Description

High-frequency circuit design continues to enjoy significant industrial attention, triggered by a host of radio-frequency (RF) and microwave (MW) products. Improved semiconductor devices, new board materials, and advanced fabrication technologies have made possible a proliferation of high-speed digital and analog systems that profoundly influence wireless communication, global positioning, radar, remote sensing, and related electrical and computer engineering disciplines. As a consequence, this interest has translated into market demands for trained engineers and professionals with knowledge of high-frequency circuit design principles. Since the publication of the first edition of this textbook in January, 2000, the need for well-educated RF professionals has surged, making a text that teaches the fundamentals of high-frequency circuits even timelier.

The objective of this second edition remains the same: to present the fundamental RF design aspects and the underlying distributed circuit theory with minimal emphasis on electromagnetics. We have written this book in a manner that requires no EM background beyond a first year undergraduate physics course in fields and waves. Students and practicing engineers equipped with rudimentary exposure to circuit theory and/or microelectronics can read this book and grasp the entire spectrum of high-frequency circuit principles involving passive and active discrete devices, transmission lines, filters, amplifiers, mixers, oscillators and their design procedures. Lengthy mathematical derivations are either relegated to the appendices or placed in examples, thereby separating dry theoretical details from the main text. Although de-emphasizing theory creates a certain loss in precision, it promotes readability and focus on the underlying circuit concepts.

What has changed from the first edition? Besides our obvious attempt to eliminate typos and inconsistencies, the second edition was improved in several important ways. First, we have added Practically Speaking sections at the end of each chapter. In these sections, key design concepts and measurement procedures are discussed in detail. Topics such as the construction of an attenuator, a microstrip filter, or the simulation of a low noise RF amplifier with bias and matching networks, are presented similarly to a lab component that accompanies the lectures. Equipped with the right instrumentation and software simulator, the reader can easily replicate the circuits. Second, topics of interest, helpful definitions, and noteworthy observations are placed on the margins and offset from the main text. In addition to highlighting their importance, this approach allows us to emphasize and better explain items that do not directly fit into the flow of the main text. For example, the coverage of a Phase Lock Loop (PLL) system would exceed the scope of this book. However, a brief explanation of a PLL provides context and extra motivation for the underlying high-frequency circuits. It furthermore inspires the readers to explore these topics on their own. Third, more emphasis is placed on nonlinear design principles, specifically in regard to oscillators and their associated resonator circuits.

Accepting the challenge to deliver a high degree of linear and nonlinear design experience, we have included a number of examples that analyze in considerable depth, often extending over several pages, the philosophy and the intricacies of various modeling approaches. While linear scattering parameter simulations are adequate under certain conditions, nonlinear simulations, for instance the harmonic balance analysis, are required for more sophisticated designs. Oscillator and mixer, as well as amplifier designs can greatly benefit from a nonlinear circuit simulation. Naturally, the use of appropriate simulation tools creates problems in terms of their capabilities, accuracies, speeds, and not least costs. The availability of circuit simulators and RF software tools has steadily increased over the years. Indeed, the authors are routinely contacted about simulators that offer "exceptional" performances under particular constraints. It is not our goal to render an assessment or endorsement of a specific simulator (the authors have no commercial, nor professional ties with any vendor). In general, professional high-frequency simulators are expensive and require familiarity to use them effectively. Several years ago, the ECE department at WPI decided after an extensive review to adopt Advanced Design Systems (ADS) of Agilent Technologies as the default high-frequency circuit simulator for its undergraduate and graduate electrical and computer engineering students. For this reason, and because of its wide-spread industrial use, we rely on ADS simulations for most of our circuits. However, for readers without access to commercial simulators, we created a number of standard Matlab M-files that can be downloaded from our website listed in Appendix G. Because Matlab is a popular and relatively inexpensive mathematical tool, many examples discussed in this book can be executed and the results graphically displayed in a matter of seconds. Specifically, the various Smith Chart computations of impedance transformations should appeal to the reader.