Monolithic Paper-Based & Inkjet-Printed Technology for Conformal Stepped-FMCW GPR Applications First Results Anya Traille, Antony Coustou, Herve Aubert CNRS, LAAS 7 Avenue du Colonel Roche F-31400 Toulouse, France atraille@laas.fr Sangkil Kim, Manos M. Tentzeris Electrical and Computer Engineering Georgia Institute of Technology Atlanta, Georgia, USA ksangkil3@gatech.edu Abstract—The first design for a monolithic FMCW Ground Penetrating Radar system integrated onto an inkjet-printed patterned flexible substrate is presented. Using advanced materials printing and surface mounting techniques, each signal stage, including the antennas, can be built onto one continuous portable conformal substrate. This would make radar systems easy to roll up to miniaturized highly-portable sizes and volumes, that are really critical especially in “rugged” and hazardous remote environments. This paper addresses several design challenges involved in the development of monolithic paper- based radar systems including unique design, fabrication, and testing procedures that differ from the conventional radar systems. A paper-based mixer circuit is built and the performance is to be compared to that of a state of the art mixer board to verify the advantages of the newly proposed inkjet- printer approach. Keywords—Stepped FMCW Radar; ground penetrating radar; inkjet printing; portable radar; monolithic I. INTRODUCTION Frequency-Modulated Continuous Wave (FMCW) Ground Penetrating Radar has become popular in various applications, many of which are undertaken in the most extreme of environments. These include analyzing active fault zones; studying geomorphology and internal structure of desert dunes; characterizing soil, rock and snow stratigraphy; detecting clay layers; measuring or mapping the spatial variation of soil water content (soil moisture) and porosity, measuring depths to water tables, buried target detection and characterization (forensics, ancient monuments, pipes, landmines); avalanche research; sea-ice thickness measurements in Antarctica and Martian soil subsurface characterization [1, 2, 3]. The use of flexible substrates such as paper, kapton and LCP would make future systems more easily deployable by allowing them to be rolled up, transported and unrolled (or pieced together) quickly and easily for immediate operation (Fig 1) while allowing for lightweight and easy mounting in ‘rugged’ platforms, such as oil exploration drills. This provides a functional advantage for radars and antennas brought to operate in remote, hazardous and size/volume- sensitive (e.g. Space and flying/diving platforms) environments. Sometimes measurements are performed in places where heavy or bulky cargo is restricted. For many of these locations, extensive climbing or walking is required, and therefore heavy luggage is restricted. Enhanced portability will also add to the versatility of Ground Penetrating Radars. Selecting the best frequency range and operating point in order to balance the tradeoff between high resolution and large penetration depth is challenging, so often these systems are equipped with several modes of operation. In addition, one type of antenna will not be suitable for all types of targets at it may be necessary to use different antennas for planar versus linear targets. A monolithic design would facilitate the storage and transport of a multiple common platform with different functions by allowing lightweight, low profile antennas to be used. In addition to mechanical advantages, this technology will reduce the cost, time and materials needed to manufacture the full system including a variety of easy-to-add-and-subtract antennas. (a) (b) Fig. 1. System level schematic illustration of portable radar concept The GPR antenna(s) can be made compact and low profile using inkjet printing technology. Due to the fact that such antennas will still occupy most of the surface in the system, the most size efficient approach would be to place the remaining components within the antenna geometry itself [4]. 978-2-87487-031-6 © 2013 EuMA 7 -10 Oct 2013, Nuremberg, Germany Proceedings of the 43rd European Microwave Conference 13