Authors:	Florian, Bergmann
Advisor:	Gerhard, Jakob
Title:	Nonlinear Dielectric Responses of Glasses and Glass-Ceramics in the Microwave Range
Online publication date:	9-Feb-2022
Year of first publication:	2022
Language:	english
Abstract:	The ever-increasing data traffic by a growing number of communicating wireless devices calls for a larger bandwidth and for its efficient use in the fifth (5G) and sixth (6G) mobile communication generations. The bandwidth is extended by utilizing higher frequencies. However, a phenomenon that troubles the efficient use of bandwidth is passive intermodulation (PIM). PIM leads to channel cross talk and has its origin in any kind of nonlinear response. One such source is the nonlinear electric susceptibility of dielectrics in microwave devices. This work deals with the characterization of the nonlinear electric susceptibility of glasses and glass-ceramics at microwave frequencies. Glasses and glass-ceramics exhibit advantageous properties for microwave devices compared to classically employed sintered ceramics or PTFE compounds, such as better metal adhesion and higher homogeneity. The nonlinear susceptibility of a Ba 4 Al 2 Ti 10 O 27 glass-ceramic was determined to |χ 3 | = (4 ± 2) × 10 −16 m 2 /V 2 at 1GHz . The intermodulation level observed during this measurement cannot be adequately described by a classical power-law representation of the nonlinearity. While the power-law description is only applicable within its radius of convergence, an alternative approach based on Fourier coefficient integrals allows accurate description of the dependency of intermodulation levels on input power over a wider range. Using established physical nonlinear response models, this description additionally allows determining previously inaccessible model parameters, such as the linear contribution of the nonlinear mechanism (χ 1 = 10 −8 ). The experimental setup was extended to also characterize materials with lower permit- tivity, including a glass. SiO 2 immiscibilities in the glass were found to increase the nonlinear microwave response significantly without having a measurable impact on the linear dielectric properties. For comparison, the nonlinear susceptibility of the Ba 4 Al 2 Ti 10 O 27 glass-ceramic was measured with a 1kHz ultra-high precision capacitance bridge under a high DC voltage bias, resulting in a nonlinear susceptibility, which is higher by three orders of magnitude than in the GHz range. The kHz nonlinear susceptibility was shown to increase with the crystallite size in the glass-ceramic. In summary, both the experimental method as well as the theoretical description of intermodulation open new prospects in understanding dielectrics and nonlinear responses in general and thus laying a foundation for higher performance microwave devices.
DDC:	530 Physik 530 Physics 621.3 Elektrotechnik 621.3 Electric engineering
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-6343
URN:	urn:nbn:de:hebis:77-openscience-78cfe30c-571d-426f-be15-b772de57daaa0
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	http://rightsstatements.org/vocab/InC/1.0/
Extent:	135 Seiten, Illustrationen, Diagramme
Appears in collections:	JGU-Publikationen