RF Circuits and Systems - Basics of Communication Theory

The second course in this seven-course series focuses on the fundamentals of communication theory. OF particular importance is the concept of modulation and demodulation. We will learn that the information that is being transmitted and received by a communication device often occupies frequencies from DC to a few megahertz (gigahertz in the case of data). Effective communication over a long distance often requires frequency-upconversion of the information, which is called baseband signal, to high frequency using another signal called carrier. The information can be featuring different attributes of the carrier such as its amplitude, phase, or frequency. Placing the information on the amplitude of the carrier leads to the notion of amplitude modulation (AM). Likewise, in the case that the phase or frequency of the carrier varies by the baseband signal, we will achieve phase modulation (PM) and frequency modulation (FM).  Modern communication systems all employ digital modulation. Digital modulation allows the use of digital signal processing techniques to vastly improve spectral efficiency during signal transmission. To more efficiently use the spectrum to transmit data, thus increasing the information rate, the information bits can be formed into "symbols." Each symbol is comprised of several bits. The symbol transmission allows for sending more information bit at specific instances of time. The symbol formation together with frequency upconversion constitutes the digital modulation. In this course, we will learn about different digital modulation techniques including amplitude, phase, and frequency shift keying, and quadrature amplitude modulation (QAM). Widely used advanced techniques such as orthogonal frequency division multiplexing (OFDM) will also be discussed in this course.