A Novel OFDM Chirp Waveform Scheme for Use of Multiple Transmitters in SAR

Abstract

In this letter, we present a new waveform technique for the use of multiple transmitters in synthetic aperture radar (SAR) data acquisition. This approach is based on the principle of the orthogonal-frequency-division-multiplexing technique. Unlike multiple subband approaches, the proposed scheme allows the generation of multiple orthogonal waveforms on common spectral support and thereby enables to exploit the full bandwidth for each waveform. This letter introduces the modulation and the demodulation processing in regard to typical spaceborne SAR receive signals. The proposed processing techniques are verified by a simulation for the case of pointlike targets. Index Terms-Digital beamforming (DBF), multiple-input multiple-output (MIMO) synthetic aperture radar (SAR), orthogonal frequency division multiplexing (OFDM), orthogonal waveform, SAR.

Mimo Radar With Digital Beamforming

“…The main innovative characteristic of forthcoming generations of SAR systems is the use of multiple elevation and/or azimuth receiver channels combined with digital beamforming (DBF) capability [18] [19]. This allows for the synthesis of multiple or dynamic digital receiver beams.…”

Signal Processing for a Multiple-Input, Multiple-Output (MIMO) Video Synthetic Aperture Radar (SAR) with Beat Frequency Division Frequency-Modulated Continuous Wave (FMCW)

“…This problem was solved by adopting multi-channel processing techniques to create a high-resolution wide swath (HRWS) SAR system [6][7][8][9][10]. By adding multiple transmit antennas to the HRWS SAR system using multiple-input multiple-output (MIMO) technology, it is possible to operate a single SAR system Orthogonal frequency division multiplexing (OFDM) chirp [24,25], short-term shift orthogonal (STSO) waveforms [26], and OFDM chirp diverse waveforms [27] have been studied with pulsed MIMO SAR.…”

“…Since an FMCW SAR has a long sweep duration, the motion of the target object within the sweep must be considered [11]. Doppler shift is more sensitive in OFDM chirp waveforms [24,25], than in linear frequency modulation (LFM) [29]. It is therefore difficult to apply Doppler compensation techniques when the sweep duration is long, as in FMCW SAR.…”

An Improved DBF Processor With a Large Receiving Antenna for Echoes Separation in Spaceborne Sar

“…To further improve the HRWS imaging capacity, multiple innovative spaceborne SAR imaging modes with the scheme of several sub-pulses transmitted with different time delays in a single pulse repetition interval (PRI) have been proposed in recent years [7][8][9][10][11][12]. The key point of processing SAR data of these modes is echoes separation corresponding to different sub-pulses [7,[12][13][14].…”

“…The key point of processing SAR data of these modes is echoes separation corresponding to different sub-pulses [7,[12][13][14]. As different sub-pulses are transmitted with different time delays, their corresponding echoes in the mixed receiving window can be separated by a DBF processor to form a sharp receiving beam in elevation based on the time delay and the side looking SAR imaging geometry.…”