"Optimized Antenna Element Excitations for Ground Based Controlled Reception Pattern Antenna System"

Abstract

"Controlled Reception Pattern Antennas (CRPA) are widely used for reception of GNSS signals and for rejecting interference by steering nulls in their directions. A simplified system model of a ground based CRPA is considered with seven isotropic antenna elements. Six antenna elements are placed at the six corners of an imaginary hexagon, and one antenna element is placed at its centre. The centre frequency is considered to be 1.575 GHz. The edges of the hexagon as well as the distance of every vertex of the hexagon from the centre are half wavelength long corresponding to the centre frequency. Since isotropic antenna elements are considered, the pattern for any set of excitations is the same for z>= 0 as well as for z<=0. Since ground based CRPA is considered, interference is expected only for directions above z = 0. For a set of elevation and azimuth angle combinations (elevation angle varying from 2 degrees to 90 degrees and azimuth angle varying from 2 degrees to 90 degrees), optimal antenna element excitations are computed using nature inspired evolutionary optimization algorithm to obtain the nearly best null in that direction. Since the distance between any pair of antenna elements is greater than or equal to half wavelength, the mutual impedance effects are considered negligible. Two datasets are provided. One dataset contains the Cartesian coordinate positions of the antenna elements. The second dataset contains the antenna element excitations (amplitude and phase excitations for each of the seven elements) so that a null can be obtained for a given direction (specified by a combination of elevation and azimuth angles). Only one interfering signal is assumed."