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(a) Cylindrical parabolic reflector made of perfect metal with a layer of plasma on its surface that a set of electromagnetic waves parallel to its symmetry axis come down on its surface. (b) One typical electromagnetic ray comes down on the parabolic plasma layer ( E i ) and the next reflected ( E r )
Source publication
The deviation of the energy distribution along the focal axis of a long metallic cylindrical parabolic reflector, which on its surface contains a uniform cold collisionless plasma, is investigated. In addition, the effects of some physical parameters such as the plasma and wave frequencies and the thickness of plasma layer on this energy distributi...
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Context 1
... configuration under consideration is a cylindrical par- abolic reflector made of perfect metal in the presence of a plasma layer (Fig. 1). We assume that the incident electro- magnetic waves on the surface of the reflector are parallel to its symmetry axis. The equation of metallic parabolic reflector is given ...
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Citations
... 5 In the past three decades, many focusing technologies have been developed. (1) Parabolic reflector, 6 however, it is difficult to obtain a feed of plane wave in the near-field region. (2) The ellipsoidal reflector antenna, which can transfer microwave power from one focus to another, 7 but it is difficult to manufacture curved surface. ...
In this paper, a near field focusing transmission metasurface (MS) based on polarization sensitivity is developed at microwave frequency. The MS unit cell has only three metal layers, which is less than the published dual‐polarized transmission structure. And the phase shifting range can cover 320° for x‐ and y‐polarized waves. The biggest bright spot of the focusing MS made of the proposed units is its changeable focus point by rotating the horn 0°–90° round its central axis: focusing switching between one and two focusing points. In addition, the developed MS has the following advantages: multifunctional, low sidelobe, high focusing efficiency, small size, wideband, and less layer number. The focusing relative bandwidth is 9.7%, and the maximum focusing efficiency is 30% at center frequency 15.5 GHz. The efficiency is higher than that of published results in transmission orthogonal polarization mode. The proposed MS has potential applications in medical treatment, noncontact sensing system.
... Many researchers have studied the interaction of electromagnetic waves with tunable plasma material; this area of research has received valuable attention and is a "hot topic" in plasma technology [5][6][7][8][9][10]. The enhanced performance of absorption, transmission, and the optical reflection of stealth applications, radio astronomy, and radio communication may be obtained using plasma as a cover layer on a communication system [11,12]. Moreover, when a space vehicle reenters the atmosphere at hypersonic speed, it is wrapped by a plasma sheath due to highly ionized gases [13][14][15]. ...
... La antena con reflector cilindro parabólico tiene la propiedad de que los rayos salientes de la línea focal al reflejarse en la superficie se convierten en un conjunto de rayos paralelos [7]. Igualmente por el principio de reciprocidad los rayos paralelos que inciden de forma normal al receptor convergen en la misma línea focal [15]. Desde otra óptica se puede decir que la superficie convierte un frente de onda esférico en un frente de onda plano [9]. ...
In coastal radar, In addition to a direct radiation pattern, a level of secondary lobes or small parasites is required. With the aim of reduce the width of the half-power beam of the original FURUNO radar antenna to 3 degrees, in this article the reader is shown the design of an offset parabolic cylindrical reflector antenna in the X band at 9.4 GHz. The analysis of the antenna in two planes is proposed separately. In the vertical plane, a sector horn antenna is proposed as an excitation antenna. In the horizontal plane, a uniform linear array of 129 elements is proposed. From the results obtained it is seen how with the presented design a greater directivity is achieved, an increase of the gain in approximately 8dB which results in an increase in the noise Gain-Temperature ratio, secondary lobe levels of -25 dB and in addition, theoretically, it is possible to increase the scope of the coastal radar by more than twice.
... Las antenas con reflector parabólico tienen la propiedad, producto de la geometría de la superficie reflectora, de que los rayos salientes del punto focal al reflejarse en la superficie se convierten en un conjunto de rayos paralelos. Igualmente por el principio de reciprocidad los rayos paralelos que inciden de forma normal al receptor convergen en el mismo punto focal [14]. Desde otra óptica se puede decir que la superficie convierte 2 un frente de onda esférico en un frente de onda plano. ...
In this article, we propose the design of an offset parabolic antenna in the X band at 9.4 GHz that can be replaced by the original antenna of the FURUNO radar by reducing the beam of half power in the vertical plane to 6o. The design of a smooth pyramidal horn antenna as excitation antenna is proposed. The theoretical models and the simulation of the excitation antenna are carried out, arriving at results in them. After the simulation of the feeder-reflector system, it can be seen that with the presented design a greater directivity is achieved, an increase of the gain in approximately 1dB which brings as consequence an increase in the ratio Gain-Temperature of noise, secondary lobe levels -25 dB and in addition to the theoretical way it is possible to increase the range of the coastal radar.
... Una manera de lograr este cambio en el frente de onda a partir de la radiación de una bocina piramidal es con el empleo de un reflector o dos reflectores [17] en los casos más comunes. El análisis de los reflectores se puede realizar mediante técnicas de trazado de rayos [18] o la Óptica Geométrica, seguida del análisis del método de campos en la abertura y el cálculo de los campos radiados [19]. Un estudio más detallado de la radiación requiere el estudio de la difracción en los bordes. ...
Current article offers a general overview of the aperture antennas. Main geometric expressions for the analysis of the parabolic antennas of displaced focus (offset) are addressed, which can be treated as circular openings and analyzed by Geometric Optics (GO), followed by the method of distribution of the fields in the opening with modified functions and the calculation of radiated fields. With the aim of increasing precision in the radiation characteristic of the openings and applying the method in offset parabolic antennas. The expressions are modified and an analysis is made regarding parameters of interest such as directivity, level of secondary lobes and the coefficient parameter considering antenna aperture for different focus-diameter relationships with different illumination values. The program developed to this purpose in the software Mathcad 14.0 shows that for parabolic antennas with a long focus offset with asymmetric lighting, the correction angle becomes null, the level of the first secondary lobe does not change and remains below -26.4 dB, the coefficient parameter to describe opening is constant and equal to 0.8605.
... Las antenas de bocinas lisas convencionales tienen un patrón de radiación asimétrico [6], el cual tiene un nivel de lóbulos secundarios en el plano E de aproximadamente -10dB respecto al máximo de radiación, a pesar de lo cual se pueden obtener bocinas con una eficiencia de radiación elevada [7]. Esta característica provoca que mucha energía llegue a las paredes de la cámara producto de los lóbulos laterales de la antena que influyen también en la ganancia de la misma [8], provocando reflexiones no deseadas que pueden afectar la medición. Con el propósito de reducir los lóbulos laterales [9] y obtener simetría en el patrón de radiación ,en el sentido de una medición en el espacio libre [10], se presenta en este artículo el diseño de una antena de bocina corrugada. ...
In both anechoic chambers and parabolic reflector feeders, horn antennas play an essential role. The former simulate a location free of interference and independent of weather conditions, allowing the correct measurement of the main parameters of electromagnetic devices. These are formed by three fundamental parts: the outer coating or Faraday cage, the absorbent materials inside the chamber and the measuring antennas or standard antenna. This paper, based on the study of corrugated horn antennas, proposes the design of a corrugated pyramidal horn with fixed depth slots in the Mathcat14 development environment for use in anechoic chambers. The effect of the corrugations on the walls of the horn, especially the surface currents, is analyzed, comparing some parameters of these with those of
a smooth one, highlighting its main advantages in function of its use in anechoic chambers. Finally some of its radiation characteristics are theoretically tested.
... High velocity space vehicles with metallic antennas, as reflector antennas for example, encounter plasma effect when re-entering into the Earth's atmosphere. Thus, usually antennas of space vehicles are in surface contact with a plasma layer that affects the radiation characteristics of such antennas [12,13]. Similarly, the existence of a plasma layer on metallic targets changes the reflected and scattered wave energies. ...
Theoretical formulations of the electromagnetic (EM) field distribution in the focal or caustic region of an elliptical reflector with its curved surface coated by collisional magnetized anisotropic plasma have been derived. Both parallel and perpendicular polarizations of the normal incident wave are considered. Expressions for the EM field intensity along the focal region have been obtained accurately using Maslov’s method. The effect of the plasma-layer thickness on the reflected and transmitted field intensity distributions was investigated. Other physical parameters such as the plasma electron density, the cyclotron frequencies, and the collisional frequency have been noticed to have an evident influence on the levels of the transmitted field-intensities along the focal region. The problem discussed in this paper has, also, been solved using Kirchhoff’s approximation and the results of the two methods are found to be in a good agreement.
... In our previous paper, the energy distribution of a metallic cylindrical parabolic reflector covered with an unmagnetized plasma layer had been investigated. 34 In the present work, we are going to study the interaction of the electromagnetic waves with a collisionless magnetized plasma layer located on the surface of a long metallic cylindrical parabolic reflector and demonstrate a general model for the energy distribution. Here, it has been assumed that the direction of the external magnetic field is parallel with the reflector surface. ...
... In a weakly magnetized plasma layer, these effects are negligible for the both S and P-polarized. 34 This phenomenon refers to the total transparency of the stationary non-magnetic and magnetic plasma layers to the incident p-polarized wave. [36][37][38] This figure is plotted for the constant parameters f x p =c ¼ 10 3 ; dx p =c ¼ 0:05; x=x p ¼ 100, and two values of f x c =c ¼ 2000 and 10 000. ...
The energy distribution along the focal axis of a long metallic cylindrical parabolic reflector with a plasma layer on its surface in the presence of an external magnetic field is investigated. The effects of some physical parameters, such as the plasma frequency, the wave frequency and the thickness of plasma layer on the energy distribution and the reflected and transmitted electromagnetic fields, are simulated. These investigations for both S- and P-polarizations have been done separately. It is found that the maximum value of the reflected intensity increases by increasing the incident wave frequency and by decreasing the plasma layer thickness and the plasma frequency for both polarizations. Furthermore, the results show that the increase of the magnetic field strength can cause an increase in the reflected intensity for S-polarization and a slight decrease for P-polarization.
In telecommunications, whether viewed as single antennas or as parabolic reflector feeders, horn antennas are widely used for their good response over large bandwidth and symmetry in their radiation pattern. That is why they play a leading role in wireless communications systems and, above all, in RADAR systems. This paper proposes the design of a corrugated horn antenna with slots of varying depths in the Matlab development environment with the help of Mathcad software for use in RADAR applications. The advantages of the use of variable corrugations will be highlighted as a function of their use as feeder antenna and an analysis of their radi-ation characteristics will be made.
A theoretical investigation has been carried out to analyze the optical focusing electromagnetic field by a perfect electromagnetic conductor elliptical reflector in un-magnetized plasma environment. The presented analysis and formulations are general for any perfect conductor elliptical cylinder (PEC, PMC, or PEMC). The co-polarized and the cross-polarized components of the focal region electromagnetic field expressions have been obtained using Maslov’s method. The electromagnetic field behaviors at Caustic or focal point for the cases of PEMC, PEC (perfect electric conductor) and PMC (perfect magnetic conductor) elliptical reflector have been computed and compared. The behavior of the electromagnetic field behaviors at Caustic or focal point with the variation of the admittance parameter, plasma frequency and effective collision frequency for the co-polarized and the cross polarized fields is also investigated. The comparisons of the computed results of the presented formulations with the published results of some special cases confirm the accuracy of the presented analysis. © 2015, National Institute of Optoelectronics. All rights reserved.
