Qualcomm Analog & Mixed-Signal IC Design Engineer interview questions

HR contacted me via email to set up a phone interview. The interviewer asked mostly about my research, followed by a couple of simple technical questions. A few days later, HR contacted me again for a second phone interview. This time, the interviewer briefly asked about my research, then followed by a more in-depth technical questions. I got a rejection email two days later. I think I should have answered the questions better, and also, based on my impression after talking to both interviewers, my research background probably doesn't sound like a perfect fit for them.