School of Electronics and Information Engineering, Beihang University, Beijing 100083, China.
Department of Applied Science and Frontier Technology, Qian Xuesen Laboratory of Space Technology, Beijing 100094, China.
Sensors (Basel). 2018 Dec 9;18(12):4343. doi: 10.3390/s18124343.
Sub-Nyquist sampling technology can ease the conflict between high resolution and wide swath in a synthetic aperture radar (SAR) system. However, the existing sub-Nyquist SAR imposes a constraint on the type of the observed scene and can only reconstruct the scene with small sparsity (i.e., number of significant coefficients). The information channel model of microwave imaging radar based on information theory, in which scene, echo, and the mapping relation between the two correspond to information source, sink, and channel, is built, and noisy-channel coding theorem explains the reason for the aforementioned under this model. To allow the wider application of sub-Nyquist SAR, this paper proposes sub-Nyquist SAR based on pseudo-random space-time modulation. This modulation is the spatial and temporal phase modulation to the traditional SAR raw data and can increase the mutual information of information source and sink so that the scenes with large sparsity can be reconstructed. Simulations of scenes with different sparsity, e.g., an ocean with several ships and urban scenes, were run to verify the validity of our proposed method, and the results show that the scenes with large sparsity can be successfully reconstructed.
亚奈奎斯特采样技术可以缓解合成孔径雷达（SAR）系统中高分辨率和大测绘带之间的冲突。然而，现有的亚奈奎斯特 SAR 对观测场景的类型施加了限制，只能重建稀疏性较小的场景（即，有意义的系数数量较少）。基于信息论的微波成像雷达的信息通道模型，其中场景、回波以及两者之间的映射关系对应于信息源、汇和通道，在此模型下，建立了噪声通道编码定理解释了上述原因。为了允许更广泛地应用亚奈奎斯特 SAR，本文提出了基于伪随机空时调制的亚奈奎斯特 SAR。这种调制是对传统 SAR 原始数据的时空相位调制，可以增加信息源和汇之间的互信息，从而可以重建稀疏性较大的场景。对具有不同稀疏性的场景（例如，有几艘船的海洋和城市场景）进行了模拟，以验证我们提出的方法的有效性，结果表明，可以成功重建稀疏性较大的场景。
