Kepei Sun

Analysis of rectangular waveguide containing uniaxial medium with aligned optic axis

A rectangular waveguide filled with uniaxial medium is treated. Different orientations of the optic axis are considered. Results of wave decompositions with respect to the optic axis are presented and compared with conventional transverse-to-z solutions. Computations show that the effect of anisotropy not only changes the field distributions, but also leads to changes of dominant modes in the waveguide.

High directivity negative-resistance composite right/left-handed leaky-wave antenna

A novel negative-resistance composite right/left-handed (NR-CRLH) leaky-wave antenna (LWA) is presented. The conventional CRLH unit cell is made configurable by using the negative resistance (NR) circuit. An LWA constituted by the proposed unit cells allows manipulation of the current distributions over the radiating surface of the antenna. Consequently, the radiation pattern, and directivity can be adjusted to the desired values. The fabricated prototype of the proposed NR-CRLH LWA demonstrates enhanced directivity compared to the conventional all passive CRLH LWA. The proposed method provides simple current amplitude control while minimally influencing the desired dispersive/transmission characteristics of the LWA.

Rectangular waveguide containing uniaxial medium with tilted optic axis in sidewall plane

Solutions of a metallic rectangular waveguide filled with uniaxial medium are obtained with a new approach. The direction of the optic axis is tilted but lying in one of the sidewall planes of the waveguide. The formulation is based on decomposition into ordinary and extraordinary waves. The proposed method seeks wavenumbers of supported travelling modes, and is also able to calculate both cutoff frequencies and field magnitudes of every mode supported.

Hybrid mode analysis of rectangular waveguide filled with uniaxial media with tilted optic axis lying in sidewall planes

Computational results of the cutoff frequencies of the hybrid modes in a rectangular waveguide filled with the uniaxial medium are presented. The optic axis orientation of the inserted uniaxial medium is tilted from any of the coordinate axes but lying in one of the sidewall planes of the rectangular waveguide. The calculated results not only show the changes of the cutoff frequency of the lowest hybrid mode as the constitutive parameters and the waveguide dimensions change, but also justify the correctness of the computational process and the formulations.

Ray Tracing Theory in a Radially Uniaxial Sphere

Ray tracing theory for a radially uniaxial dielectric sphere is presented in this communication. Reflection and transmission of the plane waves obliquely incident on the spherical interface between air and uniaxial are briefly examined and the general formulations for phase velocities as well as the refractive indices of the ordinary and extraordinary waves propagating in a radially uniaxial medium are investigated. The ray tracing method is implemented for both ordinary and extraordinary rays and the results are applied to evaluate the propagation paths and arrival times of the shortcut wave returns appearing in the transient backscattering response of a uniaxial dielectric sphere. The effect of the variation in relative permittivity on the arrival times of shortcut waves is studied. The results of the ray tracing method are compared with those computed using the Mie and Debye series solutions with good agreement.

Field distributions of the hybrid modes in rectangular waveguides filled with uniaxial media with tilted optic axis lying in sidewall planes

The field distributions of various modes in rectangular waveguides filled with uniaxial media are presented. The presented cases include aligned cases when the optic axis is parallel to one of the coordinate axes and the tilted cases when the optic axis is not parallel to any of the coordinate axes but still lies within one of the two side-wall planes. In the aligned uniaxial-z case the analytical solution is compared with the results of the dyadic greens functions (DGF). In other aligned cases the field distributions of selected extra-ordinary wave modes are also plotted and to be compared with the isotropic case. In the tilted cases, the field distributions of the hybrid modes which are coupled ordinary-waves and extra-ordinary waves show asymmetry which is not seen in the aligned cases and isotropic case. The validity of the hybrid mode field plots are verified by comparing a limiting tilted case with analytical solutions of an aligned case.

Miniaturized quasi-Yagi antenna based on metaedge reflector

This paper presents a novel quasi-Yagi antenna (QYA) design in which the conventional PEC reflectors are replaced by metaedges, one-dimensional artificial perfect-magnetic-conductor-like edges. The unique reflection property of the metaedge helps miniaturize overall dimensions of the QYAs while maintaining high-gain performances. We demonstrate that the separation between the radiators and the reflectors in the metaedge based QYAs can be reduced to be much less than a quarter-wavelength. The radiative gain of 5.2 dBi is achived even without the addition of the directors.

Shortcut waves in a radially uniaxial sphere

Ray tracing theory for a uniaxial dielectric sphere is presented in this paper. The ordinary and extraordinary rays and waves in a uniaxial medium are studied. The reflection and transmission of the wave at the air-uniaxial boundary surface are investigated. The propagation path and the arrival time of the shortcut wave return in a uniaxial dielectric sphere are computed. The results are in good agreement with those provided by the Mie and Debye series solutions.