Abstract: The interface between radar signal processor and radar simulator is discussed for a biphase coded radar. The method of producing BK code and M code radar echo signals is analyzed while the pulse repeat period is changing. Based on a hardware realization scheme in which the digital signal processor is the key device, the radar echo signal is modulated by the biphase code, Doppler frequency, and the diagram of antenna direction. Moreover, the distance ambiguity and speed ambiguity are simulated and the target is synthesized with a digital method. When a closed-loop system is formed by the radar signal processor and the simulator, ability of the signal processor in searching and tracking multi-target can be verified.