M. Sc. Christin Bald Room: C-01.022 (ZEVS) Kaiserstraße 2, 24143 Kiel, Germany Phone: +49 431 880-6129 E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Research: Real-time Signal Processing for Magnetoelectric Sensors

To measure signals emitted by bio-medical sources like the heart or a skeleton muscle with a high temporal resolution, the generated electrical potentials on the body surface or the generated magnetic flux are usually measured. One big difference between the two measurement types (and the main advantage of the measurement of the magnetic flux) is that the magnetically measured signals are less distorted by surrounding materials of the source compared to their electric counterparts. Unfortunately, the operation of suitable state-of-the-art sensors, which are mainly based on super-conducting quantum interference devices (SQUIDs), is in general very expensive.

Sensors based on the magneto-electric (ME) effect have the potential to be a suitable alternative. During the last years the new ME sensors, developed in collaborative research groups at Kiel University, reached a sensitivity level which makes it possible to detect the human heart beat. Since no cooling is required for this sensor type, the operational cost are relative low. This could lead to an increased number of magnetic measurements for medical diagnostics in the future. In addition the sensors can be placed closer to the measured object and arrays of higher sensor probability can be built up, because the sensors are smaller in size.

The challenging part arises, because these sensors also record mechanical vibrations, whereby the desired signals are superimposed by unwanted signal components. To reduce this coupling effect and increase the usability of such sensors in measurement environments signal processing techniques are applied. Approaches are based on adaptive noise cancellers using non-magnetic noise reference sensors or intelligent sensor read-out schemes.

Related topics:

• Noise cancellation and suppression
• Signal combination
• Beamforming
• Signal analysis
• Biomagnetic measurements

Further interests:

• Real-time digital signal processing
• Localization

Short CV

Publications

1. J. Hoffmann, C. Bald, T. Schmidt, M. Boueke, E. Engelhardt, K. Krüger, E. Elzenheimer, C. Hansen, W. Maetzler, G. Schmidt: Designing and Validating Magnetic Motion Sensing Approaches with a Real-time Simulation Pipeline, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 455-458, doi: 10.1515/cdbme-2023-1114

2. M. Boueke, J. Hoffmann, T. Schmidt, C. Bald, R. Bergholz, G. Schmidt: Model-based Tracking of Magnetic Sensor Gloves in Real Time, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 85-88, doi: 10.1515/cdbme-2023-1022 , open access

3. M. Gerhardt, L. Zimoch, C. Dorn, E. Elzenheimer, C. Bald, T. Lerg, J. Hoffmann, S. Kaps, M. Höft, G. Schmidt, S. Wulfinghoff, R. Adelung: Self-powered Elementary Hybrid Magnetoelectric Sensor, Nano Energy, Volume 115, July 2023, doi: 10.1016/j.nanoen.2023.108720

4. C. Bald, R. Bergholz, G. Schmidt: Automatic Localization of an Ultrasound Probe with the Help of Magnetic Sensors, Current Directions in Biomedical Engineering, vol. 8, no. 2, 2022, pp. 317-320.

5. E. Elzenheimer, C. Bald, E. Engelhardt, J. Hoffmann, P. Hayes, J. Arbistin, A. Bahr, E. Quandt, M. Höft, G. Schmidt: Quantitative Evaluation for Magnetoelectric Sensor Systems in Biomagnetic Diagnostics, Sensors 2022, 22(3), 1018, doi: 10.3390/s22031018 , open access

6. P. Piepjohn, C. Bald, G. Kuhlenbäumer, J.S. Becktepe, G. Deuschl, G. Schmidt: Real-time classification of movement patterns of tremor patients, Biomedical Engineering / Biomedizinische Technik, vol. 67, no. 2, 2022, pp. 119-130. doi: https://doi.org/10.1515/bmt-2021-0140

7. B. Spetzler, P. Wiegand, F. Ilgaz, C. Bald, C. Kirchhof, G. Schmidt, D. Meyners, R. Rieger, F. Faupel: Delta-E Effect Magnetic Field Sensors for Sensor Arrays, Proc. IIM, Kiel, Germany, 2022

8. J. Hoffmann, E. Elzenheimer, C. Bald, C. Hansen, W. Maetzler, G. Schmidt: Active Magnetoelectric Motion Sensing: Examining Performance Metrics with an Experimental Setup, Sensors 2021, 21(23), 8000, doi: 10.3390/s21238000, open access

9. C. Bald, G. Schmidt: Processing Chain for Localization of Magnetoelectric Sensors in Real Time. Sensors 2021, 21, 5675. DOI: doi.org/10.3390/s21165675

10. B. Spetzler, C. Bald, P. Durdaut, J. Reermann, C. Kirchhof, A. Teplyuk, D. Meyners, E. Quandt, M. Höft, G. Schmidt, F. Faupel: Exchange biased delta-E effect enables the detection of low frequency pT magnetic fields with simultaneous localization, Scientific Reports, Volume 11, March 2021

11. C. Bald, N. Simoski, E. Elzenheimer, G. Schmidt: Aktive Schirmung optisch gepumpter Magnetometer mittels Helmholtzspulen, Biosignale Workshop, 2020, Kiel, Germany

12. P. Piepjohn, C. Bald, G. Kuhlenbäumer, G. Deuschl, G. Schmidt: Echtzeitklassifizierung von Bewegungsmustern von Tremorpatienten, Biosignale Workshop, 2020, Kiel, Germany

13. J. Hoffmann, E. Elzenheimer, C. Bald, C. Hansen, W. Maetzler, G. Schmidt: Magnetoelektrische Sensoren zur Bewegungsdetektion und -analyse, Biosignale Workshop, 2020, Kiel, Germany

14. C. Bald, E. Elzenheimer, J. Reermann, T. Sander-Thömmes, G. Schmidt: Amplitudenverlauf des Herzmagnetfeldes als Funktion des Abstandes, Biosignale Workshop, 2018, Erfurt, Germany

15. J. Reermann, C. Bald, P. Durdaut, A.Piorra, D. Meyners, E. Quandt, M. Höft, and G. Schmidt: Adaptive mehrkanalige Geräuschkompensation für magnetoelektrische Sensoren, Proc. DAGA, Kiel, Germany, open access, 2017

16. J. Reermann, C. Bald, S. Salzer, P. Durdaut, A. Piorra, D. Meyners, E. Quandt, M. Höft, and G. Schmidt: Comparison of Reference Sensors for Noise Cancellation of Magnetoelectric Sensors, IEEE Sensors 2016, Orlando, November 2016

Poster

1. C. Bald, E. Elzenheimer, J. Kreisel, N. Simoski, A. Namenas, J. Reermann, T. Demming, N. Frey, G. Schmidt: Magnetocardiography with Optically Pumped Magnetometers Integrated in a Patient Bed, BMT Frankfurt, September 2019