Precise aperture‐dependent motion compensation for high‐resolution synthetic aperture radar imaging

Wang, Guanyong; Zhang, Lei; Li, Jun; Hu, Qiangqiang

doi:10.1049/iet-rsn.2016.0195

“…In this sub-block, the reference range used by the differential decoupling is 53 m. The difference between the target range and reference range denotes the half width of the sub-block. The BP algorithm [18] based on (1) is viewed as the precise method. Here, the results of the BP algorithm [22] are used as the criteria.…”

Section: Influence Of Sub-block Width On Imagerymentioning

confidence: 99%

“…However, a distributed target suffers from the distortion. In [18,19], the two-way range was expanded into a power series with respect to the slow time. Additionally, the PSP was expanded into a power series based on the series reversion method.…”

mentioning

confidence: 99%

“…Considering that the triangle whose vertices were the transmitter, receiver and target, the fourth order equation with respect to half bistatic angle was obtained based on the theorem of sine and some basic algebra skills. In [21], this equation was solved using the series reversion method [18,19]. The accuracy of the PTRS is also limited by the number of terms in the power series.Using an accurate time delay of the transmitted signal [12], the back projection (BP) algorithm [22] can provide high resolution results.…”

mentioning

confidence: 99%

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Imaging Algorithm for Multireceiver Synthetic Aperture Sonar

Zhang

¹

,

Yang²

2019

J. Electr. Eng. Technol.

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For the multireceiver synthetic aperture sonar (SAS), the point target reference spectrum (PTRS) in the two-dimensional (2D) frequency domain and azimuth modulation in the range Doppler domain were first deduced based on a numerical evaluation method and accurate time delay. Then, the difference between the PTRS and azimuth modulation generated the coupling term in the 2D frequency domain. Compared with traditional methods, the PTRS, azimuth modulation and coupling term was better at avoiding approximations. Based on three functions, an imaging algorithm is presented in this paper. Considering the fact that the coupling term is characterized by range variance, the range-dependent sub-block processing method was exploited to perform the decoupling. Simulation results showed that the presented method improved the imaging performance across the whole swath in comparison with existing multireceiver SAS processor. Furthermore, real data was used to validate the presented method.have presented an analytic PTRS. Their method was based on the approximation that the transmitter and receiver contribute equally to the Doppler frequency. Based on the method of stationary phase [9], two PSPs corresponding to the transmitter's phase and receiver's phase were deduced. The phase history of the transmitter and that of the receiver were expanded into a power series at their individual PSPs. Both phases were then combined to generate a quadratic function. It can be found that two approximations are exploited by this method. One is the equal Doppler contribution of the transmitter and receiver, and the other is the Taylor approximation of the transmitter's phase and receiver's phase. In general, this method only applies to the narrow beam case [14,15]. There are still some other methods deducing the analytic PTRS. The basic idea relies on series approximation. In [16], the quadratic approximation of the two-way range was exploited. This introduced a large residual error, which degraded the imaging performance at close range. Moreover, this method did not consider the compensation of the stop-and-hop error [12]. A single target suffers from the coordinate deviation in azimuth [17]. However, a distributed target suffers from the distortion. In [18,19], the two-way range was expanded into a power series with respect to the slow time. Additionally, the PSP was expanded into a power series based on the series reversion method. The accuracy of the two-way range and PSP was limited by the number of terms in the polynomial. With this method, the series approximation was used twice. The approximation error increased with the slow time. The accumulative error would be large when the SAS system works with the wide beam case. In [20,21], the instantaneous Doppler wavenumber was exploited to deduce the analytic PTRS. The two-way slant range was formulated as a function of equivalent bistatic squint angle and half bistatic angle [20,21]. Based on the method of stationary phase [9], the azimuth wavenumber can also be expressed as a function of equ...

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“…On the other hand, given precise motion records with high-precision INS, numerous azimuth-variant MOCO algorithms, such as subaperture topography and aperture (SATA) dependent algorithm [33], precise topography and aperture dependent algorithm (PTA) [34,35], and the PTA derivation algorithms [36,37], are developed based on accurate calculation of the residual azimuth-variant phase error with INS records. However, the requirements are inapplicable for UAV SAR imaging.…”

Section: Introductionmentioning

confidence: 99%

Robust Two-Dimensional Spatial-Variant Map-Drift Algorithm for UAV SAR Autofocusing

Wang

¹

,

Zhang

²

,

Huang

³

et al. 2019

Self Cite

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Autofocus has attracted wide attention for unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) systems, because autofocus process is crucial and difficult when the phase error is spatially dependent on both range and azimuth directions. In this paper, a novel two-dimensional spatial-variant map-drift algorithm (2D-SVMDA) is developed to provide robust autofocusing performance for UAV SAR imagery. This proposed algorithm combines two enhanced map-drift kernels. On the one hand, based on the azimuth-dependent phase correction, a novel azimuth-variant map-drift algorithm (AVMDA) is established to model the residual phase error as a linear function in the azimuth direction. Then the model coefficients are efficiently estimated by a quadratic Newton optimization with modified maximum cross-correlation. On the other hand, by concatenating the existing range-dependent map-drift algorithm (RDMDA) and the proposed AVMDA in this paper, a phase autofocus procedure of 2D-SVMDA is finally established. The proposed 2D-SVMDA can handle spatial-variance problems induced by strong phase errors. Simulated and real measured data are employed to demonstrate that the proposed algorithm compensates both the range- and azimuth-variant phase errors effectively.

show abstract

“…However, a distributed target suffers from the distortion. In [18,19], the two-way range was expanded into a power series with respect to the slow time. Additionally, the PSP was expanded into a power series based on the series reversion method.…”

Section: Introductionmentioning

confidence: 99%

An Imaging Algorithm for Multireceiver Synthetic Aperture Sonar

Zhang

¹

,

Tan

²

,

Ying³

2019

View full text Add to dashboard Cite

For the multireceiver synthetic aperture sonar (SAS), the point target reference spectrum (PTRS) in the two-dimensional (2D) frequency domain and azimuth modulation in the range Doppler domain were first deduced based on a numerical evaluation method and accurate time delay. Then, the difference between the PTRS and azimuth modulation generated the coupling term in the 2D frequency domain. Compared with traditional methods, the PTRS, azimuth modulation and coupling term was better at avoiding approximations. Based on three functions, an imaging algorithm is presented in this paper. Considering the fact that the coupling term is characterized by range variance, the range-dependent sub-block processing method was exploited to perform the decoupling. Simulation results showed that the presented method improved the imaging performance across the whole swath in comparison with existing multireceiver SAS processor. Furthermore, real data was used to validate the presented method.

show abstract

Precise aperture‐dependent motion compensation for high‐resolution synthetic aperture radar imaging

Cited by 18 publications

References 18 publications

Imaging Algorithm for Multireceiver Synthetic Aperture Sonar

Imaging Algorithm for Multireceiver Synthetic Aperture Sonar

Robust Two-Dimensional Spatial-Variant Map-Drift Algorithm for UAV SAR Autofocusing

An Imaging Algorithm for Multireceiver Synthetic Aperture Sonar

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