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    Radio Frequency Measurement and Modeling of Miniaturized Components for High-Speed Applications
    With increasing development of high-speed and high-integration electric and electronic systems, miniaturized components, for example, surface mounted device (SMD) capacitors, diodes, transistors and monolithic microwave integrated circuit (MMIC), are widely used in distributed radio frequency (RF) designs. As a result, accurate modeling of the impedance characteristic for miniaturized components becomes a concern in final designs. This project co-funded by DAAD and CSC aims at developing parameterized, scalable model generation illustrated in the figure below. The key research fields are: (1) identification of major parasitic effects, (2) de-embedding/calibration techniques for both simulation and measurements, and (3) automated model synthesis.
      55
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    Properties of Orbital Angular Momentum (OAM) Waves with Respect to Wireless Communication in Complex Environments and to Electromagnetic Interference
    The proposed project here aims to contribute scientifically in the area of wireless communication based on the Orbital Angular Momentum (OAM) property of electromagnetic waves in the lower part of the microwave spectrum (up to 10 GHz). OAM carrying waves have been explored and used in the past mostly in the optical regime. Only about ten to fifteen years ago utilization for wireless communication at “radio frequencies” started to be explored and is still being explored. While it could be shown during this time that OAM antennas are in principle equivalent to MIMO antennas and, hence, there is no real bandwidth advantage over existing technology there are still many open scientific questions related to OAM waves generation, propagation, and reception. Questions being explored in this project pertain both to the fundamental electromagnetic perspective (reflection, diffraction, scattering, shielding, superposition/interference etc.) as well as to the more applied communication engineering perspective (individual antenna choice, array design, mode isolation, impedance matching, useful range of distances, bandwidth considerations, behavior in complex environments and environments with aggressors etc.). To allow this, the project proposes a combination of numerical and experimental approaches. Numerical simulations will be performed an in-house tool based on the method of moments. In parallel, prototypes of OAM antennas will be designed and tested in an antenna measurement chamber at TUHH, the results of which will be compared to results of simulations for validation. The specific objectives of project are as follows: (1) Better understanding and description of fundamental electromagnetic properties of OAM waves such as reflection, diffraction, scattering, shielding, superposition/interference as well as behavior in complex environments leading to multi-path propagation. (2) Generation of guidelines for OAM antenna array design both with respect to the contribution from the individual antenna element as well as the contribution of the array design. (3) Quantification and evaluation of OAM based communication in complex environments and subject to electromagnetic interference. (4) Development of a measurement procedure for OAM antenna arrays and OAM based communication using an existing antenna measurement system at TUHH and validation of selected numerical results. We are convinced that the results of this project will also help to further elucidate the practical, engineering side of the question whether OAM based communication has the potential for a wider range of applications or not.
      195
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      154
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    Hybrid Simulation of Electromagnetic Field Interaction with Metallic Structures Showing Massive Nonlinear Loading
    The proposed project aims to contribute scientifically at the intersection of three different research areas: (1) the physics of electromagnetic field interaction with nonlinearly loaded, electrically large structures and surfaces, (2) novel engineering applications for such structures and surfaces, and (3) efficient and stable numerical modeling and simulation of such structures and surfaces. The massive loading of metallic structures, i.e. the connection of several hundreds of nonlinear loads over an electrically large area, has been of high interest in the recent past and poses new challenges and opportunities for fundamental research. Examples and applications that are foreseen or already looked at for these kind of structures and surfaces include energy-selective shielding, waveform-dependent absorption, self-focusing of surface waves, RF limiters, subwavelength imaging, nonlinear radar and switching, and time-domain windowing among others. Due to this high interest it is very likely that there will be an increasing demand for efficient and validated numerical methods for design and optimization of nonlinearly loaded structures and surfaces in the near future. Based on previous work of the groups of Prof. Schuster at Hamburg University of Technology (TUHH) and the group of Prof. Grivet-Talocia at Politecnico di Torino (POLITO) it is proposed to generate a novel hybrid simulation technique addressing this need. The technique will use the integral equation based Method of Moments (MoM) for characterization of the linear part (i.e. the metallic structures and surfaces) of the problem and a combination of Model Order Reduction (MOR) and Waveform Relaxation (WR) for dealing with the complete system including many nonlinear loads. The research challenge lies in the suitable combination and adaption of these well-known methods (MoM, MOR, WR) for meeting the demands on accuracy, stability, and efficiency of the numerical simulation of massively nonlinearly loaded (i.e. 1000 and more nonlinear loads), electrically large structures and surfaces.
      183
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    HIRF Protection Using Energy Selective Diode Arrays
    With more and more electromagnetic energy being transmitted by radar, radio, TV, mobile, hotspot (Wi-Fi), satellite, and other transmitters, detrimental effects of electromagnetic waves on the environment, e.g. disturbance or even damage of electronic equipment, become more and more a concern. To ensure safe operation of various electronic systems in transmitting or receiving states, electromagnetic protection should be considered especially against high intensity radiation fields (HIRFs). This project focuses on diode arrays for implementation of self-activated and energy selective blocking of electromagnetic wave. Based on the nonlinear behavior of diodes, diode arrays can be shown to be transparent with respect to small field amplitudes and opaque to large field amplitudes. In theory, we expect the structure to work like a spatial switch, while in practice its protection performance is limited by several factors, such as the response time and operating frequency range of the diodes, the transmission loss of the protective structure and near field coupling effects. Therefore, accurate full wave simulation are being used for evaluation of the electromagnetic performance of protective diode arrays. Up to now, mostly infinitely periodic diode arrays have been studied. Next steps include the simulation of finite and non-periodic diode arrays using the electromagnetic field simulator CONCEPT-II.
      94