I. Introduction
Passive detection system is a receiver-only radar system that dissociates the receiving antenna from the transmitter, and it can detect and track targets of interest by utilizing noncooperative illuminators of opportunity (IOs), such as radio, television, and cellular signals [1]. In recent years, passive detection system is much better than a conventional radar system in different ways. Passive bistatic radar has strong anti-interference ability, high concealment, large coverage and other advantages [2]. In addition, passive detection radar can lead to spatial diversity and improve the detection capability of the target.