In some earth observation applications there is a requirement for low cost, high performance imaging radar systems small enough to be operated from small, even unmanned, aircraft. The existing pulse radars are non-cost effective complex systems. Therefore they are not suited for these applications. Frequency Modulated Continuous Wave (FM-CW) radar systems are on the other hand generally very compact and relatively cheap to purchase and to use. IRCTR, together with TNO, is investigating the feasibility of combining FM-CW technology and high resolution Synthetic Aperture Radar (SAR) techniques. This research has led to the development of two different systems. An FM-CW millimetre wave SAR sensor (35 GHz) was built and is being tested. The system is battery powered and uses a PC to control the radar and store the data, including GPS and data from motion sensors. The system is mounted in a pod attached to a light motor glider. Furthermore, a detailed system model has been developed in order to estimate and analyze the performance of the demonstrator system. The measuerementsw made with the demonstrator system are evaluated and the findings are used to improve the system model. This improved model will be a strong aid in the design of future higher performance FM-CW SAR systems. The second development regards a miniature P-band (450 MHz) polarimetric FM-CW SAR. This system is intended for use with an ultra-light aircraft. It is designed for tropical forest monitoring studies but could be used in foliage penetration applications as well. This system will be battery powered and uses a small memory stick to store the raw data. Data processing is now foreseen as an off-line activity. The design of the system is still under study and the realization is expected to start in the second half of 2005. This system will employ a Direct Digital Synthesizer to generate the waveform that is transmitted at P-band. Two separate dual polarized patch antennas will be used for transmit and receive.@en

At TNO a new concept to synthesize maps of building structures with stand-off, through-the-wall radar has been developed: SAPPHIRE. The system concept exploits particular phase behavior in the 3D radar data to extract dominant scatterers inside a building. The phase relations are extracted from the radar data by using an overcomplete dictionary and sparse reconstruction. In this paper, the reconstruction algorithm and first results will be presented.@en