"Microwave engineering pertains to the study and design of microwave circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. In recent years, ascending development of wireless communication products and huge trend for commercial market in this ground caused significant improvement in modeling and simulation approaches of radio frequency (RF) and microwave circuits. Such high-frequency circuits are leading to the development of a large variety of microwave models for passive and active devices and circuit components. Modeling and computer-aided design (CAD) methods have an essential role in microwave designs and simulations. The ever increasing use of wireless devices, such as mobile phones, wireless computing, and remote sensing has resulted in an increased demand and reliance on the use of batteries. But the amount of energy available in the batteries is not only finite but also low, which limits the lifetime of the systems. The research activities in this area encompass both network and transceiver link level issues. Microwave Engineering covers state-of-the-art studies as possible in order to cover in a single volume the main aspects of microwave systems and applications. The book will introduce the basic building blocks of microwave engineering viz. microwave transmission system, passive circuit components at microwave frequency and microwave active devices. The contributed chapters are written by eminent experts, researchers, academics, and microwave engineers, providing wide-ranging information and depicting a wide range of topics on all aspects of microwave engineering and applications. Nowadays advancements in communications systems, in conjunction with the great increasing request for miniaturization and size reduction of wireless systems and devices, have led to an increase of performances and space reduction of modern communications systems and devices. Several RF building blocks have consequently been successfully implemented as integrated circuits (ICs) with different technologies. A very simple approach for the design of tunable, high-quality factor, stable active inductors by means of an active inductor is presented here. Design of antennas with high gain and wide bandwidth is crucial to maximize the received power. Various antenna topologies have been reported in the literature for RF energy harvesting transparent or opaque antennas."