Processing of Multichannel Sliding Spotlight SAR Data with Large Pulse Bandwidth and Azimuth Steering Angle

Xu, Wei; Hu, Jialuo; Huang, Pingping; Tan, Weixian; Dong, Yifan

doi:10.1109/tgrs.2021.3057762

Cited by 5 publications

(6 citation statements)

References 31 publications

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“…In addition, the BV-PRF scheme results in azimuth non-uniform sampling. However, the azimuth up-sampling technology, the traditional two-step pre-processing algorithm and full-aperture focusing method [ 14 ] will become inapplicable. To solve the above two problems, an azimuth pre-processing approach combining the BV-PRF and full-aperture processing is proposed in this section.…”

Section: Azimuth Pre-processingmentioning

confidence: 99%

“…However, in addition to the desired higher azimuth resolution, some areas are required to be clarified for future spaceborne SAR missions [ 10 ]. The squint sliding-spotlight mode [ 11 , 12 ] can obtain multiple images of a desired area with a fine azimuth resolution and different observation angles [ 13 , 14 ], and it will be widely adopted then future spaceborne SAR missions.…”

Section: Introductionmentioning

confidence: 99%

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Azimuth Full-Aperture Processing of Spaceborne Squint SAR Data with Block Varying PRF

Zhang

Huang

et al. 2022

Sensors

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The block varying pulse repetition frequency (BV-PRF) scheme applied to spaceborne squint sliding-spotlight synthetic aperture radar (SAR) can resolve large-range cell migration (RCM) and reduce azimuth signal non-uniformity. However, in the BV-PRF scheme, different raw data blocks have different PRFs, and the raw data in each block are insufficiently sampled. To resolve the two problems, a novel azimuth full-aperture pre-processing method is proposed to handle the SAR raw data formed by the BV-PRF scheme. The key point of the approach is the resampling of block data with different PRFs and the continuous splicing of azimuth data. The method mainly consists of four parts: de-skewing, resampling, azimuth continuous combination, and Doppler history recovery. After de-skewing, the raw data with different PRFs can be resampled individually to obtain a uniform azimuth sampling interval, and an appropriate azimuth time shift is introduced to ensure the continuous combination of the azimuth signal. Consequently, the resulting raw data are sufficiently and uniformly sampled in azimuth, which could be well handled by classical SAR-focusing algorithms. Simulation results on point targets validate the proposed azimuth pre-processing approach. Furthermore, compared with methods to process SAR data with continuous PRF, the proposed method is more effective.

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Section: Azimuth Pre-processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Azimuth Full-Aperture Processing of Spaceborne Squint SAR Data with Block Varying PRF

Zhang

Huang

et al. 2022

Sensors

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“…Non-uniform fast Fourier transform (NUFFT) could be instead of azimuth interpolation and FFT to improve the computational efficiency as shown in Figure 8 . Consequently, the second transfer function for multiplication in azimuth pre-filtering is expressed as [ 34 ]:

where

indicates the azimuth time sampling interval after upsampling in azimuth pre-filtering,

is the total Doppler bandwidth of the imaged scene, and

is the number of azimuth samples after upsampling. In order to efficiently apply FFT to implement azimuth convolution between the SAR raw data and the selected chirp signal, P should be [ 30 ]:

where

is the original average azimuth time sampling interval.…”

Section: High Resolution Low Sidelobe Imagingmentioning

confidence: 99%

“…Non-uniform fast Fourier transform (NUFFT) could be instead of azimuth interpolation and FFT to improve the computational efficiency as shown in Figure 8. Consequently, the second transfer function for multiplication in azimuth pre-filtering is expressed as [34]:…”

Section: Modified Stolt Interpolationmentioning

confidence: 99%

Staring Spotlight SAR with Nonlinear Frequency Modulation Signal and Azimuth Non-Uniform Sampling for Low Sidelobe Imaging

Zhang

Fang³

et al. 2021

Sensors

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In synthetic aperture radar (SAR) imaging, geometric resolution, sidelobe level (SLL) and signal-to-noise ratio (SNR) are the most important parameters for measuring the SAR image quality. The staring spotlight mode continuously transmits signals to a fixed area by steering the azimuth beam to acquire azimuth high geometric resolution, and its two-dimensional (2D) impulse response with the low SLL is usually obtained from the 2D weighted power spectral density (PSD) by the selected weighting window function. However, this results in the SNR reduction due to 2D amplitude window weighting. In this paper, the staring spotlight SAR with nonlinear frequency modulation (NLFM) signal and azimuth non-uniform sampling (ANUS) is proposed to obtain high geometric resolution SAR images with the low SLL and almost without any SNR reduction. The NLFM signal obtains non-equal interval frequency sampling points under uniform time sampling by adjusting the instantaneous chirp rate. Its corresponding PSD is similar to the weighting window function, and its pulse compression result without amplitude window weighting has low sidelobes. To obtain a similar Doppler frequency distribution for low sidelobe imaging in azimuth, the received SAR echoes are designed to be non-uniformly sampled in azimuth, in which the sampling sequence is dense in middle and sparse in both ends, and azimuth compression result with window weighting would also have low sidelobes. According to the echo model of the proposed imaging mode, both the back projection algorithm (BPA) and range migration algorithm (RMA) are modified and presented to handle the raw data of the proposed imaging mode. Both imaging results on simulated targets and experimental real SAR data processing results of a ground-based radar validate the proposed low sidelobe imaging mode.

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“…The advent of the concept of spaceborne large-squint terrain-matching SAR was a breakthrough [1]. This was followed by advancements in processing multichannel SAR data, particularly those with large pulse bandwidth and azimuth steering angle [2]. These advancements included the development of a novel three-step image formation scheme [3] and a wide nonlinear chirp scaling algorithm [4].…”

Section: Introductionmentioning

confidence: 99%

A new spaceborne wide swath sliding spotlight mode with a high squint angle

Huang

et al. 2023

Second International Conference on Optoelectronic Information and Computer Engineering (OICE 2023)

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The spaceborne squint sliding spotlight mode provides the capacity to observe the Earth in high resolution with different angles. However, with the increased squint angle, the imaged swath is obviously reduced due to the large range cell migration. To extend the reduced swath, a new spaceborne wide swath sliding spotlight mode with a high squint angle is proposed in this paper. Besides azimuth beam steering to improve the azimuth resolution, antenna beam is also steered in elevation to improve the swath width. The imaging principle of the proposed imaging mode is described in detail, while its corresponding flowcharts of SAR system design and imaging processing are given. Furthermore, the beam steering law of the designed system example with azimuth resolution of 0.5m and swath width of 20km is given, while the imaging result of the designed scene with three targets is given. Both simulation results validate the proposed imaging mode in the high squint case.

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Processing of Multichannel Sliding Spotlight SAR Data with Large Pulse Bandwidth and Azimuth Steering Angle

Cited by 5 publications

References 31 publications

Azimuth Full-Aperture Processing of Spaceborne Squint SAR Data with Block Varying PRF

Azimuth Full-Aperture Processing of Spaceborne Squint SAR Data with Block Varying PRF

Staring Spotlight SAR with Nonlinear Frequency Modulation Signal and Azimuth Non-Uniform Sampling for Low Sidelobe Imaging

A new spaceborne wide swath sliding spotlight mode with a high squint angle

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