Historical overview of phased array antennas for defense application in Japan

In this paper, we introduce the research activities on phased array antennas over past two decades in the Technical Research and Development Institute (TRDI) of the Japan Defense Agency. Then, we present several examples of the applications of phased array antennas to radar systems by Japan Self Defense forces. The introduction of the research activities includes the development of transmitting and receiving modules for active phased array antennas, the engineering models of array antennas and current efforts on the phased array antennas such as conformal antennas and millimeter wave phased array antennas.