As respective major tools for detection underwater and in air, sonar and radar play an important role in both military and civilian applications. They use acoustic wave and electromagnetic wave respectively as the signal carrier, sensing target and environmental features via signal transmission/noise radiation and signal/noise receiving. Although the signal carriers are different, they share many common theories and methodologies in system design and data processing.   This course introduces the basic principles of sonar and radar, including the basic architecture of active and passive sonar/radar systems, transducer and antenna, data acquisition, and signaling mechanism. The emphasis is on the theory and methods of sonar and radar signal processing and data analysis, including sonar/radar equation, matched filtering and ambiguity function, range/Doppler resolution-oriented signal design, detection and estimation, compressive sensing, system performance analysis, and system examples.   The course introduces the principles of sonar and radar and the associated signal processing methods from the perspective of the system, aiming to training the students on system concept and having them grasp some basic methodologies and applications of such two important detection systems.