A Novel Approximation Algorithm For Calculating Three-Dimensional Radiation Patterns Of Antennas

In this thesis, the approximation algorithm for calculating the three-dimensional (3D) radiation patterns of antennas is studied. Getting the 3D radiation patterns of antennas by the measurement is a troublesome and may be an impossible work. Generally the measured radiation patterns only in several cuts, e.g. E- and H-planes, can be obtained. The directivity of the antenna may be approximately calculated based on the radiation patterns in the E- and H-planes, however its calculation accuracy is always restricted by the selected experiential formula. Thus some approximation algorithms are needed to resume the 3D radiation patterns based on the obtained E- and H-plane patterns. In addition, the accurate directivity of the antenna could be calculated according to the obtained 3D radiation pattern.This thesis presents a novel approximation algorithm first. At the point of interest, the approximated antenna gain is calculated by the weighting functions, and the radiation patterns in the E- and H-planes. Here, the weighting functions are computed according to the distances between the point of interest and the E-/H-plane. For the omni-directional antennas and directional antennas, 3D radiation patterns are calculated by using the proposed algorithm. The error differences between the obtained results and the theoretical patterns are also calculated. Then the absolute errors are compared with those provided by two existing algorithms. The results of these comparisons indicate that the proposed algorithm exhibits lower approximation errors, which can be used for calculating the 3D radiation patterns of antennas efficiently. Based on the generated three-dimensional radiation patterns, the directivities of these antennas are also calculated. The obtained directivities are in good agreement with the theoretical values.Moreover, the Vivaldi antenna used as the element of the ultra-wideband dual polarized antenna array for ATR (Antenna Test Range) system is designed. Two Vivaldi antenna elements are simulated and designed, one operates at 0.6~8GHz band, and the other operates at 1~12.5GHz band. Two different types of slot line are used to realize these two antenna elements respectively. These two antenna elements are then fabricated and measured. The simulated and measured results are also given. These two Vivaldi antenna elements meet almost the design requirements.