Amazon Lab126 Hardware Development Engineer interview questions

I met a recruiter at a university career fair and handed them my resume. They emailed me about a month later to schedule 4 back to back 45 minute interviews. These were the only interviews I had to do with them. They got back to me about 3 weeks later. They asked me a couple questions about my experiences at my internships, but most of the questions were about evaluating circuits, signals, and filters.