Maxim Integrated RF Applications Engineer interview questions

I was sent an E-mail asking for my availability, when I agreed on the dates,I had a phone interview with one of the engineers, Started with simple questions and gradually went into extremely complicated and tough questions, Interview went on for about 45 mins at which point I was lost for words. Responded a week later saying that they wanted to move on with other candidates, by the way this was for an entry level position.