Multi-channel Phase Error Estimation Method Based on an Error Backpropagation Algorithm for a Multichannel SAR
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摘要: 方位向多通道合成孔径雷达(SAR)可实现高分辨率宽测绘带成像,准确估计通道间相位误差是保障成像质量的关键。该文提出了基于误差反向传播训练优化的通道相位误差估计方法,该方法根据多通道SAR回波生成的物理过程,构建含有通道间相位误差待估计参数的观测矩阵,通过初始化的通道误差和初始化的目标散射系数参数生成初始化的SAR回波,并计算该回波与多通道SAR实测回波之间的误差,通过深度学习中常用的误差反向传播的方法,不断训练优化上述参数,最终获得通道间相位误差的估计值,同时也得到了对稀疏目标散射系数的估计。该方法基于误差反向传播方法,并将该方法与通道误差的形成原理相结合,在稀疏假设下同时完成了相位估计和成像,为多通道SAR误差估计提供了一种全新的思路。多通道SAR仿真数据验证了该文算法的有效性。Abstract: An azimuth multi-channel Synthetic Aperture Radar (SAR) can be used to obtain high-resolution wide-swath SAR images. Accurate estimation of the phase error between channels is the key to ensuring image quality. In this study, we present a channel phase error estimation method based on the error backpropagation algorithm. During the physical process of a multi-channel SAR echo generation, this method constructs an observation matrix with the parameters to be estimated including the phase error between channels. The initial SAR echo is generated using the initial channel error matrix and initial target scattering coefficient matrix, and the error between the echo and measured multi-channel SAR echo is calculated. Using the backpropagation algorithm commonly used in deep learning, the abovementioned parameters are continuously trained and optimized. Finally, the estimation of the phase error between channels is obtained along with the target scattering coefficient. This method combines the error backpropagation method with the principle of multi-channel SAR channel error. Phase estimation and imaging are realized based on the sparsity assumption, which provides a new approach for estimating an error in a multi-channel SAR. The effectiveness of the presented method is validated using multi-channel SAR simulation data.
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表 1 仿真实验系统参数
Table 1. Parameters of simulation experiment system
参数 取值 通道数 4 雷达载频(GHz) 5.35 信号带宽(MHz) 210.00 脉冲重复频率(Hz) 335.10 方位向波束宽度(°) 5.14 雷达高度(m) 4950.00 雷达距场景中心的距离(m) 7000.00 雷达方位向等效速度(m/s) 123.00 场景方位向宽度(m) 20.00 场景地距向宽度(m) 20.00 距离采样个数 4096 方位回波个数 3166 表 2 通道间相位误差估计结果(°)
Table 2. Estimation results of channel phase error (°)
相位误差 通道1/2相位误差 通道2/3相位误差 通道3/4相位误差 实际相位偏差 –9.82 6.44 –2.34 无噪估计 –9.81 6.44 –2.34 SNR=0 dB估计 –9.87 6.46 –2.33 SNR=–5 dB估计 –9.35 6.30 –2.76 -
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