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Different Issues
Published in Boris Levin, Antenna Engineering, 2017
shows that there is a critical frequency for a wave propagating along the slot in this case too. When ω = ω0, the antenna characteristics are similar to characteristics of an ideal magnetic radiator. However, as the frequency increases, the magnitude of the propagation constant increases also. As a result, a great number of current half-waves are placed along the antenna. Their fields mutually cancel each other, and the real length of the radiating antenna quickly decreases. Therefore, this antenna is effective in a narrow frequency band. However, this antenna has been applied as a receiving VHF antenna [129]. Unfortunately, in this article, these antennas are considered as loop antennas. This approach does not allow explain the dependence of the first resonant frequency on the antenna length and also the existence of additional resonances.
Measurement of system parameters
Published in Geoff Lewis, Communications Technology Handbook, 2013
Neper. The propagation constant for a transmission system is complex, consisting of a real attenuation constant and an imaginary phase constant. If logs to the base e are used to express the attenuation as logeI1/I2, where I1 and I2 are the input and output current, respectively, the loss is expressed in nepers. Strictly, this unit is reserved for dealing with transmission line currents and 1 neper = 8.686 dB. As this is a relatively large unit, decinepers (dN) are commonly used.
Transmission Line Analysis
Published in A. P. Sakis Meliopoulos, Power System Grounding and Transients, 2017
Note that p is dependent on the frequency f(ω = 2πf). The dimensions of the constant p are the inverse of length. The constant p characterizes the propagation of voltage through the transmission line. For this reason it is called the propagation constant. The real and imaginary parts of the propagation constant will be called the attenuation and phase constant, respectively. That is, p = k + jη, where k is the attenuation constant and η is the phase constant.
Characteristics of wave propagation, vibration transmission and acoustic emission in fluid-filled coaxial periodic shells
Published in Mechanics of Advanced Materials and Structures, 2020
Huijie Shen, Zhiyin Tang, Yongsheng Su, Jiangwei Liu, Dianlong Yu, Ruojun Zhang
Now, consider the two coaxial periodic shells with light fluid (e.g., air, whose acoustic speed and density of air are 340 m/s and 1.225 kg/m3, respectively) loading in both the inner shell and annular domain. The “beam mode” band structure for this coaxial periodic shell system is presented in Figure 3. The attenuation constant and phase constant are respectively associated with the real and imaginary parts of propagation constant μ. The semicircular-arch curves that appear in the attenuation constant correspond to the far-field wave, and their value denotes the damping factor. The multiple evanescent waves, i.e., the near-field wave branches in the attenuation constant branches, do not alter the energy/vibration transmission to a far field. Thus, it is reasonable to focus analysis only on the far-field wave branches. Based on this criteria, we can known that waves propagate freely in the frequency ranges where only imaginary value of μ occurs and totally forbidden when real value of the far-field wave existed.
Evaluation of the glioblastoma multiforme treatment with hyperthermia using the finite element method
Published in Numerical Heat Transfer, Part A: Applications, 2023
Ayşe Sağıroğlu, İlke Karagöz, Öznur Özge Özcan, Türker Tekin Ergüzel, Mesut Karahan, Nevzat Tarhan
The propagation constant k used is related to the wavelength in the medium, the wavelength is λ. The equation between propagation constant and wavelength is as follows.
Concurrent Solar-Illumination and Power Line Voice Communication for Indian Underground Coal Mines – An Experimental Study
Published in IETE Journal of Research, 2022
R. N. Raul, T. Maity, S. Palit
PLC in underground coal mines has been proposed to be a smart intermediate between wired and wireless communication systems because of development in channel coding, modulation–demodulation, and signal processing technologies. The signal quality and strength in transmission through power-line depend upon the characteristics of the transmission channel as shown in [4]. So, proper modelling of the transmission channel is necessary. In case of LV-PLC, it is important to mention that channel characteristics depend on the infrastructures of the mines. In the voice frequency range, wire-line communication is a good alternative. A uniform transmission line can be defined as a line with distributed elements like For any operative frequency, a relatively long piece of line is considered containing identical sections which are chosen to be small as compared to the operating wavelength. The series impedance and the shunt admittance per unit length of the transmission line are given by where ω stands for angular frequency. The expressions for voltage and current per unit length are given respectively by where Vl(z) and Il(z) stand for the line voltage and line current respectively. The negative sign indicates a decrease in voltage and current as line (z) increases. The current and voltage are measured from the receiving end; at z = 0 and line extends in the negative z-direction. After simplification, it gives γp is a complex number that is called the propagation constant. αp, the real part, is called the attenuation constant of the propagation, whereas βp is the imaginary part called as the phase constant. Thus, propagation constant γp is the phase shift and attenuation per unit length along the line. αp and βp are expressed as The resistance is to be estimated by the conductivity, permeability, and cross-section of existing copper conductors on the basis of skin-effect. In the same way, inductance, capacitance, and conductance can be easily calculated using the permeability of free space, distance between conductors, permittivity, and conductivity of the dielectric material between conductors. Since the loads inside the mines are dynamic in nature, the load-effects cannot be modelled with constant values. Parameters like attenuation constant and phase shift can be estimated from the current values of load impedance.