Radiation and Scattering of Spiral Antennas
Abstract
This study uses the method of moments with the Electromagnetic Surface Patch Code to analyze the radiation patterns and currents developed on a planar logarithmic spiral antenna. The study also outlines a method to analyze the radar cross sections of the antenna. Three computer modelling concepts are explored. The first and most simple is the thin wire model, which is a set of straight thin wire segments which approximates the shape of the antenna. The second concept explored is that of wire grid modelling. The purpose of this model is to check the transverse components of current along the strips of the spiral's arms. The last model is the patch model, which is introduced to best model the structural scattering component of radar cross section. Unfortunately, this model proved to be infeasible unless a very fast computer system is used. Results are given for the sum and difference modes of radiation. These results show that the thin wire model is adequate for radiation analysis, but the tips of the arms must be modelled with an impedance to absorb the outward travelling energy in the current. Without this loading, the arms will develop a standing wave pattern for the current distribution, which is inconsistent with experiments. Originator supplied keywords include: Spiral antennas; Direction finding; Induced currents; and Electromagnetic radiation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1984
- Accession Number
- ADA151929
Entities
People
- John P. Skinner
Organizations
- Air Force Institute of Technology