In the digital communication class I took, people talk about how to do detection and processing at the baseband. But from what I read, it seems that many systems do the signal processing at some intermediate frequency without mixing it all the way back to baseband. My questions are why and how: 1) Why would you want to process signal at IF band? wouldn't it be "easier" if you process baseband signal? And wouldn't the sampling rate be lower at baseband? 2) How exactly do you process the signal (such as detection, etc)? I know how you do it at baseband, but how do you accomplish the same thing with a signal oscillating at IF? I have not yet been able to find the answer online and in books, I would greatly appreciate if anyone can point me to the right direction. Thanks.