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Contributions to High Range Resolution Radar Waveforms : Design of Complete Processing Chains of Various Intra-Pulse Modulated Stepped-Frequency Waveforms

Abstract : In various radar systems, a great deal of interest has been paid to selecting a waveformand designing a whole processing chain from the transmitter to the receiver toobtain the high range resolution profile (HRRP). For the last decades, radar designershave focused their attentions on different waveforms such as the pulse compressionwaveforms and the stepped frequency (SF) waveform:On the one hand, three different types of wide-band pulse compression waveforms havebeen proposed: the linear frequency modulation (LFM) waveform, the phase coded(PC) waveform, and the non-linear frequency modulation (NLFM) waveform. They arevery popular but the sampling frequency at the receiver is usually large. This hence requiresan expensive analog-to-digital convertor (ADC). In addition, the PC and NLFMwaveforms may be preferable in some high range resolution applications since they leadto peak sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR) better than the onesobtained with the LFM waveform.On the other hand, when dealing with SF waveforms, a small sampling frequency canbe considered, making it possible to use a cheap ADC.Pulse compression and SF waveforms can be combined to take advantage of both. Althoughthe standard combination of PC or NLFM with SF leads to the exploitation ofa cheap ADC, the performance of the PC waveform or NLFM waveform in terms ofPSLR and ISLR cannot be attained. As the PSLR and the ISLR have a great influenceon the probability of detection and probability of false alarm, our purpose in the PhDdissertation is to present two new processing chains, from the transmitter to the receiver:1)In the first approach, the spectrum of a wide-band pulse compression pulse is splitinto a predetermined number of portions. Then, the time-domain transformedversions of these various portions are transmitted. At the receiver, the receivedechoes can be either processed with a modified FD algorithm or a novel timewaveformreconstruction (TWR) algorithm. A comparative study is carried outbetween the different processing chains, from the transmitter to the receiver, thatcan be designed. Our simulations show that the performance in terms of PSLRand ISLR obtained with the TWR algorithm is better than that of the modified FDalgorithm for a certain number of portions. This comes at the expense of an additionalcomputational cost. Moreover, whatever the pulse compression used, the approach we present outperforms the standard SF waveforms in terms of PSLRand ISLR.2)In the second approach, we suggest approximating the wide-band NLFM by apiecewise linear waveform and then using it in a SF framework. Thus, a variablechirp rate SF-LFM waveform is proposed where SF is combined with a train ofLFM pulses having different chirp rates with different durations and bandwidths.The parameters of the proposed waveform are derived from the wide-band NLFMwaveform. Then, their selection is done by considering a multi-objective optimization issue taking into account the PSLR, the ISLR and the range resolution.The latter is addressed by using a genetic algorithm. Depending on the weightsused in the multi-objective criterion and the number of LFM pulses that is considered, the performance of the resulting waveforms vary.An appendix is finally provided in which additional works are presented dealing withmodel comparison based on Jeffreys divergence.
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Mahdi Saleh. Contributions to High Range Resolution Radar Waveforms : Design of Complete Processing Chains of Various Intra-Pulse Modulated Stepped-Frequency Waveforms. Automatic Control Engineering. Université de Bordeaux, 2020. English. ⟨NNT : 2020BORD0024⟩. ⟨tel-02945776⟩

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