18.1 Introduction

The need for sources of clean, calibrated electrical signals arose with the development of receivers, which required testing and characterization to determine performance and to make adjustments, e.g., alignment of intermediate frequency (if) blocks, local oscillators (LOs), etc. As microwave receiver technologies and capabilities became more sophisticated, the corresponding signal generator performance demands grew far beyond what could be provided by the unwieldy, manually tuned klystron signal generators of the 1950s.

Modern communications, satellite, radar, navigational, electronic warfare (EW), and surveillance receivers require various degrees of amplitude and frequency precision, frequency range, dynamic range, modulation capabilities, tuning speed, and freedom from undesired spurious signals. Many require programmability under computer control in production test environments.

Accurate component and subsystem testing requires precision swept sources to operate with scalar and vector network analyzers. The modern signal generator combines synthesis and solid-state oscillator technologies (see Chap. 8) with microprocessor control to provide sophisticated frequency and level control, programmability, self-test, and diagnostics, as well as internal and external calibration. This results in high levels of accuracy, useful feature sets, and low cost of ownership.

In this chapter, various types of microwave signal generators are described together with some of their fundamental applications. Implementations are discussed at a block diagram level, and with reference to material in Chap. 8 on microwave sources. Signal generator performance specifications and their relevance to certain applications are described.

18.2 Types of Signal Generators

Several varieties of microwave signal generators, each...