I got this interview by reaching out to the hiring manager post's on LinkedIn. It was a 30 mins technical interview. I was asked questions on RF fundamentals, LNA design, PA design and linearity. Also I was asked to explain OFDM and types of PA classes and relation with PAPR. The interviewer said he was impressed and suggested referring me for other RF roles at Apple as he was also looking for someone with strong C/C++, OOP skills and I hadn't done that in a long time.