128 elements switched wideband antenna for Land-mine detection radar

Description

We have designed, made and measured a 7 m linear antenna operating between 2 and 4 GHz for land-mine detection radar application.In 20013, Chile and France signed a co-operation agreement for the promotion and development of systems that help to get rid of the mines in the desert of North-Chile. The Electromagnetic (EM) Non-Destructive Evaluation (NDE) sys-tems, like radars, have been intensively investigated for this application becau-se they enable to scan the area without touching the land mines. Radars locali-ze and identify the mines, and therefore enable a safe removal, but the problem remains challenging because in-fl ight radar have to compromise between the transporter carriage capacity and the high resolution requirements linked to the small size of the land mines. Therefore we have settled the design requirements to (7*7*7cm) resolution with a scan area of 4km2 per day for a carrier fl ying 10m below the ground. High resolution is im-plemented with SAR postprocessing.We take advantage of the transporter's displacement for getting the resolutionalong the fl ight path, resolution in the other dimension being obtained with the large 1D antenna.We go through design, fabrication and evaluation steps of the antenna. It con-sists of 128-switched elements of loaded Vivaldi type arranged in 16 sub-arrays. The feed of the antenna consists of a swit-ching network that operates in three sta-ges: 16*8 SP8T on the fi rst one, 2*SP8T on the second, and 1*SP2T at the input. The switching network is embedded in a metallic rail placed below the radiating elements. The rail is designed onpurpose for avoiding unwanted coupling and back-ward radiation between the radiating ele-ments and the coupling network. Antenna is coated with a Tefl on radome that also acts as air-tightness structure. We have fi rst conducted the overall checking of the antenna. Then, we have successfully detected a dielectric block placed on a metallic plate(assumed as severe environment). For this, we use a sub-array of 8 elements driven by the radar front-end that will be further used on board. We use a neutra-lization technique for the front-end calibration.

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International audience

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