Georgia Tech Research Institute RF Hardware Engineer interview questions

This is the hardest interview I have had. It lasted a whole day, the guy who was going to be my direct boss told me he had OCD tendency towards work and talked in a weird tone like he was nervous and exited at the same time. I had to prepare a 30min - 1hour technical presentation, the panel were mostly PHDs and mainly asked me technical questions. I was also intervied one on one with many PHDs in different departments. The environment seems very stressful, not quite friendly place. I was then interviewed for the GTRI at Marietta, the environment seemed a bit friendlier there however, the interview still was difficult with technical questions and a panel interview, very stressful.