Dielectric Rod Waveguide Research Articles

Mode Cutoff Frequencies In Screened Dielectric Rod Waveguide (Correspondence)

The geometry of the screened dielectric rod waveguide is shown in Fig. 1. The theory for this waveguide has been solved by Beam and Wachowski for the case of /spl mu//sub 1/= /spl mu//sub 2/ = 1.

Power flow and negative wave impedance in the dielectric-rod waveguide

In most waveguides of practical interest the wave impedance in the direction of propagation of the wave is positive and its magnitude does not vary with position. It is shown that, in general, a guiding structure supporting a hybrid mode, i.e. a mode having axial components of both the electric and magnetic fields, can present a negative wave impedance. The case of the EH11 mode on a dielectric rod is then considered, and it is shown that for this mode the wave impedance is negative over part of the transverse plane and hence leads to regions of negative power flow if the usual interpretation of the Poynting vector is employed. The total power flow, however, is still positive, since the negative power density and the negative wave impedance occur only in a restricted part of the cross-section.The orthogonality of the fields is also discussed, and it is shown that for hybrid modes the transverse electric and magnetic fields are not at right angles to each other.

Launching Efficiency of Wires and Slots for a Dielectric Rod Waveguide

This paper describes an experimental investigation of surface wave launching efficiency. Wires, rings, and slots are considered as exciters of the HE/sub 11/ mode on a dielectric rod image line. A formula is derived which relates the efficiency of a launcher to its impedance as a scatterer on the surface waveguide. Efficiency is obtained by using this formula and also by applying Deschamps' method for determtimg the scattering matrix coefficients of a port junction. Graphs are presented which illustrate the variation of efficiency with the dimensions of the launchers and with the parameter lambda/sub g//lambda, the ratio of the guide wavelength to the free space wavelength.

A technique for controlling the radiation from dielectric rod waveguides

This paper describes a technique for controlling the radiation from a dielectric rod waveguide by placing obstacles or antenna elements at appropriate points along the waveguide. The HE_{11} mode on a dielectric rod was used to excite concentric rings and radial wires. The coupling of the obstacles to the HE_{11} mode was determined by constructing an image line with a slotted section for impedance measurements. This information was used to design several antenna arrays with different types of patterns. The measured patterns were very satisfactory.

The elliptic surface wave

In this paper formulae are derived for the surface wave of the elliptic cylinder. The mode described is an E-mode that possesses the evanescent structure in the transverse plane of the cylinder. The elliptic surface wave is shown to be similar in some respects to the surface wave associated with single wire transmission lines of circular symmetry to which form the elliptic surface wave degenerates when the eccentricity of the ellipse tends to zero. In a separate section a slightly deformed circular guide is discussed in detail and it is shown that the performance of a circular guide is substantially unaffected by slight deformation of its geometry. The last section of the paper deals with different types of elliptic guides that are likely to be encountered. The elliptic dielectric rod waveguide and a corrugated elliptical guide are typical examples, while the homogeneous metal guide and the dielectric coated perfectly conducting elliptical rod are analysed in detail.