一种低相噪高线性度宽带微波光子直接下变频方法

A Broadband Microwave Photonic Direct Downconversion Approach with Low Phase Noise and High Linearity

本文结合光电振荡器(OEO)、光域预失真补偿和数字线性化补偿技术,给出了一种低相噪高线性度宽带微波光子直接下变频方案并进行了相关的实验验证。来自于OEO的光26 GHz本振信号和接收到的30 GHz射频信号一起馈送至双重并行马赫增德尔调制器(DPMZM),通过适当的偏置点控制,该DPMZM完成光域预失真补偿及混频,DPMZM输出信号经光电转换后得到下变频信号,该信号随后经数字线性化补偿进一步抑制交调失真,得到高线性度的下变频电信号。实验结果表明该方案在实现宽带微波信号变频(30至4 GHz变频)的同时,变频无杂散动态范围达126 dB·Hz^2/3以上,具有大动态、高线性特性。此外,该技术方案的变频增益优于-10 dB,噪声系数为23.5 dB,具有良好的变频系统性能。

Based on optoelectronic oscillators(OEO),optical pre-distortion compensation and digital linearization techniques,a broadband microwave photonic direct downconverter with low phase noise and high linearity is proposed and demonstrated.The local oscillator signal from OEO with 26 GHz and radio frequency(RF)signal with 30 GHz are fed to a dual-parallel Mach-zehnder modulator(DPMZM)with optimal point to realize linear downconversion at optical domain,and the downconversion signal is output by a photodetector(PD).The achieved electrical signal is then digitally linearized to suppress the intermodulation distortion.The experiment shows the converter has low phase noise,wide bandwidth and high linearity.With the broadband microwave photonic direct downconverter,the spurious-free dynamic range(SFDR)is improved to above 126 dB·Hz 2/3,the conversion efficiency is better than-10 dB,and the noise figure is 23.5 dB.