The chapter begins with a discussion of resistor as a source of noise and also shows how noise affects when there is a network of multiple resistors and resistors with reactive elements. The concept of available thermal noise power and noise temperature is described. Two port networks are the basic building block of any receiving system. A detailed discussion on noise available at the two port network output and its bandwidth are presented. Noise figure and concept of equivalent noise temperature are introduced which effectively characterize a cascaded network. The noise performance of antenna in communication is presented with system level calculations.
