The agreement contains FS-X technology flow-back guarantees, including U.S. participation in the manufacture and testing of new technology components such as advanced co-cured composite wings, new avionics, and phased-array radar.

CENTERFORSECURITYPOLICY: The US-Japan FS-X Fighter Agreement: Assessing The Stakes

The trailer-mounted radar is a "phased array" type - it scans the sky with a narrow beam which flicks between thousands of locations each second.

BBC: Fact file: Patriot missile defence