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-reviewedpublished Otevřený přístup Simultaneous Optimization of Mismatched Filters and Controlled Amplitude Signals for Long-Range MIMO Radars(IEEE (Institute of Electrical and Electronics Engineers), 2022) Bezoušek, Pavel; Karamazov, SimeonThis study presents a new signal and filter design procedure for long-range multiple-input multiple-output (MIMO) radars with a pulse length shorter than the return time of signals reflected by the most distant targets. The proposed algorithm adopts and radically improves the method of alternating the optimization of filters and signals, which was recently published by the same authors. It introduces full control of the signal envelope variation during the pulse, preserving acceptable peak-to-average power ratio (PAR) and signal-to-noise ratio (SNR) loss values. This state-of-the-art method allows calculation simplicity and is important for high-speed computations in adaptive applications. A gradient algorithm was used for the signal amplitude and phase optimization. The signal amplitude was controlled using a special signal construction consisting of two complex exponentials.Článekpeer-reviewedpublished Otevřený přístup Joint Optimization of Signal Waveforms and Filters for Long-Range MIMO Radars(IEEE (Institute of Electrical and Electronics Engineers), 2022) Bezoušek, Pavel; Karamazov, SimeonThis paper describes a new cyclic algorithm for minimization of signal sidelobes and crosstalk in multiple-input multiple-output (MIMO) radar. The designed algorithm, called SWAP by the authors, is suitable mainly for long-range radars, such as ground-based surveillance, approach, or weather radar. The minimization of energy or amplitude of side lobes, and crosstalk were used as the optimization criteria. The effect of the Doppler shift is also included in the optimization. Although the optimized signals do not maintain a strictly constant envelope, the peak-to-average power ratio (PAR) can be maintained below 1.7. This value is acceptable, especially for radars with modern transmitters based on GaN HEMTs. The algorithm allows for any arbitrary choice of elements weights, enabling the optimization of calculations for a wide range of applications. This paper also presents the results of algorithm testing under various conditions. The designed algorithm makes it possible to suppress the side lobes and crosstalk by up to 20 dB more than the matched filters. These results were achieved at the cost of a slight deterioration in signal-to-noise ratio (SNR) loss (less than 1 dB) and an increase in PAR (up to 2). The resolution of weak close targets is also slightly deteriorated. The algorithm converged quickly, and already after ten or 20 iterations, the results changed only minimally.Článekpeer-reviewedpublished version Otevřený přístup MIMO radar signals with better correlation characteristics(Slovenská technická univezita v Bratislave, 2020) Bezoušek, Pavel; Karamazov, SimeonMIMO radars employ multiple transmitting and receiving antennae. For each transmitting antenna, an independent and easily distinguishable signal is required, and appropriate filters must be used by the receiver. For this, the transmitted signals should have characteristics, enabling their effective separation. In this paper the correlation characteristics of selected signals are compared, and the appropriate signal coding is suggested. For differentiation, we address signals with basic linear or nonlinear frequency modulation (LFM or NLFM) multiplied by Gold, PRN, or frequency diversity (FD) codes. The analysis shows that better signal characteristics are achieved using the FD than the other codes. Using matched filters with filter length of 511, sidelobes and cross-correlations are suppressed by 40 dB with FD codes, while with the other codes only 20 dB was achieved. It was also proven, that the FD codes are more tolerant to the Doppler shift. On the other hand, the FD codes application leads to an extension of the overall transmitted signal bandwidth. This however, only represents a serious barrier for very broadband radar systems.