Microwave photonic radars enable fast or even real-time high-resolution imaging thanks to its broad bandwidth. Nevertheless, the frequency range of the radars usually overlaps with other existed radio-frequency (RF) applications, and only a centimeter-level imaging resolution has been reported, making them insufficient for civilian applications. Here, we propose a microwave photonic imaging radar with a sub-centimeter-level resolution by introducing a frequency-stepped chirp signal based on an optical frequency shifting loop. As compared with the conventional linear-frequency modulated (LFM) signal, the frequency-stepped chirp signal can bring the system excellent capability of anti-interference. In an experiment, a frequency-stepped chirp signal with a total bandwidth of 18.2 GHz (16.9 to 35.1 GHz) is generated. Postprocessing the radar echo, radar imaging with a two-dimensional imaging resolution of ∼8.5 mm × ∼8.3 mm is achieved. An auto-regressive algorithm is used to reconstruct the disturbed signal when a frequency interference exists, and the high-resolution imaging is sustained.

中文翻译：

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亚厘米级分辨率的微波光子成像雷达

由于其宽带宽，微波光子雷达能够实现快速甚至实时的高分辨率成像。然而，雷达的频率范围通常与其他现有的射频（RF）应用重叠，并且仅报道了厘米级成像分辨率，这使得它们不足以满足民用应用需求。在这里，我们通过引入基于光频移环路的频率步进啁啾信号，提出了一种具有亚厘米级分辨率的微波光子成像雷达。与传统的线性调频（LFM）信号相比，频率步进的线性调频信号可以为系统带来优异的抗干扰能力。在实验中，生成了总带宽为 18.2 GHz（16.9 至 35.1 GHz）的频率步进线性调频信号。对雷达回波进行后处理，实现了二维成像分辨率为∼8.5 mm × ∼8.3 mm 的雷达成像。当存在频率干扰时，采用自回归算法重建受干扰信号，保持高分辨率成像。