Impact of experimental calibration on the performance of conventional direction finders

An important idea for improving the practical performance of direction finding (DF) systems involves the use of calibration tables. These are generally based on experimental measurements of systemic errors obtained using a known signal to illuminate the antenna. However, the accuracy of the calibration data, and therefore that of the system, is affected by various error mechanisms. This paper uses full-wave analysis to investigate the errors resulting from a spherical wave front and from ground reflections when experimental methods are used to produce calibration data. These results show that the distance between the calibration source and the DF system should be larger than previously believed and that additional restrictions on the operating frequency ranges of the DF system may be necessary when experimental calibration data is used.