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Physical Aspects of Radiofrequency Radiation Dosimetry
Published in Marko Markov, Dosimetry in Bioelectromagnetics, 2017
Marko S. Andjelković, Goran S. Ristić
Electric and magnetic field strength meters are narrowband devices. They consist of an antenna, cable(s) to carry the signal from the antenna, and a signal conditioning/readout instrument. Field strength meters may use linear antennas, such as monopoles, dipoles, loops, biconical or conical log spiral antennas, horns, or parabolic reflectors. The appropriate field parameters can be determined from a measurement of voltage or power at the selected frequency and at the antenna terminal. The electric (or magnetic) field strength can be derived from information on the antenna gain or antenna factor and the loss in the connecting cable.
Application of Ground-Penetrating Radar (GPR) as supporting technology for monitoring cracks at Bening Dam, East Java, Indonesia
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
Factors that affect amplitude decay (attenuation) are: (a) geometrical spreading, (b) energy scattering due to the homogeneity of the medium, (c) reflection of energy in medium boundary fields, (d) absorption of energy (attenuation), and (e) antenna factor.
EMC Measurements and Testing
Published in Christos Christopoulos, Principles and Techniques of Electromagnetic Compatibility, 2022
Knowledge of the antenna factor and measurement of the receiver voltage permits the calculation of the electric field from Equation 14.2. Similar expressions apply for the antenna factor of antennas sensitive to the magnetic field.
Ionospheric delay estimation of Loran skywave using simple cosine model
Published in Electromagnetics, 2023
Kai Zhang, Fan Yang, WeiDong Wang, Chen Zheng, Borong Zou, Hui Li
There are four components of the skywave delay. Except the delay of skywave signal on the propagation path, the other three are error correction items in the propagation process. The first term is the error of receiving and transmitting antenna factors. It is due to the influence of the curved earth on vertical radiation pattern when antenna is close to the ground. The antenna factor is affected by the signal frequency and position. It is calculated for land, sea, and ice conditions, which are defined by their electrical characteristics (conductivity and permittivity) and usually changed little in Loran receiving system. The second term is the ionospheric focusing factor. The ionospheric reflection model is equivalent to planar reflection, but the actual ionospheric is curved. Therefore, the ionospheric focusing factor is used to represent the change of wave propagation law. This error has small value and gentle variation, which is affected by signal frequency and time. The last term is error effect of the skywave passing through the ionosphere, which is expressed by the equivalent ionospheric reflection coefficient. This is also the most important variation of the propagation delay of the whole skywave path.
Analytical Modelling of Terahertz Photomixing Antennas
Published in IETE Journal of Research, 2022
Mrinmoy Bharadwaj, Jitendra Prajapati, Ratnajit Bhattacharjee
Radiation from a PMA occurs from the time varying current densities expressed in Equations (17) and (18). These current densities are separated in space both horizontally as well as vertically by the subsequent electrode widths and gaps and the electrode lengths , respectively. If ( being the radiated wavelength), the spatial phase difference between the current densities may be ignored in the far field. Otherwise, the spatial phase has to be considered in the far-field by modelling the location of individual current elements as that from a two-dimensional antenna array. Here, we present the radiated fields in the first scenario and present the antenna factor expression for the second scenario.