A Novel MIMO–SAR Solution Based on Azimuth Phase Coding Waveforms and Digital Beamforming

Abstract

In multiple-input multiple-output synthetic aperture radar (MIMO–SAR) signal processing, a reliable separation of multiple transmitted waveforms is one of the most important and challenging issues, for the unseparated signal will degrade the performance of most MIMO–SAR applications. As a solution to this problem, a novel APC–MIMO–SAR system is proposed based on the azimuth phase coding (APC) technique to transmit multiple waveforms simultaneously. Although the echo aliasing occurs in the time domain and Doppler domain, the echoes can be separated well without performance degradation by implementing the azimuth digital beamforming (DBF) technique, comparing to the performance of the orthogonal waveforms. The proposed MIMO–SAR solution based on the APC waveforms indicates the feasibility and the spatial diversity of the MIMO–SAR system. It forms a longer baseline in elevation, which gives the potential to expand the application of MIMO–SAR in elevation, such as improving the performance of multibaseline InSAR and three-dimensional SAR imaging. Simulated results on both a point target and distributed targets validate the effectiveness of the echo separation and reconstruction method with the azimuth DBF. The feasibility and advantage of the proposed MIMO–SAR solution based on the APC waveforms are demonstrated by comparing with the imaging result of the up- and down-chirp waveforms.

Ultra-High Resolution Imaging Method for Distributed Small Satellite Spotlight MIMO-SAR Based on Sub-Aperture Image Fusion

“…If the full-aperture MIMO-SAR algorithm can image correctly, the PRF cannot be less than 1/3 of the full-aperture Doppler bandwidth. APC algorithm [ 12 , 13 , 14 ] is similar. Its PRF is larger than Doppler bandwidth, so it cannot image correctly under the parameters shown in Table 1 , as well.…”

“…In order to obtain a wide swath without ambiguity, two kinds of MIMO-SAR algorithms are widely used: range ambiguity suppression algorithm and azimuth deblurring algorithm. The range ambiguity suppression algorithm is often implemented by azimuth phase coding (APC) [ 12 , 13 , 14 ]. But this kind of algorithm requires the PRF to be larger than the Doppler bandwidth of the echo.…”

“…First, the spatial filtering technology is used to remove the azimuth ambiguity of the sub-aperture signal, and then an improved TBS method is proposed to realize the synthesis of the step frequency signal. Compared with the APC algorithms in [ 12 , 13 , 14 ], the PRF of the proposed method can be a few times of the sub-aperture Doppler bandwidth, which greatly reduces the amount of data collected by satellites. The sub-aperture processing decreases ambiguity of the processed signal, which ensures the sufficiency of the spatial degree of freedom.…”

A GPU‐based real‐time processing system for frequency division multiple‐input‐multiple‐output radar

“…MIMO radar has been widely applied to Vehicle radar for driving-assistance [5][6][7], human posture detection [8,9], and perimeter security [10]. References [11,12] utilise the waveform diversity characteristic of MIMO radar to achieve multi-mode synthetic aperture radar (SAR) imaging. Some of the transmitting beams of the MIMO radar are chosen in refs.…”

A Novel MIMO-SAR System Based on Simultaneous Digital Beam Forming of Both Transceiver and Receiver

“…This method modulates the transmitted signals of different channels to different Doppler center frequencies. The above two azimuth phase modulation methods use the weighting of the azimuth two-way antenna pattern to achieve the suppression of ambiguity energy, and separate multiple signal echoes through band-pass filtering in the Doppler frequency domain or azimuth digital beam forming (DBF) [ 26 ]. The system PRF can ensure that when the azimuth spectrum of each orthogonal signal does not overlap, it can effectively isolate the energy of different signals.…”