A fully analytic treatment of resonant inductive coupling in the far field

For the application of resonant inductive coupling for wireless power transfer, fabrication of flat spiral coils using ribbon wire allows for analytic expressions of the capacitance and inductance of the coils and therefore the resonant frequency. The expressions can also be used in an approximate way for the analysis of coils constructed from cylindrical wire. Ribbon wire constructed from both standard metals as well as high temperature superconducting material is commercially available, so using these derived expressions as a basis, a fully analytic treatment is presented that allows for design trades to be made for hybrid designs incorporating either technology. The model is then extended to analyze the performance of the technology as applied to inductively coupled communications, which has been demonstrated as having an advantage in circumstances where radiated signals would suffer unacceptable levels of attenuation.

► An analytic framework finds power and efficiency for resonant inductive coupling.
► The framework supports superconducting, resistive and dielectric elements.
► Maximum power transfer occurs at an efficiency of 50% when in close proximity.
► A 100 turn superconducting design achieves 10% efficiency out to 280 coil radii.
► The system response to narrow band amplitude modulation is modeled and presented.