Recent Submissions

Now showing 1 - 5 of 17
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    An Efficient Super-Resolution DOA Estimator Based on Grid Learning
    (Společnost pro radioelektronické inženýrství, 2019-12) Wei, Zhenyu; Li, Xin; Wang, Ben; Wang, Wei; Liu, Qi
    Direction-of-arrival (DOA) estimation based on sparse signal reconstruction (SSR) is always vulnerable to off-grid error. To address this issue, an efficient super-resolution DOA estimation algorithm is proposed in this work. Utilizing the Taylor series expansion, the sparse dictionary matrix is constructed under the off-grid model. Then, a polynomial optimization function is established based on the orthogonality principle. By minimizing the given objective function, we derive an efficient closed-form solution of the off-grid errors. Using the estimated off-grid errors, the discretized grid can be iteratively learned and approaches the true DOAs. With the newly learned grid, accurate DOA estimations can be achieved through the SSR scheme. The proposed algorithm converges fast and achieves precise DOA estimations even the step size of the discretized grid is large. The superior performance of the proposed algorithm is demonstrated by the simulation results.
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    Small Boat Detection Using OFDM Radar
    (Společnost pro radioelektronické inženýrství, 2019-12) Singh, Uday Kumar; Bhatia, Vimal; Mishra, Amit Kumar
    Orthogonal frequency division multiplexing (OFDM) based radar systems have recently attracted a lot of research interest. However, demonstration of OFDM radar's capability for target detection using real data is not reported in the open literature. In this work, we demonstrate a method to employ OFDM radar for small boat detection. For this objective, we propose a technique to generate radar return for OFDM waveform using collected radar return data when stepped frequency waveform is transmitted. We, then, derive system model for the estimated radar return data specific to OFDM waveform. Further, a detection test is proposed for the derived signal model and surveillance environment. Close match between the derived analytical expressions and simulation results validates the proposed detector's performance.
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    A New Motion Model Selection Approach for Multi-Model Particle Filters
    (Společnost pro radioelektronické inženýrství, 2019-12) Ucar, Murat Barkan; Yilmaz, Derya
    One of the important factors in real-time tracking of the moving radar targets is the speed of the algorithm. In the multi-model particle filters (MMPFs) which is frequently preferred tracking of such targets, the numbers of particles and motion models are important parameters determining the speed of the filter. Reducing the number of particles and/or the model transitions processes as much as possible will facilitate real-time tracking of moving targets by accelerating the algorithm. In this study, for reducing the time cost of the MMPF, a new approach called weighted statistical model selection (WSMS) which reduces the number of model estimation calculations is proposed. A new basic MMPF algorithm that allows the use of the WSMS approach is also constituted. In order to evaluate the success of the WSMS; the MMPFs integrated with the WSMS, are simulated for different noise variances, particle numbers, and scenarios. The simulation results are compared based on processing time and prediction error criterions. The results demonstrate that the WSMS approach increases the speed of the algorithm by reducing the processing time at high rates without any change in the prediction error and, thus it can be used in real-time tracking of the moving targets.
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    3-D MIMO Radar Imaging of Ship Target with Rotational Motions
    (Společnost pro radioelektronické inženýrství, 2019-12) Wang, Wei; Hu, Ziying; Huang, Ping
    The problem of image defocusing and distortion occurs in synthetic aperture radar (SAR) imaging of ship target with rotations. Although many literatures have analyzed this problem, it cannot efficiently be solved due to the coherent accumulation time for SAR target imaging, which results from their working principle and mechanism. In this paper, three-dimensional MIMO radar imaging of ship target with rotations is proposed. The real-time advantage of MIMO radar imaging is utilized to achieve high-precision imaging of ship target with rotations. Firstly, the ship rotations characteristics and imaging distortion effects are analyzed in detail. Then, the three-dimensional real-time MIMO radar echo model is built to correct the scattering positions in time, geometrical analysis is carried out to analyze and optimize the target scattering coefficient variation process. Finally, a sparse imaging algorithm based on maximum a posterior (MAP) method is proposed to obtain accurate imaging result. Theoretical analysis and simulation results show that the three-dimensional imaging of ship target based on MIMO radar has better imaging accuracy and real-time performance compared with SAR, and can effectively solve the problem of image defocusing and distortion.
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    Determination of the Traffic Properties of Cells with Mobile Users Using a Mixed Traffic
    (Společnost pro radioelektronické inženýrství, 2019-12) Mitic, Dragan; Lebl, Aleksandar; Markov, Zarko; Kosjer, Vladimir
    This paper presents a two-dimensional Markov traffic model of the mobile users' network where there exist handover calls from the surrounding cells to the considered cell and where, also, primary calls are generated. The two emphasized types of calls form together mixed traffic. The new, two-dimensional model allows us to calculate some characteristic variables for the systems, which may not be determined based on the analysis of one-dimensional model. The developed simulation program is verified comparing the obtained system state probabilities as also primary and handover calls loss rate to the corresponding values from the calculation process. We analyzed cells with a number of channels reserved only for handover calls. This system performances are compared to the performances of some other systems from literature and it is proved that their characteristics are comparable whereby our system improves handover calls dropping rate. It is also proved that users’ speed increase and cell radius decrease cause both primary and, especially, handover calls loss rate increase. The results of calculation and simulation are obtained after a number of iterations (calculation or simulation cycles), where the new loss probability values from one iteration become the input values for the next iteration. In the case that call loss values do not converge during simulation, we implemented the original algorithm for input call loss probability estimation for the next iteration.