Wang Haojie, Li Shangyuan, Xue Xiaoxiao, Xiao Xuedi, Zheng Xiaoping
Opt Express. 2020 Oct 12;28(21):31241-31252. doi: 10.1364/OE.405465.
In this paper, we present a distributed aperture coherent microwave photonic radar (DCMPR) system by means of a high-precision fiber-optic time-frequency synchronization network (OTFSN). The microwave photonic radar units distributed at different geographic locations are connected with the fiber network. Meanwhile, the time and frequency reference of the central controlling station are stably transferred over the fiber network to each radar unit, of which transmit and receive times are synchronized by the reference signal to cohere the multiple radar apertures. Experimentally, we demonstrate a two-unit DCMPR system with a 12-km OTFSN, where both radar units are operated in X-band and with a bandwidth of 4 GHz. Through the OTFSN, the time difference of the transmitted waveforms at the two radar units can be maintained within about 26 ps. When full coherence on transmit and receive is achieved, the signal-to-noise ratio (SNR) can be increased by about 8.1 dB and 7.9 dB respectively for two unit radars. Moreover, three radar reflectors are clearly imaged and probed by utilizing the mutually coherent operation, yet they are not be detectable by the single radar case.
在本文中，我们借助高精度光纤时频同步网络（OTFSN）提出了一种分布式孔径相干微波光子雷达（DCMPR）系统。分布在不同地理位置的微波光子雷达单元与光纤网络相连。同时，中央控制站的时间和频率基准通过光纤网络稳定地传输到每个雷达单元，其发射和接收时间由基准信号同步，以使多个雷达孔径相干。通过实验，我们展示了一个具有12公里OTFSN的双单元DCMPR系统，其中两个雷达单元均工作在X波段，带宽为4 GHz。通过OTFSN，两个雷达单元发射波形的时间差可保持在约26皮秒以内。当在发射和接收上实现完全相干时，两个单元雷达的信噪比（SNR）可分别提高约8.1 dB和7.9 dB。此外，利用相互相干操作可以清晰地对三个雷达反射器进行成像和探测，但在单雷达情况下则无法检测到它们。
