Small Antenna Design
Keeping mathematics to the absolute minimum, this guide describes the theory behind effective small antenna design while providing design techniques and examples for small antennas for different operating frequencies.
TABLE OF CONTENTS Small Antenna Design
Chapter 5: Programmed Modeling
5.0 Introduction
As is often said, numerical experiment and design require a lot of trips around the modify-run-examine loop. In the last chapter, I showed how the SY command in 4nec2 can be used to simplify the modify step. In the next section, you will see that there are NEC commands that generate a whole set of wire descriptions. After that, I describe using a programming language, C++, to generate a NEC input file from a relatively simple file that describes the geometry, operating conditions, and desired output.
5.1 Using Wire-List Generators in NEC
Simple antenna structures can be readily described and altered in a direct NEC-command text file. A more complex structure, such as a spiral antenna on a box, would take a large number of GW commands, and altering the geometry would require altering a great many GW commands. The writers of NEC recognized this problem and provided some commands to make this job easier. You have already seen the GA (Geometry Arc) command in the last chapter. The first I describe here is the GM (Geometry Move) command. This command generates a specified number of duplicates of a previously described structure that are rotated and translated incrementally from each other and the original. Suppose you want a wire list to describe a short monopole on a PEC ground, with four radials at the top. You have to have a GW line to specify the vertical wire and another GW line to specify the first radial. Then you...
Copyright Elsevier Inc. 2006 under license agreement with Books24x7
