Half-hourly mean winds have been obtained using ground-based low-frequency and very high frequency radio observations of the mesopause region at Collm, Germany, since 1984. Long-term changes of wind variances, which are proxies for short-period atmospheric gravity waves, have been analysed. Gravity wave amplitudes increase with time in winter, but mainly decrease in summer. The trends are consistent with mean wind changes according to wave theory. 

A new analytical solution for the scalar scattering by a circular aperture in an infinite screen is presented. The field is expanded by means of complete spherical-multipole expansions. The unknown expansion coefficients are found from the conditions of continuity, leading to a quadratic system of linear equations.  The numerical evaluation validates and improves numerical results found in the literature. Further numerical results prove the robustness and convergence of the proposed method.

A hand sprayer is used to deposit droplets on the radome of an antenna. Before and during the drying process, measurements of the antenna reflection coefficient are performed repeatedly over time and frequency using a vector network analyzer. Continuous drifts from the wet state back to the initial dry state are demonstrated for individual antennas and frequency ranges. The obtained insights qualify the antenna reflection coefficient to be a promising indicator of momentary radome wetness.

The paper describes a method to derive the electrical characteristics of the sea surface from Earth observation data and compute the ground-wave signal delay across sea-ice covered areas.
It is used in a tool chain to simulate signal propagation in a real-world scenario for the medium-frequency radio navigation R-Mode and assess the impact of sea ice on the signal propagation delays. The results indicate, that the effect of sea ice is significant and needs to be compensated.

This work presents a possible application for radar angular resolution testing. To enable actual conditions, the signal from the radar target simulator is reflected on a parabolic mirror. However, more than one radar target simulator is necessary for angular testing so that they have an offset to the mirror's focal point. The occurring effects,  such as mispositioning and target splitting, are analyzed and explained. Overall, the system is suitable to enable angular resolution testing.

This study explores how electromagnetic waves at 92 GHz potentially ignite explosive atmospheres. Different materials were exposed to high-frequency waves and the resulting temperature increase was measured. A material was selected and controlled ignition tests in explosive gas-air mixtures were conducted. The results show that up to 800 mW can be safely used without triggering an explosion. This suggests that current safety standards (limited to 60 GHz) could be expanded to higher frequencies.

This work explores the special type of passive device to tracking an object without needing its own power source. A special tag placed on the object reflects signals from an external scanner. The scanner sends out waves, and the tag bounces them back, helping detect the objects. The work is aiming at warehouse application to track item boxes in the stock by fixing the tag to the box.

Automotive radar systems help vehicles detect objects and improve safety. This research presents a new antenna design that operates at two different frequencies to enhance both detection range and field of view. The design improves radar performance while keeping the system compact and cost-effective. By carefully analyzing the antenna, its reliability is confirmed. This innovation can support advanced driver assistance systems, making future vehicles safer and more efficient.

This work shows that continuous wavelet transformation (CWT) is very useful for analyzing transient abnormalities in energy grids. Scalograms are used to visualize the results. It is demonstrated that the family of complex wavelets can be used to analyze the transfer of active power in the power system, even during transient events. This can be used to analyze resonant power grid structures and to identify the causes of violations of current and voltage limits at the grid connection point.

This paper presents a cost-effective automotive radar system that monitors street conditions while maintaining standard radar operations. Using a novel frequency-selective approach, the system operates at 76.5 GHz for standard radar operations and 80.5 GHz for street condition monitoring, eliminating the need for additional hardware. The findings demonstrate reliable detection of different street types and conditions, enhancing vehicle safety in diverse environments.