An investigation of two broadband HF shipboard communication antennas

Abstract

The capability of an electromagnetic radiating system depends on its ability to operate effectively in a complex environment, where its pattern performance can be limited by pattern distortion effects. On a modern military ship, this task is complicated by the large number of systems that are competing for prime locations. It is recommended, therefore, that a given situation be studied systematically, looking at individual pieces of the problem separately and developing intermediate conclusions. This thesis investigates computer antenna models to improve shipboard antenna systems performance for HF, VHF and UHF bands. Possible improvements for present ships might lead to the reduction of the number of existing antennas. Two different computer models are investigated for various geometry: (1) a 'multi-wire' whip antenna and (2) an inverted cone antenna. Both are modeled by using wire grids, in the Numerical Electromagnetics Code (NEC). Average power gain, input impedance and radiation patterns of most of the models are presented, in the frequency range of 4-300 MHz. It is seen that good performance occurs for the inverted cone antenna over perfect ground in the frequency range 4-152 MHz and over a wire grid box (approximately a ship's shape), for 8-48 MHz.