An improved method for determining normalized site attenuationusing log periodic dipole arrays

摘要

A normalized site attenuation (NSA) measurement, made using LPDAfree-space antenna factors (AF) as specified in ANSI C63.4, has up to 3dB of systematic errors due to limitations in the current theory. TheANSI model fails to account for the log periodic antenna's radiationpattern and its active phase center position, which were shown to be thedominant effects causing these errors. An enhanced theoretical model isintroduced in this paper to take these two effects into account. In theenhanced model, antenna radiation patterns and active phase centerpositions are assumed to be unknown. At each frequency, the unknowns aresolved by fitting the theoretical magnitude or phase response to ameasured antenna response taken at different heights. The complex fitNSA (CFNSA) is then obtained by including the varied phase center andradiation pattern of the antennas under test. It is shown that the CFNSAmodel reduces the systematic errors in the current NSA to less than a dB