This paper presents experimental multi-frequency radar measurements of rain obtained simultaneously at K -, Ka -, and W -band frequencies using colocated vertically pointing radars operating at 24,35, and 94 GHz. The analysis focuses on frequency-dependent behavior of radar reflectivity and mean Doppler velocity during an hour precipitation event. Systematic differences in reflectivity are observed across the three frequency bands, with increasing impact of non-Rayleigh scattering and rain-induced attenuation toward higher frequencies. Doppler velocity measurements reveal consistent reduction of mean fall velocity at Ka- and W-band due to enhanced sensitivity to small-drop populations. Surface rain-gauge observations indicate intermittent precipitation reaching the ground, highlighting the importance of vertical context and sub-cloud evaporation for interpretation of radar measurements. The results demonstrate the complementary nature of multi-frequency radar observations and their potential for improved characterization of precipitation processes.

This paper is devoted to discussing peculiarities of multi-instrument measurements of rain using millimeter band radar and laser optical disdrometers as basic sensors with application of weather station and radiometer as sources of additional information. After brief discussion of meteorological radar application for quantitative information obtaining, the paper considers the problems and their possible solutions in respect to data fusion and comparison the results of measurements with sensors of different physical nature. 94 GHz radar, laser optical disdrometers, weather station and potentially the radiometer are considered as information sources. Experimental part of the research is based on measurements of rain provided during several years at the experimental range located in Cabauw, the Netherlands.

This paper describes the results of the research fulfilled in TU-Delft by joint Ukrainian and Dutch team. It analyzes multi-instrument rain observations, using the instrument set, which includes W-band cloud radar, laser optical disdrometers, weather station, and microwave radiometer. New friendly interface software is developed, presented, and used as a tool for comparison and fusion of diverse sensors datasets. The results obtained demonstrate the synergy of multi-instrument measurements and corresponds to the overarching trends of big data analysis. The intricacies of combining data from various sources to enhance calibration and improve the accuracy of atmospheric studies is discussed. In particular, analysis of 94 GHz cloud radar calibration based on disdrometer measurements with application of additional multi-instrument measurements is performed.

This article proposes a receiving device in which arbitrary input signals are subject to pre-detector processing for the subsequent implementation of the idea of compressing broadband modulated pulses with a matched filter to increase the signal-to-noise ratio and improve resolution. For this purpose, a model of a dispersive delay line is developed based on series-connected high-frequency time delay lines with taps in the form of bandpass filters, and analysis of this model is performed as a part of the radio receiving device with chirp signal compression. The article presents the mathematical description of the processes of formation and compression of chirp signals based on their matched filtering using the developed model and proposes the block diagram of a radio receiving device using the principle of compression of received signals. The proposed model can be implemented in devices for receiving unknown signals, in particular in passive radar. It also can be used for studying signal compression processes based on linear frequency modulation in traditional radar systems.

This paper is devoted to discussing peculiarities of W-band cloud radar calibration. After a brief overview of meteorological radar calibration methods for quantitative information retrieval, we focus on problems and their possible solutions with respect to mm-wave radar calibration. The experimental part of the research is based on multi-instrument measurements performed during several years in the Cabauw experimental meteorological site in the Netherlands. The accumulated data are used for comparison of 94 GHz radar rain measurements with non-radar droplet size distribution measurements, provided by laser disdrometers. Calculations are done taking into account data of other in situ meteorological measurements. A specialized MATLAB software tool for processing such complex data and radar calibration is developed and demonstrated.

This paper proposes generalized mathematical model of different passive interferences and develops an effective algorithm of digital signal processing for detection on the background of them. Models of interferences as random process of K-distribution is used with parametrization for the unwanted reflections from atmosphere, land, and sea. Robust algorithm for signal detection on the background of such interferences, in particular in case of non-gaussian distribution, is developed. Its effectiveness is researched and confirmed.

This paper considers generalized coherent-polarimetric method of retrieving information about remote objects using electromagnetic waves. Both active and passive electronic systems as well as different objects under observation, operating frequency bands, and physical meaning (interpretation) of the frequency as spectral argument can be used. As an example, retrieving information about turbulence using microwave weather radar is considered.