A new meta-surface structure (MSS) with a near-zero refractive index (NZRI) is proposed to enhance the performance of a square loop antenna array. The main challenge to improve the antenna performance is increment of the overall antenna volume that is mitigated by assimilating the planar NZRI MSS at the back of the antenna structure. The proposed NZRI MSS-loaded CPW-fed (Co-Planar Waveguide) fo...

NASA Langley Research Center (LaRC) has pursued the development of tensioned membrane antenna technology for several years. For many applications, it is desirable to have space-based antennas which are very large. As the physical size increases, antennas constructed of conventional materials quickly become too bulky and heavy to be practical for space applications. For some of these application...

A Rectangular Dielectric Resonator Antenna (RDRA) is theoretically analyzed using the Conventional Dielectric Waveguide Model (CDWM), numerically simulated using the High Frequency Structure Simulator (HFSS) based on the Finite Element Method (FEM) software package and experimentally investigated with the consideration of the fundamental mode TE 111. Antenna parameters under investigation inclu...

Prism coupling and reflection spectroscopy are used to characterize bound modes within composite right/left handed terahertz metamaterial waveguides. The cavity antenna model is used to understand the polarization dependence of the radiative coupling to TM00 and TM01 waveguide modes. Furthermore, the cavity model along with transmission-line theory is used to derive a surface impedance model fo...

An efficient design procedure for a radial waveguide feed network for an array antenna, whose radiating elements are pin-fed, is presented. A model of the feed network is considered and relevant design parameters are expressed by simple analytic terms. To facilitate the design of the feed, a useful coupling chart for a pin-loaded radial waveguide is suggested. It shows graphically the dependenc...

In this study, an efficient power combiner for mm-wave frequency transmitters is investigated. The based on a parallel plate waveguide (PPW) excited with multiple feeds. Doherty scheme also integrated in the proposed concept, to increase efficiency of amplifiers when implementing amplitude modulation. advantage PPW respect other concepts, example, ones substrate-integrated waveguide, wider band...

this paper presents a miniaturized open-ended rectangular waveguide antenna radiating below the cut-off frequency of the waveguide with a large bandwidth. Waveguide miniaturization is achieved by periodically loading the antenna with electromagnetic metamaterials consisting of infinity shaped resonators. The metamaterial cell is designed to have a high effective dielectric permittivity in the f...

The current work covers the evaluation of ultrasonic and electromagnetic (EM) techniques applied to temperature measurement and flow characterization for Enhanced Geothermal System (EGS). We have evaluated both ultrasonic techniques and microwave radiometry for temperature gradient and profile measurements. A waveguide-based ultrasonic probe was developed to measure the temperature gradient. A ...

Hollow-waveguide slot array antennas [1] have been widely used in the milli-meter band since they do have neither radiation loss nor dielectric loss. Furthermore, they have been developed especially for military application such as radars. For commercial application such as fixed wires access system, mass production at low cost has been required and single layer hollow-waveguide slot array ante...