The merit of evolutionary algorithms (EA) to solve convex optimization problems is widely acknowledged. In this paper, a genetic algorithm (GA) optimization based waveform design framework is used to improve the features of radar pulses relying on the orthogonal frequency division multiplexing (OFDM) structure. Our optimization techniques focus on finding optimal phase code sequences for the OFDM signal. Several optimality criteria are used since we consider two different radar processing solutions which call either for single- or multiple-objective optimizations (MOO). When minimization of the so-called peak-to-mean envelope power ratio (PMEPR) single-objective is tackled, we compare our findings with existing methods and emphasize on the merit of our approach. In the scope of the two-objective optimization, we first address PMEPR and peak-to-sidelobe level ratio (PSLR) and show that our approach based on the nondominated sorting genetic algorithm-II (NSGA-II) provides design solutions with noticeable improvements as opposed to random sets of phase codes. We then look at another case of interest where the objective functions are two measures of the sidelobe level, namely PSLR and the integrated-sidelobe level ratio (ISLR) and propose to modify the NSGA-II to include a constraint on the PMEPR instead. In the last part, we illustrate via a case study how our encoding solution makes it possible to minimize the single objective PMEPR while enabling a target detection enhancement strategy, when the signal-to-noise ratio (SNR) metric would be chosen for the detection framework.

This paper demonstrates a method to produce high resolution SAR images using stepped-frequencies. An advantage of the stepped-frequency approach is the reduction of the instantaneous bandwidth and sampling rate requirements of the radar system, as well as the possibility of skipping frequencies that might be corrupted due to external interfering frequency sources. The technique described involves the construction of a wide-bandwidth chirp pulse produced from a burst of narrow-bandwidth chirp pulses transmitted at stepped-frequency intervals. A description of this technique is given and simulation results are shown.

Recent developments involving the orthogonal frequency division multiplexing (OFDM) structure call for new potentials in radar. In this paper, a novel wideband OFDM based waveform is presented and the high range resolution (HRR) processing is derived.We show by means of comparisons with standard wideband waveforms the benefits of this concept. Radial velocities can be retrieved unambiguously and high velocities can be handled at no extra computational effort since the range migration constraint is related to the small pulse bandwidth as opposed to the large synthetic bandwidth. In our analysis, we inspect the impact of Doppler modulation on the processing and give recommendations for improvement in terms of the OFDM parameters. We address the problem caused by a correlation artefact and discuss the risk of intersymbol interference (ISI) typical with OFDM. Lastly, we show that our concept has inherent low probability of detection (LPD) characteristics.

This paper describes a processing technique for combining stepped-frequency waveforms efficiently to obtain higher range resolution. Essentially this method involves the reconstruction of a wider portion of the target's reflectivity spectrum by combining the individual spectra of the transmitted narrow-bandwidth pulses in the frequency domain. This paper describes the signal processing steps involved, and shows simulation results which validate and illustrate the method.

Radio frequency interference (RFI) suppression in SAR images often requires a great amount of computation. The authors describe how significant computational savings can be achieved by integrating the RFI suppression stage, implemented with a least-mean-squared (LMS) adaptive filter, with the range compression stage of the range/Doppler SAR processing algorithm.