| In a dipole array backed by a ground plane there exists an inductance effect which is mostly introduced by the ground plane and, to a lesser extent, by the element itself. This inductance can be compensated for by inserting a series capacitance between the tips of neighbouring elements. The result of this compensation will be a near-constant current along the elements of the array which will imitate the infinite current sheet array introduced by Wheeler. The series capacitances between the tips of neighbouring elements mentioned above can either be realised by inserting physical capacitors or by increasing the inherent capacitance present between neighbouring elements by careful placement of the array elements.
This square meter DDA prototype consists of a 10x10x2 array of densely packed printed dipoles above a ground plane. Array elements are connected in parallel-pairs and fed differentially through a common-mode suppressing feed-board.
The work forms part of the PhD work of Jacki Gilmore from Stellenbosch University in collaboration with ASTRON through MIDPREP. The PCB manufacturing was done in-house by Albert van Duin and the mechanical design and manufacturing was done by Sjouke Kuindersma. The measurements will be done at Stellenbosch University in the near future.