融合UNet与扩散模型的雷达回波图像复原方法
Radar Echo Image Restoration with UNet and a Diffusion Model
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摘要: 机载脉冲多普勒雷达(Pulse-Doppler Radar)在目标探测、环境感知及制导监测等任务中发挥着核心作用,但其在工作频段内极易受到无线通信、广播电视以及电子对抗等多源复杂电磁干扰的影响,导致雷达回波信号结构扭曲、噪声增强及纹理特征退化,严重制约了雷达成像与运动参数估计的精度。针对这一问题,本文提出一种 UNet 与扩散模型相结合的两阶段抗干扰图像复原框架。在第一阶段,UNet网络利用多尺度特征编码与跳跃连接机制实现目标结构的初步重建与能量分布校正,确保全局形态的准确恢复;第二阶段采用条件扩散模型引入软先验混合策略(Soft Prior Fusion),对局部纹理与细节进行生成式增强,从而在不依赖显式遮罩的前提下实现柔性重建。本文基于仿真生成的多类型干扰(梳状谱、噪声卷积、频谱弥散、切片重构)雷达数据集,系统评估了该方法在不同信噪比与信干比条件下的性能表现。实验结果表明,该框架在结构保持性、纹理真实性及感知质量方面均优于单一模型,其中在高干扰条件下平均提升峰值信噪比(Peak Signal-to-Noise Ratio, PSNR)约2.1 dB、学习感知图像块相似性(Learned Perceptual Image Patch Similarity, LPIPS)降低48%。进一步的参数估计实验验证了复原图像对目标高度、速度与俯仰角的估计精度显著提高,尤其在俯仰角估计中平均绝对百分比误差(Mean Absolute Percentage Error, MAPE)降低超过45%。研究表明,所提出的两阶段方法在兼顾确定性回归与概率生成特性的同时,实现了结构与感知层面的最优平衡,为雷达图像复原与运动参数提取提供了一种高鲁棒性的新思路。Abstract: Airborne pulse-Doppler radar plays a crucial role in target detection, environmental perception, and guidance monitoring. However, existing equipment is highly susceptible to multi-source complex electromagnetic interference from wireless communications, broadcasting, and electronic countermeasures within its operating frequency band. Such interference leads to signal distortion, noise amplification, and texture degradation in radar echoes, which severely restricts imaging quality and the accuracy with which motion parameters can be estimated. To address this problem, we propose a two-stage interference suppression and image reconstruction framework that integrates a deterministic model based on a UNet architecture with a denoising diffusion probabilistic model (DDPM). In the first stage, the UNet model performs preliminary structural restoration and energy redistribution through multiscale feature encoding and skip connections to ensure accurate recovery of the global morphology. In the second stage, a conditional diffusion model introduces a soft prior fusion strategy to enable generative enhancement of local textures and fine details without relying on explicit masks to achieve flexible reconstruction. The proposed method was systematically evaluated under conditions with varying signal-to-noise ratio (SNR) and signal-to-jamming ratio (SJR) using simulated radar datasets containing multiple types of interference including comb-spectrum, noise-convolution interference, spectral diffusion, and slice reconstruction interference. The experimental results demonstrate that the proposed framework significantly outperformed approaches based on a single model in terms of structural consistency, texture fidelity, and perceptual quality. In scenarios with high levels of interference, the method achieved an average improvement in peak SNR (PSNR) of approximately 2.1 dB and a 48% reduction in learned perceptual image patch similarity (LPIPS). Furthermore, the results of parameter estimation experiments validate that the reconstructed images substantially improved the estimation accuracy of target altitude, velocity, and pitch angle, with the mean absolute percentage error (MAPE) in pitch estimation reduced by more than 45%. These results indicate that the proposed two-stage method effectively balanced deterministic regression and probabilistic generation to achieve an optimal trade-off between structural accuracy and perceptual realism. Thus, the proposed approach provides a robust and efficient solution for radar image restoration and motion parameter inversion under complex interference environments.
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