# FSK-based Simultaneous Wireless Information and Power Transfer in Inductively Coupled Resonant Circuits Exploiting Frequency Splitting

## TL;DR

This paper explores FSK modulation for simultaneous wireless power transfer in inductively coupled resonant circuits, addressing frequency splitting effects and proposing a rectified FSK scheme with analytical, numerical, and experimental validation.

## Contribution

It introduces a novel FSK-based modulation scheme tailored for frequency splitting phenomena in inductive power transfer, including a rectified version with comprehensive analysis and experimental validation.

## Key findings

- FSK matches the double-peak transfer function at high Q
- Rectified FSK improves output power and implementation simplicity
- Proposed receiver achieves low-cost, incoherent detection

## Abstract

Inductively coupled resonant circuits are affected by the so-called frequency splitting phenomenon at short distances. In the area of power electronics, tracking of one of the peak frequencies is state-of-the-art. In the data transmission community, however, the frequency splitting effect is often ignored. Particularly, modulation schemes have not yet been adapted to the bifurcation phenomenon. We argue that binary frequency shift keying (2-ary FSK) is a low-cost modulation scheme which well matches the double-peak voltage transfer function $H(s)$, particularly when the quality factor $Q$ is large, whereas most other modulation schemes suffer from the small bandwidths of the peaks. Additionally we show that a rectified version of 2-ary FSK, coined rectified FSK (RFSK), is even more attractive from output power and implementation points of view. Analytical and numerical contributions include the efficiency factor, the impulse response, and the bit error performance. A low-cost incoherent receiver is proposed. Theoretical examinations are supported by an experimental prototype.