Ka and Q band propagation experiments in Toulouse using ASTRA 3B and ALPHASAT satellites

From January 2008 to March 2011, ONERA operated in Toulouse, France, a beacon receiver able to collect the 19.7‐GHz beacon signal of the HotBird 6 satellite. In March 2011, the radio frequency chain was modified to be able to receive the 20.2‐GHz ASTRA 3B beacon to benefit from a higher Equivalent Isotropically Radiated Power of the satellite. Since June 2015, a second beacon receiver has been installed and is able to record the 39.4‐GHz beacon signal of the Alphasat satellite. The objective of this paper is to present the results of the first 2 years of measurements (June 2015 to May 2017) of the Q‐band Alphasat propagation experiment in Toulouse, as well as concurrent measurements collected at Ka‐band with ASTRA 3B. First of all, the propagation experiments are briefly described. Second, the results of the statistical analysis are highlighted. Finally, a deep analysis of the performances of the 2 frequency scaling prediction methods recommended in ITU‐R P.618‐13 is performed.     

Centimeter and millimeter-wave radio signals attenuation inexplosions

The mechanisms of centimetre and millimetre radio wave attenuation in the explosion area of chemical explosives are analyzed. It is shown that the dominant factor is the attenuation caused by absorption in finely dispersed solid explosion products. The results of experimental measurement of the attenuation factor, the area dimensions important for attenuation and the duration of its existence for wavelengths of 0.4, 0.8, 3 cm are presented. A comparison of experimental data with results of derivations is performed     

Summary of millimeter wave propagation experiments using Japan’s first geostationary satellite «Kiku-2»

A one year millimeter wave propagation experiment with a satellite-to-earth link was performed using Japan’s first geostationary satellite «Kiku-2». The satellite carries a beacon transmitter with three coherent frequencies, 1.7, 11.5 and 34.5 GHz. A coherent receiving system with a 10 m diameter antenna was employed. Other instrumentation included a C band rain radar. The experiment was carried out on 24 h-a-day basis and achieved nearly eight thousand hours of test time. The results show that a 20 dB rain margin is necessary for a millimeter wave satellite communication link with 99.9 % reliability. This paper describes the experiment and the results in outline.     

Slow wave propagation using interconnections for IC technologies

A microstrip slow wave transmission line, based on a periodic structure made with the two metallic levels used in ICs, is described. Using on-wafer measurements, an effective permittivity as high as 20 in a wide microwave frequency range is reported. The transmission line has also been measured to obtain the characteristic impedance and the losses. Using the basic periodic structure theory the propagation constant of this media has been computed and good agreement has been obtained with that of the measurement. This slow wave structure is very promising for use in MMIC because of its very compact design.<>     

复杂边界电波传播损耗的神经网络估计方法

针对抛物方程用于模拟复杂地面边界电波传播计算时间随着频率升高急剧增加的缺点,提出利用抛物方程给神经网络提供训练数据,用电磁波频率和水平方向的距离作为神经网络的输入,传播损耗作为神经网络输出的电波传播损耗的分析估计方法.与传统抛物方程的计算结果对比表明,所提出的复杂边界电波传播损耗的估计方法,在保证了较高计算精度的同时,计算速度得到很大的提高.     

A microwave beacon and guiding signals for airports and their approaches

A novel circular array of 90 equally spaced vertical dipoles is described. It is driven by just one element. When the spacing, length, and radius of the identical elements are properly chosen, the entire array is resonant with large currents in each element. These alternate 180/spl deg/ in phase and set up a far field that consists of 90 sharp spikes separated by 90 s. When dimensioned for a microwave frequency of 3 GHz, the array generates a field pattern that can be applied to provide a microwave beacon and guiding signals for aircraft approaching an airport. These would supplement the normal central high-intensity light and the approach lights, and provide a potentially useful guidance system for coastal airports embedded in dense fog that obscures the lights.     

A discrete‐components millimeter‐wave satellite beacon receiver for Q‐band propagation experiment

Ever increasing bandwidth requirements in satellite communications continuously push the frequency limits. Q‐ band (33 – 50 GHz) is the next frequency band to be populated; however, at these frequencies, the Earth's troposphere (weather) profoundly alters the radio propagation conditions. Therefore, in order to properly plan radio links, accurate statistical models of radio channels are necessary. These statistical models are built upon empirical data, ie, measurements, which are furthermore used to design appropriate Propagation Impairment Mitigation Techniques. The Q‐ band lacks such data, hence the statistical models are inadequate. To address this problem, we propose a cost‐effective, easy to replicate Q‐ band beacon receiver to leverage the Alphasat propagation campaign. We present a step‐by‐step implementation process of the receiver's fundamental part, a Low‐Noise Block, which translates input 39.402 GHz signal into 162 MHz output signal with a conversion gain of 52 dB. The receiver furthermore utilizes software define radio for signal processing and other data manipulation. Here, we describe the receiver implementations in great details, supplementing the crucial parts with laboratory validation results. Finally, we show 2 example datasets, showing usual data obtained during heavy showers and on a quiet day, respectively.     

LSD波点燃和初始阶段传播的光学干涉研究

本文首先从动力学出发分析了LSD波点燃过程,导出了LSD波速度、压力等物理量表达式.用马赫-曾德尔干涉仪同步研究了Nd:YAG激光与铝靶表面相互作用过程,首次获得了LSD波点燃和初始阶段传播的系列干涉图象,为LSD波理论模型研究提供了可靠实验数据.     

Centimeter and millimeter wave attenuation by atmospheric gases and rainfall at a tropical station

The radiowave attenuation due to oxygen and water vapour has been computed over the frequency range 3–350 GHz making use of the mean surface air pressure, temperature and water vapour at Ile-Ife (geog. lat 7.5°N, long 4.5°E) in Southern Nigeria. It is observed that the attenuation at this tropical location is generally higher than at temperate climates. A similar analysis was performed for rainfall attenuation using rainfall intensity measurements. The results obtained with three different expressions for the rain height showed that a rain height of 3 km is a reasonable assumption for estimating earth-space rainfall attenuation at this location. It is found that for frequencies above 200 GHz, the polarization dependence of the specific attenuation due to rainfal becomes negligible. The computed attenuation is lower that that predicted using the corresponding CCIR rain climate data. The results show that whilst the contribution of oxygen and water vapour to the total atmospheric attenuation could be neglected when compared with rainfall attenuation up to about 150 GHz, the contribution becomes significant for frequencies above 190 GHz.     

Reconstruction of nonuniformly sampled time-limited signals using prolate spheroidal wave functions

Shannon's sampling theory is based on the reconstruction of bandlimited signals which requires infinite number of uniform time samples. Indeed, one can only have finite number of samples for numerical implementation. In this paper, as a dual of the bandlimited reconstruction, a solution for time-limited signal reconstruction from nonuniform samples is proposed. The system model we present is based on the idea that time-limited signals which are also nearly bandlimited can be well approximated by a low-dimensional subspace. This can be done by using prolate spheroidal wave functions as the basis. The order of the projection on this basis is obtained by means of the time–frequency dimension of the signal, especially in the case of non-stationary signals. The reconstruction requires the estimation of the nonuniform sampling times by means of an annihilating filter. We obtain the reconstruction parameters by solving a linear system of equations and show that our finite-dimensional model is not ill-conditioned. The practical aspects of our method including the dimensionality reduction are demonstrated by processing synthetic as well as real signals.     

Laser wave propagation through the atmosphere

Communications with coherent light through the atmosphere bring out new system limitations besides the ones imposed by attenuation and scattering normally associated with incoherent waves. This is so because the laser directivity and coherence responsible for increased channel capacity are easily destroyed or at least degraded by the presence of random thermal turbulences. Simple expressions describing the effects of atmospheric turbulence on laser beam propagation are obtained. Corresponding calculations yield the order of magnitude of such random phenomena as beam scanning, phase variation, beam cross-section change, amplitude and frequency modulation. In particular, the polarization fluctuation is predicted quantitatively in terms of the atmosphere mean square refractive index and its turbulence correlation length.     

Positioning beacon system using digital camera and LEDs

This paper is on a novel use of lighting or signaling devices constructed by light-emitting diodes (LEDs) as a positioning beacon. The idea is that the surface of the LED lighting device is divided into regions and used to show different visual patterns that are not noticeable by the human eye due to the high-frequency switching of the LEDs. A digital camera is used as a receiver to capture a sequence of images of the LED positioning beacon transmitter. Image-processing algorithms are used to decode the location code that is encoded in the visual patterns transmitted by the LED device. This idea can be applied to any LED traffic lights or signaling devices on the road and turn them into parts of a positioning beacon system. Such a system made up of high-brightness visible LEDs can provide the function of open-space wireless broadcasting of the positioning signal. The LED signaling method, transmission protocol, camera frame rate, LED flash rate, together with an implemented system and the experimental results, are presented in this paper.     

Teaching of wave propagation phenomena using MATLAB GUIs at the Universidad Politecnica of Valencia

The use of interactive graphics and animations is a fundamental tool for teaching electromagnetic concepts. This is especially true for the study of wave propagation, where the propagation properties of waves are hard to understand with oral explanations or simple, static, chalk drawings on the blackboard. The traditional blackboard or the more recent slides are increasingly giving way to the use of electronic material for illustrating propagation phenomena in the classroom. Several works where computer tools are used in order to improve electromagnetic teaching have already been published (Mathematica, Maple, MATHCAD, Java, MATLAB, Mefisto, and VRML). Of all these tools, MATLAB has been chosen to design several graphical user interfaces (GUIs) that allow the creation of wave-propagation animations under user-specified conditions. These GUIs have been assessed for the teaching of a course on "Electromagnetic Fields and Waves." The main objectives of the course are the knowledge of the main parameters of plane and guided waves, and an understanding of the main propagation phenomena of these two types of waves.     

反射信号对卫星C波段干扰的分析

卫星通信系统是一种开放系统,相对于其他通信方式较易受到干扰。卫星信号受到干扰,会影响卫星数字视频广播信号的传输。对卫星地面接入系     

Semi-Markov multistate modeling of the land mobile propagation channel for geostationary satellites

This paper describes a new semi-Markov propagation channel model for land mobile satellite systems using geostationary satellites. The multistate model switches between propagation states representing line-of-sight, shadowing, or blockage of the signal. The duration of times spent in each state follow probability distributions recommended by the radiocommunication sector of the International Telecommunication Union (ITU-R). The actual parameters to be used with the ITU-R distributions were modified and fitted to observed data. The open-area state durations follow a power-law distribution, while the state durations for both the shadowed and the blocked states follow a lognormal distribution. Parameters for both two- and three-state models are extracted from an L-band measurement campaign performed by Inmarsat in the United Kingdom. Propagation channel models characterizing the fading within the open, shadowed, or blocked propagation states are described as well. The semi-Markov models represent an improvement over the more commonly used Markov models where the duration in each state follows an exponential distribution. The new model enables more accurate prediction and simulation of system performance and availability.     

INTELSAT propagation experiments: the focus and results of recentcampaigns

The work presented here aims at a detailed understanding of propagation impairments likely to be encountered on a given path, which is one of the factors needed in transmission link design to provide satellite service at the quality customers demand. The author discusses the background to INTELSAT's need for propagation information, describes the focus of recent INTELSAT Ku- and Ka-band measurements, and provides some of the results and conclusions of these measurements     

EEG信号中癫痫棘波的小波变换检测

基于小波变换良好的时频局部化特性,研究了一种利用连续小波变换提取脑电信号中的癫痫棘波的方法,实验结果表明这种方法能够方便而有效地对脑电信号中的癫痫棘波进行检测。     

太赫兹电波传播及信道特性

首先,综述太赫兹电波相较于低频电波传播的不同特性,包括气象因素和材料粗糙表面对电磁波的影响。接着,提出利用射线跟踪技术仅通过有限的信道测量数据校准目标场景中的三维环境模型以及材料电磁参数;然后,利用从射线跟踪仿真反演出的参数在类似场景中进行大量仿真,代替信道测量生成大量真实有效的全维度信道数据;最后,提取并分析信道特性,例如路径损耗、阴影衰落、莱斯K因子、均方根时延扩展、角度扩展及多普勒参数。2个案例研究是从室内桌面通信到室外智能车联网场景,分别代表了6G移动通信从近到远用例的两端,对于室外场景还额外考虑了不同气象条件下对信道参数的影响,对太赫兹系统的设计和评估具有重大意义。     

Line-of-sight wave propagation through the turbulent atmosphere

A review of the recent developments in the field of random fluctuations of an electromagnetic wave propagated over a line-of-sight path is presented. The major interest is in the optical to millimeter wavelength range where fluctuations in amplitude, phase, and angle-of-arrival are important system considerations. It is assumed that the fluctuations are the result of variations in the refractive index caused by turbulence in the atmosphere. The review concentrates on the major approximations involved in the theoretical developments, and in particular, attempts to put in perspective the arguments over Rytov's method. The paper includes a number of previously untranslated results from the Russian literature, and some previously unpublished results of the author's. A brief assessment of new theoretical approaches and a discussion of some extremely important experimental work are given.