Professorship for the Reliability of Technical Systems and Electrical Measurement Technology

The research project "Adaptation and extension of test procedures for networked aircraft to test procedures for networked automobiles in road traffic", funded by the Federal Ministry of Transport and Digital Infrastructure and with Daimler AG and Airbus as associated partners, is in the field of electromagnetic compatibility (EMC). The background to this is the steadily increasing proportion of wireless communication systems with regard to autonomous driving, whose function must be ensured under the influence of electromagnetic interference fields.

The aim of the research project is to partially replace the interference immunity tests via antenna irradiation (HIRF = High Intensity Radiated Field), which are widely used in the automotive sector, with an alternative EMC test procedure that is already established in the aviation industry. Here, currents are injected directly onto the surface of the test object (DCI = Direct Current Injection), which are approximately equivalent in their effect to a field-based immunity test. For this purpose, the equivalence of HIRF and DCI tests must first be verified by means of numerical simulations using characteristic mode analysis. Then, on this basis, suitable test adapters for current injection are to be designed that enable DCI tests to be carried out in an economically practicable manner. In order to include statistically distributed system parameters in these tests, such as ageing effects or other random events, a corresponding mathematical description must also be developed.

Electrical circuits are constantly exposed to interference coupling during operation. To ensure reliable operation, electrical circuits must be protected accordingly in order to meet the required interference immunity. The interference can affect a circuit via various types of coupling (galvanic, capacitive, inductive or radiation coupling).

To protect against radiation coupling, sensitive circuits are usually located in metallic housings that absorb electric fields or redirect magnetic fields depending on the frequency spectrum of the interference coupling. If there is interference with frequency components in the microwave range, such as occurs with broadband pulses (HPEM, LEMP or NEMP), these can couple into the circuits. In this case, the housing also acts as a resonator.

It should now be taken into account that the circuits contain elements with non-linear current-voltage characteristics. This circumstance leads to already known intermodulation phenomena. Non-linear components can therefore significantly influence the reception or interference behavior of an arrangement.

Usually, the description of coupling paths between an interference source and an interference sink is based on terms that are defined in the frequency domain. However, this requires linear transfer functions. One way of generalizing existing methods to interference sinks with non-linear transmission behaviour is to assume that the element with the non-linear characteristic is spatially limited. The receive structure is then split into two parts: The first part has a linear characteristic and contains all the field-theoretic information. It is then possible to model an equivalent network model of this part and to extend it to structures inside resonators. These models are then loaded with a non-linear component. In particular, the network models must reflect the input impedance of the receiving structure under consideration.

Images: Network model of a nonlinearly loaded loop antenna in free space (right) and a nonlinearly loaded loop antenna in a resonator (left). (The non-linear load is shown here as a diode with the given parameters).

In order to check the quality of the equivalent networks, the voltage curve across the diode is determined using a circuit simulator(LTSpice). In addition, a 3D field simulation is carried out with the receiver structure in the time domain(CST MICROWAVE ^STUDIO®). The voltage drops across the diodes from the respective simulation are compared.

Images: top, left: simulation with antenna in free space
top, right: simulation with antenna inside a resonator
bottom: Full-wave simulation in CST MICROWAVE STUDIO

In the field simulation, the loop antenna is subjected to the pulse shown in the form of an electromagnetic wave (red area on the left). The voltage drop across the diode is determined. In the right-hand image, the loop antenna is located in a resonator.

For topic suggestions, please contact Prof. Dr. rer. nat. habil. Frank Gronwald

Master theses

Bachelor theses

• Simulation of states of charge and internal resistances of an assembled battery module to optimize cell pre-sorting and performance (Till Hartmann)

Student research projects

• Topic on AI-supported fabrication of printed circuit boards (leo Scheid)
• Development of an experimental setup for online layer thickness measurement of oil layers on moving metal strips using imaging infrared ellipsometry (Florian Burghaus)

Dissertations

• Jan Ortmann: Theoretical investigation to increase the transmission performance of multi-conductor systems, University of Siegen 2023, http://dx.doi.org/10.25819/ubsi/10437
• Parthib Khound: A Unified Adaptive Cruise Control Framework for Over-damped String Stable Platooning Systems, Shaker Verlag 2023, ISBN: 978-3-8440-9224-0
• Fabian Happ: Method of Moment Analysis of Layered Carbon Fiber Composites with Applications to Electromagnetic Compatibility, Shaker Verlag 2017, ISBN: 978-3-8440-5630-3

Master theses

Bachelor theses

Student research projects