In electronics, resonance occurs when the admittances of circuit components, the imaginary parts of the component impedances, cancel each other out. Operation of circuits at their resonant frequencies can cause oscillation of signals at extreme levels. Nikola Tesla developed the concept of harnessing the capabilities of resonance by transmitting energy wirelessly between two inductively resonant coils. In 1897, his newly patented design, known as the Tesla coil, was an early prototype used to realize his theory. However, only in relatively recent history has the idea been expanded upon and used for commercial applications. Medical devices, such as pacemakers, are powered through resonant inductive coupling; this form of wireless technology has been in use since the 1960s. Battery-operated toothbrushes are typically charged with one or more small coils in the toothbrush and in the cradle, with power transmitted from the cradle to the toothbrush wirelessly. Newer emerging technology, such as radio-frequency identification (RFID) and near field communication (NFC) has provided end-users with relatively simple products for proximity dependent interaction with their personal devices, such as smartphones. This paper describes the theory and limitations of this emerging technology through the design and construction of a wireless NiCd battery charger, as well as through an investigation of some of the more common protocols for wireless data transmission.
Raymond, Seth C., "Wireless Power and Data Transfer Using Inductively Resonant Coils" (2018). Honors College. 428.