RF and Microwave Wireless Systems

CHAPTER FOUR

Various Components and Their System Parameters

4.1   INTRODUCTION AND HISTORY

An RF and microwave system consists of many different components connected by transmission lines. In general, the components are classified as passive components and active (or solid-state) components. The passive components include resistors, capacitors, inductors, connectors, transitions, transformers, tapers, tuners, matching networks, couplers, hybrids, power dividers/combiners, baluns, resonators, filters, multiplexers, isolators, circulators, delay lines, and antennas. The solid-state devices include detectors, mixers, switches, phase shifters, modulators, oscillators, and amplifiers. Strictly speaking, active components are devices that have negative resistance capable of generating RF power from the DC biases. But a more general definition includes all solid-state devices.

Historically, wires, waveguides, and tubes were commonly used before 1950. After 1950, solid-state devices and integrated circuits began emerging. Today, monolithic integrated circuits (or chips) are widely used for many commercial and military systems. Figure 4.1 shows a brief history of microwave technologies. The commonly used solid-state devices are MESFETs (metal–semiconductor field-effect transistors), HEMTs (high-electron-mobility transistors), and HBTs (heterojunction bipolar transistors). Gallium-arsenide semiconductor materials are commonly used to fabricate these devices and the MMICs, since the electron ...