集成微波任意波形发生中的多波形高速更新研究

In this project, a novel method of integrated RF arbitrary waveform generation based on electrooptic waveguide Bragg gratings (WBG) and waveguide optical switches is presented, concentrating on the integrated RF arbitrary waveform generation with more waveform types and high update rates. Two types of electrooptic WBGs, the electrooptic triggered WBG and the electrooptic tunable WBG, are to be designed and fabricated, and their optical properties and influencing factors are investigated. The two types of WBG are then combined to achieve a single channel of RF arbitrary waveform generation. The cascaded electrooptic triggered WBG is employed for the generation of a pulse train in which each pulse can be fast switched between the "ON" and the "OFF" states, while the electrooptic tunable WBG is emplyed to fast tune the time delay of each pulse in the pulse train. After the bandwith-limited photodiode the specific RF waveform is obtained, whose frequency and amplitude can both be manipulated in high speed. The electrooptic switch is then combined with multiple RF waveform generation channels to switch between different types of waveforms in high speed. The waveform types are increased with the update time less than 100 nanoseconds, and the requirement on the reconfiguability of the device is relieved. Important development has been made associated with the design and fabrication of the WBGs and the integrated electrooptic switchs. This project can provide imiportant experimental evidence for the research of the integrated RF arbitrary waveform generation chips.

本项目提出了一种基于电光波导布拉格光栅（WBG）和波导电光开关的集成微波任意波形发生的新方法，针对具有丰富的波形种类和高更新速率的微波任意波形发生技术进行研究。我们拟设计制作两类电光WBG，即电光触发WBG和电光调谐WBG，并对其光学特性和影响因素进行研究。我们进而将二者结合，获得单个脉冲整形通道。我们采用级联式电光触发WBG实现任意脉冲可高速开关调制的脉冲序列的发生，采用级联式电光调谐WBG实现对脉冲序列中各个脉冲延时量的高速调谐，经过光电转换获得频率和振幅均可高速调谐的微波波形。我们将波导电光开关与多个脉冲整形通道相结合，进行多种微波波形间的高速切换，进一步增加了可高速更新的微波波形种类，更新时间小于100ns，并缓解了对器件可重构能力的要求。我们在WBG以及波导电光开关的设计与制作上已经取得了重要进展。本研究将对集成化微波任意波形发生芯片的研究提供重要的实验依据。

微波任意波形发生技术在高速通信、雷达、电子对抗等领域有广泛的应用前景，目前商用的微波任意波形一般采用电子学方法产生，因而受限于“电子瓶颈”。与之相比，光子学方法具有天然优势，能够产生高载频、大带宽的微波信号，因此成为研究热点。为进一步解决成本、尺寸、重量、功耗、稳定性等问题，我们对基于光子集成的微波任意波形发生技术进行研究。我们首先提出一种微波任意波形发生的集成系统，包括若干波形发生单元和波形选择单元，利用波形选择单元对波形发生单元产生的波形进行高速切换。我们基于SOI平台对该系统的关键器件进行了设计，获得了响应时间7ns的光开关和谐振波长可调的光谱整形器，并对系统输出进行了模拟，实现了波形的高速更新。针对目前广泛采用的波长-时间映射方案，我们针对其集成化进行研究，提出了基于啁啾波导布拉格光栅的片上波长-时间映射方案，与高速光开关相结合，实现了两种微波突发波形的高速更新。另外，锆钛酸铅镧（PLZT）由于具有高电光系数和偏振不敏感特性等优点，适于进行电光开关等集成器件的制备。我们针对PLZT光波导薄膜的制备进行研究，制备了PLZT脊形光波导，实现了波导通光，为实现基于PLZT材料平台的集成微波任意波形发生系统奠定了基础。我们还对PLZT光波导薄膜的低成本制备工艺进行研究，获得了表面平坦、结构致密的PLZT薄膜，为集成器件的实用化提供了条件。我们的工作在推动微波任意波形发生技术的集成化方面具有重要意义，未来有望应用于脉冲压缩雷达、超宽带和多址无线通信等领域。