Advances in Complex Fit Normalized Site Attenuation using log periodic dipole arrays

Complex Fit Normalized Site Attenuation (CFNSA) is an improved theoretical model for transmission between broadband antennas over a conducting ground plane. The CFNSA model overcomes the limitations of the original NSA model proposed by Smith, German and Pate, by allowing variable radiation pattern and variable phase center positions as a function frequency. The CFNSA model is well suited for log periodic dipole arrays (LPDAs) from 200 MHz to 1000 MHz because the variable phase centers and antenna pattern deviations relative to dipoles are the dominant source of errors. CFNSA has been shown to be effective to reduce systematic errors in the theoretical NSA model for LPDAs by up to 1 dB per antenna factor (or 2 dB in a site attenuation measurement). Antenna calibration and site validations above 1 GHz are increasingly addressed by using fully anechoic rooms (FAR). This makes earlier efforts to improve the CFNSA model above 1 GHz to be of limited application at present. This paper concentrates on improving the model for below 1 GHz. In this study, the antenna patterns are shown to be better represented by a piecewise function versus radiation angle, as compared to the earlier proposed functions, such as cosⁿ θ, or polynomial functions. Efforts are also made to clarify the mathematical process, so that CFNSA can be adopted by the antenna calibration standards, e.g. ANSI C63.5.