Investigations on OFDM Signal for Range Ambiguity Suppression in SAR Configuration

Abstract

International audienceThis paper presents an opportunity to cancel range ambiguities in synthetic aperture radar (SAR) configuration. One of the limitations of SAR systems is the range ambiguity phenomenon that appears with long delayed echoes. The reflected signal corresponding to one pulse is detected when the radar has already transmitted the next pulse. Thus, this signal is considered as an echo from the next pulse. This paper investigates the opportunity of coding the transmitted pulses using an orthogonal frequency-division multiplexing pulse. The results show that coded-OFDM signals outperform conventional chirp signal and make it possible to relax constraints placed upon the pulse repetition frequency

OFDM Synthetic Aperture Radar Imaging With Sufficient Cyclic Prefix

“…wherew ′ m is from the noise and its variance is the same as that in (18) For N > M, there are some zeros in the vector γ in (19). Considering (19) and (20), we notice that part of the transmitted OFDM sequence is used to estimate the unreal weighting RCS coefficients, i.e., the zeros in γ. is the maximal swath width that we can obtain without IRCI.…”

“…Considering (19) and (20), we notice that part of the transmitted OFDM sequence is used to estimate the unreal weighting RCS coefficients, i.e., the zeros in γ. is the maximal swath width that we can obtain without IRCI. Thus, the optimal time duration of the OFDM pulse is T o = (2N − 1)T s with CP length N − 1, which is the maximal possible CP length for an OFDM sequence of length N.…”

“…Adaptive OFDM radar was investigated for moving target detection and low-grazing angle target tracking in [14], [15], [16]. Using OFDM signals for SAR applications was proposed in [17], [18], [19], [20], [21], [22], [23]. In [17], [18], [19], adaptive OFDM signal design was studied for range ambiguity suppression in SAR imaging.…”

“…Using OFDM signals for SAR applications was proposed in [17], [18], [19], [20], [21], [22], [23]. In [17], [18], [19], adaptive OFDM signal design was studied for range ambiguity suppression in SAR imaging. The reconstruction of the crossrange profiles is studied in [22], [23].…”

“…The received pulses from different scatterers are overlapped with May 9, 2014 DRAFT each other and cause energy interferences between these scatterers. To mitigate the impact of the energy interferences and achieve high resolution, the transmitted pulse is coded using frequency or phase modulation (i.e., LFM signal and step frequency signal) or random noise type signals in random noise radar to achieve a bandwidth B which is large compared to that of an uncoded pulse with the same time duration [31].…”