Numerical modeling for direction finding applications

The Numerical Electromagnetic Code (NEC) has proven to be an excellent tool for the design and evaluation of complex direction finding (DF) antenna systems. Research at Southwest Research Institute (SwRI^®) has focused for many years on the installation of distributed DF arrays on cluttered platforms in which the platform becomes an integral part of the DF array. For the past 8 years, SwRI has developed a concentrated research program in the use of numerical models for these applications, in particular HF DF on large naval ships. A logical choice for this application was NEC. In particular, research has been conducted in the following areas: 1) the ability of numerical models to predict basic DF array characteristics such as array response beamwidth and sidelobe levels; 2) the comparison of complex numerical responses to real world measurements; 3) techniques to evaluate numerical model accuracies; 4) the use of numerical models to develop DF algorithms; 5) the use of numerical models to reduce data collection; 6) optimization of DF antenna elements, their placement and their array geometry.