-> Analyze The RCS Of A Plasma Antenna. 4/6/2013. - Plasma antennas offer some advantages over metal antennas for stealth applications, although they still exhibit an RCS when operating for transmission or reception in a system. - Electronic-warfare (EW) strategies often involve detecting the radar cross section (RCS) of an opponent’s antennas which, for one thing, can provide details on the opponent’s location. Fortunately, in some antenna designs, such as high-frequency plasma antennas, it is possible to make the antenna’s RCS virtually disappear from detection. - Plasma antennas offer some special qualities that make them attractive for electronic-warfare (EW), radar, and other applications that may require stealth operation. The plasma in these antennas is essentially a blend of electrons, ions, and neutrons. When the density of the plasma is high enough, an electromagnetic (EM) wave will travel on its surface rather than deep into it. The plasma will exhibit the properties of a conductor, serving as an antenna for transmitting and receiving signals. - Consequently, a plasma column can be used as a radiative element in place of a metallic conductor. The plasma becomes conductive when energized by an RF source, and nonconductive once the source is removed. As a result, it can be made to have a radar cross section (RCS) that virtually disappears to an enemy radar once the RF source is removed.1 Another advantage of a plasma antenna compared with its metal counterpart is that it can be reconfigured; its radiation characteristics can be changed conveniently by electrical rather than mechanical control. - Much study has focused on plasma antennas—mainly to understand their radiation characteristics, including the input impedance, the radiation pattern, and the loss of the plasma column by means of analytical solutions or numerical simulations.3-5 Because a plasma antenna has little or no RCS when it is turned off, it has had great appeal for defense applications. But when it is on, whether transmitting or receiving, it does have an RCS and can be detected by an enemy radar. Understanding its RCS characteristics when it is powered on is important for applying these antennas to stealth applications. - Unfortunately, of the studies performed so far on plasma antennas, none has addressed the RCS characteristics of these antennas. As is known, plasma is a dispersive media for which the relative permittivity is dependent upon frequency. Various approaches can be used to simulate the interaction of EM waves with a plasma antenna. The two main methods based on finite-difference-time-domain (FDTD) analysis are the direct integration and the recursive convolution methods. Yoonjae Lee6 and Fan Luo7 studied the radiation characteristics of plasma antennas using the former method. Xue-Shi Li8 investigated the input impedance and radiation patterns of plasma antennas with nonuniform distribution of the plasma using the latter method. But neither addressed scattering fields from plasma antennas. - In the present study, FDTD analysis using the Z-transform will be applied for simulating the interaction of EM waves and an unmagnetized plasma antenna. Considering a plasma antenna as an infinite square column with a dielectric tube, it can be simulated by means of iterative formulas. The simulations can be applied to analyze the antenna’s RCS characteristics in terms of inhomogeneous plasma density, different EM incident frequencies, different plasma collision frequencies, and different relative dielectric constants for the tube containing the plasma.
Posted on: Thu, 12 Sep 2013 07:37:34 +0000
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