Receivers and Sub‐Systems

The superheterodyne (superhet) receiver is the most widely used receiver configuration for RF and microwave applications, and it is the main focus of this chapter. Noise is an important issue in the design of receiver circuits, and the chapter commences with a review of noise sources and their circuit specifications, leading to an analysis of the effects of noise in superhet receivers, and the use of noise budget graphs. Frequency mixers are often regarded as the critical components in the front‐end of a superhet receiver. The noise which is received by an antenna is represented by an effective noise temperature, known simply as the antenna noise temperature, which is not related to the physical temperature of the antenna. Noise budget graphs show how the noise and signal‐to‐noise ratios vary through a receiver sub‐system. The chapter concludes with a review of the various types of mixer used at RF and microwave frequencies.