DARPA awarded a contract to IFT. In this project, IFT proposes an emitter localization technique based on the fusion of DOA obtained at two flying small UAS. Each UAS is equipped with a nonlinear distributed smart antenna system and a GPS receiver. The GPS receiver provides the UAS position and the pulse per second (PPS) signal. The nonlinear smart antenna system (1) detects the emitter signal using an analog received signal strength indicator (RSSI) and (2) estimates the emitter DOA using a hierarchical delay and sum (DAS) searching method. After an emitter’s signal is detected, its spectrum signature is analyzed and its DOA is estimated, in addition the DOA is marked with the time, at which it is obtained in the GPS time system. The DOA with time mark and the corresponding signal’s spectrum character and the UAS position are transmitted to the ground control station through the control channel. At the control station the DOA coming from the two UAS are aligned based on the time mark and spectrum signature and then fused to localize the emitter. The proposed localization method does not need any communication between the two UAS, which saves a transmitter and a synchronization receiver on each UAS as well as on-board power. The emitter signal detection process consumes less than 150ms, when an emitter signal lasts more than 200ms, to detect and localize a signal.