Estimation of range and bearing of RF emitters using direction-of-arrival data

This paper presents results of ongoing research to develop a passive transportable system for measuring the range and bearing of RF emitters in the PCS band (1850-1910 MHz). Among several possible candidate approaches that were considered in the initial stages of the program the one chosen for further development employs emitter signal direction-of-arrival (DOA) information measured with two array antennas whose phase centers are displaced by a known distance (baseline). In keeping with the transportability requirement of the system one of the key objectives was to minimize the baseline while maintaining good range estimation accuracy. The design goal was set for a baseline on the order of 1 m while accommodating emitter ranges up to 1 km. This translates into a DOA estimation accuracy of better than 0.1 degree. To achieve such accuracy levels novel DOA algorithms and antenna array design approaches are employed. The design approach and system performance evaluation will be presented using numerical simulations of a dual 4-element patch array together with the associated RF and DSP components. A data collection system incorporating the patch antenna array was designed and built and is currently being used to validate the theoretical predictions. Preliminary results on range estimation accuracy and bearing indicate good agreement with theory.