Complex fit normalized site attenuation using complex magnitude and phase patterns

Due to the diverse designs in log periodic dipole arrays (LPDAs), it is impractical to develop a set of unified correction factors for all types of LPDAs in site attenuation measurements. Even for log antennas with similar frequency ranges and appearances, large variations can be expected in their patterns and phase center positions because of the differences in the feed sections, boom sizes, relative spacings (a) and scale factors (τ) (Lo, Y.T. and Lee, S.W., 1988). Complex fit normalized site attenuation (CFNSA) has been used successfully by allowing phase centers to move along the centerline of the antenna boom, and by using analytical functions to represent radiation patterns. Approximately 1 dB improvement in antenna factors is observed over the ANSI C63.4/5 model for horizontal polarization. Similar improvements are shown in the vertical polarization. The paper also studies a method that may extend the frequency range by permitting phase centers to vary off-axis, or by using angle dependent phase center positions (which is equivalent to using complex magnitude and phase patterns).