how can measure current distribution on antenna?

http://www.ctsystemes.com/zeland/pub...ted-dtu123.pdf

If it is a planar antenna, just run it at high power for a while, then turn off othe power (so you don't cook yourself) and take an infra-red picture of the antenna. Hot areas have high current, etc. For HF, just hook up a small inductor, detector, and meter and walk around the antenna. Keep the power level under a hundred watts or so and don't spend days doing this kind of thing. If you really want to amaze people, just take a flourescent light and hold it next to the antenna. It lights up where the highest current is.

Use a near field/EMC scanner.