Near-field coupled antennas for use in Inductive Power Transfer Communication Systems

This paper presents the design, implementation and performance of a high bandwidth communications channel for both new and existing inductive (contact-less) power transfer (IPT) applications, wherein power is transferred in the frequency range of 10 kHz to 50 kHz. Two novel near field capacitive or inductive antennas are introduced that are specifically designed to operate in close proximity to a communications track and to inject and receive data signals at a data rate of 10 Mbps or higher with an appropriate modem. The channel operates in the frequency range of 100 MHz to 600 MHz and therefore is unaffected by the IPT power frequencies and any associated switching harmonics, enabling all of the advantageous characteristics of IPT systems to be maintained. The ability of the antennas to function reliably when subjected to horizontal and vertical displacements has been proven by extensive measurements. Magnetic coupling theory can be applied to determine both the power transfer and the insertion loss of the antennas to the communications track. These calculations have been verified by both practical measurements and simulations of the channel using an FEM magnetic modelling package. For an inductive antenna and 300 ohm ribbon cable communications track a theoretical insertion loss of 29.6 dB was calculated which compares favourably with a measured loss of 32 dB and a simulated loss of 29.4 dB. The communications system was implemented on an industrial mono-rail system and a high bandwidth channel was successfully achieved.