Dirk Plettemeier | Searcharxiv

arXiv2026

Articulatory movements influence electromagnetic wave transmission through the vocal tract

This study experimentally validates a numerical model of electromagnetic propagation through the human head during the pronunciation of different vowels, with the goal of improving our understanding of the underlying physical phenomena. A realistic finite element model was created from magnetic resonance images acquired while pronouncing the vowels /a/, /i/, and /u/. The model was validated against scattering matrix measurements obtained from two subjects whose geometries were modeled. Despite several potential sources of discrepancy, the simulations and measurements showed good qualitative agreement, confirming the validity of the approach. Similar transmission coefficient patterns were observed across subjects for the same vowels. Within the investigated frequency range of (1-6~GHz), the electric field exhibited a Mie scattering pattern. Local minima and maxima in the transmission coefficient, characterizing different articulatory configurations, were correlated with local variations in the electric field amplitude. The transmission coefficient's shape results from an interplay between resonance patterns and antenna placement, while the degree of mouth opening influences the shape of scattering modes. Although technically challenging, this numerical approach proved effective for studying electromagnetic propagation in the human head. The resulting robust numerical model and improved understanding of the underlying physics are expected to facilitate the development of radio-frequency-based silent speech interfaces.

physics.app-ph↗

arXiv2020

Influence of dispersive element on phase noise suppression in Talbot effect based optical upconversion scheme

The temporal Talbot effect supports the generation of RF signals with high purity in optical domain. This allows for example a remote RF generation without the need for costly high-end electronic circuits and resource sharing. However, one of the most interesting features of the approach is its inherent ability to suppress phase noise during the carrier generation process. Besides the comb laser source, the dispersive element is the key component in this upconversion scheme. Ideally, it provides the right amount of dispersion over the whole spectral range of the comb. Broader combs are expected to allow a higher degree of phase noise suppression. The simulation of phase noise of an RF tone generated by an optical scheme is challenging in terms of computational and memory effort. Therefore, a simulation tool taking advantage of the properties of the comb and the Talbot effect had to be developed. In this paper, the dependency of the phase noise suppression on the dispersion characteristic is investigated yielding an important input to the design of these elements. First, the implemented simulation tool and the simulation parameters ensuring a correct estimation of the phase noise before and after dispersion influence are introduced. Then, the effect of different dispersion characteristics on the phase noise behavior is analyzed. It could be shown and explained how the phase noise at different offset frequencies to the carrier is affected differently depending on the dispersion characteristic and also the comb width. Design rules for the required comb width as well as the acceptable variation of the produced dispersion from the ideal value depending on the demands for the phase noise improvements could be developed and will be presented.

eess.SP↗