Japan's radar problem was production as well as invention

Why was Japan behind in radar technology during the war?

Japan had worthwhile radar ideas, but lacked the manufacturing and infrastructure needed to produce and field systems on the Allied scale.

Japan had worthwhile radar research and experimental work. Its larger weakness was the capacity to turn that work into equipment in large numbers. Britain already had a manufacturing base before the war and spread production to Canada and elsewhere, although bombing threatened factories and skilled personnel. The United States could expand its existing industry without attacks on the production base, while Japan started with less infrastructure. One interpretation links Japan's later emphasis on railways to wartime difficulties moving goods, people, and technical skills.