The paper investigates the efficiency of transformation of traveling wave into radiation in longitudinally inhomogeneous plasma cylinder. The plasma is limited by a dielectric shell of finite thickness. The investigation involves the use of the method of spectral field expansion in terms of a set of functions including the surface and spatial waves of plasma cylinder with dielectric shell. A system of integro-differential equations for expansion coefficients has been obtained. These coefficients determine the amplitudes of transmitted, reflected, and scattered waves and also radiation patterns (RP). The system of equations is solved for the case of strong longitudinal variation of plasma density. The relationships of the transformation coefficients of surface wave energy as a function of the plasma density gradient, electrical length of section of plasma inhomogeneity, the electric radius of plasma cylinder, dielectric permittivity, and the thickness of dielectric were calculated. The fraction of surface wave energy that is transformed into radiation at acute angles can amount to 35%. The resultant narrow-beam RPs have only one lobe. The radiation maximum fits into an angle of several degrees with respect to the direction of surface wave propagation. With an increase of plasma density gradient, the lobe width is reduced, while its position shifts to 0°. The impact of dielectric properties on radiation characteristics has been also investigated.

中文翻译：

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等离子介电行波天线

本文研究了行波在纵向非均匀等离子体圆柱体中转化为辐射的效率。等离子体受到有限厚度的介电壳的限制。该研究涉及在一组函数方面使用谱场扩展方法，包括具有介电壳的等离子体圆柱的表面和空间波。已经获得了膨胀系数的积分微分方程组。这些系数决定了透射波、反射波和散射波的幅度以及辐​​射模式 (RP)。该方程组是针对等离子体密度的强纵向变化的情况求解的。表面波能量转换系数与等离子体密度梯度的关系，计算了等离子体不均匀截面的电长度、等离子体圆柱的电半径、介电常数和电介质的厚度。以锐角转化为辐射的表面波能量的比例可达 35%。由此产生的窄波束 RP 只有一个波瓣。辐射最大值与表面波传播方向成几度角。随着等离子体密度梯度的增加，波瓣宽度减小，而其位置向0°移动。还研究了介电特性对辐射特性的影响。以锐角转化为辐射的表面波能量的比例可达 35%。由此产生的窄波束 RP 只有一个波瓣。辐射最大值与表面波传播方向成几度角。随着等离子体密度梯度的增加，波瓣宽度减小，而其位置向0°移动。还研究了介电特性对辐射特性的影响。以锐角转化为辐射的表面波能量的比例可达 35%。由此产生的窄波束 RP 只有一个波瓣。辐射最大值与表面波传播方向成几度角。随着等离子体密度梯度的增加，波瓣宽度减小，而其位置向0°移动。还研究了介电特性对辐射特性的影响。