P2ww'd'el e @@& .4 paraboloidal reflector antenna fed by a pyramidal horn has found widespread application in radar and communication engineering. However, the reflector antenna has very useful characteristics when it is fed or illuminated by two or four-conductor transmission lines. We have am.lyzed, designed, fabricated, and tested a reflector antenna fed by a pair of conical transmission Iin...

The long-term scientific objective of this project is to increase our understanding of sound propagation in ocean bottom sediments, including water-saturated sands and muds, gas-bearing sands and muds, and sediments which support seagrass. This in turn benefits buried object detection, sonar operation and acoustic communications in shallow water. The proposed study includes continued analysis o...

A modal decomposition method for computing the solution to an eddy-current problem is presented. Modes are computed using the finite element method and the modes produced are simplified to a magnetic polarizability dyadic in the form of a singularity expansion. This reduced form is a very compact and easily-implemented model for the scatterer’s reaction to an arbitrary magnetic field. Due to sc...

Ground Penetrating Radar (GPR) is a promising sensor for landmine detection, however there are two major problems to overcome. One is the rough ground surface. The other problem is the distance between the antennas of GPR. It remains irremovable clutters on a sub-surface image output from GPR by first problem. Geography adaptive scanning is useful to image objects beneath rough ground surface. ...

We present here a recently developed approach of Terahertz Time Domain Spectroscopy (THz-TDS) and its application on rapid and precise Non-Destructive Testing (NDT) of composites and concealed objects. Electromagnetic radiation of THz frequencies can penetrate dielectric materials without ionizing effect; it allows the contact-free testing of dielectric volumes or buried metallic surfaces and c...

This study reports an adaptation of a parametric echosounder system using 15 kHz as secondary frequency to investigate the angular response of sub-bottom backscatter strength of layered mud, providing a new method for enhanced acoustic detection of buried targets. Adaptions to achieve both vertical (0°) and non-vertical inclination (1– 15°, 30°, 45° and 60°) comprise mechanical tilting of the a...