Passive Localization Algorithm for Radiation Source Based on Long Synthetic Aperture

When the direction-of-arrival estimation is made by a single platform, the localization accuracy decreases with increases in the distance from the radiation source, which means the localization accuracy of the azimuth of the radiation source at long distances must be improved. To address this problem, we propose a radiation-source localization algorithm based on a long synthetic aperture. This algorithm introduces the use of synthetic aperture imaging to the passive localization of radiation sources. A long virtual aperture is obtained by movement of the platform, and received data is processed in the form of synthetic aperture radar to obtain high azimuth localization accuracy. For a single-frequency radiation source, the received signal is equivalent to a linear frequency-modulation signal in the azimuth domain, and its chirp rate is inversely proportional to the distance from the radiation source. A range search and azimuth-focusing method are used to perform signal focusing in the range–azimuth domain, and the localization of the radiation source is obtained directly by two-dimensional imaging. Moreover, with respect to the characteristics of wide-beam reconnaissance, we analyzed the range–azimuth coupling relationship of the chirp rate at a low sampling frequency. On this basis, methods for direction-of-arrival estimation and two-dimensional imaging localization are proposed. Our theoretical derivation and experimental data processing results verify the validity of this algorithm.