Zhang Xuyan, Peng Di, Ma Yangxue, Wang Botao, Wang Mengke, Li Zhengkai, Zhang Zhiyao, Zhang Shangjian, Li Heping, Liu Yong
Appl Opt. 2020 Sep 20;59(27):8056-8065. doi: 10.1364/AO.401483.
A photonic-assisted broadband and high-resolution microwave frequency measurement scheme is proposed and demonstrated based on undersampling via using three cavity-less optical pulse sources with coprime repetition rates. After undersampling by three ultrashort pulse trains with repetition rates in the order of gigahertz, input microwave signal is down-converted to three intermediate-frequency (IF) signals located in the first Nyquist frequency range. Through measuring the frequencies of the IF signals via fast Fourier transform after digitization by the commercially available analog-to-digital convertors, the input microwave signal frequency can be retrieved based on the frequency identification algorithm. In the proof-of-concept experiment, three ultrashort pulse trains with repetition rates of 2.99, 3.07, and 3.10 GHz are generated by a cavity-less optical pulse source, where the pulse widths are 9.5, 9.6, and 9.8 ps, respectively. Through using these three ultrashort optical pulse trains, a frequency measurement range up to 40 GHz is realized, where the frequency measurement error is less than ±5, and the spurious-free dynamic range is 91.25.
提出并演示了一种基于欠采样的光子辅助宽带高分辨率微波频率测量方案，该方案通过使用具有互质重复率的三个无腔光脉冲源来实现。在被重复率处于千兆赫兹量级的三个超短脉冲序列进行欠采样之后，输入微波信号被下变频为位于第一奈奎斯特频率范围内的三个中频（IF）信号。通过在由商用模数转换器数字化之后经由快速傅里叶变换测量IF信号的频率，可以基于频率识别算法检索输入微波信号的频率。在概念验证实验中，由一个无腔光脉冲源产生了重复率分别为2.99、3.07和3.10 GHz的三个超短脉冲序列，其脉冲宽度分别为9.5、9.6和9.8 ps。通过使用这三个超短光脉冲序列，实现了高达40 GHz的频率测量范围，其中频率测量误差小于±5，无杂散动态范围为91.25。
