为了克服电混频器的瓶颈, 实现大带宽的信号混频, 提出了一种基于双偏振双平行马赫-曾德尔调制器的微波光子混频方案。通过调节调制器的6个直流偏置电压进行载波抑制单边带调制, 射频(RF)信号和本振(LO)信号分别注入调制器, 相互隔离, 各自调制, 且在2个相互正交的偏振态上传输, 最后经偏振控制器和检偏器调整到同一偏振态上进行拍频, 上、下变频模式的切换只需要改变其中一个直流偏置电压。仿真与实验表明: 该方案切实可行, 输入的RF频率在11~25 GHz时, 输出的上变频或下变频信号的RF杂散抑制比不低于25 dB, 频谱纯度高, 可调谐性好, 变频模式之间切换方便, 系统的RF/LO隔离度达到-49 dB。

In order to overcome the bottleneck of electric mixer and achieve wide bandwidth signal mixing, a microwave photonic mixing scheme based on dual polarization double parallel Mach-Zehnder modulator is proposed. Carrier suppression single sideband modulation is achieved by adjusting six direct-currentbias voltages. Radio frequency(RF) and Local oscillator(LO) signals are injected into modulators separately, separated from each other and modulated separately. They are transmitted on two orthogonal polarization states. Finally, both of them are adjusted to the same polarization state by polarization controller and polarizerto beat the frequency. The switching of up-conversion and down-conversion only needs to change one of the direct-current bias voltages. The simulation and experiment results show that the scheme is feasible. When the RF frequency ranges from 11 GHz to 25 GHz, the RF spurious rejection ratio of the up-converted or down-converted signals output by the scheme is no less than 25 dB, and the spectrum purity is high and the tunability is good. The switching between the frequency conversion modes is convenient, the RF/LO isolation of the system reaches -49 dB.