基于光子混频的微波频率测量技术

Approach for measuring microwave frequency based on photonic mixing

提出了一种基于光子混频的光子学微波频率测量 方法。方法采用可调微波延时线控制射频（RF）通道与光通道之间延时,利用两个级联马赫曾 德调制器（MZM）进行 光子混频,进而建立微波频率与直流光功率之间关系。通过仿真与分析,合理 设计RF通道与光通道之间 延时,优化了系统频率测量范围。仿真结果表明,光通道延时与RF通道1的延时 差Δτ1选取在15ps附近,两个RF通 道之间延时差Δτ选择在20ps附近时,对于 1～6GHz范围的频率测量较为合适。实验中,采用矢量网络分析仪对延时进行 测量, 得到Δτ1为17.7ps,Δτ为16. 9ps。测试结果表明,在1～6GHz频率下,系统测量精 度在±0.2GHz以内。系统的测量误差主要来自于矢量网络分析仪对 相位测量的不 确定度,以及激光器输出光功率的波动,通过采取相应的措施可以提高系统测量 精度。本文方法为微波频率测量提供了一种低成本光子学解决手段。

We propose a photonics method of measuring microwave frequency based on photonic mixing.In this approach,a tunable microwave delay line （TMDL） is utilized to control the time delay between radio-frequency （RF） path and optica l path. By employing two cascaded Mach-Zehnder modulators to realize photonic mixing,w e can establish the relationship between microwave frequency and direct current （D C） optical power,and also our system has the advantage in reducing cost.After simul at ing and analyzing the established theory model,we can design the time delay betw een RF path and optical path,so that the system frequency measurement range will be optimized.The simulation results show that it is suitable for the frequency ran ge of 1-6GHz to select the time delay Δτ1 between optic al path and RF path 1around 15ps,and the time delay Δτ between the two RF pat hs around 20ps.In the experiment,a vector network analyzer is utilized to measure the time delay,we got Δτ1 as 17.7ps,Δτ as 16.9ps,and then the measured f requency range of 1to 6GHz with a measurement error less than ±0.2GHz is demonstrated experimental ly. The source of the measurement error is mainly from the phase measurement uncertainty of the vector network analyzer and the power fluctuation of the las er.The measurement accuracy can be improved by taking appropriate measures.This method can provide a low cost photonics solution for microwave frequency measurement.