China
Africa
Explore chapters and articles related to this topic
Aperture and Phased Array Antennas
Published in Habibur Rahman, Fundamental Principles of Radar, 2019
Polarization of a radiated wave is defined as “that property of a radiated electromagnetic wave describing the time varying direction and relative magnitude of electric-field vector; specifically, the figure traced as function of time extremity of the vector at a fixed location in space, and the sense in which it is traced, as observer along the direction of propagation.” Polarization may be categorized into linear, elliptical, or circular. If the electric field vector at a point in space as a function of time is always directed along a line, the field is called linearly polarized. Elliptical polarization may be considered as the combination of two linearly polarized waves of the same frequency, traveling in the same direction, which is perpendicular to each other in space. If the amplitudes of the two waves are equal, and if they are 90° out of phase, the polarization is circular. Circular polarization and linear polarization are special cases of elliptical polarization. Clockwise rotation of the electric field is called right-hand polarization and counterclockwise as left-hand polarization.
Light
Published in David M. Scott, Industrial Process Sensors, 2018
Another important characteristic of light is its polarization. The oscillating electric and magnetic fields that comprise an electromagnetic wave are always perpendicular to each other and to the direction of propagation of the wave. If the plane defined by the oscillation of the electric field vector and the direction of propagation maintains a constant orientation, the light is linearly polarized; see Figure 4.1a (Halliday et al., 2005, p. 902). If on the other hand the electric field vector rotates clockwise or counterclockwise while maintaining a constant amplitude of oscillation, the light is circularly polarized (Figure 4.1b and Figure 4.1c). Circular polarization is a special case of elliptical polarization, in which the amplitude of the electric field oscillation describes an ellipse (as depicted in Figure 4.1d).
E
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
where U N (w) is a Jacobian elliptic function. See also Butterworth filter, Chebychev filter. elliptical polarization the polarization state of a radiated electromagnetic field in which the tip of the electric field vector traces an ellipse as a function of time for a fixed position. The sense of rotation of the electric field vector is either right-hand or left-hand (clockwise or counterclockwise). Circular polarization and linear polarization are special cases of elliptical polarization. embedded computer (1) a computing machine contained in a device whose purpose is not to be a computer. For example, the computers in automobiles and household appliances are embedded computers.
High efficiency and broadband wide-angle linear polarization converter based on dumbbell-like resonant structure
Published in Waves in Random and Complex Media, 2023
Ze Wang, Jinping Tian, Rongcao Yang
Electromagnetic (EM) waves are transverse, of which the polarization is defined as the direction of the electric field oscillation in a plane transverse to the propagation [1]. Polarization is also an intrinsic property of EM waves, and polarized EM waves can be divided into three categories: linear polarization, circular polarization and elliptical polarization. The electric field component of linear polarization waves polarized either in the y-direction or in the x-direction. The circular polarization means that the two mutually perpendicular electric field components have the same amplitude but the phase difference is π/2. Elliptical polarization corresponds to the case where the two components of the electric field are not equal in amplitude, and there is a phase difference between them. Polarization is useful in many areas of scientific research and practical application, such as astronomy, chemistry, display, industry test, life science microscopy [2], electronic communication, and so on. For example, in the field of electronic countermeasures, we often need to use antennas with horizontally polarized EM waves to suppress interference from vertically polarized EM waves. In satellite communication, it is often necessary to use circularly polarized EM waves to complete the communication due to the fact that circular polarization can keep the signal constant regardless of the anomalies existed in the ionosphere. Considering that EM waves with different polarization states are so widely used, it is especially important to control the polarization state or to convert the polarization state of EM waves effectively. Traditional devices used for polarization conversion are often designed based on the birefringence effect [3,4], such as grating [5], dichroic crystal [6], and twisted nematic crystals [7,8] etc. Since the refractive index difference of the birefringent material is small, therefore, in order to obtain a larger phase difference, the material needs to have a certain thickness. Furthermore, devices with polarization conversion function made of this material often have the disadvantages of not easy to miniaturize and integrate and narrow frequency band. In order to overcome these disadvantages, devices of polarization controlling based on metamaterials were introduced.