In phase I, we developed an emitter localization technique based on the fusion of Direction of Arrival (DOA) measurements obtained from two flying small UAS and a terrain map. We have designed novel mini UWB antenna to cover VHF/UHF bands. For hardware, we designed a thin, small size (51mm×61mm×9mm), light weight (4.5 Oz) onboard DOA hardware system with very low power consumption equipped with fast signal capture capability (within 200ms). Detail DOA hardware schematic was created and 95% components were identified .The designed DOA receiver has high dynamic range and can cover a very wide frequency range at min power consumption(A typical 1200mWh battery can support over 5 hour flight mission with 11800 DOA estimations ). For the software part, we have developed the smart antenna calibration, hierarchical delay and sum (DAS) DOA estimation, and terrain data aided DOA fusion 3D localization. We also constructed a 3D simulation and visualization tool by integrating the hardware design, signal processing software algorithms, and UAS flight controls. With a real terrain map, we conducted the simulation and obtained the desired results of 100m accuracy. The system can track dual targets within a second in a typical application and may take a few more seconds in a difficult condition. In Phase II, we plan to coordinate with government POCs, academic researchers and industrial partners on research and development. We will refine the antenna, hardware design and software algorithms in our emitter localization solution. The refined phase I prototype will be fabricated and installed on UAVs to demonstrate the overall performance for realistic field fight scenarios.