THE PLASMA ANTENNA WITH AZIMUTHAL-ASYMMETRICAL TRAVELING WAVES OF CURRENT

Abstract

In paper the plasma antenna with azimuthally asymmetrical traveling waves operating at a harmonic with an azimuth number m = 1 is theoretically and numerically investigated. Besides the collisions of electrons with atoms are taken into account. Plasma is assumed to be cold and isotropic. The method of the dispersion equation is used. The propagation constant and the attenuation coefficient of the traveling wave can be obtained from the real and imaginary parts of the solution of this equation, respectively. In order to find the directional patterns, the delayed potentials in the far zone are calculated. The directional patterns depend strongly on the slowing of waves in the antenna. The dependences of the slowing of the wave on the plasma density are obtained. The dependence of the pattern on the plasma density, the geometrical parameters of the plasma cylinder and the frequency of electron-atom collisions is investigated. The minimum values of the plasma density, at which the normalized antenna patterns are highly directional and have a main lobe located at a zero angle to the antenna axis, are obtained. Advantages of the antenna operating at the harmonic with m = 1, as compared to the antenna working on an azimuthally-symmetrical wave, are shown: the working plasma density of such an antenna is much lower; the radiation is in a strictly axial direction; a small level of the side lobes of the directional pattern. The antenna pattern is less dependent on the electron-atom collisions. It is also shown that, by dispersion properties, a plasma antenna with m = 1 is closer to a metallic antenna than an antenna with m = 0.