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Unmanned Aircraft Systems (UAS) Communications
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
In the case of elliptical polarization, the electric field vector traces out an ellipse (Figure 13.10) in a plane perpendicular to the direction of propagation. The polarization in this case may either be right-handed (clockwise) or left-handed (counterclockwise). Circularly polarized antennas have E-vectors that trace out a circle in a right-handed or left-handed sense. In the case of elliptical or circular polarization, it is not enough to have the matching polarization between transmitting and receiving antennas; the sense must match as well. As an example, circularly polarized patch antennas are commonly used in UAVs for receiving GPS signals from satellites.
Fundamentals of electrodynamics of gyrotropic media
Published in A.G. Gurevich, G.A. Melkov, and Waves, 2020
The problems of reflection from and passing through interfaces, normal to the direction of propagation, are easily solved in the case of longitudinal magnetization, as well as the problem of passage through a gyrotropic layer. Waves with circular polarization pass through and reflect from the interfaces of different media without change of the polarization, and the complex amplitudes of the reflected and transmitted waves are easily found from the boundary conditions. The incident wave with an arbitrary elliptical (e.g., a linear) polarization is resolved into two waves with circular polarization. Their transmission and reflection are considered, and then the complex amplitudes of transmitted and reflected waves with circular polarization are summed to get the total transmitted and total reflected waves. Two results of such calculations are to be mentioned. First, the magnetooptical Kerr effect, i.e., the turn of the major axis of the polarization ellipse of the wave reflected from an interface of an isotropic and lossy gyrotropic media. The second interesting result is the oscillating dependence of the angle of the polarization turn on the thickness of the gyrotropic layer [140].
Basic Theory and Design of Printed Antennas
Published in Binod Kumar Kanaujia, Surendra Kumar Gupta, Jugul Kishor, Deepak Gangwar, Printed Antennas, 2020
Shilpee Patil, Binod Kumar Kanaujia, Anil Kumar Singh
The term polarization is stated as the orientation of electric field vectors in an electromagnetic field. If the orientation of electric field vectors is in single plane, linear polarization is achieved. The fundamental patch of an antenna mostly generates linearly polarized waves in which the orientation of the electric field falls in one direction. There are two cases obtained in linear polarization, i.e. vertical polarization and horizontal polarization. In the first case, the orientation of electric field vectors is in vertical plane, and in the second case, the orientation of electric field vectors is in horizontal plane. The earth’s surface is taken the reference for the orientation of field vectors.
Wideband Frequency Agile and Polarization Reconfigurable Antenna for Wireless Applications
Published in IETE Journal of Research, 2023
Suresh Kumar Muthuvel, Yogesh Kumar Choukiker
Both polarization reconfigurability and frequency agility of concentric microstrip patch antenna have been presented. The frequency agility is achieved by incorporating four varactor diodes in the antenna and setting the capacitance values between 4.15pF to 0.84pF by varying reverse bias voltage from 0 V to 7.5 V. The frequency agility bandwidth is achieved from 2.0–3.0 GHz. The polarization schemes (H-LP, V-LP, RHCP, and LHCP) are realized by OSCBLC feed network configuration. Hence, the designed antenna is capable of radiating in different polarization modes. Satisfactory gain radiation patterns are observed for selected frequencies. The designed antenna configuration was verified experimentally and results show good agreement. The designed antenna covers the lower spectrum of S-band applications.
Circularly Polarized Parasitic Strips Loaded Broadband Printed Antenna for Sub-6 GHz (n77/n78/n79) Domain
Published in IETE Journal of Research, 2023
M. N. Manjunath, Ajay Kumar Dwivedi, Nagesh Kallollu Narayanaswamy, Anand Sharma, Vivek Singh
Circular polarization is produced by two electric field components (horizontal (EX) and vertical (EY)) of identical amplitude but 90 degrees out of phase with one another. The surface current distribution of the proposed model without parasitic strips is shown in Figure 8(a). It can be seen in Figure 8(a) that the components of the horizontal surface current in the ground plane are going in the opposite direction. As a result, in the far-field scenario, the horizontal radiation is negligible as the power is canceled out. However, it can be seen in Figure 8(b), asymmetric parasitic strips placement around the feed line produces two orthogonal currents, one horizontal (JX) and one vertical (JY). Strong EX and EY components are generated as a consequence of the currents produced on the strips. At the same time, the ground plane's current distributions are also changed because of the parasitic strips’ asymmetrical orientation.
Monostatic microwave ellipsometry for material characterization
Published in Waves in Random and Complex Media, 2021
R. Izhar, M. Amin, O. Siddiqui, Farooq A. Tahir
Polarization state or the direction of the electric field vector is an important property of an electromagnetic wave. The changes in the light's polarization states as it traverses through a medium can provide valuable insight about the wave-matter interaction that occurs during the process. Spectroscopic Ellipsometry [1,2] is an optical measurement method in which material samples (more commonly thin films) are characterized by determining the state of the reflected light's polarization. Figure 1 illustrates a basic ellipsometry set-up in which p- and s- polarized waves are incident on the sample-dielectric interface. At the analyzer, polarization states are generated from the amplitude ratio (tanψ) and phase difference (Δ) of the two waves: