Chapter 10 evaluates the application of multicarrier waveforms to improve the efficiency of wireless power transfer systems, and proposes efficient power transmitter architectures, including one based on a mode-locked active antenna array.

Chapter 9 addresses the concept of wake-up radios for IoT and describes the implementation of a wake-up radio system with addressing capabilities for wireless sensor network application.

Chapter 11 concludes the book with an elegant demonstration of wireless power transfer and backscatter communication applied to a practical problem by proposing and prototyping a remote control system that operates without batteries or other local power source in the remote control unit.

Chapter 2 describes the fundamentals, applications, standardization, and operating principles of RFID technology and offers a glimpse into the design considerations and architectures of modern UHF RFID readers.

Chapter 6 explores low-cost and low-complexity techniques for the design of an ISO 18000-63-compliant RFID reader and presents an experimental prototype to validate the proposed concepts.

Chapter 3 discusses the fundamentals of backscatter radio communications, analyzes the RFID backscatter channel, its major limitations and mitigation approaches, and presents recent advances including novel RFID quadrature backscatter modulation techniques.

Chapter 1 walks the reader through the fascinating history and evolution of RFID technology from the early days of radio transmissions in the nineteenth century to today’s internet of things.

In the last few chapters we have examined the propagation of electromagnetic waves; freely propagating waves in Chapter 8, waves guided along transmission lines in Chapter 9, and waves guided within waveguides in Chapter 10. But we paid no attention in these discussions to the generation of these waves. In this chapter our goal is to remedy this shortcoming. As we will show, an oscillating current in an open-ended wire can produce an electromagnetic wave. We will examine the distribution of the radiated power, the total radiated power, the efficiency of the power generation, the polarization of the wave, and the input impedance of a few simple radiating systems. We will start by examining a short, or elemental, dipole antenna, and then expand this to longer, more efficient, antennas. We will also look at the field distribution and power density produced by an array of antennas, and show how the distribution varies with the relative phase of the radiators.

We have now reached the end of our journey exploring the fundamentals and simple applications of electromagnetics. We are surrounded by applications of these concepts in our daily lives. A partial list includes electric motors and generators, microwave ovens, remote controls for our television or garage door opener, magnetic resonance imaging, broadcast, satellite, or cable television, high-speed chip-to-chip communications on printed circuits, and many, many more. While we have not dealt much here with the specific engineering principles of many of these devices, we have tried to lay the fundamental concepts on which they are based.