This paper presents the recently research of the harmonic radar at National Taiwan University and National Chung Cheng University. The topic includes the radar base, portable radar, and the transponder. In the radar base, high sensitivity radar using the correlation of PRN code is developed. To isolate the transmitter and the receiver, a cancellation technique of the local leakage signal is investigated. In the portable radar, an analog correlator network is designed so that the high speed oscilloscope can be replaced by the portable monitor. This portable radar can search a transponder at a distance of 1 m. The transponder design needs to minimize the loss of bee's body, and both ground plane shieling and the virtual ground plane are used to reduce the loss of the body. The reduction of the influence by the bee's body for the transponder using either method is 3-4 dB.