 Besides antenna measurements performed
on helicopter models, one of the major efforts of the AHE group
is numerical prediction of antenna radiation patterns, input impedance,
efficiency and gain. This process involves numerical simulations
of the individual antenna elements in the absence of the helicopter
as well as in the presence of the helicopter. The location of the
antenna is often optimized according to the specifications through
numerous computer simulations. The final predictions are validated
against measurements performed in the electromagnetics anechoic
chamber.
Design and analysis of antennas on complex structures such as helicopters
are performed using advanced electromagnetic codes. Most of these
codes are based on a full-wave formulation of the Maxwell's equations
and associated boundary conditions. Some other codes are based on
an asymptotic solution of the Maxwell's equations. The use of a
specific code usually depends on the particular application, expected
accuracy, computational time and frequency of operation. Some of
the codes we are currently using for the AHE consortium include
the following:
1. Finite-Difference Time-Domain method (NEWS, X-NEWS)
2. Finite Element Method (FEM, X-FEM)
3. High Frequency Structure Simulator (HFSS)
4. WirePlate (WIPL)
5. FEKO
6. Numerical Electromagnetic Code (NEC)
7. Electromagnetic Surface Patch (ESP)
8. NEWAIR (GTD based)
The overall simulation effort involves geometry modeling using CAD
(Computer Aided Design) software, interfacing with the above computational
engines, and visualization of the numerical results. These computer
codes are constantly updated and improved. In terms of hardware,
the AHE team uses powerful workstations such as SGI (Indigo 2 and
Octane), IBM and HP, in addition to Personal Computers (PC's).
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