Complex Mode Dispersion Characteristics of Dielectric Loaded Radially Thick Helix

Abstract

In this article, a generalized analytical and computational numerical theory, for both the guided and leaky modes, has been developed to investigate the dispersive behavior of dielectric-loaded radially thick helix (DLRTH). The complex root finding Muller iterative algorithm is used to compute the normalized phase and attenuation constants. A unique way has been adopted for the classification of HE and EH hybrid modes present in the proposed structure, and based on that, for the first time, we report that this structure shows physical leaky and trapped surface wave propagation characteristics. Furthermore, in the guided mode, it is seen that both slow wave (SW) and backward wave (BW) exist due to the inherently skewed boundary of the helical geometry. The parametric study of helix radius and pitch angle as well as dielectric constant gives optimized parameter values, which help in designing the proposed structure in the desired mode and at the desired frequencies. Moreover, it is reported that pitch angle aids in controlling and figuring out the leaky mode bandwidth. The analytical cum numerical MATLAB results are successfully verified using CST Microwave Studio computational analysis and are found to be in good agreement. The improved characteristic equations for guided mode find practical applications in the design and performance evaluation of the SW structure (SWS) for the phase delay applications. The leaky mode will find application for beam scanning helical antennas.