In the project SUPREM ("Svårupptäckt precisionsmålsökare") is investigated how multi-sensor systems where SAR is a vital sensor, can be designed for UCAV-systems with respect to for instance low probability of intercept. In this report the duel between an LPI-radar based on noise radar technology and different types of radar warning systems is investigated. It is further described how a SAR sensor can be designed to reduce the risk of being detected by radar warning systems. The results show that for the SAR-sensor it is apparent that attention should be paid to the design of the antenna lobe, preferably with an AESA antenna (active electronically scanned array) with beam forming capability, and that the output power is adjustable with respect to the current needs. The SAR-sensor is, however, not detectable with present operative systems under the circumstances used in this report. New kinds of radar warning systems based on radiometry or, above all, cross correlation seem to be useful for LPI-radar detection. This type of radar sensors constitutes a threat to Swedish armed forces in international campaigns and further investigations, with both theoretical and experimental studies, is needed to explore how this new technology can be utilized and how we can protect our forces against it.