提出了基于级联马赫 -曾德尔调制器( Mach-Zehnder Modulators, MZMs)的宽带微波光子下变频方法, 并且通过该方法产生的中频信号( Intermediate Frequency, IF)得到被探测目标的距离信息。在该方案中, 通过控制 MZM的工作偏置点和调制指数来实现线性调频( Linear Frequency Modulation, LFM)信号的倍频处理。倍频后的 LFM信号通过电延时进行传输来模拟被探测目标的返回信号。同时, 通过 MZM调制被延迟后的光边带信号。然后, 通过低通滤波器得到带有目标距离信息的中频信号。通过模拟仿真实现了中心频率分别为 10. 8, 21. 8, 32. 4 GHz的二倍、四倍、六倍频信号, 其信号带宽分别为 2. 7, 5. 6, 8. 4 GHz。随着电延时的增加, IF频率值呈线性减小。该方法灵活性高、精度高, 易于实现, 在雷达系统的宽带成像系统中具有很大的应用潜力。

Based on cascade Mach-Zehnder modulators(MZMs), a broadband microwave frequency down-conversion method was proposed, and the target distance information was derived from the down-converted intermediate frequency(IF). In the proposed scheme, a linear frequency modulated microwave signal was multiplicated by controlling the bias point and modulation index of MZM. The multiplicated sig. nal was then transferred through an electric time delay to simulate the retuning signal of the target, and the transferring delayed optical sidebands are modulated on MZM. The IF signal carrying the target distance information was obtained after a low-pass filter. Analogous simulations of frequency doubling, quadrupli. cating, and sextupling of central frequencies of 10. 8, 21. 8, and 32. 4 GHz and bandwidths of 2. 7, 5. 6, and 8. 4 GHz are achieved. Moreover, as the electrical time delay increases, the IF linearly decreases. The proposed method is proven to be flexible, highly accurate, and easily implemented, demonstrating its great potential in radar systems for wideband imaging systems.