Simulating Magnetoelectric Sensors in Inhomogeneous Magnetic Fields

The scope of this dissertation includes finite element method (FEM) modeling and simulation of magnetoelectric (ME) magnetic field sensors, arrays of ME sensors, as well as combined models including simplified and magnetic resonance imaging (MRI) based human heads as excitation sources for sensor arrays. The ME sensor behavior is simulated through excitation with homogeneous and inhomogeneous magnetic fields, different orientations and positions of the sensors, as well as different excitation mechanisms, including a small coil around the ME sensor or a dipole source inside a human head.

Results show that cantilever ME sensors exhibit highly position-dependent sensitivity and a simple theoretical point-sensor approximation at the geometric center of the sensor is not accurate. 
Furthermore, simulations with a combined model consisting of three orthogonal ME sensors and a simplified human head containing a dipole source show highly position- and direction-dependent behavior of the individual sensors in the array. The sensor output depends on the position and orientation of the source inside of the head, as well as the location and orientation of the individual sensors inside the array, as the ME sensors exhibit a strong sinusoidal dependence with a maximum response at incident magnetic field angles that are parallel to the long axis of the cantilever.
Lastly, improving the head model and using an MRI-based head geometry, combined with an array of fifteen ME sensors, results in valuable insights on the magnetic crosstalk effect between adjacent ME sensors in array configurations. Within such an array in a homogeneous excitation field, the outermost ME sensors exhibit significantly less crosstalk than the innermost sensors, and crosstalk decreases with increasing distance between neighboring sensors.

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