Radio waves at frequencies greater than 3 GHz are what we call "microwaves".
Now, recently, these days, as we learn to build communications equipment at higher and higher frequencies, a new name has been invented, for radio waves at frequencies between 30 GHz and 300 GHz. Those are called "millimeter waves".
There are many types of radar systems, operating at frequencies from 1 GHz to beyond 30 GHz.
Examples:
-- Various weather radars: L-band, 1-2 GHz; S-band, 2-4 GHz; C-band, 4-8 GHz; X-band, 8-12 GHz; K-band, 12-18 GHz and 27-40 GHz.
-- Police "speed-radar" ... 10.525 GHz.
