# Adaptive Impedance Matching Network for Contactless Power and Data Transfer in E-Textiles

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Methods

#### 2.1. Link Design

#### 2.1.1. Link Characterization

#### 2.1.2. Link Compensation

#### 2.1.3. Quality Factor

#### 2.1.4. Non-Idealities

#### 2.1.5. Practical Implementation

#### 2.2. Supporting Electronics

#### 2.2.1. Carrier Generator

#### 2.2.2. Modulation and Demodulation

#### 2.2.3. Coupling Detection

#### 2.2.4. Practical Implementation

## 3. Results and Discussion

#### 3.1. Maximum Data Speeds

#### 3.2. Power Transfer Capabilities

#### 3.3. Coupling Correction

#### 3.4. Future Work

## 4. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 6.**System Q for various loads and coupling factors (k). $L=500$ nH and $\omega =2\pi \xb713.56$ MHz.

**Figure 7.**A grid of Nyquist plots showing how the real part (x-axis) and imaginary part (y-axis) of the input impedance of the link change as one of the link parameters (${k}_{1}$, ${k}_{2}$, and ${L}_{11}$–${L}_{22}$) is varied from −10% to +10% of its nominal value. Each column of plots corresponds to a different parameter, whereas the rows indicate different nominal values for L. A longer line indicates a greater sensitivity to the selected parameter. The tick-marks on the axis are placed at a 50 $\Omega $ distance from the origin. Each simulation was performed at a frequency of $13.56$ MHz with a 50 $\Omega $ load and a nominal coupling factor of 0.7.

**Figure 8.**Nyquist plot of the link input impedance as the length of the transmission line between ${L}_{12}$ and ${L}_{21}$ increases from 0 to 0.5 m. The various traces correspond to different characteristic transmission line impedances. The transmission line used in the simulation has a wave propagation speed of $0.6c$ and is terminated in a 50 $\Omega $ load.

**Figure 10.**(

**a**) Simulated time-domain waveforms of the output signal of the modified class-E amplifier. (

**b**) Spectral use of the output signal.

**Figure 12.**Image of the prototype. In this picture, coil pair #2 is placed in a holder with a fixed spacing, and coil pair #1 is loose.

**Figure 13.**Signal waveforms during square wave communication. (

**a**) Master-to-slave communication at 120 kHz. The top signal is the modulated carrier sent by the master. The bottom signal is the demodulated signal output by the slave. The vertical scale is 5 V/div. (

**b**) Slave to master communication at 180 kHz. The top signal is the data stream presented to the input of the slave. The bottom signal is the demodulated signal output by the master. The vertical scale is 2 V/div.

**Figure 15.**Measured DC efficiency and phase detector output for various DC loads at a coil distance of 1.5 mm.

**Table 1.**Common values for primary compensation capacitors and their resulting transmission matrices at resonance ($\omega ={\omega}_{0}$).

Topology | ${\mathit{C}}_{\mathit{p}}$ | ${\mathit{C}}_{\mathit{s}}$ | $\left[\begin{array}{c}\mathit{T}\end{array}\right]$ |
---|---|---|---|

SS | $\frac{1}{{\omega}_{0}^{2}\widehat{L}}$ | $\frac{1}{{\omega}_{0}^{2}\widehat{L}}$ | $\left[\begin{array}{cc}0& \frac{{\omega}_{0}\widehat{k}\widehat{L}}{j}\\ \frac{j}{{\omega}_{0}\widehat{k}\widehat{L}}& 0\end{array}\right]$ |

SP | $\frac{\widehat{1}}{{\omega}_{0}^{2}\widehat{L}(1-{\widehat{k}}^{2})}$ | $\frac{1}{{\omega}_{0}^{2}\widehat{L}}$ | $\left[\begin{array}{cc}\widehat{k}& 0\\ 0& \frac{1}{\widehat{k}}\end{array}\right]$ |

PP | $\frac{(1-{\widehat{k}}^{2})\widehat{L}}{{\omega}_{0}^{2}{\widehat{L}}^{2}{(1-{\widehat{k}}^{2})}^{2}+{\widehat{k}}^{4}{Z}_{l}^{2}}$ | $\frac{1}{{\omega}_{0}^{2}\widehat{L}}$ | $\left[\begin{array}{cc}\widehat{k}& \frac{\widehat{L}{\omega}_{0}(1-{\widehat{k}}^{2})}{\widehat{k}}\\ \frac{j{\omega}_{0}\widehat{L}\widehat{k}(1-{\widehat{k}}^{2})}{{\omega}_{0}^{2}{\widehat{L}}^{2}{(1-{\widehat{k}}^{2})}^{2}+{Z}_{l}{\widehat{k}}^{4}}& \frac{{Z}_{l}{\widehat{k}}^{4}}{{\omega}_{0}^{2}{\widehat{L}}^{2}{(1-{\widehat{k}}^{2})}^{2}+{Z}_{l}{\widehat{k}}^{4}}\end{array}\right]$ |

PS | $\frac{{Z}_{l}^{2}}{{\omega}_{0}^{2}\widehat{L}{Z}_{l}^{2}+{\omega}_{0}^{3}\widehat{L}{\widehat{k}}^{4}}$ | $\frac{1}{{\omega}_{0}^{2}\widehat{L}}$ | $\left[\begin{array}{cc}\frac{1}{\widehat{k}}& \frac{{\omega}_{0}\widehat{k}\widehat{L}}{j}\\ \frac{\widehat{L}{\widehat{k}}^{3}{\omega}_{0}}{j{\widehat{L}}^{2}{\widehat{k}}^{4}{\omega}_{0}^{2}+j{Z}_{l}}& \frac{\widehat{k}{Z}_{l}}{{\widehat{L}}^{2}{\widehat{k}}^{4}{\omega}_{0}^{2}+{Z}_{l}}\end{array}\right]$ |

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**MDPI and ACS Style**

Lindeman, P.; Steijlen, A.; Bastemeijer, J.; Bossche, A.
Adaptive Impedance Matching Network for Contactless Power and Data Transfer in E-Textiles. *Sensors* **2023**, *23*, 2943.
https://doi.org/10.3390/s23062943

**AMA Style**

Lindeman P, Steijlen A, Bastemeijer J, Bossche A.
Adaptive Impedance Matching Network for Contactless Power and Data Transfer in E-Textiles. *Sensors*. 2023; 23(6):2943.
https://doi.org/10.3390/s23062943

**Chicago/Turabian Style**

Lindeman, Pim, Annemarijn Steijlen, Jeroen Bastemeijer, and Andre Bossche.
2023. "Adaptive Impedance Matching Network for Contactless Power and Data Transfer in E-Textiles" *Sensors* 23, no. 6: 2943.
https://doi.org/10.3390/s23062943