Project B2 - Digital Signal Processing

This project forms the key connection between the sensor system outputs of the investigated magnetoelectric (ME) sensors (A projects) following the first analogue enhancement (B1) and the medical applications of the CRC (remaining B projects). Multi-stage enhancement using digital signal processing techniques have been implemented and localization as well as calibration systems are developed. During the current (second) funding period, multichannel read-out schemes are implemented for the concurrent use of multiple sensors, possibly in geometrical array structures. Blind source separation algorithms are in place, allowing, for example, the separation of heart signals of fetuses with respect to the mothers’, which was the test setup investigated using a model torso and artificial signals. Additionally, a processing pipeline was developed, at the core of which an algorithm determines the position and orientation of the sensors using actuator coils for a known field excitation. This is based on a forward modelling approach, considering point models for the sensors and a lead field matrix for the localization space under investigation. Lastly, nonlinear and automated noise cancellation approaches are investigated. These advances are made available to the different application projects for the more informed and prepared solution of the respective inverse problems.

In the forthcoming (third) funding period, our objective is to advance the attained outcomes through the employment of more sophisticated processing methodologies. This endeavor will be facilitated through collaboration with medical practitioners from the UKSH Kiel, with a primary focus on the innovation of groundbreaking medical apparatuses designed to enhance the diagnosis and therapeutic interventions for patients. A pivotal objective encompasses the formulation of a precision-driven method, intended for the real-time electromagnetic localization of an ultrasound probe (PI: Bergholz). This innovative pursuit involves the meticulous capture of both the positional coordinates and the line-of-sight attributes pertinent to the ultrasound probe. Subsequently, the amalgamation of these parameters engenders a resultant vector, poised to potentially facilitate the creation of a three-dimensional rendition based on the initial two-dimensional ultrasound image. If successful, this shall herald an entirely unprecedented paradigm of three-dimensional imaging, obviating the prerequisite for ionizing radiation. The subsequent undertaking (PI: Ellrichmann), is centered upon the determination of the spatial coordinates and angular orientation of both an endoscope and an endoscopic wireless motility capsule. These instruments, enhanced with innovative magnetoelectric sensors or microelectromechanical systems (MEMS) actuators, are the subject of investigation, collaborating closely with project B13. The configuration employs an array of multiple sensors and actuators, deployed in fixed arrangements with respect to the patient bed setup, thus, relating them to the investigated patient.

The intended scope of this venture encompasses an augmentation of the existing algorithmic framework that was realized in the current funding period. To this end, an extension towards gradient-based methodologies and swarm optimization techniques is proposed, aiming to enhance precision and performance. Additionally, tailor-made adjustments such as enhanced sensor and actuator models, adaptive selection of localization (transmit) signals, position-specific power adjustment and adaptive adjustment of frame duration will be instituted to adapt the algorithms to the specific requirements of the intended applications. Concurrent with algorithmic advancements, the requisite experimental setups will be meticulously devised. Leveraging proprietary designs emanating from parallel projects within the Collaborative Research Centre (CRC), essential hardware components (such as printed-circuit-boards-based coils) will be extended and corresponding processing structures (such as automatic calibration procedures) will be made available. Special emphases will be put on calibration and equalization scheme for 3D sensor setups with corresponding 3D (direction- and frequency-dependent) equalization schemes. An integral facet of the project involves an exploration of adaptive signal enhancement stages in the context of sensor operations immersed in magnetic alternating current (AC) fields. This endeavor is particularly germane to the operation of MEMS cantilever actuators, as employed in the endoscopic wireless motility capsules (WMC) designed in B13.

Involved Researchers

Person		Role
	M.Sc. Christin Bald Electrical Engineering Digital Signal Processig and System Theory	Doctoral researcher (parental leave)
	M.Sc. Moritz Boueke Electrical Engineering Digital Signal Processig and System Theory	Doctoral researcher
	Prof. Dr. Gerhard Schmidt Electrical Engineering Digital Signal Processig and System Theory	Principal investigator

Role within the Collaborative Research Centre

B2 will participate in the focus groups F3 - Comparison of Sensor Concepts and F6 - Biomedical Applications. Close cooperation is planned with the following projects:

Project-related Publications

M. Gerhard, 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, vol. 115, 108720, 2023.

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, 85-88, 2023.

H. Wolframm, J. Hoffmann, R. Burgardt, E. Elzenheimer, G. Schmidt, M. Höft: PCB Coil Enables In Situ Calibration of Magnetoelectric Sensor Systems, Current Directions in Biomedical Engineering, vol. 9, no. 1, 567-570, 2023.

A. Kumar, E. Lyzhko, L. Hamid, A. Srivastav, U. Stephani, N. Japaridze:  Neuronal Networks Underlying Ictal and Subclinical Discharges in Childhood Absence Epilepsy, J Neurol, Mar., 270(3), 1402-1415, 2023.

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, pp. 317-320, 2022.

E. Elzenheimer, C. Bald, E. Engelhardt, J. Hoffmann, P. Hayes, J. Arbustini, A. Bahr, E. Quandt, M. Höft, G. Schmidt: Quantitative Evaluation for Magnetoelectric Sensor Systems in Biomagnetic Diagnostics, MDPI Sensors, vol. 22, no. 3, 1018, 2022.

C. Bald, G. Schmidt: Processing Chain for Localization of Magnetoelectric Sensors in Real Time, Sensors, vol. 21, issue 16, 5675, 2021.

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 11, Article no. 5269, 2021.

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

B. Spetzler, C. Kirchhof, J. Reermann, P. Durdaut, M. Höft, G. Schmidt, E. Quandt, F. Faupel: Influence of the Quality Factor on the Signal to Noise Ratio of Magnetoelectric Sensors Based on the Delta-E Effect, Applied Physics Letters, vol. 114, issue 18, 183504, 2019.

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

S. Salzer, V. Röbisch, M. Klug, P. Durdaut, J. McCord, D. Meyners, J. Reermann, M. Höft, R. Knöchel: Noise Limits in Thin-Film Magnetoelectric Sensors With Magnetic Frequency Conversion, IEEE Sensors Journal, vol. 18, no. 2, pp. 596-604, 2018.

A. Kittmann, P. Durdaut, S. Zabel, J. Reermann, J. Schmalz, B. Spetzler, D. Meyners, N. X. Sun, J. McCord, M. Gerken, G. Schmidt, M. Höft, R. Knöchel, F. Faupel, E. Quandt: Wide Band Low Noise Love Wave Magnetic Field Sensor System, Scientific Reports, vol. 8, no. 278, 2018.

P. Durdaut, J. Reermann, S. Zabel, C. Kirchhof, E. Quandt, F. Faupel, G. Schmidt, R. Knöchel, M. Höft: Modeling and Analysis of Noise Sources for Thin-Film Magnetoelectric Sensors Based on the Delta-E Effect, IEEE Transactions on Instrumentation and Measurement, vol. 66, no. 10, pp. 2771-2779, 2017.

J. Reermann, C. Bald, P. Durdaut, A.Piorra, D. Meyners, E. Quandt, M. Höft, G. Schmidt: Adaptive Mehrkanalige Geräuschkompensation für Magnetoelektrische Sensoren, Proc. DAGA, Kiel, Germany, 2017.

P. Durdaut, S. Salzer, J. Reermann, V. Röbisch, J. McCord, D. Meyners, E. Quandt, G. Schmidt, R. Knöchel, M. Höft: Improved Magnetic Frequency Conversion Approach for Magnetoelectric Sensors, IEEE Sensors Letters, vol. 1, no. 3 , 2017.

P. Durdaut, S. Salzer, J. Reermann, V. Röbisch, P. Hayes, A. Piorra, D. Meyners, E. Quandt, G. Schmidt, R. Knöchel, M. Höft: Thermal-Mechanical Noise in Resonant Thin-Film Magnetoelectric Sensors, IEEE Sensors Journal, vol. 17, no. 8, pp. 2338-2348, 2017.

L. Hamid, A. Dalaf, I. Merlet, N. Japaridze, U. Heute, U. Stephani, A Galka, F. Wendling, M. Siniatchkin: Source Reconstruction Via the Spatiotemporal Kalman Filter and LORETA from EEG Time Series with 32 or Fewer Electrodes, Engineering in Medicine and Biology Society (EMBC), 2017 39th Annual International Conference of the IEEE, Seogwipo, South Korea, pp. 2218-2222, 2017.

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