tailieunhanh - Lò vi sóng RF và hệ thống không dây P4

Various Components and Their System Parameters 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. . | RF and Microwave Wireless Systems. Kai Chang Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-35199-7 Hardback 0-471-22432-4 Electronic CHAPTER FOUR Various Components and Their System Parameters 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 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 mobility in GaAs is higher than that in silicon. Higher electron mobility means that the device can operate at higher frequencies or higher speeds. Below 2 GHz silicon technology is dominant because of its lower cost and higher yield. The solid-state devices used in RF are mainly silicon transistors metal-oxide-semiconductor FETs MOSFETs and complementary MOS CMOS devices. High-level monolithic .