Frequency modulated continuous-wave (FMCW) radar systems suffer from permanent leakage from the transmitted signal into the receiver, which will reduce the dynamic range of the system and degrade the receiver sensitivity. Herein, a photonic-assisted leakage cancellation method for a wideband FMCW radar transceiver is proposed and experimentally demonstrated. At the remote antenna unit (RAU), a local oscillator (LO) signal, and a leakage signal are converted to optical signals with orthogonally polarization states by using a polarization-division-multiplexed Mach–Zehnder modulator (PDM-MZM). After the transmission of 10 km single mode fiber (SMF), the leakage signal is cancelled by using a variable optical attenuator (VOA), a variable optical delay line (VODL), and a balanced photodetector (BPD) at central office (CO). Compared with other analog cancellation methods, the proposed one has wider sweeping bandwidth and simpler structure. In the experiment, the LO signal and leakage signal are emulated by using an arbitrary waveform generator (AWG), a power divider, and two different length radio frequency lines. Then, experimental results show that a leakage cancellation depth of 17.5 dB at the carrier frequency of 15 GHz with a sweeping rate of 2 GHz/4 us is achieved.

中文翻译：

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宽带调频连续波雷达收发器的光子辅助泄漏消除

调频连续波 (FMCW) 雷达系统会遭受从发射信号到接收器的永久性泄漏，这会降低系统的动态范围并降低接收器的灵敏度。在此，提出并实验证明了一种用于宽带 FMCW 雷达收发器的光子辅助泄漏消除方法。在远程天线单元 (RAU)，本地振荡器 (LO) 信号和泄漏信号通过使用偏振分复用马赫-曾德调制器 (PDM-MZM) 转换为具有正交偏振态的光信号。10公里单模光纤（SMF）传输后，通过中心局（CO）的可变光衰减器（VOA）、可变光延迟线（VODL）和平衡光电探测器（BPD）消除泄漏信号. 与其他模拟消除方法相比，所提出的一种具有更宽的扫描带宽和更简单的结构。在实验中，使用任意波形发生器（AWG）、功率分配器和两条不同长度的射频线来仿真本振信号和泄漏信号。然后，实验结果表明，在15 GHz的载频和2 GHz/4 us的扫描速率下实现了17.5 dB的泄漏消除深度。