Where did Christian Doppler invent the Doppler Radar?

Christian Doppler did not invent Doppler Radar. He described what is now known as the Doppler effect in 1842 in Austria. It is used to describe the behavior of waves (such as light or sound) that are emitted by a moving object.

Doppler radar, which utilizes the Doppler effect, was developed in the United States during World War II.