CHAPTER ONE
INTRODUCTION
1.1. Overview of Wireless Power Transfer
Wireless power transfer (WPT) is the transmission of electrical energy without wires as a
physical link. In a wireless power transmission system, a transmitter device, driven by
electric power from a power source, generates a time-varying electromagnetic field, which
transmits power across space to a receiver device, which extracts power from the field and
supplies it to an electrical load. The technology of wireless power transmission can eliminate
the use of the wires and batteries, thus increasing the mobility, convenience, and safety of an
electronic device for all users. Wireless power transfer is useful to power electrical devices
where interconnecting wires are inconvenient, hazardous, or are not possible.[1]
The idea of wireless power transfer (WPT) has been around since the inception of electricity.
In the late 19th century, Nikola Tesla described the freedom to transfer energy between two
points without the need for a physical connection to a power source as an “all-surpassing
importance to man.”[2]
While several methods of wireless power have been introduced since Tesla’s work, including
near-field magnetic resonance and inductive coupling, laser-based optical power
transmission, and far-field Radio Frequency (RF) /Microwave energy transmission, only
RF/microwave and laser-based systems are truly long-range methods.[3]
In general a wireless power system consists of a "transmitter" device connected to a source of
power such as a mains power line, which converts the power to a time-varying
electromagnetic field, and one or more "receiver" devices which receive the power and
convert it back to DC or AC electric current which is used by an electrical load.[4][5]
