Lehrstuhl für Informations- und Codierungstheorie

Simultaneous Wireless Information and Power Transfer


Simultaneous wireless information and power transfer (SWIPT) is an extension of wireless power transfer (WPT), known from contactless smartphone charging. Besides wireless power transfer, in SWIPT data is transmitted simultaneously via the same magnetic or electro-magnetic field. The emerging research area of SWIPT is useful for a wide range of applications, ranging from low-energy harvesting (e.g., wireless sensor networks, wearables, and implants), to medium-energy devices (e.g., smartphones and notebooks), up to high-power devices (e.g., electric vehicles, robots, and underwater vehicles). Short-range medium-to-high energy applications are usually based on magnetic fields generated by coils, whereas long-range low-energy use cases are typically based on electromagnetic fields radiated by antennas.

At our chair, different aspects of optimizing the waveform design have been investigated. In [1], a binary frequency-shift keying approach has been published for inductively coupled resonant circuits. This work is motivated by the fact that at short distances the center frequency of inductively coupled resonant circuits splits into two frequencies. This effect is known as frequency splitting or as bifurcation. Binary frequency shift keying is naturally matched to the bifurcation phenomenon, as long as the "mark" and "space" frequencies of the FSK design are adapted to the two splitting frequencies. A power efficiency of about 90% is reported, which is similar to that of advanced WPT systems. In other words, the FSK-based data modulation has a minor impact on the power efficiency factor.

In [2], a different approach is targeted: power transmission and data transmission are conducted in different frequency bands. Concerning power transmission, the bandwidth should be as narrow as possible, i.e., the coils should be in resonance. At below 100 kHz, switching losses are reasonable. Vice versa, for data transmission the bandwidth should be maximized in order to support sufficiently large data rates. In order to take these conflicting design rules into account, expertise in circuit design, digital modulation, and power electronics are mandatory. A 200 W prototype has been implemented and tested in sea water. Currently, effort is taken to shift the power range by using high-power GaN switches.

In unpublished work, our chair has contributed to the development of a contactless underwater docking station. Towards this goal, different SWIPT technologies have been assembled and compared.


Selected References:

[1] P.A. Hoeher, "FSK-based simultaneous wireless information and power transfer in inductively coupled resonant circuits exploiting frequency splitting," IEEE Access, vol. 7, pp. 40183-40194, Mar. 2019.

[2] J.M. Placzek, P.A. Hoeher, P.K. Prasobhu, M. Liserre, and G. Buticchi, "Simultaneous wireless information and GaN-based power transfer exploiting a dual frequency band," in Proc. 44th Annual Conference of the IEEE Industrial Electronics Society (IECON '18), Washington DC, pp. 4840-4845, Oct. 2018.


The projects have been sponsored by: