Doubly coded costas signals for grating lobes mitigation

Touati, Nadjah; Tatkeu, Charles; Chonavel, Thierry; Rivenq, Atika

doi:10.1109/pimrc.2013.6666184

Cited by 6 publications

(9 citation statements)

References 9 publications

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“…In this section, other Costas codes are used to encode the initial Costas pulses. The doubly coded Costas signal consists in replacing rectangular pulses by another Costas signal [22]. Indeed, under some conditions upon secondary Costas parameters, we have shown that such a double Costas coding approach can be efficient in eliminating grating lobes.…”

Section: Proposed Designsmentioning

confidence: 99%

Design and performances evaluation of new Costas‐based radar waveforms with pulse coding diversity

Touati

Tatkeu

Chonavel³

et al. 2016

IET Radar, Sonar & Navigation

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Costas codes are a variant of pulse compression waveforms, largely studied for their attractive time-frequency properties. Their 'thumbtack-like' ambiguity function (AF) makes them highly suitable for delay and Doppler estimation, in radar and sonar applications. However, this behaviour depends heavily on the length of the code: the improvement in delay-Doppler resolutions and AF sidelobes level needs an increase in the size of the code. In this study, designs that allow good performance without increasing the size of the code are proposed. They are based on a modification of Costas codes by widening frequency separation between hops and replacing rectangular pulses by other waveforms. This will lead to a removal of autocorrelation function grating lobes that normally appear when frequency separation is increased. The originality of the work lies in the proposal of diversified pulse waveforms, such as phase codes, Slepian sequences, and other Costas codes, to encode main Costas pulses. A performance comparison of the proposed approaches is supplied. Such waveforms could also be of interest for applications where waveform diversity is desired

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Section: Proposed Designsmentioning

confidence: 99%

Design and performances evaluation of new Costas‐based radar waveforms with pulse coding diversity

Touati

Tatkeu

Chonavel³

et al. 2016

IET Radar, Sonar & Navigation

Self Cite

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“…The instantaneous frequency of up-chirp LFM is given by (1) Where, f0 is the radar center frequency, and µ= (2πB)/ is the LFM coefficient, B=bandwidth and  is pulse width. Similarly, the instantaneous frequency for down-chirp LFM is given by (2) Adding linear frequency modulation widens the bandwidth and because of this, the range resolution enhances by a factor equal to the time-bandwidth product [3]. Yet, the LFM has large side-lobes in matched filter output which is the major drawback for which amplitude weighting (windowing) or data tapering is required to reduce the side lobes.…”

Section: Introductionmentioning

confidence: 99%

An Algorithm for Computing Side Lobe Values of a Designed NLFM function

Adithyavalli¹

2019

IJATCSE

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Several applications in radar systems entail low range side lobe performance to identify the targets. It is achieved by pulse compression processing. The chirp signal also known as linear frequency modulation (LFM) signal is most widely used for this purpose. Since it exhibits high first side-lobe value in the autocorrelation, non linear chirp signals (NLFM) are introduced as a solution to suppress the sidelobes. NLFM signals can be generated by using simple two-stage piece wise linear frequency modulation (PWLFM) functions. The chirp rates of the two stages are selected differently. This NLFM signal exhibited better peak to sidelobe level (PSLR) values compared to its counterpart LFM signal. In this paper we present a complete contour map of the computed side lobe values, to identify the optimum chirp rates of the two stages. The side lobes are computed based on algorithm written in python scripting language. This map helped us to identify two interwoven fluctuations in the spectrum of side-lobe values that can be used to decide the breakpoint value for a given bandwidth and pulse width. The best NLFM is generated by identifying the optimum slopes of the two LFM stages, which is further combined with the windows functions to achieve a significant reduction in PSLR.

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“…The latter consists in introducing a second level coding in the sub‐pulses of the main Costas code (size M , pulse duration t p and frequency spacing Δ f ), using another Costas code (size L , pulse duration t s and frequency spacing Δ f s ). Parameters of main and sub‐pulse codes are chosen so that the overall AAF show reduced sidelobes especially in the presence of grating lobes due to the non‐fulfilment of the orthogonality condition (case