1-bit SAR Imaging Method Based on Single-frequency Time-varying Threshold
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摘要: 该文提出一种基于单频时变阈值的1-bit合成孔径雷达(SAR)成像方法,通过将回波数据与时变阈值比较,将其量化为1-bit采样数据,从而降低SAR回波数据的位宽,达到简化系统、提升效率的目的。传统的1-bit采样将信号与0阈值比较,这将造成信号相对幅度的非线性失真,影响成像质量。而随机时变阈值虽然能够保留幅度信息,却会引入额外的类噪声干扰。单频时变阈值将能够有效地保留1-bit采样量化中丢失的相对幅度信息,同时避免引入类噪声干扰,有效地提高了1-bit采样量化下的SAR成像质量。通过仿真实验定量分析了算法的成像聚焦质量、幅度信息保持能力,并通过对场景目标的成像验证了算法的有效性。Abstract: This paper proposes a 1-bit Synthetic Aperture Radar (SAR) imaging method based on a single-frequency time-varying threshold. Synthetic aperture radar echoes are quantized to 1-bit sampling data by comparing the data with the threshold; this reduces the data-width of the SAR echoes, consequently simplifying the system and improving efficiency. The conventional 1-bit sampling compares the signal to a zero threshold, bringing nonlinear distortion to the relative amplitude and degrading the imaging quality. The random threshold can keep the amplitude information, but it introduces additional noise-like interferences. In contrary, the single-frequency time-varying threshold can maintain the amplitude information lost during the 1-bit sampling and quantization, and at the same time, eliminate noise-like interferences; thus, the imaging quality of SAR using 1-bit sampling and quantization can be improved. The focusing quality and the amplitude-maintaining ability of the proposed approach is quantitatively analyzed, and the effectiveness of the approach is verified by an imaging experiment on a scene.
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Key words:
- Synthetic Aperture Radar (SAR) /
- 1-bit sampling /
- Time-varying threshold
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表 1 SAR参数
Table 1. SAR parameters
参数名称 参数值 信号带宽(MHz) 300 脉冲宽度(μs) 1 采样率(GHz) 6.9 载频(GHz) 37.6 单频阈值频率(GHz) 16.2 信号阈值比(dB) 0 场景中心斜距(km) 10 天线孔径(m) 1 载机速度(m/s) 50 脉冲重复频率(Hz) 400 表 2 单散射点聚焦质量指标
Table 2. Focusing quality indexes of the single scatterer
采样方法 PSLR (dB) ISLR (dB) IRW (m) 均值 方差 均值 方差 均值 方差 传统采样 –13.7217 – –10.1301 – 0.4435 – 传统1-bit采样 –13.4556 – –9.3684 – 0.4435 – Gaussian 1-bit采样 –13.4054 0.0059 –8.0347 0.0007 0.4435 0.2163×10–5 Sinusoid 1-bit采样 –13.8106 0.0016 –9.3048 0.0005 0.4474 0.1621×10–5 表 3 多散射点幅度质量指标
Table 3. Amplitude quality indexes of multiple scatterers
采样方法 幅度1 幅度2 幅度3 均值 误差 方差 均值 误差 方差 均值 误差 方差 传统采样 0.9729 2.71% – 1.9683 1.58% – 2.9775 0.75% – 传统1-bit采样 0.1818 – – 0.3185 – – 0.5067 – – 传统1-bit采样(缩放) 1.1311 13.11% – 1.7710 11.45% – 3.0834 2.78% – Gaussian 1-bit采样 1.0477 4.77% 0.0633 1.9870 0.65% 0.0629 2.9920 0.27% 0.0617 Sinusoid 1-bit采样 1.0181 1.81% 0.0377 2.0186 0.93% 0.0189 2.9812 0.63% 0.0108 -
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