DRDO takes technical field related employees. You can join any technical field like engineering (i.e. electronics and communication, information and technology) or any ITI course for selection in drdo. Also it does not have a campus selection we have to apply online from their site and than there are two part in the selection process 1st is the written test and 2nd is he interview round. It will be benificial if you take your projects which you havedone in your whole acadamic sessions it will help you there for showing them howclear you are in your related field. you can choose Engineering fields like electronics and communication, electronics engineering, information and technology, electrical engineering as per your interest.

Hey,
Yes DRDO conducts open campus competition for all engineering students.
Mechanical, Chemical, Meatllurgical, Civil , Electronic, Electric, Nuclear branches are accepted by DRDO.

You can go for any one of the branch listed above.
For further details you can open the link given below,
https://engineering.careers360.com/articles/isro-drdo-barc-dae-how-work-here
Hope this works