Passive radar fixed target frequency domain direction-finding method based on external radiation source

The invention discloses a passive radar fixed target frequency domain direction-finding method based on an external radiation source. The passive radar fixed target frequency domain direction-finding method comprises the steps of establishing a direction-finding system model; deducing a slant range progress of a single-scattering-point target; deducing a demodulated single-scattering-point target echo signal model and performing variable substitution for obtaining a frequency domain expression; expanding the frequency domain expression of the single-scattering-point target echo signal to a multi-target condition, modifying a target scattering strength function, and obtaining a relationship between the frequency domain expression of a multi-target echo signal and the modified target strength function; and calculating the direction of each target by means of a polar coordinate algorithm. The passive radar fixed target frequency domain direction-finding method is realized based on a narrow-band external radiation source signal in a two-dimensional space; the polar coordinate algorithm is used; and convolution operation is performed. The convolution operation can be processed through fast Fourier transform and inverse transformation, thereby greatly reducing calculation amount of the algorithm, realizing high robustness, obtaining relatively high direction finding precision and simultaneously finding a plurality of target directions in an observing area.