Vol 36 (04) ◽  
pp. 987-995 ◽  
Author(s):  
Jan Hansen ◽  
Matthias Reitzner
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Wireless Communication ◽  
Uniform Distribution ◽  
Surface Area ◽  
Convex Domain ◽  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Wireless Communication Systems ◽  
Received Power

In a convex domain K in ℝ d , a transmitter and a receiver are placed at random according to the uniform distribution. The statistics of the power received by the receiver is an important quantity for the design of wireless communication systems. Bounds for the moments of the received power are given, which depend only on the volume and the surface area of the convex domain.

scholarly journals Electromagnetic wave propagation in spatially homogeneous yet smoothly time-varying dielectric media

2016 ◽  
Vol 178 ◽  
pp. 158-166 ◽  
Author(s):  
Armen G. Hayrapetyan ◽  
Jörg B. Götte ◽  
Karen K. Grigoryan ◽  
Stephan Fritzsche ◽  
Rubik G. Petrosyan
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Electromagnetic Wave Propagation ◽  
Time Varying ◽  
Dielectric Media ◽  
Spatially Homogeneous

Utilizing higher moments to detect time-varying target in radar echo with non-stationary background

2015 ◽  
Vol 8 (2) ◽  
pp. 215-219 ◽  
Author(s):  
Renzhou Gui
Keyword(s):  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Synthetic Aperture ◽  
Higher Moments ◽  
Time Varying ◽  
Signal Model ◽  
Stationary Noise ◽  
Radar Echoes ◽  
Radar Echo ◽  
Stationary Background

Detecting time-varying target in non-stationary background is difficult and attractive problem. Time-varying movement exists widely in radar and communication systems. The non-linear processing with higher moments is discussed in the situation. Firstly the signal model of time-varying target with fix acceleration is analyzed. Then the radar echoes from synthetic aperture radar (SAR) are processed with higher moments. It not only restrains Gaussian noise automatically, but also suppresses non-stationary noise. Time-varying targets are different from the non-stationary background clutters. Moreover, the influences of the shadows about time-varying targets are reduced in the algorithm of higher moments. The proposal mentioned above utilizes higher moments to avoid analyzing the complex electromagnetic wave propagation and scatter theory. The differences of detection probability are compared between the chip with time-varying target and the clutter chip. The performances among different number order moments are compared by processing lots of actual SAR data added non-stationary noise. Lastly, the suitable number order moments are suggested by comparing the results from processing the actual radar echoes.

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