The chapter begins with an overview of the electronic communication systems. Using a system level block diagram it introduces concepts like modulation, multiplexing, distortion, noise interference, signal to noise ratio, bandwidth, channel capacity, coding and use of spectrum. This follows a discussion on classification of signals, means to characterize it, e.g. energy, power, correlation etc. and certain basic signal operations like shifting, scaling etc. A detailed discussion on Fourier series expansion, useful for identifying frequency information of periodic signals and Fourier transform, useful for aperiodic signals is presented. In each cases, important properties are discussed, judicious application of which makes many complex problems look simple. The chapter also discusses orthogonal representation of signal and presents technique like Gram-Schmidt rotation that uses only a finite set of signals for orthogonal representation. Correspondence between signals and vectors are discussed with its use in enhancing distinguishability between various types of signals. At the end an extensive illustration of various concepts developed in this chapter is presented through MATLAB simulations.
