Improvement of the NEC code´s upper limit and pattern prediction of a helicopter structure

The capacity of the NEC (numerical electromagnetics code) has been doubled by modifying its file type of matrix storage. The loss of I/O (input/output) access speed due to using a direct-access file to store an out-of-core matrix has been compensated by reorganizing the sequence of matrix block factorization. Some factors that are important to the geometry modeling of electrically large complex structures have been considered in an attempt to balance the numerical accuracy and computational efficiency. The mesh generating program GEOM is introduced, and used to compute the antenna patterns of a 1:7 helicopter model made up of nearly 6000 elements. The predicted antenna patterns of the helicopter are compared with measurements at 1.492 GHz. The results showed good agreement with measurements.<>