Removal of unwanted structural interactions from antenna measurements

Abstract

Operation of antennas deviates from free-space or intended deployment conditions because of interactions with neighboring objects (like support structures), and often with its own feeding (like in balancing issues) [1, 2]; the problem is all the more evident in compact antennas. This problem is important in measurement setups. Undesired interactions affect antenna input impedance and/or radiation pattern, possibly invalidating lengthy measurements (not to mention poor performance upon device deployment). This work addresses the issue of removing these unwanted effects from measured data (typically in near field), so that one synthetically regains the desired reference conditions (e.g. free-space operation) in the processed data. This class of problems is well illustrated by the undesired interaction of the antenna under test (AUT) with the feeding cable, which has received considerable attention in literature [1, 3, 4]. Some of the techniques employed to cope with this situation involve the use of devices during the measurement stage: baluns, electro-optic transducer and chokes, and computer simulation to find the best placement of these.