Fakulta elektrotechniky a informatiky / Faculty of Electrical Engineering and Informatics
Stálý URI pro tuto komunituhttps://hdl.handle.net/10195/3847
Práce obhájené před rokem 2008 jsou uloženy pouze v kolekci Vysokoškolské kvalifikační práce
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Článekpeer-reviewedpostprint Omezený přístup Whitening Filters Application for Ionospheric Propagation Delay Extraction(IEEE (Institute of Electrical and Electronics Engineers), 2023) Rejfek, Luboš; Juryca, Karel; Nguyen, Tan N. N; Beran, Ladislav; Voznak, MiroslavPreprocessed signals from Global Positioning System (GPS) satellites can be used for ionospheric research. Important ionospheric characteristics are for example ionospheric propagation delays and scintillations. These characteristics are important for understanding the ionosphere and showing how the ionosphere reacts to external forces (e.g., geomagnetic disturbance, solar eclipse, etc.). Dual-frequency systems use an approach based on the difference between two pseudoranges. However, this approach has two possible disadvantages: 1) the price of the dual frequency receiver is relatively high and 2) both pseudoranges can affect the obtained results so the operators cannot separately analyze their relative contribution. The objective of the article is to demonstrate an algorithm for processing data from a GPS receiver. The algorithm does not merge the pseudoranges obtained from different carrier waves. Accordingly, it was decided to use whitening filters to accomplish this task for every frequency separately. Compared with the dual-frequency approach, the obtained results of the newly developed algorithm demonstrate that this algorithm works accurately, and the propagation delays can be estimated independently of the used frequency.Článekpeer-reviewedpostprint Otevřený přístup Speaker Verification Using Autoregressive Spectrum of Speech Signal in Composite Vector Stochastic Processes Model Representation(Institute of Mechanics of Continua and Mathematical Sciences, 2019) Chmelařová, Natalija; Tykhonov, Vyacheslav A.; Bezruk, Valerij M.; Chmelař, Pavel; Rejfek, LubošThis paper deals with the speaker verification system similar to a fingerprint or an eye scanner. For these purpose a long-term words' model and its spectral characteristics were used. The speaker verification method uses the word's sound parametric spectrum factorization in composite vector stochastic process representation based on the multiplicative autoregressive model. The developed method enables to receive the words' features with stable characteristics for the same speaker and differ for different speakers. During the training phase speaker's etalon frequencies has to be estimated for a pronounced word repeated several times. In the verification phase a speaker pronouncing the same word, word's frequencies are estimated and compared with the etalon frequencies database to find the best match or his deny. The results presented in the paper showed the high correct identification probability.Článekpeer-reviewedpublished version Otevřený přístup Neural Networks Application for Processing of the Data from the FMICW Radars(MDPI, 2019) Rejfek, Luboš; Nguyen, Tan N.; Chmelař, Pavel; Beran, Ladislav; Phuong, Tran T.In this paper the results of the Neural Networks and machine learning applications for radar signal processing are presented. The radar output from the primary radar signal processing is represented as a 2D image composed from echoes of the targets and noise background. The Frequency Modulated Interrupted ContinuousWave (FMICW) radar PCDR35 (Portable Cloud Doppler Radar at the frequency 35.4 GHz) was used. Presently, the processing is realized via a National Instruments industrial computer. The neural network of the proposed system is using four or five (optional for the user) signal processing steps. These steps are 2D spectrum filtration, thresholding, unification of the target, target area transforming to the rectangular shape (optional step), and target board line detection. The proposed neural network was tested with sets of four cases (100 tests for every case). This neural network provides image processing of the 2D spectrum. The results obtained from this new system are much better than the results of our previous algorithm.Článekpeer-reviewedpublished Otevřený přístup Test of Methods Eliminating Regular Signal Level Variations due to Spatial Alphasat Satellite Motion(2018) Pek, Viktor; Fišer, Ondřej; Rejfek, LubošMany countries receive the Alphasat satellite signal in both Ka and Q bands in order to analyze the random atmospheric attenuation. The received signal from the Alphasat satellite is influenced not only by the atmosphere but also by the quasi regular satellite motion causing the “cosinusoidal” signal level fluctuations of about 24 hour period. In this contribution we describe mathematical methods eliminating this fluctuation and perform tests of the suitability of particular methods. To test these methods we developed and used the signal level software simulator as we must know the “true” attenuation values while the simulated values are the “true” ones from our testing viewpoint. The tests showed that we should recommend the MY method developed at the Institute of Atmospheric Physics Prague but the differences among tested methods are low and all described methods are acceptable.Článekpeer-reviewedpublished Otevřený přístup Position estimation of robotic platform using optical flow(2018) Beran, Ladislav; Rejfek, Luboš; Chmelař, Pavel; Matoušek, DavidThis paper deals with a base research of an alternative type of navigation for our project ARES (Autonomous Research Exploration System). This system is focused on exploration of unknown areas. The navigation of this platform is based on fusion of several navigation methods. The first method is based on the visual odometry using SURF (Speeded Up Robust Feature). The second navigation method is based on Hector Slam and Lidar sensor. The third method is based on optical flow. The implementation of third method based on the Lucas-Kanade method is descripted in this paper.Článekpeer-reviewedpublished Otevřený přístup Navigation of robotics platform in unknown spaces using LIDAR, Raspberry PI and Hector SLAM(2018) Vaníček, Petr; Beran, Ladislav; Rejfek, LubošThis research is a base research of an alternative type navigation for our project ARES – Autonomous Research Exploration System. This system is focused on exploration of dangerous indoor spaces like caves, abandoned mines, ruins etc. In many cases, there is poor or no signal from satellite navigation systems and it is necessary to develop accurate navigation for our platform. Our platform is based on several systems like navigation using an inertial navigation unit, visual odometry and 3D space mapping. The result of our system will be a 3D map of space. The developed 3D space mapping needs accurate position for creation of a space map. This paper deals with development of an alternative position estimation method and implementation of LIDAR sensor and Raspberry PI for 2D space mapping.Článekpeer-reviewedpublished Otevřený přístup Desk games digitalization using Radon transformation and Color segmentation(2018) Horáček, Michal; Beran, Ladislav; Rejfek, LubošThe research is focused on real-time digitalization of board games. The information about the game progress in real time is frequently demanded by media in broadcasted tournaments. Recent solutions usually consist of an electronically modified playing board and modified playing objects. This system tends to be expensive and fits to top level tournaments more than casual regional tournaments with limited resources. The goal was to create a system, which is easy to assemble and use while keeping the transmission and processing in real-time. The chosen solution utilizes a digital camera to obtain input data as a video stream. The data are then processed by Image processing methods. The proposed algorithm includes Radon transformation for board and playing field localization, then methods of Color segmentation for detecting the objects on the playing board. The system was modified and tested in a Chess game.Článekpeer-reviewedpublished Otevřený přístup Filtration of the FMICW radar output signals by the advanced windows(2017) Rejfek, Luboš; Chmelařová, Natalija; Beran, Ladislav; Chmelař, PavelThis paper deals with the special types of windows application on the two dimensional spectrum obtained using the FMICW radar. This processing will improve the signal interpretation for the user. We want to implement this signal processing in our SW for the automatic detection of targets. The obtained results are described in detail with the recommendation for achieving the best processing result. We developed several windows, which can be used, for our algorithm.Článekpeer-reviewedpublished Otevřený přístup Point Cloud Plane Visualization by Using Level Image(2018) Chmelař, Pavel; Rejfek, Luboš; Beran, Ladislav; Chmelařová, Natalija; Dobrovolný, MartinThis paper presents the point cloud plane visualization by using the level image. A created level image indicates the point presence in a space at a specific level. By knowledge its origin position in a space, the physical pixel size and the detected rotation angle we can easily visualize planes in an analyzed point cloud. The connection of image processing methods with the physical measurement points offers besides the visualization also obtaining important properties about a scanned space. The described algorithm includes also a color point cloud visualization. Presented results showing the level images advantages for point clouds processing.Článekpeer-reviewedpublished Otevřený přístup Automatic detection of the unknown number point targets in FMICW radar signals(2017) Rejfek, Luboš; Mošna, Zbyšek; Beran, Ladislav; Fišer, Ondřej; Dobrovolný, MartinThis paper deals with algorithm for detection of unknown number of the targets and estimation of parameters of these targets. Automatic detection of the targets in the signal is important for the speed-up of the signal processing. Point targets were selected for the test of our algorithm. Algorithm is developed for the frequency modulated interrupted continuous wave radar. We present results for different combinations of targets.
