Ultra light-weight antenna system for full polarimetric GPR applications

Abstract

International audienceThe motivation to develop an ultra light-weight antenna system was driven by a space borne radar application. The experiment ldquowater ice and subsurface deposit observations on Marsrdquo (WISDOM) is a ground penetrating radar (GPR) selected to be part of the Pasteur payload on board the rover of the ExoMars mission. Among the Pasteur panoramic instruments on the ExoMars rover, only WISDOM can provide a view of the subsurface structure. WISDOM is the first GPR on a planetary rover. It has been designed to characterize the shallow subsurface structure of Mars. WISDOM will for the first time give access to the geological structure, electromagnetic nature, and, possibly, hydrological state of the shallow subsurface by retrieving the layering and properties of the buried reflectors. It will address important scientific questions regarding the planet's present state and past evolution. The measured data will also be used to determine the most promising locations to obtain underground samples with the drilling system mounted on board the rover. The instrument's objective is to get high-resolution measurements down to 2 m depth in the Martian crust. The radar is a gated step frequency system covering a frequency range from 500 MHz to 3 GHz. The radar is fully polarimetric and makes use of an ultra wideband antenna system based on Vivaldi antenna elements. The paper describes antenna requirements to fulfil for this very specific GPR application and it gives an overview about the light-weight design and its realization. Simulated and measured antenna performance is compared in this paper. Test measurements were performed in permafrost regions on earth

Compact Dual-Polarized Vivaldi Antenna with High Gain and High Polarization Purity for GPR Applications

“…Dual-polarized Vivaldi antennas are generally realized by orthogonally inserting two Vivaldi elements into each other, forming a cross shape [ 20 , 21 , 22 , 23 , 24 ]. The feeding lines of the elements need to be slightly shifted to avoid their intersection and to improve port isolation.…”

“…Microstrip-to-slot balun [ 22 ] and two-stage quarter-wave balun [ 23 ] have been used to achieve a broad bandwidth. An ultra-lightweight dual-polarized antenna design was developed using glass fiber-reinforced epoxy with copper layers [ 24 ]. Most of the dual-polarized antennas presented have a wide operating bandwidth with a moderate port isolation level of around 25 dB, cross-polarization discrimination of less than 20 dB, and a moderate averaged gain of about 5.5 dBi.…”

Advance of WISDOM GPR antenna for ExoMars 2018 mission

“…The GPR antenna system described in this paper is the consequent progression of former developments [1,2] incorporating changed requirements and further optimizations. Main constraints are the mass, the temperature range as well as the ultra-wide band demand.…”