The field of high-frequency circuit design is receiving significant industrial attention due to a host of radio-frequency (RF) and microwave (MW) applications. Improved semiconductor devices have made possible a proliferation of high-speed digital and analog systems as observed in wireless communication, global positioning, RADAR, and related electrical and computer engineering disciplines. This interest has translated into a strong demand for engineers with comprehensive knowledge of high-frequency circuit design principles.

For the student, the professional engineer, and even the faculty member teaching this material there is, however, a general problem. The majority of existing textbooks appear to target two separate audiences:
   A) the advanced graduate-level population with a broad theoretical background, and
   B) the technologists with little interest in mathematical and physical rigor.
As a result, RF circuit design has been presented in two very different formats.
For the advanced students the entry into this field is often pursued through an electromagnetic field approach, while for the technologists the basic circuit aspect embedded in Kirchhoff's laws is the preferred treatment. Both approaches make it difficult to adequately address the theoretical and practical issues surrounding high-frequency design principles. The basic circuit approach lacks, or only superficially covers, the wave nature of currents and voltages whose reflection and transmission properties constitute indispensable ingredients of the RF circuit behavior. The electromagnetic field approach certainly covers the wave guide and transmission line aspects, but falls far short of reaching the important aspects of designing high-frequency amplifier, oscillator, and mixer circuits.

The objective of this textbook is to develop the RF circuit design aspects in such a way that the need of transmission line principles is made clear without adopting an electromagnetic field approach. Therefore, no EM background is necessary beyond a first year undergraduate physics course in fields and waves as provided by most colleges and universities. Students equipped with the knowledge of basic circuit theory and/or an exposure to microelectronics can use this book and cover the entire spectrum from the basic principles of transmission and microstrip lines to the various high-frequency circuit design procedures. Lengthy mathematical derivations are either relegated to the appendices or placed in examples, separated from the main text. This allows the omission of some of the dry theoretical details and thus focuses on the main concepts.

Accepting the challenge of providing a high degree of design experience, we have included many examples that discuss in considerable detail, in many cases extending over several pages, the philosophy and the intricacies of the various design approaches. This has caused some problems as well, specifically with respect to the circuit simulations. Obviously, we cannot expect the reader to have ready access to modern computer simulation tools such as MMICAD or ADS to name but two of the popular choices. Professional high-frequency simulation packages are generally expensive and require familiarity to use them effectively. For this reason we have created a considerable number of MATLAB M-files that the interested student can download from this website. Since MATLAB is a widely used relatively inexpensive mathematical spreadsheet, many examples discussed in this book can be reproduced and graphically displayed in a matter of seconds. Specifically the various Smith-Chart computations of the impedance transformations should appeal to the reader. Nonetheless, all design examples, specifically the ones presented in Chapters 8 to 10, have been independently simulated and verified in MMICAD for the linear circuit models, and ADS for the non-linear oscillator and mixer models.