一种基于并联MZM循环频移环路的多载频信号生成方法

Multiple Carrier Signals Generation Based on Parallel Mach-Zehnder Modulators with Recirculating Frequency Shifting Loop

随着卫星通信大容量、跨频段、多业务需求的不断增加,卫星载荷正朝着多频段一体化综合接收处理方向发展。为满足卫星载荷大容量、多信号处理功能,需要同时提供多个载频信号作为参考。采用微波光子技术可根据用户需求生成光频梳作为多载频信号,满足多频段一体化综合接收处理对多本振源的需求。文章首先从现有多载频信号生成方法的局限性出发,确定高质量光载波抑制单边带信号(SSB-OCS)结合循环频移的多载频信号生成方法。接着提出基于并联马赫-曾德尔调制器(MZM)的光载波抑制单边带信号生成方法,使得其中两个MZM工作在单边带调制方式,另一个MZM工作在偶数阶抑制方式,结合90度和180度光移,产生具有高边带抑制比的光载波抑制单边带信号。最后在此基础上给出基于并联MZM循环频移的多载频信号生成方法,仿真结果表明所生成的多载频信号载波数目为60以上、边带抑制比为30dB、最大功率起伏为4.4dB,且其中有20个载波的功率起伏在1dB以内。该方法可有效生成高平坦高边带抑制比多载频信号,为卫星载荷的多频段一体化综合接收处理提供相应技术支撑。

With the increasing demand of large capacity,cross band and multi service of satellite communication,satellite payload is developing towards the direction of multi band integrated receiving and processing.In order to meet the large capacity and multi signal processing function of satellite payload,it is necessary to provide multiple carrier signals as a reference at the same time.The traditional local oscillator with electronic technology has a single frequency,which can not generate multi carrier signals at the same time.By using microwave photonic technology,the optical comb can be generated as the multi carrier signals according to the user's requirements,which can meet the requirements of multi-band integrated receiving and processing for multiple local sources.In this paper,firstly,from the limitation of the existing generation method of multi carrier signals,the generation method of high-quality single sideband signal with optical carrier suppression(SSB-OCS)combined with recirculating frequency shifting loop is determined.Then,a method of generating SSB-OCS signal based on parallel Mach Zehnder modulators(MZMs)is proposed.By optimizing two MZMs working in single sideband signal(SSB)modulation and the other MZM working in even order suppression modulation,combined with 90 degree and 180 degree optical phase shifters,the SSB-OCS signal with high SMSR is generated.Theoretical analysis and simulation results show that this method can generate the SSB-OCS signal with sidemode Suppression ratio(SMSR)up to 36 dB.Finally,On the basis of the proposed SSB-OCS generator,a multiple carrier frequency signals generator with recirculating frequency shifting loop is proposed.Simulation results show that the number of generated multiple carrier signals is more than 60,the SMSR is about 30dB,the maximum power fluctuation is 4.4dB,and the power fluctuation of 20 carriers is within 1dB.