This book was last updated in January 2020. RF and microwave circuit design is a fascinating and fulfilling career path. It is also an extremely vast subject with topics ranging from semiconductor physics to electromagnetic theory and techniques. The Fundamentals of RF and Microwave Circuit Design book covers the subject from a Computer Aided Design (CAD) standpoint using the low-cost or free software such as LTspice, AppCAD, Smith V3.10, and TXLINE. Topics discussed in this book include RF and microwave concepts and components, transmission lines, network parameters and the Smith chart, resonant circuits and filter designs, power transfer and lumped impedance matching network design, distributed impedance matching network design, and various amplifier circuits utilizing SPICE simulator software. LTspice is capable of time-domain, FFT, and linear circuit simulation. As such, a spice model has been utilized for design of several amplifiers. A DC analysis has been performed first and transistor DC-IV curves have been generated for proper selection of DC operating points. An AC analysis is then followed to generate S-parameters at desired DC biasing condition. From simulated two port parameters, RF parameters of interest including stability factors can be generated using LTspice equation editor. Furthermore, a model has been developed to simulate and predict noise figure of a LNA circuit. Almost all the subject matters covered in this book are accompanied by practical examples. University students will find this book as a potent learning tool and practicing engineers will find it very useful as a reference guide to quickly setup designs using the inexpensive software.