PLASMA ANTENNA WITH THE AZIMUTHAL-ASYMMETRICAL WAVES OF CURRENT

In the present paper, the plasma antenna with azimuthally asymmetrical traveling waves operating at a harmonic with an azimuth number m = 1 is investigated theoretically and numerically. In addition, 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 radiation patterns (RP), the delayed potentials in the far zone are calculated. The RP strongly depends on the slowing of waves in the antenna. The dependences of the slowing of the wave on the plasma density are obtained, and the dependence of RP on the plasma density, geometrical parameters of plasma cylinder and frequency of electron-atom collisions is investigated. The minimum values of plasma density, at which the normalized radiation patterns are highly directional and have a main lobe located at a zero angle to the antenna axis, are obtained. Advantages of antenna operating at harmonic with m = 1, as compared to the antenna working on an azimuthally-symmetrical wave, are shown: the working plasma density of such antenna is much lower; the radiation is in a strictly axial direction; a small level of the side lobes of the RP; the RP 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.