The ACE-DTU Planar Near-Field GPR Antenna Test Facility



Hans-Rudolph Lenler-Eriksen
Peter Meincke


January 2003 - December 2005 


Technical University of Denmark and Antenna Centre of Excellence (ACE).


The ACE GPR antenna test facility has been established in order to enable comparisons of GPR antenna radiation characteristics in a controlled and consistent environment. The facility consists of a soil-filled wooden box with length 3.8 m, width 3.3 m, and depth 1 m.

Above the box a mechanical-scanning system is installed, able to move the GPR Antenna Under Test (AUT) along two orthogonal directions in a plane parallel to the air-soil interface. The scanning of the AUT is performed by two motors connected to associated motor controllers.



At the center of the box a probe is buried at a depth of 20.3 cm. The probe is a loop antenna with radius 17.8 mm, made of semi-rigid cable UT-141A with wire diameter 3.5 mm and total length 5 m. The figure to the righgt shows the probe mounted on a supporting plastic rod. The semi-rigid cable is connected to one port of a HP8753A vector network analyzer, and the other port is attached to the AUT through a phase-stable Sucoflex 104PA coaxial cable. The HP8753A and the motors of the scanning system are controlled by a PC with a MATLAB GUI. For each desired position of the AUT, the network analyzer measures the scattering matrix parameter S12, from which various information about the AUT can be extracted. 



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The Figure to the left shows the mounting arrangement for the AUT. The cylindrical rod, to which the AUT is attached, has a diameter of 22 mm. The rod has a number of holes for a pawl of diameter 6 mm. The pawl is used to set the distance from the AUT to the air-soil interface, as well as to rotate the AUT to control the measurement of two orthogonal polarizations.