High-resolution Detection by Multiband Fusion of Photonics-based Radars

In recent years, microwave photonic technologies have been applied to overcome the bandwidth limitation of traditional radars. Previously reported photonics-based radars can achieve a high range resolution up to centimeter-level. However, due to unavailability of suitable wideband Radio Frequency (RF) front-ends and strict regulation of the frequency usage in the electromagnetic (EM) spectrum, practical applications of photonics-based radars are still challenging. Multiband radar fusion is a promising solution to these problems, which improves the range resolution by fusing the target frequency responses of different frequency bands of multiple radars into a wider bandwidth frequency response. In this report, we demonstrate high-resolution detection based on multiband fusion of photonics-based radars that work in different frequency bands. Four photonics-based radars having the same bandwidth of 2 GHz are established, of which the operation spectral ranges are 18–20GHz, 20–22GHz, 22–24 GHz and 24–26GHz, respectively. The range resolution of each photonics-based radar is measured to be about 8 cm. To coherently fusing the radar echoes of the multiband photonics-based radars, coherent processing is first implemented to compensate for the incoherent phases (ICPs) between different radars, in which a modified root multiple signal classification (root-MUSIC) and least squares are adopted to estimate the ICPs. After coherent processing, the radar echoes of the four photonics-based radars are synthesized to obtain an equivalent 8-GHz bandwidth signal in the time domain. The measured range resolution after multiband fusion is improved to be 2 cm.