One method involved in wireless power transfer (WPT) technology is to employ magnetic resonance with tight magnetic coupling. Researchers have measured a resonance in vertical multi-coupled coils that have tight magnetic coupling. They also analyzed the transferred power with respect to resonances of vertical multi-coupled coils.
Tests have been validated and determined that both series and parallel resonant frequencies of input impedance coincide with the frequency at which the transferred power is increased. It’s also been validated that the series resonant frequencies of the input impedance coincide with the frequencies at which the EMI has increased for a constant ac voltage source.