A simple and all-optical Doppler frequency shift (DFS) measurement system is presented. It is based on a dual-drive Mach Zehnder modulator (DDMZM) driven by a transmitted signal and an echo signal received by an antenna. A low-frequency sawtooth wave is applied to the DDMZM DC port to frequency shift the carrier and sidebands generated by the transmitted signal. Beating of a frequency-shifted transmitted signal sideband and an echo signal sideband at the photodetector produces a low-frequency electrical signal. The DFS, and consequently the speed and moving direction of a target, can be obtained from the frequency of this low-frequency electrical signal. The DDMZM used in the proposed DFS measurement system does not need to be operated at a specific point in the transfer function and hence it has no bias drift problem. The proposed DFS measurement technique can be used in both CW and pulsed radar systems. Experimental results demonstrate the proposed DFS measurement system has a wide operating frequency range of 10 GHz to 19.95 GHz, small DFS measurement error of less than ±0.6 Hz and long-term stable performance. Results also demonstrate, for the first time, DFS measurement of a pulsed signal using a microwave photonic technique.

中文翻译：

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全光脉冲信号多普勒频移测量系统


提出了一种简单的全光学多普勒频移（DFS）测量系统。它基于双驱动马赫曾德尔调制器 (DDMZM)，由发射信号和天线接收的回波信号驱动。低频锯齿波应用于 DDMZM DC 端口，以对传输信号生成的载波和边带进行频移。光电探测器处的频移发射信号边带和回波信号边带的跳动产生低频电信号。可以从该低频电信号的频率获得 DFS，从而获得目标的速度和移动方向。所提出的 DFS 测量系统中使用的 DDMZM 不需要在传递函数中的特定点操作，因此不存在偏置漂移问题。所提出的 DFS 测量技术可用于 CW 和脉冲雷达系统。实验结果表明，所提出的DFS测量系统具有10 GHz至19.95 GHz的宽工作频率范围、小于±0.6 Hz的小DFS测量误差以及长期稳定的性能。结果还首次证明了使用微波光子技术对脉冲信号进行 DFS 测量。