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Item type:Publication, Access status: with files , Optimization of airborne antenna geometry for ocean surface scatterometric measurements(Multidisciplinary Digital Publishing Institute (MDPI), 2018-09-20); ; ; ; We consider different antenna configurations, ranging from simple X-configuration to multi-beam star geometries, for airborne scatterometric measurements of the wind vector near the ocean surface. For all geometries, track-stabilized antenna configurations, as well as horizontal transmitter and receiver polarizations, are considered. The wind vector retrieval algorithm is generalized here for an arbitrary star geometry antenna configuration and tested using the Ku-Band geophysical model function. Using Monte Carlo simulations for the fixed total measurement time, we show explicitly that the relative wind speed estimation accuracy barely depends on the chosen antenna geometry, while the maximum wind direction retrieval error reduces moderately with increasing angular resolution, although at the cost of increased retrieval algorithm computational complexity, thus, limiting online analysis options with onboard equipment. Remarkably, the simplest X-configuration, while the simplest in terms of hardware implementation and computational time, appears an outlier, yielding considerably higher maximum retrieval errors when compared to all other configurations. We believe that our results are useful for the optimization of both hardware and software design for modern airborne scatterometric measurement systems based on tunable antenna arrays especially, those requiring online data processing.Publicationtype: Journal ArticleScopus© Citations 12 297 319 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On off-nadir wind retrieval over the sea surface using apr-2 or similar radar geometry(2018-09-17); ; ; In some cases, nadiral wind retrieval algorithms are not applicable for wind measurements due to the specificity of a radar instrument measuring geometry or its mounting on aircraft, and so off-nadir backscattering measurements can only be performed. In this paper, a method for off-nadir wind retrieval over the sea based on the sea-surface backscattering measurements with the Airborne Precipitation Radar-2 or similar radar measuring geometry has been proposed. The study is based on a theory of the quasi-specular microwave backscattering from the sea surface. An anisotropic water surface approach is considered. The wind vector is retrieved from the system of equations for measured normalized radar cross sections (NRCS) by using the relationships between the speed of the sea-surface wind and the standard deviations of the sea-surface slopes along the up-and cross-wind directions. A wind vector recovery with the cross-track scanning measurement geometry has been simulated. The maximum errors of the wind speed and direction estimations are within typical errors of wind measurements by a scatterometer. A maximum altitude of the method applicability for this geometry has been defined. Recommendations to perform the measurements have been described in detail.Publicationtype: Journal Article122 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Possibilities of increasing the low altitude measurement precision of airborne radio altimeters(Multidisciplinary Digital Publishing Institute (MDPI), 2018-09-11); ; ; ; The paper focuses on the new trend of increasing the accuracy of low altitudes measurement by frequency-modulated continuous-wave (FMCW) radio altimeters. The method of increasing the altitude measurement accuracy has been realized in a form of a frequency deviation increase with the help of the carrier frequency increase. In this way, the height measurement precision has been established at the value of ±0.75 m. Modern digital processing of a differential frequency cannot increase the accuracy limitation considerably. It can be seen that further increase of the height measurement precision is possible through the method of innovatory processing of so-called height pulses. This paper thoroughly analyzes the laws of height pulse shaping from the differential frequency presented by the number that represents the information about the measured altitude for this purpose. This paper presents the results of the laboratory experimental altitude measurement with the use of a so-called double-channel method. The application of obtained results could contribute to the increase of air traffic safety, mainly in the phase of the aircraft approaching for landing and landing itself.Publicationtype: Journal ArticleScopus© Citations 8 253 1762 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , An algorithm of daubechies wavelet transform in the final field when processing speech signals(Multidisciplinary Digital Publishing Institute (MDPI), 2018-07-18); ; Development and improvement of a mathematical model for a large-scale analysis based on the Daubechies discrete wavelet transform will be implemented in an algebraic system possessing a property of ring and field suitable for speech signals processing. Modular codes are widely used in many areas of modern information technologies. The use of these non-positional codes can provide high-speed data processing. Therefore, these algebraic systems should be used in the algorithms of digital processing of signals, which are characterized by processing large amounts of data in real time. In addition, modular codes make it possible to implement large-scale signal processing using the wavelet transform. The paper discusses examples of the Daubechies wavelet transform application. Integer processing, presented in the paper, will reduce the number of rounding errors when processing the speech signals.Publicationtype: Journal ArticleScopus© Citations 20 297 258 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A Ka-band geophysical model function(2017-12); ; A Ka-band geophysical model function is proposed. The model function is based on a similar previously-developed backscatter model, which showed a disadvantage at near cross-wind azimuths for incidence angles of 47° to 50°. The new Ka-band geophysical model function is valid for incidence angles of 30° to 50° at vertical transmit and receive polarization. Several particular cases of water-surface backscattering are presented by using this function.Publicationtype: Journal Article64 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Airborne weather radar concept for measuring water surface backscattering signature and sea wind at circular flight(2016-12-01); A concept for measuring water surface backscattering signature and wind over sea using airborne weather radar is discussed. The radar operates in the ground-mapping mode as a scatterometer, in addition to its meteorological and navigation application. An aircraft circular flight is used under such measurement. Recommendations to perform measurement of the water surface backscattering signature along with a sea wind retrieval algorithm are proposed. A simulation study of wind vector estimation is performed. The results obtained show that airborne weather radar can provide reasonable sea wind vector retrieval accuracy.Publicationtype: Journal Article79 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Sea surface wind measurement by airborne weather radar scanning in a wide-size sector(Multidisciplinary Digital Publishing Institute (MDPI), 2016-05-23); ; ; We suggest a conceptual approach for measuring the near-surface wind vector over water using the airborne weather radar, in addition to its standard meteorological and navigation applications. The airborne weather radar operates in the ground-mapping mode in the range of high to medium incidence angles as a scatterometer. Using the aircraft rectilinear flight over the water surface, measuring the geometry and the geophysical model function, we show that the wind vector can be successfully recovered from the azimuth normalized radar cross-section data obtained from a scanning sector of up to ±100°. The efficiency and accuracy of the proposed wind vector measurement algorithms are supported by computer simulations indicating their potential as a powerful tool for the wind field reconstruction. Some limitations and recommendations of the suggested approach are further discussed.Publicationtype: Journal ArticleScopus© Citations 12 314 282