Radio Frequency Circuit Design, 2nd Edition

CHAPTER ONE

Information Transfer Technology

1.1 INTRODUCTION

The design of radio frequency (RF) circuits borrows from methods used in low frequency audio circuits as well as from methods used in design of microwave circuits. However, there are also important departures from audio and microwave frequency methods, so that design of radio frequency circuits requires some specialized techniques not found in these other frequency ranges. The radio frequency range for present purposes will be taken to be approximately somewhere between 300 MHz and 3 GHz. It is this frequency range where much of the present day activity in wireless communication occurs. In this range of frequencies, the engineer must be concerned with radiation, stray coupling, and frequency response of circuit elements that, from the point of view of lumped, low frequency analysis, might be expected to be independent of frequency. At the same time, the use of common microwave circuit elements such as quarter wave transformers is impractical because of the long line lengths required. The use of monolithic circuits have enabled many high frequency designs to be implemented with lumped elements, yet the frequency response of these “lumped” elements still must be carefully considered. The small size of lumped elements in integrated circuits has provided practical designs of filters, transformers, couplers, etc. in lumped element form. Therefore discussion of designs for low noise amplifiers, power amplifiers, oscillators, ...