Abstract: In the passive location system based on the FM broadcast, signals are uncooperative and non-stationary. With the generation theory of the signals taken into account, it is pointed out that the range resolution of the modulated signals declines because of the intermission of modulating signals. The method for confirming intermission based on the derivative of the signals is presented. The method for setting the intermission to zeros is analyzed to improve the range resolution. The results of the procession of the field data validate the proposed method to improve the range resolution with low computation and easy real-time procession.

Key words: non-stationary, FM broadcast, range resolution