SAR Saturated Interference Suppression Method Guided by Precise Saturation Model

DUAN Lunhao; LU Xingyu; TAN Ke; LIU Yushuang; YANG Jianchao; YU Jing; GU Hong

doi:10.11999/JEIT251283

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DUAN Lunhao, LU Xingyu, TAN Ke, LIU Yushuang, YANG Jianchao, YU Jing, GU Hong. SAR Saturated Interference Suppression Method Guided by Precise Saturation Model[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT251283

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DUAN Lunhao, LU Xingyu, TAN Ke, LIU Yushuang, YANG Jianchao, YU Jing, GU Hong. SAR Saturated Interference Suppression Method Guided by Precise Saturation Model[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT251283

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SAR Saturated Interference Suppression Method Guided by Precise Saturation Model

doi: 10.11999/JEIT251283 cstr: 32379.14.JEIT251283

School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

Funds: National Natural Science Foundation of China (62101260, 62001229, 62101264)

Received Date: 2025-12-03
Accepted Date: 2026-01-30
Rev Recd Date: 2026-01-30

Available Online: 2026-02-14

Abstract

Abstract

Objective With the increasing number of electromagnetic devices, Synthetic Aperture Radar (SAR) is highly vulnerable to Radio Frequency Interference (RFI) in the same frequency band. RFI will appear as bright streaks in SAR images, seriously degrading the image quality. Currently, relevant scholars have conducted in-depth research on interference suppression and proposed many effective interference suppression methods. However, most methods fail to consider the nonlinear saturation of interfered echoes. In practical scenarios, due to the generally high power of interference, the gain controller in the SAR receiver struggles to effectively adjust the amplitude of the interfered echoes. This causes the input signal amplitude of the Analog-to-Digital Converter (ADC) to exceed its dynamic range, thus driving the SAR receiver into saturation and eventually leading to nonlinear distortion in the interfered echoes. This phenomenon is commonly observed in SAR systems, with documented cases of receiver saturation in the LuTan-1 satellite and various airborne SAR platforms. Analysis of SAR data further confirms the presence of saturated interference in systems including Sentinel-1, Gaofen-3, and several other spaceborne SAR platforms. Following saturation, the echo spectrum exhibits various spurious components and spectral artifacts, which leads to a mismatch between existing suppression methods and the actual characteristics of saturated interference. Therefore, some of the existing interference suppression methods have difficulty effectively mitigating this type of saturated interference. Moreover, there is currently a lack of accurate models capable of precisely characterizing the output components of saturated interfered echoes. To address these issues, this paper introduces a precise saturated interference analytical model and, based on this model, further proposes an effective saturated interference suppression method. Methods Through the processing of the basic saturation model, this paper first establishes a mathematical model capable of accurately characterizing the output components of saturated interference. Furthermore, the model's accuracy in amplitude and phase characterization was validated through simulation, and a comprehensive analysis was conducted on various output components of the interfered echoes under saturation conditions. Compared with the one-bit sampling model and the traditional tanh saturation model, the model proposed achieves higher accuracy in describing amplitude information. In addition, it is not limited to the sampling bit width of ADCs and can theoretically be extended to the saturation output description of other types of radar receivers. Based on the finding that harmonic phases can be expressed as a linear combination of the phases of the original signal components, and leveraging the high-power characteristic of the interference fundamental harmonic, a saturated interference suppression method is proposed. First, given the relatively high power of the interference fundamental harmonic, it can be effectively extracted through eigen-subspace decomposition; then, by leveraging the harmonic phase relationships together with the extracted interference fundamental harmonic and the SAR transmitted signal, interference harmonics—including higher-order interference harmonics, target harmonics, and intermodulation harmonics—are systematically constructed, thus forming a complete dictionary; finally, a sparse optimization problem is solved to achieve the separation and suppression of saturated interference. The superiority and effectiveness of the proposed method are validated using Gaofen-3 measured data. Results and Discussions This paper conducted experiments on both simulated and measured data to validate the effectiveness of the proposed method in mitigating saturated interference. For the simulated data, the proposed method completely removes interference stripes in the SAR image (Fig. 7). Analysis of the time-frequency spectrum of the processed echoes (Fig. 8 and Fig. 9) shows that traditional methods struggle to eliminate higher-order harmonics. As a result, the proposed approach improves the TBR by 1.76 dB and achieves the lowest RMSE of 0.0783 (Table 3). For the measured data from Gaofen-3, analysis of the processed images and time-frequency spectra of echoes confirms the proposed method's effective interference suppression capability, whereas conventional approaches consistently exhibit residual interference issues (Fig. 10 and Fig. 11). Conclusions With the increasing deployment of electromagnetic devices, SAR has become highly susceptible to in-band interference. Furthermore, high-power interference can easily drive the SAR receiver into saturation, resulting in nonlinear distortion that renders traditional interference suppression methods ineffective against saturated interference. To address this challenge, this paper establishes a model capable of precisely characterizing the saturated output components of interfered echoes. Based on this model, an interference suppression method capable of effectively dealing with saturated interference is proposed. Simulation and experiment demonstrate that the model accurately characterizes saturation behavior and that the method effectively suppresses saturated interference.
- Synthetic Aperture Radar (SAR),
- Saturated interference,
- Saturation model,
- Interference suppression

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References(28)

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