Of all the integrated circuits manufactured and sold, around 80 percent are purely digital and 20 percent involve some processing to convert analog signals into digital, so the field is significant economically. My students and I and several others in EECS work on the interface between analog and digital. For example, micromachined accelerometers and other components often integrate a sensor with a circuit. Accomplishing this presents many challenges in computer-aided design, circuit design, architecture, and other areas. Right now, most of my students are working on RF radios, a type of analog mixed-signal system.
Cellular phones are a perfect example.
They take an analog RF radio signal out of the air, sense it, amplify it, and convert it into digital bits, process it, and convert it back to an analog signal, which is the voice you hear over the phone. So, it goes from analog to digital and back to analog. We are trying to make cheaper, better, lower-power components that handle this RF processing. Ultimately, we want a cellular phone on a chip, like one of the chips you would put in a wrist watch. By keeping in close contact with industry, you can see in which direction technology is going.