In [2, 3], the circuit model and evaluation method for conventional and multiple-coil WPT systems are presented to discuss the frequency splitting properties.

Yang et al., "A method of using nonidentical resonant coils for frequency splitting elimination in wireless power transfer," IEEE Transactions on Power Electronics, vol.

However, the added repeater brings the problems of

frequency splitting and sensitivity reduction.

Frequency splitting can be clearly observed as there are two peak output powers.

Shen, "Coupled-mode analysis of

frequency splitting phenomena in CPT systems," Electronics Letters, vol.

Frequency tuning has been carried out to mitigate the

frequency splitting effect and to obtain high efficiency at close distances [11].

Capable of simultaneously processing digital signals across a wide spectrum in real-time, the basic PFT architecture utilises a series of

frequency splitting stages to sub-divide the signal-of-interest band.

For the operating frequency of 10 MHz, the frequency with the maximum transmission coefficient bifurcates at the critical coupling resulting in the well-known

frequency splitting phenomenon.

This two extrema are in accordance with the

frequency splitting observed in Fig.

The authors focus the attention on four sensing strategies: (i) resonance frequency variation, (ii) coupling modulation through symmetry disruption (causing variation of the notch depth), (iii)

frequency splitting (also exploiting symmetry properties), and (iv) amplitude modulation of a harmonic signal.

The

frequency splitting phenomena and constant efficiency characteristics in the over-coupled region can be seen clearly.

Such sensing strategies are resonance frequency variation, coupling modulation through symmetry disruption (causing variation of the notch depth),

frequency splitting (also exploiting symmetry properties), and amplitude modulation of a harmonic signal.