Generalized, field-corrected antenna measurements (GFAM)

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Antennas are the indispensable transducers between guided and free-space waves. They are key elements for every high-frequency wireless system, be it mobile communications or radar sensors.The antenna radiation characteristic is obtained empirically by a near- or far-field measurement using a second antenna as test antenna. However, it is important to ensure that the measurement result is independent of the test antenna’s radiation characteristic. In far-field measurements this is achieved by placing the antennas in the far field (R→∞) of each other. In near-field measurements an analytical test antenna correction based on its radiation pattern is used. Both methods assume an ideal environment and propagation path without reflections and field interaction. The test zone field distribution based on these assumptions does only approximate the real field distribution and is, hence, a source of measurement error.Replacing the analytically derived test zone field by a measured test zone field overcomes limitations of the classical antenna measurement model. The measured test zone field encompasses the contributions from all sources such as range reflections or leakage. Furthermore, the actual alignment and range geometry is also taken into account. Using the measured field entering the test zone, leads to a generalized field-corrected antenna measurement technique. Antenna properties can be precisely determined from measurements in an arbitrary but known test zone field. The methods of near-field and far-field antenna measurements are thereby combined in a single theory.The objective of this project is to develop and analyze comprehensively this generalized, field-corrected antenna measurement technique.The project will apply the spherical scanning theory to the test zone field measurement and will thus in turn generalize it so that the antenna measurement can be corrected with information about the incoming electromagnetic test zone field. A critical aspect of the measurement realization is the accuracy. A comprehensive sensitivity analysis of the technique is mandatory to derive requirements for the test zone field scanning setup. Preliminary investigations have shown that positioning errors and probe related effects are crucial. The gathered information will be used to build an optimized field scanning setup. The generalized, field-corrected antenna measurement technique will be tested extensively including an uncertainty analysis with measured data. Since the required measurement time for full sphere scans is a disadvantage, the accuracy achievable with incomplete spherical scans will be investigated for both the test zone field and the antenna measurement.This new methodology is expected to open new research avenues with plethora of possible applications. It will, for example, provide uncountable many degrees of freedom in the design of measurement systems and will increase the measurement accuracy of existing systems.