'Unknown' by Unknown - Page 3 of 6

XGTD: A Ray-Based Approach

(continued from Page 2)

Geometric Model

Transmit and Receive Antenna Models

XGTD can be applied to a wide range of complex shapes

One of the strongest features in XGTD is the fidelity with

including curved surfaces. There is no need to first construct

which the directionality and polarization of the transmitting

an approximate geometric model from simpler shapes, such

and receiving antennas are accounted for in the calculations.

as plates, cylinders,

The antennas can either be mounted on the surface of a

spheres, or cones,

structure, or they can be placed above the surface. Any

since XGTD applies

number of transmitting and receiving antennas can be

diffraction theory

modeled in a single simulation. Antenna arrays can either be

directly to a model

modeled as a collection of individual elements, or it can be

consisting of planar

modeled using a single pattern for the entire array.

facets, which is exactly

what is found in most

The radiation pattern of the antenna by itself can be evaluated

CAD files. As with

first with XFDTD, and then imported into XGTD to determine

XFDTD, XGTD can

the effects of the structure on which the antenna is mounted.

import geometric data

The relatively simple format used to import data also allows

from a wide range

for antenna pattern data to be imported from full wave EM

of CAD file formats.

However, if a simple

shape is all that is required, XGTD also has an object editor for

creating such shapes. The more powerful XFDTD geometric

modeling tools can also be used to create more complex

structures. Once the geometric model has been created, any

number of electromagnetic material properties can quickly be

assigned to the facets, either individually or in groups.

Primary Applications

The applications for which XGTD is appropriate generally

fall into one of the following five categories:

· Antenna radiation patterns

· Antenna coupling and interference

· Scattering and radar cross section analysis

· Propagation in areas with many large obstructions

· Propagation in anechoic chambers

solvers using methods other than FDTD. XGTD also has the

large number of built in models using frequency dependent

A few typical applications of XGTD are illustrated in the

approximations for the radiation patterns for a number of

figures below. Calculations such as these can often be run in

common types of antennas, including monopoles, dipoles,

less than an hour.

patches, apertures and horns.

The software has a number of special features for simulating

Overview of Capabilities

EM wave propagation inside an anechoic chamber using

frequency dependent reflectivity coefficients for many

XGTD's many capabilities include the following:

commercially available pyramidal and wedge absorber types.

· Edge diffraction from metallic and non-metallic surfaces

· Creeping waves on convex curved surfaces

· Compute far field antenna gain patterns

· Frequency dispersion of wideband signals

· Time and frequency domain output

· Thin lossy dielectric coatings and plates

· Ray path and time domain field visualization

· Model transmit and receive

antennas by 3-D antenna

patterns with complete

polarization and phase

information

· Linear and circular polarized

antennas

· Very fast computations after

changing waveforms and

antennas

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