Electromagnetics
Modified NEC
NEC is a user-oriented computer program that can help design or analyze the electromagnetic characteristics of an antenna or other metallic structure. The code solves a set of integral equations for the currents induced on the structure by incident fields or sources. One integral equation models smooth surfaces, another, a wide variety of structures. NEC can model radiating systems in free space or over ground, which may conduct either perfectly or imperfectly. The structure may be isolated from the ground plane or may touch or penetrate the earth/air interface. The model may include lumped-element loading, perfect or imperfect conductors, non-radiating networks, or transmission lines interconnecting parts of the system.
Excitation may include plane waves of either linear or elliptic polarization or voltage sources located at arbitrary points on the structure. The output may consist of currents or charges on wire segments, radiation patterns, near and far electric and magnetic fields, and antenna feedpoint parameters.
Several options are available for modeling antennas that are located near the ground. Either perfect or imperfect ground may be specified, with the user supplying values for the conductivity, sigma, and relative permittivity, or in the case of finite ground. The finite-ground solution may be performed in one of two ways, either as a reflection-coefficient approximation (fast but less accurate), or by using a Sommerfeld-Norton method (requiring more memory but more precise).
NEC has been constantly developing since the early 1970s, with many improvements and additions, all in the present code. We are now restructuring it using structured programming techniques. The code has been greatly benefited DoD and DOE users, at both LLNL and other centers.
Successful and efficient use of the code’s features requires excellent familiarity with it. We have involved ourselves with the code’s phases of development and have that familiarity.
Moreover, we have developed a user-friendly version of the code, along with accessory packages. The complete package can operate on a suitable 80486-based machine. All necessary pre- and post-processing software programs are developed, well-documented, tested, and validated.