It is claimed that Unmanned Aerial Vehicles (UAVs) used for civilian/public domain applications will be dominant in the near future. Compared to UAVs used by the military, civilian UAVs are often operated by pilots without formal training, and hence they require increased levels of autonomy and intelligence, especially with regard to reducing threats to public safety. UAV integration into the National Air Space will require that the UAVs support multiple, complementary sense-and-avoid mechanisms, including detection and identification of other UAV-sized targets. Currently, the majority of available sensors are based on infrared detectors, focal plane arrays, optical and ultrasonic rangefinders. These sensors are generally not able to detect or identify other UAV-sized targets and, when detection is possible, considerable computational power may be required for successful identification. By contrast, this paper describes the design of a light weight, X-Band (10.5GHz) radar system for use on a small-scale (<; 25 kg) rotorcraft. The prototype radar implementation is small enough to be carried by any miniature UAV, and it is capable of differentiating other miniature rotorcraft by their doppler signature. In addition to the overall hardware and software design of the prototype system, a performance analysis of various signature matching algorithms is presented demonstrating the capabilities of the system in a laboratory setting.