C1.2 - 77-GHz SAR Measurements with Integrated Sensors

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
C1 - Wireless Sensors I
J. Schrattenecker, A. Haderer, A. Stelzer - Johannes Kepler University, Linz (Austria)
370 - 375


Recent advances enable the realization of low-cost and high performance mm-wave radar sensors suitable for miscellaneous applications. In this contribution a 77-GHz frequency-modulated continuous-wave (FMCW) radar is used to realize a mm-wave imaging system. When dealing with distances up to a few hundred meters, FMCW radar systems gained increased importance due to their simple and cheap system architecture. In addition these sensors are robust against environmental stress like fume, dust, temperature, etc.. Hence, these radar systems are of great importance in many industrial applications, e.g. filling level measurements or speed and range measurements in automotive usage.
Radar systems with a turnable antenna have limited angular resolution capabilities depending on the directivity of the antenna. Therefore, objects located at the same range but at distinct angles of observation can not be identified as separate targets in general. This major disadvantage can be overcome by conducting measurements at spatially separated locations in order to reconstruct a high resolution image of the illuminated scene. This concept is known as synthetic aperture radar (SAR).
In our work the actual image calculation is done offline by means of digital signal processing, where the measured data are coherently accumulated. When operating SAR systems at mm-wave frequencies, cross-range resolutions of a few millimeters can be achieved.
In order to conduct measurements we mounted the FMCW radar prototype on a cantilever. Letters made of copper were positioned on two-dimensional portal axes in a distance of 0.7 m beneath the FMCW radar system. Afterwards the target was moved on a two-dimensional grid, and measurements were taken. The sampled data were transferred to a PC and the signal processing was done within a Matlab environment. With the used measurement setup a cross-range resolution of a few millimeters can be achieved. This property makes them attractive for different types of measurements, like edge detection, surface scanning and positioning of robot systems.