Implementation of the Numerical Electromagnetic Code (NEC-2) for Modeling the VOR (Very-High-Frequency Omni-Directional Range) Navigation System in the Presence of Parasitic Scatterers.

摘要

A computer model has been developed that estimates bearing error for a VOR airborne navigation system operating in the presence of small, parasitic scatterers such as antennas, antenna masts, and guy wires. This model, which is written using FORTRAN 77, interacts with an unmodified version of the Numerical Electromagnetics Code (NEC-2) to obtain the pertinent scattered-field data. These data are then used to calculate the composite field, and indicated bearing, at the airborne receiver location. Modeled results consist of plots of bearing error versus 'true' bearing. Comparisons of modeled and measured data are presented. The azimuth angle of an aircraft with respect to a VOR station is determined by the phase of the received audio sinusoid generated by a limacon radiation pattern that rotates in space due to appropriate time varying phasing between four Alford loop antennas.